[HN Gopher] The Thought Experiments That Fray the Fabric of Spac...
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The Thought Experiments That Fray the Fabric of Space-Time
Author : thcipriani
Score : 27 points
Date : 2024-10-21 21:08 UTC (1 hours ago)
(HTM) web link (www.quantamagazine.org)
(TXT) w3m dump (www.quantamagazine.org)
| kelseyfrog wrote:
| I still don't understand why a black holes needs an inside at
| all. If they are equivalent to their surface then why not
| dispense with having an interior and just _be_ a surface?
| twiceaday wrote:
| Why isn't the surface smaller then? Probably something inside
| is pushing out? It's full? Also on the way to a black hole
| bodies clearly have insides. Do they somehow evaporate the
| moment a black hole forms?
|
| Edit: My understanding is that all bodies are the size that
| they are because the inner/outer pressure equalizes, and this
| has many equilibriums based on the makeup of the body. Black
| holes are the ultimate degenerate last-stand where the make up
| is basically raw "information" which cannot be compressed any
| further while allowing said information to be recovered, which
| seems to be a fact of our universe. And it just so happens that
| the amount of information is proportional to the surface area
| of the black hole rather than its volume, which is probably a
| statement about how efficiently information can be compressed
| in our universe. One dimension is redundant?
| crackez wrote:
| Since when is the surface of the universe that of a
| hypersphere?
| enkid wrote:
| "Pressure" as a concept doesn't apply to black holes. They
| are the size they are because of their mass. The bigger the
| mass, the larger area where their gravity is so great light
| can't escape. Scientists model black holes as only have a
| mass and a spin on the inside because that's all the external
| universe cares about. Information being inscribed on the
| exterior is an artifact of tike dilating as an object
| approaches a black hole, iirc.
| nvader wrote:
| Black holes also have a charge!
| JumpCrisscross wrote:
| > _Why isn 't the surface smaller then? Probably something
| inside is pushing out?_
|
| The surface of space doesn't require something in a higher
| dimension pushing it out. That such an object may appear to
| have internal volume from our perspective doesn't need to be
| any more real than the apparent depth behind a mirror.
| lisper wrote:
| Because if you free-fall into a black hole you can go past the
| event horizon.
| kelseyfrog wrote:
| Can we? Is there a way to test this assumption? If not, then
| it's not science, right?
| bongodongobob wrote:
| A surface implies an interior, otherwise it's a just a point. A
| surface is a boundary, by definition there is another side,
| something that is being partitioned.
| kelseyfrog wrote:
| I'm not a topological expert, but I'm pretty sure you can
| have a surface without an interior. A unit sphere would be a
| good example of a surface without an interior.
| bongodongobob wrote:
| ? It by definition has a radius of 1.
| krukah wrote:
| unit sphere != unit ball
|
| The former is the boundary, the latter is the interior +
| boundary. One of the great arbitrary naming conventions
| of math.
| thebricklayr wrote:
| Agreed. Couldn't black holes warp spacetime to the extent that
| there is no such place as "inside"? Time dilation is infinite
| at the event horizon after all.
|
| As you approach the event horizon, your frame of reference
| slows asymptotically to match that of the black hole while the
| universe around you fast-forwards toward heat death. I'd expect
| the hawking radiation to blue shift the closer you got until it
| was so bright as to be indistinguishable from a white hole.
| You'd never cross the event horizon; you'd be disintegrated and
| blasted outward into the distant future as part of that hawking
| radiation.
| lisper wrote:
| There is an even simpler thought experiment you can do to reach
| this conclusion: consider what the result of measuring anything
| to an infinite precision could possibly look like. It would
| require somehow recording an infinite amount of information. How
| would you do that, particularly when you take into account that
| everything you can interact with to make an information storage
| device is subject to the Heisenberg uncertainty principle?
| oniony wrote:
| It would simply be written down on an infinitely long strip of
| paper.
| tonetegeatinst wrote:
| Mobius strip for double surface area....I can practically see
| the cheese TV comercial
| enkid wrote:
| Just because you can't record something doesn't mean it doesn't
| exist.
| lisper wrote:
| Who said anything about recording? What would the subjective
| experience of measuring something with infinite precision
| possibly be like?
| JumpCrisscross wrote:
| > would require somehow recording an infinite amount of
| information...
|
| >> Just because you can't record something...
|
| >>> Who said anything about recording?
| JumpCrisscross wrote:
| > _consider what the result of measuring anything to an
| infinite precision could possibly look like. It would require
| somehow recording an infinite amount of information_
|
| This is Zeno's dichotomy paradox [1]. Finitely-defined
| infinitely-complex systems ( _e.g._ fractals and anything chaos
| theory) are the escape.
|
| [1]
| https://en.wikipedia.org/wiki/Zeno%27s_paradoxes#Dichotomy_p...
| A_D_E_P_T wrote:
| There's a much simpler escape: That space is ultimately
| discrete (i.e. that there's an elementary length) rather than
| infinitely continuous.
| JumpCrisscross wrote:
| > _a much simpler escape: That space is ultimately discrete
| (i.e. that there 's an elementary length) rather than
| infinitely continuous_
|
| Sure. The point is the _gedankenexperiment_ proves nothing.
| A_D_E_P_T wrote:
| The Planck Length is a practical limit to the precision you can
| possibly attain in space.
|
| The electron might be smaller. Its diameter is known to be
| smaller than 10^-22m, but could be much smaller than that.
|
| Further below the Planck Length, there are strong indications
| that the universe isn't continuous -- it's discrete. That
| there's an absolute limit to precision, something really quite
| analogous to a pixel. This elementary length could be somewhere
| around 10^-93m.
| JumpCrisscross wrote:
| > _there are strong indications that the universe isn 't
| continuous -- it's discrete_
|
| There are indications discrete space is _plausible_. It 's
| actively debated.
|
| There are also strong indications space is continous, _e.g._
| Lorentz symmetry. (This was recently the death knell for a
| branch of LQG.)
| pazimzadeh wrote:
| I have similar reasons for not believing that the world that we
| experience is a computer simulation.
| JohnMakin wrote:
| Please stop trying to present information in this style of
| webpage, I am begging you. Besides being an abysmal way to
| present scientific information, every time someone posts one of
| these it happens to be a topic I am extraordinarily interested
| in, but due to disabilities I have, I cannot read it even if I
| wasn't tremendously annoyed by it.
| selimthegrim wrote:
| How could it be made more accessible to you?
| JohnMakin wrote:
| reader mode supported. sometimes they are sometimes no.
| oniony wrote:
| They could be regular web pages without the silly scroll
| animations, just like in the good old days.
| pmontra wrote:
| It's really bad even for me on my phone. The text content fades
| away before I can scroll it completely into view. No reader
| mode available.
| mopenstein wrote:
| I liked the presentation and it worked great on my phone.
|
| I'm sorry you have issues but I'm glad the world doesn't cater
| to a single individual's issue.
|
| I can't swim because of a whole in my ear drum from when the
| Nun at the free clinic my poor mother took me to popped that
| bad boy with a enthusiastic squeeze from an ear syringe and my
| tinnitus rings like a son-of-a-bitch when I wear ear plugs but
| I don't demand they fill in every swimming pool with concrete.
| I just walk by on those hot summer days wistfully jealous of
| the guy doing a cannonball and the lady doing the hand stand
| thing where your feet are in dry air but your head is 2 feet
| below the water level.
| the_gipsy wrote:
| You're a moron if you believe these two things compare even
| remotely
| wholinator2 wrote:
| I agree, this is abysmal ux. Doesn't even remotely work on my
| phone. All those stupid animations literally removing
| information from my screen before I've had a chance to read it.
| Drastically reducing the "reading surface" of the actual
| information attempting to be conveyed. Animations are cool and
| useful but they too could just be placed on a static page.
|
| The whole thing seems like some over excited marketing person
| enshittifying the literal idea of static pages of informative
| just to make something "new".
| DiscourseFan wrote:
| I've said this so many times now. Contemporary physics would
| greatly benefit from reading Kant. The extent of his influence on
| contemporary physics, especially with regard to space and time,
| is so great and the knowledge of his work so little in the
| scientific community of today. Almost all the great physicists of
| the 20th century were familiar with Kantian philosophy and were
| heavily informed by it.
| JumpCrisscross wrote:
| What would Kant add to this discussion that the physicists in
| the article haven't considered?
|
| (Saying this as someone who's read Kant twice and agrees with
| almost everything he says outside taste in music.)
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(page generated 2024-10-21 23:00 UTC)