[HN Gopher] A delightful quirk of relativity theory
___________________________________________________________________
A delightful quirk of relativity theory
Author : sohkamyung
Score : 312 points
Date : 2022-01-18 09:47 UTC (13 hours ago)
(HTM) web link (twitter.com)
(TXT) w3m dump (twitter.com)
| enriquto wrote:
| I love the name of the scientist Al Unapietra. The thing is very
| well explained, but it's very sad to see it as a twitter thread,
| which is a mostly unreadable format.
| acadapter wrote:
| Twitter threads are in general a very sad successor of the
| blogosphere.
| alfiedotwtf wrote:
| Sure, but you can't knock it for the speed at which cool info
| like this thread spread
| stronglikedan wrote:
| Some people prefer it, and there's tools for those that don't.
| Such as [0], as another user so helpfully posted, and for which
| I am grateful, since I fall into the latter camp with you.
|
| [0] https://threadreaderapp.com/thread/1482811504424542211.html
| soneca wrote:
| Twitter threads don't bother me. The brain quickly adapts to
| skipping the irrelevant parts (username, like buttons, etc) and
| to expecting the cadency of tweets.
|
| I believe it is harder to write (due to the character limit of
| each text block), but, far from "unreadable", I can read it
| fairly easily.
| est31 wrote:
| Personally i think a lot of people do threads because it's
| easier to write. Also you can take days or weeks of writing
| threads in public, updating them with new information,
| without appearing to do "stealth" edits, or adding "Update
| <date>:" to each added section.
|
| For readers twitter threads are pretty crap tho, that's why I
| really like to use thread reader app.
| not2b wrote:
| But it isn't easier to write something like this one in the
| "tweet storm" format. The author has to carefully consider
| how to divide the explanation up into separate tweets in a
| way that flows naturally.
| derbOac wrote:
| I tune out after a certain point with these types of long
| Twitter threads. It's like reading a magazine conveyed via
| telegraph.
|
| People are correct to point out it helps material reach a
| wide audience, but that's not the point. The point is what
| could be better?
|
| The original argument was to keep communication brief,
| shorter is better, etc. The fact it keeps being circumvented
| in this way suggests sometimes a longer format is necessary.
|
| As a practical matter, in this case the person could have
| linked to a long form blog post and used Twitter as a sort of
| comment discussion section?
| enriquto wrote:
| Oh, I don't bother by the stupidly repeated usernames and
| dates. I just want to read the damn thing.
|
| But it is literally unreadable to me. I couldn't finish
| reading the thread and had to find an alternative way out of
| twitter.
|
| Fist trial, using my android phone with fennec fox. There is
| a modal that hides the content asking me to "log in"; if I
| close the modal I go back to the twitter homepage. Thus
| unreadable because I don't have a twitter account. Sometimes
| I have managed to read a few tweets by a "smart" combination
| of closing the successive modals and reloading the page, but
| not this time.
|
| Second trial, using my laptop with firefox browser and heavy
| adblocking. I can read only the first three tweets, the rest
| do not load due to some third-party javascript.
|
| No big deal. Third trial, now I open a "clean" firefox
| browser session with just ublock origin, and I manage to read
| about 30 tweets, until it starts talking about hyperbolic
| rotations. The thread obviously continues, but the sole link
| below it "show replies" does not work. When I click on it it
| says "Whoops! Something went wrong. Please try again!".
|
| Typically I wouldn't bother and stop reading. Fuck twitter.
| But today I really wanted to read this thread because I teach
| these things. Thus I learned to use nitter, which gives an
| interface of twitter that, even if it's equally ugly, it sort
| of works (in that you can actually manage to read the text).
|
| In retrospect, this is an extremely sad state of affairs. We
| have an excellent article which is made of a short text, a
| few simple formulas, and a few simple images. This could be a
| static html page of a handful of Kb with img tags. But it is
| a slow and humongous javascript monstrosity that does not
| even work, and may disappear at any time if twitter "bans"
| this user for reasons unrelated to this text.
| 300bps wrote:
| For what it's worth, I clicked on the HN link on my iPhone
| and it opened in the Twitter app (that I never use) and it
| was extremely readable. Literally no problems reading it at
| all.
| deelly wrote:
| I can't say that buying IPhone with preinstalled Twitter
| app is very convenient way of reading twitter post.
| soneca wrote:
| I got it now. Yes, Twitter is a walled garden, even if it
| has large windows to see most of things, there is
| definitely a wall there.
|
| The tricky part is that if this was published in a static
| html page it would be less likely that it would reach us
| (even if the page was linked in the thread). Distribution
| is hard.
|
| A good compromise I think is keeping the thread but having
| a link to a blogpost with the same content in the first (or
| second) tweet.
|
| A Twitter thread formatting tool that also publishes a web
| version and automatically link to it in the second tweet is
| a good micro Saas idea if anyone is looking I think.
| enriquto wrote:
| > The tricky part is that if this was published in a
| static html page it would be less likely that it would
| reach us
|
| But this is an orthogonal issue. Twitter could have
| exactly the same terms of service, but still serve a
| single, static, small, html page that would load
| instantly on all devices. But instead, they choose to
| serve a bloated mess that does not work in many browsers,
| and is slow everywhere. Just to display a few lines of
| text.
| not2b wrote:
| Yes, una pietra == a stone == ein Stein. Very cute.
| jabl wrote:
| Heh, small world. I met Markus Deserno when I was visiting MPI-P
| for a few weeks some, uh oh, 15(?) years ago, working on coarse
| grained molecular dynamics for polymer physics. Nice chap.
| pmontra wrote:
| Unrolled for sanity of readers
| https://threadreaderapp.com/thread/1482811504424542211.html
|
| I don't know if I admire more the mastery of science of the
| author or the willpower necessary to write those posts on such a
| wrong medium for them. Worse than one twit per paragraph, only
| MMSes.
| stared wrote:
| In the topic of special relativity, I wholeheartedly recommend
| recently published "Unusually Special Relativity| by Andrzej
| Dragan (https://www.amazon.com/Unusually-Special-Relativity-
| Andrzej-...). It starts from basic high-school mathematics but
| covers many paradoxes and puzzles. Some might challenge ordinary
| students, who know the formula but didn't stretch their minds on
| "what if" questions. It includes cases where velocity is higher
| than the speed of light - as there are a few caveats on "nothing
| can travel faster than light".
|
| Also, this "velocity addition for v<<c" is covered in the first
| chapter.
|
| I read its draft almost 20 years ago (back then, it was a
| collection of notes in Polish) and didn't find anything remotely
| close to it in English. Later, I had the pleasure of attending
| his course.
|
| Also, Andrzej Dragan is a notorious individual, primarily known
| in photography (https://andrzejdragan.com/). To the point that
| there are posts on "how to Draganize a picture".
| walnutclosefarm wrote:
| Not a fan of doing this via twitter, but otherwise a beautiful
| exposition. Deserno is a gifted teacher.
| silvester23 wrote:
| I might have missed it, but is there (or do we know of) a
| different model for which the velocities actually add?
| Essentially, how do we go from slopes to angles here?
| lanternfish wrote:
| In classical Newtonian mechanics, velocities add normally a+b =
| c (an approximation which works near perfect for almost all
| velocities humans interact with). I think you might be asking a
| different question, though, but I'm not sure what.
| simiones wrote:
| Yes, he introduced it near the bottom - instead of using speeds
| (which are like slopes), you use "rapidities" which are the
| angles of the hyperbolic rotations.
| Jenny8090 wrote:
| renewiltord wrote:
| Haha, 'una pietra' is 'ein stein'. Very amusing. Love the format
| too.
|
| I felt things sort of click in my head. The angle in this world
| being the important thing is _dope_. Dude, this hecka cool!
| Thomashuet wrote:
| More readable formatting:
| https://threadreaderapp.com/thread/1482811504424542211.html
| bradstewart wrote:
| Am I crazy, in that I actually _like_ Twitter threads for this
| sort of thing--at least in the hands of a capable author? When
| threaded correctly (as this one is), its easy to follow. And
| the requirement to condense and split thoughts into tweet-sized
| chunks creates natural breaks to pause and consider the content
| before continuing. I find the cadence of "each thought is a
| tweet" provides a nice rhythm.
|
| Sure, you can do this with paragraphs in a blog post. But
| Twitter works equally well in my mind!
| actually_a_dog wrote:
| You may actually have something there. The average word
| length in English is approximately 5 letters, which gives you
| an average of about 56 words per tweet. That's roughly 5-6
| solid sentences, which is... one good paragraph. It probably
| didn't work as well before they raised the character limit
| from 140 to 280.
| axg11 wrote:
| I agree with you. I can understand why a theoretical
| physicist would find this format frustrating to read. For a
| layman, the forced tempo of threads helps me understand each
| point before I move on.
| snet0 wrote:
| I think this was one of the few good Twitter threads. Each
| Tweet was a kind of step from the previous, towards the next.
|
| The only thing I think would be improved by having this in
| blogpost form is more interact-able visuals, equations and
| similar.
| kirykl wrote:
| usually this is called paragraphs
| plucas wrote:
| Note that Thread Reader loses the images attached to some of
| the tweets (at least for me).
|
| Edit: strike that, it was Firefox's social tracker protection
| blocking them. Just need to click the shield icon left of the
| address bar and temporarily disable it.
| molbioguy wrote:
| That is so much better! Thank you.
| thesz wrote:
| I cannot help but add a reference to a conformal geometric
| algebra here:
| https://en.wikipedia.org/wiki/Conformal_geometric_algebra
|
| Why? Because it describes movement as rotation from the
| infinitely far away point (a special basis vector there). And
| "coordinates" there are somewhat self-normalizing, because there
| is a special basis vector that keeps coordinates' squares.
|
| And, of course, it is investigated as a tool to think about
| relativistic coordinates, linking my comment to a tweet part that
| says "wrong tools can obscure things".
| formerly_proven wrote:
| > Because it describes movement as rotation from the infinitely
| far away point
|
| Doesn't this also work in normal geometry as the length of a
| translation goes to zero and the distance to the rotation's
| origin goes to infinity... because a big circle looks like a
| straight line up close?
| thesz wrote:
| Exactly. CGA has special point e_{inf} which is infinitely
| far away from any other regular point (with regular euclidian
| coordinates) and linear movements are rotations around that
| point.
| MattPalmer1086 wrote:
| Lovely explanation. Builds up from simple angles and suddenly
| makes what seemed weird in relativity actually kind of obvious.
|
| I particularly like how the model you choose to describe things
| can make the same phenomenon easy or hard to understand.
| alfiedotwtf wrote:
| My favourite example of this is planet epicycles vs ellipses
| around the Sun :)
| doctoboggan wrote:
| I like this, but it doesn't completely remove the
| "unintuitivenes" of relativity.
|
| For example, why do we measure in fractions of light speed? What
| happens when we are already rotated all the way to light speed
| and then fire another bullet?
|
| I guess there are other ways to reason about this, but it still
| doesn't feel intuitive to me.
| d-d wrote:
| IMO theory of relativity is obviously false; perhaps a troll on
| humanity by Einstein.
| OscarCunningham wrote:
| Lightspeed has infinite rapidity, so when you add on the
| rapidity of a bullet you just get lightspeed again
| gowld wrote:
| https://en.wikipedia.org/wiki/Rapidity
|
| That's amazing, and it was well explained in 1908! Yet
| students today are learning a horrific bastardized version of
| it. Physics is absolutely terrible when courses and books try
| to to remove the "complicated" math, and in its place they
| put something more complicated and ambiguous.
|
| Teach the math!
|
| It's like Greenspun's Tenth Rule, but for math:
|
| "Any sufficiently complicated scientific theory contains an
| ad hoc, informally-specified, bug-ridden, slow implementation
| of half of Complex Analysis."
| codeflo wrote:
| It's important that the "angle" isn't directly the fraction of
| c, but tanh^-1(v/c). This number is also called "rapidity", and
| goes to infinity as v -> c. Yes, hyperbolic angles aren't
| limited to [0, 2 pi).
|
| You can't rotate all the way to lightspeed, that would be
| rotation by an infinite angle. For any finite angle (i.e. speed
| below c), you can always add the angle of the bullet to get a
| new (finite) angle.
| messe wrote:
| An interesting quirk of this, is that the description of the path
| of a particle under constant proper acceleration in special
| relativity is mathematically very close to that of a simple
| harmonic oscillator.
|
| Now, just as you can use rotation in the complex plane (i^2 = -1)
| to describe a simple harmonic oscillator in 2D space,
| x + iy = e^(it)
|
| It's possible to use a rotation in the split-complex plane[1]
| (j^2 = 1) to describe the motion of a particle undergoing
| constant proper acceleration, x + jt =
| e^(ajt)/a - 1 [2]
|
| This is because multiplying by e^(jt) preserves the split-complex
| modulus (|x+jt|^2 = (x + jt)(x - jt) = x^2 - t^2), which is
| equivalent to the Minkowski norm. Expanding the above gets you,
| x = cosh(at)/a - 1 t = sinh(at)/a
|
| which are the more traditional expressions you would typically
| see.
|
| [1]: https://en.wikipedia.org/wiki/Split-complex_number
|
| [2]: There's a line of reasoning that allows you to write this
| down almost immediately, or in maths-speak makes it trivial, but
| I can't remember it at the moment. I spent a good deal of time
| thinking about this for a university assignment years ago in
| order to avoid spending 2 minutes doing an integral.
| perryizgr8 wrote:
| This is just the most basic consequence of relativity. It's not a
| "delightful quirk". It's literally the first thing you learn when
| you study the theory.
| krupan wrote:
| Some people hate tweet threads like this, but I feel like it
| really forces concise communication and arranging thoughts into
| small but complete chunks. I've never put my thoughts into this
| format, but I would guess it's actually pretty difficult and
| requires some careful planning to do it well, especially for a
| challenging topic like this. Thanks for sharing this to hacker
| news, sohkamyung!
| gowld wrote:
| It's like Power Point presentation. Forcing everyone to read at
| the same pace, waiting for the point to show up, instead of
| skimming to the part they need to read.
| ngcc_hk wrote:
| Quite a good description of "Lorentz transformations". Still hard
| to understand intuitive, but sort of understand "logically".
|
| Btw the blog site is so much better.
| mikewarot wrote:
| The way I think of it is we're always moving at the speed of
| light, through the time axis. Any normal 3d motion is orthogonal
| to the time dimension, so the time component shrinks ever so
| slightly as you move faster.
|
| Photons move only in the 3 dimensions, thus never experience
| time.
| topaz0 wrote:
| Markus Deserno is a fantastic scientist in my field, and always
| gives the best talk at the conference.
| cletus wrote:
| This is too longwinded (and a Twitter thread ugh). I'll repeat an
| analogy I read somewhere else.
|
| Everything in the universe moves at constant speed through (four-
| dimensional) spacetime. To simplify the analogy we'll just
| consider two dimensions: space (x-axis) and time (y-axis) with
| your spacetime vector being of constant length. At rest your
| spacetime vector is (0,1). You speed up to 10% of light speed and
| your spacetime vector is approximately (0.1, 9.99) so you're
| moving slightly slower through time.
|
| What I like about this analogy is it constrains your space vector
| to the speed of light. Warp Bubble Andys like to pump negative
| values for energy and mass into equations to rationalize
| something they want to be true: that faster-than-light travel is
| possible. To me, this is just a fundamental lack of understanding
| about the domain of a function. Velocity is no different. I
| firmly believe it's bounded by [0,c). Values outside of that
| range just don't make sense are as such undefined. Garbage in,
| garbage out.
| captainmuon wrote:
| The description of relativistic movement by hyperbolic rotations
| is really neat. One way I like to think of it is that moving with
| respect to some other observer puts you into a different "world",
| where the x and t axes are rotated towards each other. You can
| see from the diagrams that for example different events happen in
| different orders in both "worlds". And this is not just due to
| signal propagation, but there really is no "true" ordering if the
| events are sufficiently separated.
|
| Bit there is one thing I never understood, even though I have a
| PhD in physics. _Why_ does relative movement put you into a
| different "world"? Or more precise, why does relative movement
| correspond to a lorentz boost? That is not a piori neccessary. A
| stupid example is a laser pointed to the moon. If you flick it
| quickly, the spot can move faster than light over the ground. But
| you can also imagine mass moving independent of boost. You have a
| rock at x=0, t=0. At t=1, cut it and paste it at x=1. At t=2, cut
| it and paste it at x=2. Now make the time steps infintely small.
| It is moving (in the sense of dx/dy>0) but not moving (in the
| sense of v or ss = 0).
|
| My intuition is, if you look at electromagnetism, it takes some
| time for a changing electric field to create a magnetic field,
| and for the magnetic field to create an electric field. This is
| what Einstein meant when he said, time exists so that not
| everything happens at once. If you think of a relatively moving
| object - and I'm thinking of it completely in terms of EM for the
| sake of simplicity - what happens is that the fields are
| _propagating_. One field creates the next field not at the same
| space but slightly in front. So the whole thing is rotated
| towards the x axis. The "time" vector does not point completely
| in the time direction, but in the space direction. This gives you
| time dilation as well as the subjective experience of an
| intertial frame (because you are just moving forwards in time,
| but not in space from your POV). I think this microscopic
| perspective shows why motion must == boost. But does anybody here
| know if there is a canonical answer to this question?
|
| Edit: I just realize this is basically electromagnetism of moving
| bodies which Einstein already solved in 1905 :-) but I still find
| it hard to wrap my head around
| lordnacho wrote:
| Summary: For small angles, approximation makes it look like
| gradients (y/x) add simply (a+b). Similarly low velocity in
| relativity world makes it look like velocities just add as well.
| With some insight we discover how it really works, including how
| the approximation makes it look correct for small values.
| ramraj07 wrote:
| But who was actually genuine surprised or flabbergasted that
| there was an extra factor that in macro real life becomes zero
| but is there in extreme speeds? The un-intuitiveness is
| typically more to do with understanding what that factor means
| and where it came from.
| snet0 wrote:
| The insight is, in my opinion, more related to the attaching
| of the idea of "rotation" to space-time, and using that to
| explain why we can't just add velocities at high "rotations".
| everyone wrote:
| Twitter is such a piece of shit
| irthomasthomas wrote:
| This would be more fun in a blog post. Twitter is a fucking
| horrible format for a complex analysis of special relativity.
|
| That aside, my favourite quirk from relativity is this:
| "The more you move in space, the less you move in time."
|
| Like relativity in general, it sounds simple enough, but it's
| consequences are profoundly shocking. (That is, if you take the
| time to understand it, and don't leap to the conclusion that you
| know relativity better than Einstein or Penrose ;)
|
| Take the case of two people on Earth, one stationary and one
| travelling past in a car. They each have a different reference
| frame, and a different set events which make up their present.
| Now imagine that there is an alien government in Andromeda
| debating a possible invasion of Earth. In the reference frame of
| the person on Earth who is moving, the debate is still going on.
| But, in the reference frame of the stationary person, it is a day
| or so later in Andromeda, and the invasion fleet is already on
| it's way! In nature there is no absolute reference frame we can
| call base reality, and both observers reference frames are
| equally valid. Then the outcome of the invasion debate is a
| foregone conclusion. How can there be any room for free will in
| the deliberations of the alien government? This is the crux of
| the Andromeda Paradox and the Reitdijk-Putnam-Penrose argument.
|
| BTW: "Notice that neither observer can actually
| "see" what is happening in Andromeda, because light from
| Andromeda (and the hypothetical alien fleet) will take 2.5
| million years to reach Earth. The argument is not about what can
| be "seen"; it is purely about what events different observers
| consider to occur in the present moment."
|
| https://en.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam_argume...
|
| More info
| https://en.m.wikipedia.org/wiki/Relativity_of_simultaneity
|
| Edit: If you know of any serious alternatives to the 4D
| spacetime/ block universe theory then I would love to read it.
| Rescuing free-will from the jaws of spacetime would be cool!
| jahnu wrote:
| > "The more you move in space, the less you move in time."
|
| Isn't that missing a bit at the end? The less you appear to
| move in time from a different frame of reference?
|
| We all move through time at exactly 1 second per second, don't
| we?
|
| For reference: Here's Sean Carrol saying exactly that (but in
| reply to a different question)
|
| https://www.preposterousuniverse.com/podcast/2021/12/15/ama-...
|
| "...it always goes by one second per second. That's the only
| speed at which time can possibly go by, and that's true whether
| you're speeding or staying still or in a gravitational field or
| not. There's no such thing as the speed with which we move
| through space-time, the idea of a speed is the amount of
| distance we travel as a function of time, that's what speed is.
| So it just doesn't apply to going through space-time, it's a
| different kind of thing."
| ctw wrote:
| Disclaimer: I'm interested in relativity and have been
| reading about it lately but I'm no authority.
|
| > We all move through time at one second per second, don't
| we?
|
| You need to define "move through time". The only way to
| measure time is with a clock, and the clock's motion relative
| to you affects the measurement.
|
| If you let everyone define "time" as the thing measured by
| the watch on their wrist, then everyone moves through time at
| one second per second, but since people are in motion
| relative to each other and therefore have different frames of
| reference, their clocks will measure different times.
|
| Since no frame of reference is privileged, there is no
| "absolute time". Of course you could pick one and measure
| every event against that one, but that would be an arbitrary
| choice.
|
| This is my understanding. If I'm wrong, I'd be happy to be
| corrected.
| jahnu wrote:
| That's my understanding too but I am also saying that "less
| you move in time" needs to be more rigorously defined. As
| it stands above I'm not sure it makes sense, even though it
| might be a useful fiction to get a handle on the weirdness
| of it all.
|
| I'm also no authority whatsoever on the topic :)
| aaron695 wrote:
| platz wrote:
| I think Sean Carroll understands Special and General
| Relativity.
| awb wrote:
| > Take the case of two people on Earth, one stationary and one
| travelling past in a car. They each have a different reference
| frame, and a different set events which make up their present.
| Now imagine that there is an alien government in Andromeda
| debating a possible invasion of Earth. In the reference frame
| of the person on Earth who is moving, the debate is still going
| on. But, in the reference frame of the stationary person, it is
| a day or so later in Andromeda, and the invasion fleet is
| already on it's way!
|
| I'm pretty sure this is wrong (or misleading) on multiple
| levels:
|
| 1) An event in Andromeda occurs at single moment, it's our
| observation of the event that is warped. So there aren't two
| realities, one where they're still debating and one where they
| aren't. In both realities the debate has concluded, it's just
| our observation of the event takes place at different reference
| times.
|
| 2) The car would need to be moving at a non-insignificant
| fraction of the speed of light to have an observation dilution
| of a day or more. It's physically impossible for humans to move
| that fast with our current technology.
|
| https://www.quora.com/Does-time-slow-down-in-a-moving-
| vehicl...!
|
| You'd have to be traveling at 0.86c for an entire day to be
| observing 1 day slower than a stationary person.
| irthomasthomas wrote:
| I once read a physicist on this in a newspaper who said "if I
| didn't believe in free-will, then I wouldn't bother getting
| up in the morning." I thought that was cute.
|
| I think the term free-will has clouded the issue a bit.
| Forget about free-will. Scientists avoid the issue by talking
| about Determinism vs indeterminism, or nondeterminism in CS.
| These have a more precise definition than that other thing.
| The universe is deterministic if the outcome of events are
| completely determined by previous events. Or the universe is
| nondeterministic if the outcome of events are not certain,
| but follow a random distribution.
|
| As to the precise details of the speeds and distances etc, it
| is a thought experiment, swap the car for a rocket traveling
| past at 0.86c, if you like. Or instead of aliens deliberating
| all day, maybe they are more efficient than we are, and they
| make their decision instantly by flipping a digital coin
| powered by the perfectly nondeterministic quantum
| fluctuations of the vacuum.[0]
|
| For earth rocket man, there is a moment before the quantum
| dice roll when the decision is indeterminable, it's
| completely random. But at the same moment in the stationary
| frame, the fleet is already on it's way. Unless you wish to
| argue that a stationary reference frame is somehow more valid
| than a moving one, you have to accept that in the moving
| frame, the event of the dice roll has still not occurred and
| should be random, but how can it be random it has already
| happened in the equally valid stationary frame. Hence the
| paradox.
|
| I hope that cleared things up some? [0] The
| vacuum has an api: https://qrng.anu.edu.au/
| Diggsey wrote:
| Actually no, the parent comment is correct:
|
| When you undergo an acceleration, it corresponds to a
| hyperbolic rotation of the spacetime around you (from your
| frame of reference). When the acceleration is small, the
| rotation is also very, very small; however at very large
| distances, even a small rotation can have a large effect.
|
| In the example, that "large effect" is the alien debate
| moving in time forward or backwards a day (again, from the
| accelerated reference frame).
|
| This has nothing to do with the observation delay, it's just
| an artefact of what it means for two far apart events to
| happen "simultaneously": simultaneity is a relative property,
| so two things that happen simultaneously in one reference
| frame might not happen simultaneously in another.
|
| The reason this doesn't introduce a paradox is because
| without a specific reference frame, events only have a
| partial order: when you compare two events, there are three
| possible results:
|
| 1) Event A is in the past light-cone of event B.
|
| 2) Event B is in the past light-cone of event A.
|
| 3) Neither event is in the past light-cone of the other.
|
| For 1+2 this means that the _time_ between the events is
| greater than the _distance_ between the events, whereas for 3
| it means the reverse. For 1+2, the ordering of the events is
| the same for any reference frame. For 3, there will always be
| some frame of reference where both events appear to happen at
| exactly the same time, so nothing can be said about their
| order without choosing a reference frame.
| awb wrote:
| I don't think the interpretation you describe is widely
| held. Check out the criticisms of the paradox:
|
| https://en.m.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam_arg
| u...
| Jeff_Brown wrote:
| The reason the scenario posits an invasion from so far away
| is that that's about how much distance it takes for a small
| speed difference here to translate into a day long time
| difference there.
| feoren wrote:
| So as I'm driving, the debate is going on, but as soon as I
| slam on my brakes, it's already happened! They're already
| on their way! Oh but now the squirrel is out of the road
| and I'm late so I speed way back up and the debate hasn't
| even started yet now.
|
| No. The only thing that is "happening right now" on
| Andromeda from my point of view is the causality wave
| (light) that is hitting me right now. It's nonsense to talk
| about anything happening "right now" if its causality wave
| hasn't reached me yet.
| awb wrote:
| You could imagine an event happening a day later from a
| traveling car, but that's about it. Two people can't
| actually observe an event a day later from the same
| reference point (Earth), and naturally the event occurs at
| a singular time at Andromeda's reference point. Same with
| any point between Earth and Andromeda. So, if you can't
| observe it at different times from the same reference point
| did it actually happen at different times?
|
| From the Wikipedia page on the thought experiment, check
| out Criticisms:
|
| https://en.m.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam_arg
| u...
|
| > The interpretations of relativity used in the Rietdijk-
| Putnam argument and the Andromeda paradox are not
| universally accepted.
|
| > Howard Stein[5] and Steven F. Savitt[6] note that in
| relativity the present is a local concept that cannot be
| extended to global hyperplanes.
|
| > Furthermore, N. David Mermin[7] states: That no inherent
| meaning can be assigned to the simultaneity of distant
| events is the single most important lesson to be learned
| from relativity. -- David Mermin, It's About Time
| goblin89 wrote:
| A philosophical idea may not have meaningful implications
| within the scope of physics, but that doesn't make it
| useless.
|
| Rietdijk-Putnam argument, for example, appears to sort of
| elevate the idea of differing planes of simultaneity,
| taken from special relativity, to an idea of a four-
| dimensional universe. It's a curious thought experiment
| and I wonder how it reconciles with a model where the
| universe is considered to be 4D with the fourth dimension
| being time. My intuition doesn't work all that well
| beyond three dimension so I can't tell if those are
| essentially the same or not.
|
| It's not falsifiable, but neither is string theory.
| Retric wrote:
| That's not how it works.
|
| But even beyond that you have the math wrong. Andromeda
| galaxy is only 2.5 million light-years from Earth. To get a
| 1 day difference in time dilation across 2.5 million years
| would take 1 in 913 million difference which someone
| traveling at even 100MPH (45m/s) isn't going to see. (1 -
| (45^2/((3x10^8)^2))^0.5 simply isn't enough.
| penteract wrote:
| I did the calculations from https://en.wikipedia.org/wiki
| /Special_relativity#Lorentz_tra... and it comes to ~0.25
| years if the person in the car is moving towards
| Andromeda at 30m/s. g is indeed very close to 1, so the
| humans' watches would still agree closely after 2.5
| million years, but the humans would be a quarter of a
| light year apart at that point, so they need to disagree
| about something to get the same observed speed of light
| from Andromeda.
| [deleted]
| bena wrote:
| > I'm pretty sure this is wrong (or misleading) on multiple
| levels:
|
| > 1) An event in Andromeda occurs at single moment, it's our
| observation of the event that is warped. So there aren't two
| realities, one where they're still debating and one where
| they aren't. In both realities the debate has concluded, it's
| just our observation of the event takes place at different
| reference times.
|
| Yeah, they're making the mistake of assuming a minute is a
| minute.
|
| It's closer to the difference in angular motion vs linear
| motion. If you are closer to the center, you move very little
| linearly. If you are closer to the outer edge, you move very
| little angularly.
|
| Now you look at the linear distance as time passed for the
| object and the angular distance as the amount of "space-time"
| an object has gone. The amount of "space-time" is constant.
| It's a bit of a wonky model, but it's probably the simplest
| one that encapsulates the concept.
|
| So just because they spent 3 days debating, you spent 5 days
| watching, and Bob only spent 1 day watching; that doesn't
| mean Bob is 2 days ahead of Andromeda and 4 days ahead of
| you. Since we are all also traveling through space at
| different speeds, we've all traveled the same amount of
| space-time, so we're all seeing the same things.
|
| As for our perception, that more depends on our relative
| positions from each other rather than speed. Because nothing
| is faster than light, we can never experience an event before
| we see it.
| Ma8ee wrote:
| Isn't the whole point that talking about "the present moment"
| about something very far away isn't particularly meaningful
| when simultaneity for spatially separated events depends on the
| observer?
| awb wrote:
| Correct, check the criticisms on the Wikipedia page:
|
| https://en.m.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam_argu.
| ..
| lofatdairy wrote:
| I was thinking the same thing about this working better as a
| blog post. It's so frustrating for each sentence to be it's own
| line and to be interrupted every moment. The content itself is
| excellent, but I really wish there was a better platform for it
| than Twitter.
| philipov wrote:
| There is no room for free will in physics, _period_. All
| processes are completely deterministic. Even quantum processes
| might appear to be probabilistic if you look at individual
| particles, but the statistics are nevertheless completely
| deterministic: if you look at enough particles, a predictable
| shape will emerge. The future is set in stone and not only is
| there no way to change it, but the concept of changing the
| future doesn 't even _make sense_.
|
| Free will is not something that exists in nature, it is
| something that exists in the psychology of agents with limited
| information about the world they operate in. Attempting to find
| a physical basis for free will is like trying to use an optical
| drive to read data off a pancake.
| rthomas6 wrote:
| Two objections:
|
| 1. Chaos theory ensures that unless we have INFINITE
| precision measurements, even a perfect simulation of our
| universe will diverge based on even the smallest differences.
| A difference of one particle's velocity in the googolth
| decimal place will eventually cause wildly different
| simulation outcomes. So, in practice, it's impossible to know
| what's going to happen given a long enough time frame, unless
| we can get advanced enough to have literally infinite
| precision measurements.
|
| 2. Given objection 1, using the law of large numbers to
| explain away quantum processes' non-determinism from initial
| conditions seems like a cop-out to me. Yes, given enough
| particles, they converge around some predictable value. But
| given the need to have exactness in measurements to predict
| chaotic processes, if a SMALL number of individual particles
| interact with other matter, and they sometimes do, how could
| the probabilistic nature of those individual particles be
| neglected?
|
| Let me sum it up this way. If I take a quantum random number
| generator and use it to generate lat-long coordinates, and
| visit that place, could anyone or anything predict what
| happens given initial conditions before I do that? No, it is
| not bound by initial conditions.
| arbitrage wrote:
| > quantum processes [...] are nevertheless completely
| deterministic
|
| It's like you're trying to avoid mentioning hidden variables
| or bell's theorem directly. That is, you're probably not
| correct when you say something like that.
| whatshisface wrote:
| There is no room for free will in classical mechanics.
| Quantum mechanics has plenty of "room for free will," because
| either:
|
| 1. The universe is not deterministic (if you believe that
| wavefunctions collapse)
|
| 2. The mysterious thing that makes conscious entities
| experience high-amplitude events more often than low-
| amplitude events is not deterministic (if you believe in
| MWI).
|
| _Evidence_ for free will, a _definition_ of free will; those
| things physics cannot provide. But there 's _room_ for it.
| kelseyfrog wrote:
| There are more than just those two interpretations. Super
| determinism, for example
| https://en.m.wikipedia.org/wiki/Superdeterminism
| feoren wrote:
| Quite the opposite: physics is _predicated_ on the idea of
| free will in the experimenter. That is: their decision to use
| X machine to perform Y experiment at Z time is essentially an
| independent, or at least fully random, "choice" on their
| part. If the experimenter does not have free will, then you
| run into the possibility of their decision to run the
| experiment as being somehow entangled with the results. See
| "Superdeterminism"
|
| https://en.wikipedia.org/wiki/Superdeterminism
|
| But otherwise I agree that "free will" is basically just a
| silly argument over the definition of an undefinable term, or
| a way to explain away loopholes in theology.
| time_to_smile wrote:
| You can even leave out the 'physics' part there.
|
| "Free will" is a very poorly defined concept that mostly
| falls out of problems with theodicy in early moral
| philosophy. Since the idea of "free will" plays a major role
| in Christian ethics this notion has permeated a huge amount
| of the Western intellectual tradition, but only makes sense
| in the framework of other archaic philosophical questions
| around theodicy like "if god is omnipotent, omniscient, and
| omnibenevolent why is there evil?" This question is only
| remotely interesting if you have a cultural reason to need to
| believe that these three things must be true (or if you're
| curious about the development of the Western intellectual
| tradition, in which case it's a very important question to
| understand).
| whatshisface wrote:
| Free will might be hard to define but it has plenty of very
| well-defined corollaries. For example, if there is such a
| thing as free will, it would not be possible to reliably
| predict a human being's actions in advance.
| time_to_smile wrote:
| > not be possible to reliably predict a human being's
| actions in advance.
|
| That's also true for purely deterministic systems.
| Basically any complex deterministic system (and quite a
| few relatively simple ones) you very quickly get to a
| point where you can't predict future behavior.
|
| On top of that, showing exactly the issues with
| metaphysical "free will", this corollary has a lot of
| constraints that are also poorly defined. For example if
| a person's behavior were entirely unpredictable (i.e.
| completely random) we would also say that they don't have
| free will. Therefore there is only a subset of
| unpredictable behaviors we would say follow from free
| will but that subset is just as tricky to pin down as the
| notion of free will itself.
|
| "Free will" only makes sense in a particular moral world
| view with plenty of axioms most people would agree don't
| hold for them.
|
| It's also worth clarifying that "free will" only becomes
| problematic to define in when it is posed as a
| metaphysical issue. We clearly have very useful,
| practical definitions of free will such as not holding
| people accountable for doing something when held at gun
| point.
| whatshisface wrote:
| The difference between quickly getting to a point where
| you can't forecast the weather, and the fact that you
| can't predict wavefunction collapse at all, is
| significant on a more than metaphysical level. Figuring
| out which bucket human beings fall in to is a legitimate
| question.
| time_to_smile wrote:
| > the weather
|
| > wavefunction
|
| Which of these are commonly accepted (or even argued by a
| sizable minority) to have free will in a metaphysical
| sense?
|
| > Figuring out which bucket human beings fall in to is a
| legitimate question.
|
| That may be true, but it doesn't seem like it has
| anything to do with the ill-defined notion of "free
| will". I'm also not familiar with anyone who views human
| behavior to be anything like a collapsing wave form so
| I'm not entirely sure this is a "legitimate" question
| since I'm not sure there is any evidence or support for
| the one side of the argument (though I'm always up for
| pointers to arguments about this).
| gfody wrote:
| > Which of these are commonly accepted (or even argued by
| a sizable minority) to have free will in a metaphysical
| sense?
|
| both, see the free will theorem from Conway and Kochen
| whatshisface wrote:
| > _Which of these are commonly accepted (or even argued
| by a sizable minority) to have free will in a
| metaphysical sense?_
|
| Of the two that would be the wave functions, some of
| which are people, and people are what's argued to have
| free will.
|
| > _That may be true, but it doesn 't seem like it has
| anything to do with the ill-defined notion of "free
| will"._
|
| Nondeterminism in physics is the space that free will is
| allowed to fill, and if there was none, there would be no
| room for free will.
|
| > _I 'm also not familiar with anyone who views human
| behavior to be anything like a collapsing wave form_
|
| Human beings are physical systems, quite chaotic at that.
| It is possible that deep inside your brain, decisions
| turn on molecular events that are uncertain due to
| quantum mechanics. Evidence for free will? Not really,
| but it's a hole in determinism that makes false the
| statement, "physics leaves no room for free will."
| elcomet wrote:
| You can check https://unrollthread.com/t/1482811504424542211/
| to view it as a blog post
| destitude wrote:
| I was going to post this exact comment. I gave up following the
| twitter thread because it was so annoying.
| pxmpxm wrote:
| "This would be more fun in a blog post. Twitter is a fucking
| horrible format for a complex analysis of special relativity."
| My very first sentiment, having read the whole thing.
| ajuc wrote:
| At least when you think of objects moving slower than light
| there can't be reversing of casuality. But relativity allows
| for that, we just drop the faster than light solutions usually
| as non-physical.
|
| Recently there's been an interesting paper about what happens
| when we don't drop these solutions:
| https://arxiv.org/abs/1910.02780
|
| Imagine the Andromeda fleet can move faster than light. When
| you look at it from Earth POV suddenly it manifests near Earth
| out of nothing. Looks very similar to quantum mechanics
| indeterminism - if alien general decided to send the fleet it's
| there, if he didn't - it's not there, and there's no local
| cause for it appearing suddenly.
|
| What the paper above explores is - starting from relativity
| including faster-than-light objects and trying to prevent
| paradoxes they derive quantum mechanics.
| irthomasthomas wrote:
| If you think about this in the quantum-mechanical framework, it
| appears to contradict this free-will problem. In relativity,
| reality is a solid block, and future events are as immutable as
| past (no free-will). But in QM this statement would be
| expressing a level of certainty which violates the measurement
| problem and Heisenberg's Uncertainty principle. In Penrose's
| recent book he posits an interesting hypothesis on the Big Bang
| based on this. Roughly... stuff in the observable universe
| appears to be slowing down, getting colder, and further away
| from each other. Things start hot and energetic, and slowly
| lose energy, slow down and disperse. So, taking this model of
| the universe and winding it back, you get to the Big Bang, when
| the universe was infinitely hot and dense. Winding the model
| forward, you eventually reach a state when the universe is
| infinitely cold and empty. This is the heat death of the
| universe, a state of oblivion where there is absolutely no
| interaction, and no stuff.
|
| This violates Heisenberg, but QM is the map, not the territory,
| right? So maybe, in practice, reality has a way of beating
| Heisenberg? Thanks to technology, we have been able to probe
| this question quite recently. Scientist tried to create a near-
| perfect vacuum, with all the energy and stuff removed, and
| isolated from the rest of the universe. Inside the vacuum they
| created an electrical circuit fed to a computer. The circuit
| was broken by two floating polished plates, separated by an
| incredibly small gap, roughly the size of a short wavelength of
| light. So in this test chamber photons of all sizes could exist
| around the two plates, but between the plates only the smallest
| photons could fit. If any large photons enter the chamber they
| would create positive pressure around the plates, pushing them
| together, closing the circuit and registering a result. As the
| scientists pushed the vacuum closer and closer to a perfect
| vacuum, would Heisenberg get in the way? Maybe the experiment
| is not powerful enough to push the vacuum close enough to
| really challenge him?
|
| The experiment was a success. As the vacuum increased,
| eventually large photons showed up outside of the plates and
| pushed them together. Photons where appearing out of thin air
| to ensure that no perfect vacuum could be attained. We call
| these Virtual Particles. They usually annihilate themselves
| before becoming "real" and observable, but if local conditions
| are just right, like near a black-hole, some virtual particles
| are lucky enough to get pulled and stretched, and this process
| lends them enough energy to materialize. The virtual particles
| are of course random, and this apparatus is actually used now
| to generate proper random values. You can actually tap in to
| the vacuum energy with an API to get your source of entropy!
| https://en.wikipedia.org/wiki/Casimir_effect
| Vacuum energy quantum RNG: https://qrng.anu.edu.au/
|
| Back to Penrose... when the universe approaches this infinitely
| cold empty state, it turns out to be the same, mathematically,
| as the hot dense state. With everything being so distant and
| disconnected, the universe sort of forgets that it is big and
| empty. Then all it takes is the enough quantum fluctuations and
| virtual particles to appear in some small region of space, that
| they pull on each other and become real. This might, according
| to Penrose, trigger another Big Bang.
|
| What does this have to do with relativity and free will? If it
| is true that nature, at the smallest level, is fundamentally
| random, then the block universe containing a predetermined
| future cannot be real. So free will is safe? Not quite. If the
| Andromeda people are anything like us, their brains are subject
| to same laws. The electrical activity in the firing synapses,
| that we call thinking, must also be subject to the random
| fluctuations of quantum mechanics. How can they have free will,
| when the electrical impulses driving that will are
| fundamentally random and unpredictable?
|
| Weird, eh?
| tzs wrote:
| There was a PBS Space Time episode about a year ago that
| covered what I think is the same recent Penrose idea that you
| have mentioned [1].
|
| [1] https://www.youtube.com/watch?v=PC2JOQ7z5L0
| vidarh wrote:
| To me the main reason quantum effects does not affect the
| free will argument is because one can - and probably should
| given that otherwise it makes QM keep coming up -, reframe it
| to not worry about absolute determinism and instead apply
| just probabilistic models.
|
| The real question becomes one of probabilities: Unless some
| entity is able to introduce measurable _biases_ that deviates
| from predictable probabilistic distributions relative to what
| could be predicted based on its complete state (including its
| internal physical structure) and complete inputs, it makes
| little sense to suggest the entity has agency.
|
| But that leaves us with the problem of explaining how
| something could effectively break the laws of physics in a
| way that doesn't just lead to infinite regress.
|
| The day I see someone give a definition of free will that
| overcomes that, I'll be in awe. Not holding my breath.
| parineum wrote:
| > Unless some entity is able to introduce measurable biases
| that deviates from predictable probabilistic distribution
|
| This is always the problem with arguments for free will or
| at least the idea that one "could have done something
| different" that try to use physics/science.
|
| It requires metaphysical action, literally something that
| cannot be understood with physics. The whole purpose of
| physics is to define the universe as deterministic. Quantum
| randomness is exactly that, random. If it was influenceable
| in some way, it wouldn't be random. Furthermore, the
| decision to influence it would still be deterministic so
| the metaphysics doesn't even make sense.
|
| Quantum magic is just the bleeding edge of woo.
| stared wrote:
| A real paradox is if you can reach two mutually-exclusive
| conclusions. In the special relativity theory, the order of
| events depends on the frame of reference. It is not much unlike
| 2D space if something is left or right to each other depending
| on a rotation.
|
| "I don't like how does the special relativity/quantum physics
| works" is not a paradox on its own. In this case, it just
| challenges our pedestrian view of time.
| vidarh wrote:
| It's a paradox in the same sense that Zeno's paradox is. As
| in "if we assume the world is how we intuit it to be without
| thinking it through and having the proper understanding, this
| problem _seems_ self-contradictory " rather than in the sense
| of something _actually_ self-contradictory.
| vidarh wrote:
| "Rescuing free-will" would depend on there being something to
| rescue in the first place. I've yet to see a definition of free
| will that a casual observer would agree is "free" once you
| strip it of the smoke and mirrors.
|
| To me the Andromeda Paradox isn't very interesting, because the
| question is only problematic if you consider time as a process
| that events happen within simultaneously in a way that you can
| precisely globally order by positing some way of counting
| objective units of time backwards from the point the two people
| on earth both see the invasion force.
|
| If you instead look at the passage of time as simply the
| propagation of cause and effect where the propagation rate may
| differ depending on features of the events being propagated,
| then you get a dependency graph where when you interact
| different cause-effect chains meet. Only the nodes (events
| happening) matters, not the edges (the unobservable-because-
| nothing-interacted other than propagation).
|
| The notion of something happening simultaneously then becomes
| abstract - you have no objective matter of measuring something
| being simultaneous except by whether or not they directly
| interact in a given moment. You're relying on your universe
| behaving in a way that means you can count events to try to
| maintain a chronology on the basis you know how they're spaced
| apart. But the best we can do is count the number of such
| events that happens in different frames under different
| conditions between causal chains merging.
|
| Once you ditch the idea of "global ordering time" the "paradox"
| is nothing of the sort.
|
| Because in that respect talking about "when" the event in
| Andromeda happened is meaningless, because it is a conversation
| based on projecting a model of the world as it appears from one
| local part of that cause-effect graph to another on the basis
| that there's an objective global ordering outside of what we
| can impose by counting chronology comparing clock time when we
| directly interact. It may make your mental model of what
| happened when messy, but that is because thinking of what
| happened when instead of what interacted with what in which
| order is messy.
|
| (if there's _any_ way of achieving faster than light travel, my
| totally-usupported-by-any-theory bet is that it would show our
| notion of time to be too static, and that it 'd "bypass" the
| cause-and-effect paradoxes by affecting the laws of physics at
| the points of FTL interactions)
| bmitc wrote:
| Maybe subtle, but shouldn't this be:
|
| > "The more you [are observed to] move in space, the less you
| [are observed to] move in time."
| naasking wrote:
| > "The more you move in space, the less you move in time."
|
| Even better IMO: everything is moving at the max speed (c)
| through spacetime, and accelerating along one dimension means
| decelerating along other dimensions; for example, stationary
| objects have 0 speed in spatial dimensions but move at c
| through time, and photons move at c through space but are
| stationary along the time dimension.
| jules wrote:
| I think this conveys the right intuition but it's a bit
| finicky and artificial to make that concept precise so I
| think it's better to say that the concept of moving through
| spacetime at a given speed is not well-defined.
|
| Particles have a trajectory through spacetime. They don't
| move _along_ the trajectory because the time dimension is
| already part of the trajectory. So the speed at which they
| move along their spacetime trajectory seems to be a
| meaningless concept.
|
| What is true however is that if the particle takes a clock
| with it, and you mark a tick every second the clock ticks,
| then the ticks will be equally spaced along the trajectory
| (where distance is measured using the Minkowski metric).
|
| This makes a bit more precise what it means for photons to be
| stationary along the time dimension. It does not mean that
| they move horizontally in a space-time diagram. They move
| diagonally at speed c, as you expect, so for an outside
| observer they do move through time. However, the Minkowski
| distance between any two points on photon trajectories is
| zero. So if you wanted to annotate their trajectory with the
| clock tickmarks you could start somewhere and put your first
| tick there, but then your second tickmark would be infinitely
| far away on their trajectory.
|
| Thus, for an outside observer, a clock approaching the
| trajectory of a photon would appear not to tick.
|
| From a different point of view, we can reason by analogy to
| Euclidean geometry. When we have a curve through space we can
| talk about the tangent vector at any point. But the length of
| the tangent vector is not a well-defined concept. Only its
| direction is. You _can_ define the length of the tangent
| vector for a particular parameterisation p(t) but for the
| curve itself, i.e. the set {p(t) : t in R}, the length of the
| tangent vector is not defined.
|
| It is similar for a curve through spacetime. We can
| parameterise a curve with some variable x and write the curve
| as {p(x) : x in R} but this is just a set and the length of
| the tangent vector of p(x) depends on which parameterisation
| you chose for the curve. But the data of how a particle moves
| through spacetime is only the curve {p(x) : x in R} itself,
| not the function p(x): different parameterisations describe
| the same physical situation as long as the set {p(x) : x in
| R} is the same.
| cropcirclbureau wrote:
| Yeah, the video [0] by Fermilab that taught me this
| explanation blew my mind.
|
| [0]
| https://www.youtube.com/watch?v=A2JCoIGyGxc&list=LL&index=94
| thedstrat wrote:
| Both observers are just seeing what already happened millions
| of miles away. Though they see the alien fleet arriving at
| different times, it's not possible that the aliens are doing
| different things in different reference frames. They made one
| decision and then the two people see the results of that
| decision at different times
| cormacrelf wrote:
| > Twitter is a fucking horrible format for a complex analysis
| of special relativity.
|
| Keep in mind that regular people can and have simply replied to
| the theoretical physicist who posted it and received replies
| helping them understand better. In this sense it's a fantastic
| medium. The same magic that keeps reliably producing
| spectacular "ah, actually I have a phd in the thing you're
| arguing with me about" moments is at play here lowering the
| barrier to talk to really smart people.
| simsla wrote:
| I've found that people also respond to thoughtful comments on
| blogs.
| 3pt14159 wrote:
| Well, another way of looking at it is that the observer is not
| the same as the decider.
|
| So ultimately your reference frame is only current within the
| locus of your own mind and any decisions you make get
| broadcasted out to observers in the universe. They make their
| own decisions about where to be, how fast to be, and so on, and
| from their perspective it could be yesterday from when the
| decider decided, but its irrelevant just as much as being
| farther away in 3d space gives a longer delay in ping time.
|
| Whether or not the decider has free will or not I don't think
| can be argued by this specific example.
| mannykannot wrote:
| FWIW, I feel this is the right way to look at it. Furthermore
| (or perhaps I should say equivalently) the "observers" on
| Earth have not observed the decision, and thinking of them as
| such seems to be a Galilean fallacy.
| darkerside wrote:
| Wouldn't all that matters here be their relative velocities to
| Andromeda, and not to each other? And relative to Andromeda,
| the person in the car might actually be going slower.
|
| Separately, I don't think chronology is broken. It's ok that
| there is predestination because there is no way for actions
| taken here to propagate back there in time to change things. If
| a change does somehow propagate back through a wormhole or
| something, it's all good, just spinning up another dimension
| probably...
| yoaviram wrote:
| Two alternatives for 4D spacetime: - Julian Barbour argues for
| timeless physics in his book...Timeless Physics. No spacetime
| but you don't get back free will. - David Deutsch will get you
| free will back, if you are willing to go along with the many-
| worlds interpretation.
|
| https://en.wikipedia.org/wiki/Julian_Barbour
| https://en.wikipedia.org/wiki/David_Deutsch
| logifail wrote:
| > Twitter is a fucking horrible format for [..]
|
| ... any intelligent thought which takes more than a couple of
| sentences to type out?
| michaelcampbell wrote:
| > Twitter is a fucking horrible format for...
|
| Anything requiring more than about 350 chars, IMO. I'm really
| interested in that thread, but gave up after 5-6 tweets. My
| loss, I guess.
| danbruc wrote:
| _Rescuing free-will from the jaws of spacetime would be cool!_
|
| Free will does not exist. It is logically inconsistent. Either
| your choice is some function of your current state and the
| environment you are in, then the choice is not free, or it is
| independent of your current state and the environment you are
| in, then it is not your choice in any meaningful way, it is
| just the result of a coin flip.
|
| You can do some mental gymnastics, define free will as being
| able to do what you want, define it as being free of various
| kinds of constraints, call it free if the choice is not
| computable in advance, if you can not measure all necessary
| variables, in practice or in theory, ... If you are happy with
| any of those definitions, fine, then you might have this kind
| of free will, but I would not consider any of those
| particularly interesting.
| snowwrestler wrote:
| You can dismiss them as "mental gymnastics" but defining the
| term is the heart of the discussion. Philosophers argued
| about gravity and heat a lot too before we settled on
| rigorous physical definitions that could be expressed
| mathematically.
|
| At a first approximation there are obviously limits to our
| "free" will as no one has yet been able to will themselves to
| float through the air without support, go without food or
| water indefinitely, pop a pet dragon into existence, survive
| the physical destruction of their brain, etc.
|
| So it's hard to start from a position that anyone ever
| seriously thought "free will" meant no limits or
| dependencies.
| danbruc wrote:
| Mental gymnastics was probably not the best choice for the
| wording. What I really meant is defining free will as
| something that is in a certain sense trivial. If you want
| to call making choices according to your personal
| preferences free will, fine, but this is a triviality and
| we don't need to debate over this for centuries. And the
| next guy looks into the predictability of decisions and
| assigns free will to an entity if its future behavior can
| not be determined with certain resource constraints. Fine
| except that the term is now overloaded, you might have the
| first but not the second kind of free will and both
| properties are not well described by the term free will.
| antattack wrote:
| If your definition of free will existed, how would you prove
| it?
| awb wrote:
| Exactly. Free will (or lack thereof) is an untestable
| theory, better categorized as a thought experiment or
| philosophical debate.
| dalmo3 wrote:
| That's how I see it too.
|
| Determinism for human action is very popular among
| science enthusiasts because we've decided that
| determinism _elsewhere_ in science is true, and since our
| brains is part of the universe then it must also be
| deterministic.
|
| But we only perceive determinism insofar as we only
| measure what we're able to measure. Then you arrive at
| quantum probabilities, and it seems to me the multiverse
| theory is as scientific as believing quantum particles
| have free will.
| vidarh wrote:
| Free will _isn 't_ a theory before someone comes up with
| an actual definition. That is the problem. I keep asking
| people for a definition, and the outcomes are generally
| either "smoke and mirrors" (complexity hiding something
| not at all "free"), appeal to a "soul" which just leads
| to infinite regress, or failure to even try.
|
| Without someone willing to actually define what they
| mean, the discussion is moot - it makes no sense to claim
| that an undefined concept exists.
| awb wrote:
| Wikipedia has a definition:
| https://en.m.wikipedia.org/wiki/Free_will
|
| > Free will is the capacity of agents to choose between
| different possible courses of action unimpeded.
| V-2 wrote:
| The typical source of confusion is conflating "free" with
| "unpredictable". But they're not the same thing at all.
| vidarh wrote:
| "Unpredictable" is imprecise to the point of being
| meaningless.
|
| If a black box is _fully deterministic_ to the point that
| you can construct a model that is entirely accurate, then
| there 's nothing "free" about it. What you're modelling has
| no agency. For the notion of "free will" to have any
| meaning at all, it doesn't need to be "unpredictable" in
| the sense that it keeps confounding someone trying to
| predict it all the time, but it does need to deviate from
| predictions _sometimes_ or you have just an automaton, and
| it needs to do so in a way that is fundamentally impossible
| to model, and it needs to do so without just injecting
| randomness.
|
| I've yet to see anyone present a definition of "free will"
| that doesn't reduce to smoke and mirrors, because that
| would mean coming up with some _fourth category_ in a venn
| diagram of determinism, randomness and the combination of
| the two where they intersect, that is non-deterministic in
| a way that can 't be explained by layering a deterministic
| model and randomness.
| kybernetikos wrote:
| > What you're modelling has no agency
|
| I see no reason to think that just because something is
| predictable it is not free. That seems like such a
| strange constraint to me that I can only assume that we
| have different understandings of what it means to be
| free.
|
| If I know someone well, I might predict that when offered
| a free choice between an ice cream and a brussels sprout
| they will choose the ice cream. The fact that I was able
| to predict that with an incredibly high degree of
| certainty didn't stop them from being free.
| vidarh wrote:
| Given the same starting state, either you get the same
| outcome every time, or there's randomness involved, that
| is the point.
|
| I challenge you to describe a selection process that is
| not fully deterministic but where the lack of determinism
| is caused by something other than randomness.
|
| That is what you need to be able to come up with to
| define free will in a way that isn't smoke and mirrors.
|
| There's no agency. Nothing but automatons.
| kybernetikos wrote:
| > There's no agency. Nothing but automatons.
|
| Only if you define 'agency' as requiring magic. If you
| think that there's no conflict (as I do) between being an
| automaton and having agency, then there's no problem
| here.
| vidarh wrote:
| Yes, if I argue that "free" means "not free" there's no
| problem there, I agree. Which is why I keep asking those
| who believe in free will here to actually define it.
| People almost never even try, because once you do it very
| quickly becomes clear that it's _incredibly hard_ to the
| point that you 'd have a theory named after you and get
| taught in university philosophy courses if you managed to
| come up with something that isn't obviously broken.
|
| The point being that if you start asking questions to
| determine what people think free will means, you'll find
| most will argue an automaton can not have free will. In
| which case to "rescue" free will you need to come up with
| a way in which entities with supposed free will are not
| automatons.
|
| So, sure, it is possible to posit an infinite set of
| theories of "free will" that are true. But I'd claim that
| nobody has so far managed to come up with one that is
| both true and that most people will agree fits the woolly
| concept of "free will" the way most people use it.
|
| The concept is almost religious in the sense that most
| proponents of it are unwilling to try to nail down
| specific definitions that might give rise to testable
| hypotheses, and those who do tend to come up with
| definitions that are so far from the common understanding
| as to be meaningless.
| kybernetikos wrote:
| I think free will is the feeling of being a choice making
| agent in the absence of unreasonable external
| constraints. This isn't original or unique with me, and
| I've held this view for quite a large number of years
| (e.g. this comment from 6 years ago:
| https://news.ycombinator.com/item?id=11740316). It fits
| pretty well with what people mean when they say 'free
| will' or 'free choice' in normal every day life (i.e. if
| you have a gun to your head, you don't have free will,
| but in lots of other cases you do).
|
| Your definition of it being entirely nonsensical is
| clearly even worse than this definition for being
| accepted the way most people use it, since your view
| implies that there is nothing people mean when then say
| 'free will', while the fact that almost everyone can tell
| the difference between someone robbing a bank of their
| own free will and someone robbing a bank because their
| loved one is being held hostage tells you that it really
| does have meaning.
| vidarh wrote:
| Try probing what people think having free will actually
| means, and you'll quickly see that people tend to react
| very strongly if you suggest that they don't have some
| vague undefined ability to take actions that are not
| defined merely by the state of their brains and inputs.
|
| To me what you describe does not at all match what I've
| observed people try to defend as free will whenever you
| peer beneath the vague veneer of external coercion.
|
| > Your definition of it being entirely nonsensical is
| clearly even worse than this definition for being
| accepted the way most people use it, since your view
| implies that there is nothing people mean when then say
| 'free will', when there clearly is something that is
| meant.
|
| That is not at all what I meant by calling it
| nonsensical. I am very sure that people _do_ mean
| "something" and my experience is that this "something"
| includes a very strongly held belief that peoples actions
| can't be predicted based purely on the state of their
| brains and inputs. Try to suggest to people that maybe
| they're effectively just machines, and you'll find a
| _lot_ of people balking at it, because it e.g. would
| imply no soul or anything to set us apart.
|
| What I meant by calling it nonsensical is that when you
| start probing into _why_ people hold beliefs like that,
| you 'll find it evaporate as you probe. You'll find
| people can't put up arguments for, but more critically
| few can even describe a version of free will that fits
| their beliefs.
|
| You've given a definition, and that's great, but it's a
| definition that defines away the problem under discussion
| - nobody who argues against free will would disagree with
| you that there exists a feeling of being a choice making
| agent. We disagree with those who claim that we _are_
| choice making agents other than in the same way that an
| automaton can be.
|
| So you are right in the sense that free will by the
| definition you have given exists. But that's not the kind
| of free will most people here who are denying free will
| are debating.
|
| If anything, the definition you have given tends to be an
| important _answer_ to those who believe in "hard free
| will" to disambiguate them for why you should keep making
| choices if you don't have free will: Because whether or
| not it is an illusion, we _do_ have that feeling, and
| whether or not we have control over the choices made, if
| we don 't make any choices we still suffer the
| consequences. So the only logical choice, illusory or
| not, is to still make choices as if you have free will
| whether or not you think we have "hard free will".
|
| That said, once one decides that "hard free will" doesn't
| exist, it tends to have a significant effect on personal
| beliefs. E.g. punishment (as opposed to rehabilitation,
| or incarceration for protection) becomes cruel if you
| accept that "hard free will" is an illusion - a person
| may believe they have free will, but if it's an illusion
| we're punishing people for things they didn't have an
| actual choice in. (Note that this does not really affect
| the issue of _coercion_ - a person threatened with a gun
| to take your example might still be due different
| treatement than one who did something bad without being
| threatened, because the latter is still more likely to be
| a risk to others; but there 's a difference between risk
| mitigation/protection/rehabilitation and vengeance - if
| it was a truly free choice based on "hard free will"
| vengeance might well be morally justified, while without
| "hard free will" vengeance is morally horrendous)
| dalmo3 wrote:
| > ability to take actions that are not defined merely by
| the state of their brains and inputs.
|
| How would one prove/falsify that one's actions are
| _merely_ a function of their brain state and inputs?
|
| Even assuming we have a perfect mapping of the brain and
| perfect measurement of all neural action, experiments
| still happen over time and the act of observing changes
| the observed, so you'd never have repeatability.
|
| It seems to me that determinism is as unscientific as the
| soul hypothesis.
| kybernetikos wrote:
| You've got some interesting points there, but I think
| that the reaction some people have to the idea that they
| might be deterministic is actually to do with dualism and
| not free will. People try to pull free will into the
| dualism debate because they are desperately looking for
| reasons to back up their feeling that they are
| essentially more than pure material. I don't think that
| these two topics really have much to do with each other,
| which I think can be seen by looking at what people
| really mean when they actually talk about free choice and
| free will in everyday life rather than in philosophical
| conversations where they're already trying to justify a
| position.
| vidarh wrote:
| I agree that is probably part of it. In terms of "hard
| free will" that debate is of course entirely orthogonal -
| a soul would just be another part of the combined system
| under consideration, but I can very well see people
| seeing the two as combined.
|
| > I don't think that these two topics really have much to
| do with each other, which I think can be seen by looking
| at what people really mean when they actually talk about
| free choice and free will in everyday life rather than in
| philosophical conversations where they're already trying
| to justify a position.
|
| I certainly agree that people often conflate these two
| separate subjects. This is also part of why I push so
| much on definitions, because so much of the time we speak
| past each other when discussing these subjects.
| danbruc wrote:
| I understand why you would call your offer a free choice,
| the are no constraints attached to the options that could
| obviously influence the decision, for example picking the
| ice cream also requires paying a million. Different
| people with different preferences would make different
| choices.
|
| But pick one specific person, why would you call their
| pick a free choice? There choice might not be influenced
| by your offer but it will be by their preferences. Let
| them choose, rewind the universe a minute or two, let
| them choose again. They will make the same choice over
| and over and over again.
|
| Maybe not if there is true randomness in the universe and
| this choice happens to be influenced by some random
| event.
| SuoDuanDao wrote:
| This argument has always sounded like a strange bit of
| gerrymandering of identity. I suppose for some definitions of
| the terms you used that 'your current state' could be
| different from the 'you' that is deciding, but I wouldn't
| call any of those distinctions intuitive.
| wruza wrote:
| I prefer to think that it's a soulspace dynamically mapped
| onto a physical space at stochastic points designated by a
| wave function density distribution. So that at any point in
| time we have zero, one or more random souls influencing our
| behavior. So it wasn't particularly me, your honor.
| hsn915 wrote:
| > Either your choice is some function of your current state
| and the environment you are in, then the choice is not free
|
| This is as free as you can get and I don't think anyone ever
| posited "free will" as something other than this.
| danbruc wrote:
| _This is as free as you can get and I don 't think anyone
| ever posited "free will" as something other than this._
|
| I would not call this free, it's a choice completely
| determined by you and the environment. Same situation, same
| resulting choice. Every single time. And people have
| certainly used free will to mean many different things.
| prmph wrote:
| Well free does not exist only if logic is bound by what the
| human mind can conceive. It may be possible for something not
| be random, and to have no antecedent at the same time.
|
| Also, the concept of free will is bound up with the concept
| of consciousness. What is the entity that may or may not have
| free will? Until we define and understand that, free will
| will be an ill-defined concept not amenable to proper
| analysis
| kybernetikos wrote:
| You've put the dilemma nicely - it can't be both 'free' and
| 'your will' by your definitions (well, without admitting
| supernatural beings that can affect and be affected by the
| natural world, but are not part of it).
|
| Personally I'm happy with other definitions, not because I
| feel I'm doing mental gymnastics, but because the version you
| give is clearly not what normal people mean by it when they
| refer to it. It might well be related to what philosophers
| argue about, but normal people who offer you a 'free choice'
| or who say that you did something 'of your own free will' do
| not mean anything like 'your choice was not a function of the
| state of the universe'.
|
| Despite being happy with those other definitions that you
| aren't, I'm equally skeptical of the idea that free will has
| to be rescued just because different points in time can be
| observed simultaneously. What does someone even _mean_ by
| free will if it can 't cope with that?
| vidarh wrote:
| > Personally I'm happy with other definitions, not because
| I feel I'm doing mental gymnastics, but because the version
| you give is clearly not what normal people mean by it when
| they refer to it. It might well be related to what
| philosophers argue about, but normal people who offer you a
| 'free choice' or who say that you did something 'of your
| own free will' do not mean anything like 'your choice was
| not a function of the state of the universe'.
|
| There's certainly a duality here where it's fine to talk
| about people having choices even if one strictly believe
| they don't, but my experience is that if anything people
| tend to often get exasperated or outright agitated if you
| try to question to what extent their decisions are free. A
| whole lot of human society is organised around the idea
| that we have agency and that we're the product of choices
| we've made of our own volition.
|
| E.g. if you genuinely believe the notion that we have free
| will is nonsense (and I do), then the logical extension is
| to be _very uncomfortable_ with the notion of e.g. prison
| used for vengeance or anything at all other than to the
| bare minimal extent required to protect others, because the
| logical conclusion of thinking people don 't have agency is
| that there was no way other than other external stimuli in
| their lives that they could have come out making other
| decisions.
|
| It's a very uncomfortable thing to view society through a
| lens of seeing free will as an illusion. But it's also very
| hard to unsee the lack of any kind of coherent theory of
| free will that could justify anything else.
|
| The reality is that if you actually talk to people about
| this, you'll quickly find that most people go through life
| with a _very strong_ belief that they have agency and that
| people around them have agency, but the moment you start to
| question what that belief is based on, the basis for it
| tends to start to crumble very, very quickly. As I 've said
| elsewhere, in decades of discussing this subject I've never
| seen someone come up with a definition of "free will" that
| still looks either "free" or like "will" under scrutiny.
| Usually you end up with people trying variations of
| arguments that just leads to infinite regress (e.g. arguing
| our soul gives us free will, at which point the question
| just shifts to a definition soul that would give it
| agency).
| JackFr wrote:
| > if you genuinely believe the notion that we have free
| will is nonsense (and I do)
|
| Then you need to genuinely accept that you're not right,
| you're not making a cogent argument, you're just a fly
| buzzing around a giant turd.
|
| Or rather you don't, cause you can't.
| naasking wrote:
| > E.g. if you genuinely believe the notion that we have
| free will is nonsense (and I do), then the logical
| extension is to be very uncomfortable with the notion of
| e.g. prison used for vengeance or anything at all other
| than to the bare minimal extent required to protect
| others, because the logical conclusion of thinking people
| don't have agency is that there was no way other than
| other external stimuli in their lives that they could
| have come out making other decisions.
|
| I think this lacks imagination for human cruelty. If they
| had no free choice but to steal my things, then I guess I
| don't have any free choice but to torture them in
| revenge. Hard determinism does not erase the possibility
| of punishment.
| kybernetikos wrote:
| > if you genuinely believe the notion that we have free
| will is nonsense (and I do), then the logical extension
| is to be very uncomfortable with the notion of e.g.
| prison used for vengeance or anything at all other than
| to the bare minimal extent required to protect others
|
| Not really. You can view it as a game theoretic
| situation. Will the use of prison likely produce a good
| outcome or a bad outcome? Whether or not the criminal was
| deterministically required to commit the crime, the
| structure of punishments will (perhaps deterministically)
| affect the incidents and severity of future crimes.
|
| Just because the creature in Black and White may have
| made decisions deterministically doesn't mean I won't
| punish it if it behaves in an inappropriate way. If
| anything, believing the agents are deterministic would
| make me even more keen to punish in situations where it
| will change behaviour usefully.
| martinpw wrote:
| You are just agreeing with the OP here. The point is that
| prison is useful for some things, eg protecting others,
| changing behavior etc. But if there is no free will, then
| it makes no sense to say prison is for vengeance.
|
| These discussions are always interestingly recursive,
| since if I do not believe in free will then my own view
| on free will is itself not a free choice. And yet I still
| feel strongly that my not believing in free will appears
| to be my free choice.
| vidarh wrote:
| This is what I mean by setting _vengeance_ up vs. "the
| bare mininal extent required to protect others".
|
| I agree that there are still people who needs to be
| locked up, including under possibly brutal sentencing
| terms. E.g. Anders Behring Breivik who carried out the
| 2011 terrorist attacks in Norway is up on a parole
| hearing today - if he gets out (it'd take a miracle) it
| doesn't matter if it's free will (in any sense of the
| term) or purely deterministic processes that leads him to
| act if he is still probabilistically likely to carry out
| another attack - it's still more important to keep the
| public safe from him than to worry about whether or not
| he had a genuine choice.
|
| To the extent there's a measurable effect of seeing the
| punishment of others, that too _might_ be a
| justification, though I find that dicier. But if that is
| done based on a cold calculation of how it affects
| offending rates that to me is still very different from
| vengeance.
|
| So to be clear I'm not arguing it removes the
| justifications for punishments, and I agree with your
| mention of seeing it as a game theoretic situation - even
| really harsh punishments might be the best choice in some
| circumstances. But it removes "they chose this
| themselves" or "they deserve it" as a justification (the
| feeling is still valid; acting on it becomes cruel), and
| that makes for a very different legal system. It also
| shifts a focus towards considering that if it's not about
| vengeance, then you should look at how to actually
| optimise the balance between the public good and treating
| the prisoners as humanely as you can without reducing the
| public benefit of the punishment too much.
|
| Norway is far from achieving that, but if you look at
| e.g. Bastoy fengsel [1] ([2] has links to assorted longer
| articles), you can get one idea of what de-emphasising
| vengeance and taking rehabilitation and trying to address
| reoffending rates might start to look like (though Norway
| has by no means solved that, Bastoy also certainly
| haven't made it worse, but it also is _not_ the norm in
| Norway either - yet anyway). For some people, it might
| well be that harsher prisons works better, or are
| necessary (I doubt Breivik will ever get the chance to
| serve his time somewhere like Bastoy for example).
| (Bastoy is the - so far - culmination of a process of
| reform that started in the 1960 's, at a point where
| Norwegian prisons were quite brutal and the brutality of
| it eventually triggered a strong counter-reaction.)
|
| For others even less prison (Norway as it is have
| sentences that would look comically short for e.g.
| Americans or British people). But evaluating it as a
| "game theoretic situation" as you say would in any case
| very likely lead to very major change to how the legal
| system would work most places in the world (including
| Norway)
|
| [1] http://bastoyfengsel.no/English/
|
| [2] https://en.wikipedia.org/wiki/Bast%C3%B8y_Prison
| kybernetikos wrote:
| It seems that we agree that taking a game theoretic view
| can justify more than just 'the bare minimal extent
| required to protect others' as it can also include
| questions of setting examples and letting justice be seen
| to be done that can form part of the decisions of other
| future potential criminals, or victims who might feel
| like taking the law into their own hands.
|
| So, as to 'they chose this themselves', that's begging
| the question a little - as we've already seen I think
| that believing in determinism doesn't stop you from
| believing that people can choose things. As to 'they
| deserve it', questions of what people deserve is a huge
| other topic, and I think it's most likely possible to
| define desert in terms that fit within a deterministic
| viewpoint.
|
| However, perhaps you're right about its effect since I do
| in fact think that vengeance is a thoroughly dumb
| rationale for treating people badly. This is to such an
| extent that I'd feel surprised to find anyone seriously
| try to justify it, which is why I didn't really engage
| with your apparent suggestion that it was an important
| justification. There are lots of ways you can try to
| justify criminal punishment in my view but 'vengeance'
| doesn't fit into any moral system I consider valuable
| unless it's actually being used as a code for game
| theoretic concerns or rehabilitation.
|
| But I don't feel so strange thinking this, since most
| people I know think the same, even those who don't share
| my views on free will and I'm pretty sure I believed it
| before I came to that conclusion on free will.
| ngcc_hk wrote:
| Our "soul" is that being which " can affect and be affected
| by the natural world, but are not part of it". You can feel
| it as you are one of these "supernatural being". Case
| closed.
| naasking wrote:
| > You can do some mental gymnastics, define free will as
| being able to do what you want, define it as being free of
| various kinds of constraints, call it free if the choice is
| not computable in advance, if you can not measure all
| necessary variables, in practice or in theory, ... If you are
| happy with any of those definitions, fine, then you might
| have this kind of free will, but I would not consider any of
| those particularly interesting.
|
| It is quite interesting in fact, as it lets you sensibly
| assign moral responsibility to those who were acting of their
| own free will, even if the world is deterministic. Arguably
| that's the only kind of free will worth having, and what
| people mean when they talk about free will (not what people
| say they mean).
| cjameskeller wrote:
| This is conflating causation and determination. It is true
| that one's choice must have a cause, and this can either be
| internal or external to oneself. But it is not true that the
| choice must be _determined_ by the cause. The Agent Causation
| [0] view denies the notion that only states or events can
| serve as causal priors, and instead asserts that substances
| themselves may be the terminal "cause"
|
| [0] https://plato.stanford.edu/entries/incompatibilism-
| theories/...
| jasperry wrote:
| What is a substance? Does it have a definition in any
| testable theory?
|
| You claim that causation and determination were conflated,
| but if the distinction between them depends on terms that
| can't be defined scientifically, then you haven't shown
| that they are different in what they refer to in the
| universe. It's conceivable that on a physical level
| causality is just a word for a property of a deterministic
| system.
| vidarh wrote:
| That just introduces infinite regress [1] into the mix. In
| order to justify why that would introduce free will you now
| need to justify why the substance itself has free will.
| It's not a solution.
|
| [1] https://en.wikipedia.org/wiki/Infinite_regress
| syki wrote:
| Regarding your either/or line of reasoning in your first
| paragraph. Are you sure these are the only two possibilities?
| Could there be partial dependence on the current state of
| one's mind and environment? Does the same exact state always
| lead to the same exact decision? That is, if a universe began
| exactly as ours did and everything was the same up until time
| t when a decision is made by someone is that decision always
| the same? It seems to be to yes and that would support your
| view but does it have to be yes.
|
| Also, I wonder if your either/or line of reasoning depends on
| the Law of the Excluded middle. What happens to your
| reasoning if that law is not true?
| danbruc wrote:
| One can certainly also imagine a mix of both option, for
| example your preferences deterministically determine which
| options you consider but a random event determines the
| choice you make. But that doesn't make a big difference,
| it's still a mix of predetermined and random things.
|
| A third option would have to be a wild thing - a choice
| would have to neither depend on the state of the universe,
| i.e. be determined, nor be independent of the state of the
| universe, i.e. be random. I personally don't see any room
| for a third option but there are probably a lot of things
| you could try to poke holes into. Is the state of the
| universe a meaningful concept? How does it relate to time?
| Does true randomness exist?
| syki wrote:
| I was thinking of the third option. I don't have anything
| intelligent to say about that option but posed it as a
| possibility. I imagine that believing in the third option
| would roughly be equivalent to a religious belief. That
| is, one believes that option because the alternative is
| unpalatable.
| vnorilo wrote:
| What is free will but an experience? I think it is completely
| plausible that organisms that exist in a fully deterministic
| physical reality still have the experience of free will. Or
| vice versa for that matter.
|
| Why do "I" have this experience of having a viewpoint and
| making decisions? That is a mystery that I am not close to
| solving. However why would any of that define how the
| universe must work?
|
| Much like a finite being can hold thoughts of Cantor's
| classes of infinities in her finite brain. The domains in
| question are unrelated.
| CuriouslyC wrote:
| Free will implies agency, and isn't disproved by
| predictability. I love pizza and hamburgers, and just because
| you can predict that I will eat either pizza or hamburgers
| with 95+% likelihood, that does not imply that I did not
| actively choose one of the two. I had the freedom to choose
| tofu, I just decided not to because I hate it.
| [deleted]
| fpoling wrote:
| Free will just cannot be described by physics. This is very
| similar to the perception of the time flow. Time in physics
| is static. There is no now. Surely one can plug any time
| value into physical equations, but that will not explain, for
| example, why when we look at a thrown ball, we perceive a
| movement, and not, say the whole trajectory of the ball at
| the same time.
|
| And given that the free will and now are connected it is easy
| to see why we cannot describe the free will using physical
| equations. Well, at least until we will manage to describe
| now.
| burnished wrote:
| Pardon, but your argument does not appear to be coherent.
| Your example in particular does not seem connected to your
| thesis in any way. I would suggest reformulating an
| argument that does not depend on a hazy refutation of
| physics.
| fpoling wrote:
| Time in physics is similar to the number of a frame in
| video. For example, from two frames of a video of a
| thrown ball one can deduce the its whole trajectory. But
| it does now explain why when we see the video we see
| ball's movement. In a sense from a physical point of view
| the whole trajectory exists at once, there is nothing
| special about a particular point of a trajectory. There
| is no now.
|
| Now back to the freedom of will. Its feeling originates
| in now as if it exists, it is about changing the future
| following the now. But since the notion of now is not
| reflected in physical equations, those cannot describe
| the freedom of will. In physics the whole timeline exists
| at the same time. In other words time is static and
| future has already happen. Thus there is literally no
| choice in physics.
| awb wrote:
| A few issues with the "free will" debate.
|
| 1) Define "free"
|
| 2) How do you test your hypothesis?
|
| You're trying to apply logic to an untestable philosophical
| debate. If you believe free will doesn't exist, you can't
| design an experiment that would invalidate that belief. And
| if your theory is untestable and unfalsifiable, then what
| good is it other than a creative exercise?
|
| However, we do know from Quantum Mechanics that the universe
| is probabilistic and not deterministic:
|
| https://www.thegreatcoursesdaily.com/quantum-universe-
| fundam....
|
| So, we do know that the universe is not pre-determined and
| cannot be calculated in advance, but if you want to believe
| in humans as fully deterministic (or some other definition of
| no free will) inside of a non-deterministic environment, I
| haven't heard anyone propose an experiment that could test
| that, at which point the debate of "free will" is relegated
| to the realm of thought experiments rather than science.
|
| So, perhaps the better question is: Does it serve you better
| to believe there is free will or no free will? And leave it
| at that.
| tshaddox wrote:
| > 1) Define "free"
|
| It doesn't seem worth spending much time here, lest the
| entire argument becomes nothing more than a semantic one.
| If your definition of "free will" is "this thing that I
| undeniably feel" then sure, you've made it undeniable by
| definition.
| danbruc wrote:
| _However, we do know from Quantum Mechanics that the
| universe is probabilistic and not deterministic_
|
| That is not true, quantum mechanics - more specifically the
| Schrodinger equation - is deterministic. What is not
| deterministic is the wave function collapse but that is
| also incompatible with the Schrodinger equation because it
| implies non-unitary evolution of the wave function. And we
| have - as far as I know - no really good ideas how to
| resolve this. In consequence I think it would be premature
| to declare that the universe is definitively non-
| deterministic.
| awb wrote:
| From the article:
|
| > One of the key implications of the Heisenberg
| uncertainty principle is that it highlights the
| probabilistic nature of the universe
| danbruc wrote:
| The article is wrong there. I can not provide a good
| source so I will just point you to this StackExchange
| question [1].
|
| [1] https://physics.stackexchange.com/questions/63811/is-
| the-uni...
| awb wrote:
| The article you linked to seems to say the universe is
| indeterministic:
|
| > Indeterminism in Quantum Mechanics is given by another
| "evolution" that the wavefunction may experience:
| wavefunction collapse.
|
| I'll give you that it's not a fully settled issue though:
|
| > According to the Copenhagen interpretation of QM, it
| does mean the universe is non-deterministic. There are
| other interpretations of QM which allow for determinism
| though. Which is the correct interpretation (if any)?
| Currently, no one knows.
|
| Here's another article:
| https://www.theguardian.com/world/2021/apr/29/the-battle-
| for...
|
| > Most physicists would not regard the events in our
| universe as deterministic, or clockwork if you insist;
| they are in fact considered probabilistic
|
| > randomness (ie indeterminism) has been proven to be
| real by the National Institute for Science and
| Technology's work on a randomness beacon.
| vidarh wrote:
| > You're trying to apply logic to an untestable
| philosophical debate. If you believe free will doesn't
| exist, you can't design an experiment that would invalidate
| that belief. And if your theory is untestable and
| unfalsifiable, then what good is it other than a creative
| exercise?
|
| This is reversing the burden of proof. The issue with "free
| will" is getting those who think there is a meaningful
| "free will" concept to actually define what they mean.
|
| Look through this discussion and see the comments trying to
| justify the existence of free will, and look for
| definitions of what they actually mean by that.
|
| > However, we do know from Quantum Mechanics that the
| universe is probabilistic and not deterministic:
|
| That's a meaningless distinction in this context. The point
| is that nobody has presented a mechanism whereby you can
| inject any form of agency that fits a definition of "free"
| (see your own point: define "free") that doesn't devolve to
| smoke and mirrors that way.
|
| In order to do so, there'd need to be something that would
| lead to measurable biases in outcomes that can not be
| explained by the probabilities.
|
| The rest of your argument devolves to Russel's teapot: As
| long as nobody has posited a reasonable definition that'd
| give rise to a theory of what free will might mean, the
| notion is so absurd that it is entirely reasonable to say
| that free will makes no sense.
|
| If you can present a definition that can't easily be shown
| to be just smoke and mirrors and which somehow makes sense
| to people, even without coming up with ways of actually
| testing it, I might be tempted to moderate that claim, but
| I've had these discussions with people for decades, and in
| none of them have anyone ever managed to come up with a
| cohesive definition of what free will would even mean that
| doesn't very easily start looking distinctly "unfree".
|
| There are clearly definitions of free will that would allow
| something you label with that term to exist. But I
| challenge you to come up with one that people would agree
| is both "free" and "will".
| awb wrote:
| > This is reversing the burden of proof.
|
| No, in response to someone vaguely mentioning the words
| "free will", you made the claim: "Free will does not
| exist."
|
| The burden of proof is now on you to provide evidence of
| your claim as well as on you to define the terms
| contained within your claim.
|
| I am not arguing the "free will" debate either way for
| the reasons mentioned previously and do not care to
| define the terms as the entire debate is nothing more
| than a creative thought experiment as far as I can tell.
| vidarh wrote:
| Russel's teapot.
|
| If I claim Russel's teapot doesn't exist, the burden of
| proof is on you to prove it exists if you disagree with
| me, not me, because the set of claims that are so poorly
| defined and unlikely as to make it an unjustified burden
| to expect anyone to caveat the claims to make them
| technically correct is infinite - someone who makes an
| extraordinary claim without being able to provide a
| justification therefore needs to be prepared to take on
| the burden of proof.
|
| I equally claim that santa doesn't exist, and yet will
| insist the burden of anyone disagreeing with my claim
| lies on them, not on me, even if I make the initial
| claim, for exactly that reason.
|
| In this case the claim that free will does not exists
| puts the burden on those who disagree *because nobody
| here or otherwise* have presented a definition of free
| will that most people would agree to, not least because
| without narrowing the scope with a definition I have the
| freedom to apply whichever definition _I prefer_ , and I
| have several places in this thread.
|
| E.g. I'd argue that "free will" would require an entity
| to be able to do something which cannot be explained by
| the combination of determinism and randomness. Given
| we're unaware of any kind of processes that can produce
| outputs that are not either deterministic or random
| modulated by some sort of probabilistic distribution, to
| claim that a process that can produce such an output
| exist is an extraordinary claim that would give you a
| Nobel in physics if you could demonstrate it.
|
| As such: Russel's teapot.
|
| I'd _love_ to be wrong. I 'd _love_ for someone here to
| come up with a definition of free will that overcomes
| that problem, as if so I 'd be witnessing a revolution in
| philosophy surpassing anything we've seen in centuries.
|
| Just like I'd be delighted to be wrong when I say that
| santa doesn't exist, but I do believe I'm far more likely
| to be proven wrong about santa than free will, given that
| people can at least come up with definitions of santa
| that are somewhat coherent if unlikely.
| awb wrote:
| The difference between free will and Russell's teapot IMO
| is that free will to many is an internal, subjective,
| untestable experience whereas Russell's teapot is an
| external object that is theoretically existent or non-
| existent for everyone regardless of their internal
| experience.
|
| If someone says they experienced free will today when
| they chose to stand up, it's on you to disprove that it
| couldn't possibly happen to anyone ever, or come up with
| a definition of free will that means they couldn't
| possibly experience what they claim to be experiencing.
| To them their experience is real. You're claiming it's
| not, so I don't think Russell's teapot applies here. I
| think you have set forth a bold claim that someone is not
| experiencing what they report they are experiencing.
|
| > I'd argue that "free will" would require an entity to
| be able to do something which cannot be explained by the
| combination of determinism and randomness
|
| What is your benchmark for determinism? No technology we
| have can predict or determine a human action. While it's
| reasonable to assume that humans are deterministic, it's
| still just a theory at this point. If I put the onus on
| you to prove determinisms in humans, you'd certainly win
| the Nobel as well.
|
| That's kind of my point is that both sides of the free
| will debate are a far cry from having enough evidence or
| the ability to conduct an experiment to settle the issue.
| Yet many believe they experience free will everyday and
| many don't, because it's a subjective experience.
| bmh100 wrote:
| In science, when testing the existence of something, the
| burden of proof is generally on the one hypothesizing the
| existence. The existence is generally accepted if
| experiments fail to reject the hypothesis.
| awb wrote:
| But free will is a concept, a way of viewing the world.
| It's not a physical object or mechanical process that can
| be tested. It's why trying to prove it scientifically or
| through logic is just as impossible as trying to disprove
| it.
|
| It's a philosophical debate, not a science experiment. In
| philosophy, a declarative statement asserting the
| affirmative is always true is just as big a fallacy as
| saying the negative is always true.
| SuoDuanDao wrote:
| >So, perhaps the better question is: Does it serve you
| better to believe there is free will or no free will? And
| leave it at that.
|
| From a pragmatic analysis the answer is pretty
| straightforward[1] (Spoiler, believing in free will is
| better if you value moral behaviour). Glad I chose to
| believe in free will!
|
| [1]https://journals.sagepub.com/doi/abs/10.1111/j.1467-9280
| .200...
| danbruc wrote:
| I don't think that would be the best option. There is
| nothing wrong with figuring out that we don't have true
| free will - however you want to define it - and still
| behave in everyday life as if we have it. It might just
| be a useful abstraction.
| SuoDuanDao wrote:
| The study I linked indicates that people who don't
| believe in free will act as if they don't, granted, they
| weren't warned of the dangers of believing they don't so
| there might be more to explore.
|
| But the question seems to me more about pragmatism vs
| realism than pragmatism vs. realism with 'some beliefs-
| as-if'. I find realism unsatisfying philosophically
| because we can see historical beliefs being so off the
| mark that we'd have to live in a pretty special time to
| have anything close to a realistic model of the universe,
| I think making good predictions is simply the best tool
| that we have. If that comes at the cost of having a
| single internally-consistent model of the universe,
| that's unfortunate, but at least I'm not attached to the
| wrong one. So if my belief in free will and my belief in
| Newtonian Mechanics are incompatible, that's not such a
| big deal to me as a pragmatist. In fact it's a useful
| feature of the metaphysics, since the places they come
| into conflict give an idea of where they're incomplete.
| Natsu wrote:
| "Free will" is a gesture at the experience we have of
| deliberating upon and deciding our own actions, I don't
| think determinism really matters, as long as we're the ones
| doing the deterministic calculations by which we choose
| what to do.
|
| But it's okay, I understand if you have no choice but to
| argue with that.
| tsimionescu wrote:
| > However, we do know from Quantum Mechanics that the
| universe is probabilistic and not deterministic:
|
| This is not true, and there are consistent interpretations
| of QM that are fully deterministic (many worlds,
| superdeterminism, pilot wave).
|
| Still, probabilistic vs deterministic makes no difference.
| There is no free will in a throw of the dice, and no free
| will in the wave function collapse.
|
| On the other hand, the main philosophical position on this
| is compatibilism: free will in a fully deterministic
| universe (or probabilistic one). If you think of yourself
| as the sum total of all your experiences and genetics, your
| next action is of course determined by these; but, another
| agent in your shoes, one with different experiences and
| genetics, would make a different choice. So in this
| framework, your choice, even though uniquely determined by
| everything that happened before, and theoretically
| predictable 1000 years in advance, is still meaningfully
| "your choice".
|
| In fact, random chance hurts this definition, and weakens
| the case for compatibilism; if your next action is entirely
| dependent on some random quantum fluctuation, and running
| the experiment with your exact same experience and genetics
| but a different random quantum event at this exact time
| would produce 1000 entirely different actions on your part,
| then it is very hard to imagine any kind of free will. So,
| free will actually depends on some amount of determinism.
| Even the type of determinism in Many Worlds would not solve
| this - since in that interpretation, all possible outcomes
| of the quantum event actually happen, so all your "choices"
| that depend on the random event are fully real. So, if each
| of the fully real copies of you, with the exact same
| experiences and genetics, does a wildly different thing,
| then it's pretty clear there is no meaningful free will in
| any possible sense.
| SuoDuanDao wrote:
| I find the most satisfying version of compatibilism one
| where an agent is mostly determined by 'state'
| (genes/experiences etc), but the subjective experience of
| expending mental effort (e.g. when overcoming an
| addiction) is the agent nudging the wave function
| collapse this way or that. Add in the ability to
| influence future 'states' and one has a model much more
| consistent with the subjective experience of making
| difficult choices.
| JackFr wrote:
| Or you can just accept that reductive materialism is not
| an adequate description of the world.
| tsimionescu wrote:
| If only any other system of thought could make any kind
| of verifiable prediction, it would be wise to reject
| materialism. As it is though, you either have magical
| systems of thought, that reject the very framework of
| science; or ones which amount to materialism plus some
| handwaving.
| SuoDuanDao wrote:
| Oh I accept that, but I'm also wary of theories that seem
| to handwave material reality. I've found Dione Fortune's
| writings the most useful in that regard, though she can
| be... obscure. Quite influential all the same.
| tsimionescu wrote:
| That's not compatibilism - as long as "will" can
| influence the physical world, you have a non-materialist
| philosophy. Nothing wrong with that, but it's very
| strange to call it compatibilism.
|
| For what it's worth, I don't see any reason to imagine
| that hard decisions are of any other quality than easy
| decisions. It's part of my history and experience just as
| much that I prefer to eat salty foods than sweet ones as
| it is that I sometimes abstain from eating that pizza to
| try to manage my waistline, or refuse that job offer
| because I don't want to work for a company I don't find
| ethical.
| phkahler wrote:
| >> However, we do know from Quantum Mechanics that the
| universe is probabilistic and not deterministic
|
| Do we? Quantum mechanics _looks_ like there is genuine
| randomness, but one interpretation of experiments testing
| the Bell inequalities is non-locality. It could be
| completely deterministic, we just don 't know what
| determines it.
| michalf6 wrote:
| >call it free if the choice is not computable in advance
|
| Is it not essentially equivalent to "actual" free will? I am
| perfectly happy with just this.
| danbruc wrote:
| You are free to call this free will, I would not. For a
| good hash function there is no way of predicting the output
| for a given input besides executing the hash function. But
| I don't see why I would call the output free. If there is
| no better way to figure out what you will do than letting
| your brain go through its internal calculations, fine, your
| behavior is unpredictable, but how is it free?
| syki wrote:
| Your points are well stated and succinctly out. They've
| made me think about this issue more than I ever have.
| It's not a question I've ever been interested in but I
| like the reasoning you are giving.
|
| The first sentence above though helps to illustrate a
| problem when thinking about this stuff. You wrote, _You
| are free to...._ From your perspective no one has that
| freedom but our everyday experience is such that it's
| hard to really follow through with this belief. Perhaps
| consciousness and self awareness comes at a cost of not
| being able to fully embrace the notion that we don't have
| free will. It certainly feels like I have exercised free
| will but that is likely just an illusion.
| danbruc wrote:
| I also behave and talk all day long as if we have free
| will, it's just a useful abstraction. But my world view
| will not shatter if someone puts me into an MRI machine
| and tells me what I will choose for dinner later that
| day.
| guelo wrote:
| I think your argument against free will can be boiled down to
| the question of if true RNGs exist. Even leaving out quantum
| probability, we can easily consider systems of such high
| entropy that a computer the size of the universe would be
| unable to deterministically calculate the results.
| Guessnotgauss wrote:
| How about, the fact you can even argue that free will exists
| is a demonstration of it.
| coliveira wrote:
| I can think of a world without free will too. And I can
| imagine a large amount of things that don't exist.
| vidarh wrote:
| Creating something that can argue that free will exists
| requires an eliza-level chatbot, nothing more.
| bena wrote:
| First, even constrained choices can be meaningful. Just
| because I can't choose to fly by flapping my arms, wouldn't
| mean I don't have free will. If free will exists, I can still
| choose among the options available to me. I don't think
| anyone operates by the definition of "free will" that you
| seem to be proposing. Free will is the ability to select from
| among the options you are given. The opposite of that would
| be that you'd always make the same pick every time, because
| your decisions are actually the results of forces acting upon
| you. If you had the choice between red, green, and blue;
| you'd choose red every time if we could rerun your life up to
| that moment in time.
|
| Which is what makes the question kind of unknowable. Because
| we can't rerun our lives to see if we could make different
| decisions with all of the exact same conditions as before.
| Even running the choice twice isn't the same. Because the
| second time you do it, you're now a person who has previously
| made this choice. And that makes the scenario different,
| because you are different. We have no real way of testing
| free will.
|
| But better still: the question does not matter at all.
|
| Either free will exists or it doesn't. There's no spectrum of
| "50% will" or whatever. You can either make choices or you're
| essentially the result of all the forces acting upon you.
|
| So, what are the consequences of both scenarios?
|
| If free will exists, then fine, we can make choices. We can
| choose to do whatever. There's nothing really interesting to
| be said about this branch.
|
| However. If free will does not exist, then there's something
| weird going on. Because if free will does not exist, I don't
| have any choice in whether or not to post this message. I
| post this message because your post elicits that response in
| me. Just like you made your post for the same reason. And we
| just keep pulling this thread all the way back to the big
| bang.
|
| But we also don't have the choice in how we feel about this
| discussion either. You will either accept this or not based
| on the various physical, biological, and chemical processes
| going on inside of and around you. So you will either agree
| or disagree and that decision itself is preordained.
| Regardless if it is true or not. You're either the type to
| believe in free will or not and you can't choose that.
| Because if you could choose that, you'd have free will.
|
| Even if you believe you are making a change, you're not.
| Because you were going to make that change due to the forces
| at work on you. Forces that were eventually going to interact
| with you because those forces themselves are the products of
| other forces, etc. So if you hear all this, take it to heart,
| and decide to live a life of apathy because you have no free
| will and nothing matters. Then that's what was going to
| happen at this point and time regardless.
| glandium wrote:
| Related minute physics videos:
|
| https://youtu.be/Rh0pYtQG5wI
|
| https://youtu.be/R5oCXHWEL9A
|
| The whole intro to relativity series is worth a watch.
| alde wrote:
| It is interesting that "real" observations of relativistic
| objects are quite different from what you expect them to be. For
| example, a cube passing by at relativistic speed would appear as
| if it is rotating towards you. This allows you to see some of its
| sides which you normally wouldn't [1].
|
| [1] https://en.wikipedia.org/wiki/Terrell_rotation
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