[HN Gopher] Warp drive's best hope dies, as antimatter falls down
___________________________________________________________________
Warp drive's best hope dies, as antimatter falls down
Author : WithinReason
Score : 134 points
Date : 2023-10-09 10:52 UTC (12 hours ago)
(HTM) web link (bigthink.com)
(TXT) w3m dump (bigthink.com)
| jedberg wrote:
| It's ok, we still have 40 more years to figure it out.
| nv2156 wrote:
| Yeah once Dr Cochrane starts working on it :).
| jedberg wrote:
| Give him a break, he isn't even born yet!
| WendyTheWillow wrote:
| Maybe we should start naming every single person born as of
| now-ish, Zefram Cochrane, just to be safe...
| qingcharles wrote:
| I tried with Beastmaster and Swampmonster with First Wife,
| but I'm not Elon Musk so it didn't fly. I might be able to
| sell Zefram Cochrane, though. Do you think it'll matter if
| Cochrane is his middle name? :D
| ruined wrote:
| that's quite optimistic. i'd give us fifteen tops
| stevula wrote:
| It's a reference to the year warp drive will be invented by
| Zefram Cochrane in the Star Trek universe.
| OhNoNotAgain_99 wrote:
| [dead]
| davedx wrote:
| The whole article feels like a strawman, I wasn't aware anyone
| was presuming antimatter could lead to the negative energy
| required for the warp drive metrics...
|
| Antimatter is not negative mass or energy. The experiment
| verifying it falls down wasn't surprising
| andrewflnr wrote:
| The author addresses this (in a very condescending way) in the
| last couple paragraphs. But yes, I tend to agree with you.
| SkyMarshal wrote:
| _> If any sort of mechanism could exist for circumventing the
| limitations of conventional travel through spacetime --
| limitations set by the speed of light -- it must involve
| leveraging the curvature of spacetime to create such a "short-
| cut" between two otherwise disconnected points. Perhaps the most
| famous instance in all of fiction to leverage this was the idea
| of "warp drive" as developed by the Star Trek franchise._
|
| Did Star Trek actually originate the warp drive idea? I always
| assumed some scientist somewhere originated it first, then the ST
| writers picked up on it and used it in their world-building. But
| kind of mind-blowing if it was the ST writers who originally
| conceived it.
|
| _> By expending a vast amount of energy, the idea was that space
| could be severely curved, and in some sense, compressed. As the
| space ship moved through the compressed space, it would take this
| long-sought-after short-cut, enabling very rapid travel over
| great distances, without causing the outside Universe to age
| rapidly relative to the crew._
|
| There are conflicting conceptions of warp drive accelerating time
| outside the warp bubble (or decelerating it inside the bubble).
| Star Trek's warp drives obviously don't accelerate external time
| (or slow internal time). But in Cixin Lui's Three Body Series,
| curvature propulsion (aka warp drive) does slow internal warp
| bubble time. Which is correct?
| Agathos wrote:
| "Warp Drive" dates back to 1947 (John Barret, "Stellar
| Snowball") according to sfdictionary.com (a resource I love for
| this kind of question).
|
| Other phrases like "Space Warp" go back even further (Nat
| Schachner, "The Son of Redmask", 1935).
| johnchristopher wrote:
| Side note: re-watched ST2 and 3 recently and switched to french
| audio for a bit for giggles and nostalgia: warp speed got
| translated to "exponential hyper-atomic".
| phkahler wrote:
| We still don't know if regular matter is gravitationally repelled
| by antimatter. If so, we'd have violation of conservation of
| momentum and some interesting things might be possible. But I'm
| not holding my breath ;-)
| data_monkey wrote:
| I don't understand this result. How would this experiment be able
| to detect the "antigravity" of antimatter? If the Earth is
| curving space time in one direction and then antimatter is
| curving space time in the opposite direction, would not relative
| impact of the antimatter be so negligible to be undetectable? We
| are talking about the ability to "unbend" space time of what a
| particle or two relative to the mass of the earth? So what if it
| falls, that just means its barely unbending space time.
|
| To use an analogy, Let's say I am on the Amazon river (fastest
| river according to google). You want to detect which way I was
| swimming. Would you even be able to detect the marginal effects
| of me swimming upstream relative to the massively more impactful
| force from the river?
|
| I am sure the problem here is me, so if someone can correct my
| thinking.
| dmurray wrote:
| > To use an analogy, Let's say I am on the Amazon river
| (fastest river according to google). You want to detect which
| way I was swimming. Would you even be able to detect the
| marginal effects of me swimming upstream relative to the
| massively more impactful force from the river?
|
| Definitely yes! If you're even a reasonably competent swimmer
| you should be able to outswim the Amazon and make headway
| upstream at most points.
|
| I'm not sure what this says about your analogy, but I would
| think the measurement devices are millions of times more
| sensitive than needed to detect which way you were swimming.
| mnw21cam wrote:
| You're making a very interesting distinction between the
| experimental result, which is that antimatter _follows_ the
| same space-time curve as normal matter, and the dashed hope of
| warp drives, which is that antimatter _causes_ the same space-
| time curve as normal matter.
|
| However, if antimatter were to create a negative curvature but
| follow positive curvature, then you would be able to put a lump
| of normal matter next to a lump of antimatter, connect the two
| together, and the whole mechanism would spontaneously
| accelerate forever, breaking the laws of conservation of energy
| and momentum. For that reason, I think this experiment also
| gives us high confidence that antimatter causes exactly the
| same space-time curvature as normal matter, even though we
| haven't gathered enough antimatter to see it creating a normal
| space-time curvature. In essence, gravity is _symmetrical_.
| stromgo wrote:
| Maybe it helps to consider all 4 possibilities for the sign
| of the gravitational mass of antimatter, and the sign of the
| inertial mass of antimatter?
|
| (-,-): antimatter would fall down, but we could break
| conservation laws with a mechanism.
|
| (+,-): antimatter would fall up, but we could break
| conservation laws with a mechanism using electrically charged
| particles.
|
| (-,+): antimatter would fall up, but ruled out by the
| experiment.
|
| So what remains is (+,+)?
| [deleted]
| elil17 wrote:
| To my understanding, the researchers released antimatter
| particles with detector plates above and below them. The
| particles started out traveling in random directions. Some of
| the particles hit the top, some hit the bottom. They saw that
| more particles hit the bottom than the top.
|
| If the particles had "anti-gravity", they'd be repulsed by the
| large mass of the earth (instead of attracted), and you'd have
| expected more to hit the top plate than the bottom plate.
|
| The researchers also added a magnet to the top designed to
| cancel out the downward force from gravity, and they hit the
| top and bottom plate at even rates.
| pvaldes wrote:
| Hum, How can they be sure that what is hitting the plate is
| still antimatter? (Or only antimatter?)
| ben_w wrote:
| Positrons react with electrons to produce a distinctive
| pair of 511 keV photons travelling in opposite directions
| in the frame of reference of their collision.
|
| There's also a much more complex mess that happens when
| protons react with antiprotons.
| mperham wrote:
| Quanta and BigThink are such great sites, pumping out high
| quality science journalism.
| rilindo wrote:
| BigThink, ironically, is sponsored by the Charles Koch
| Foundation.
| WendyTheWillow wrote:
| Can you cite this? All I see is that BigThink is owned by
| FreeThink [0], and FreeThink appears funded by Bedrock
| Capital and MaC Venture Capital [1], neither of which I can
| tell are associated with the Charles Koch Foundation [2][3].
|
| That said, I've spent ~5 minutes on this, so I certainly
| missed something.
|
| [0] https://bigthink.com/our-mission/
|
| [1] https://www.crunchbase.com/organization/freethink-
| media/comp...
|
| [2] https://www.linkedin.com/company/bedrockcap/
|
| [3] https://www.linkedin.com/company/mac-venture-capital/
| esc861 wrote:
| I was under the impression that there were potential positive-
| energy solutions to this problem that don't require antimatter:
| https://iopscience.iop.org/article/10.1088/1361-6382/abe692
| captn3m0 wrote:
| We've lost the "best hope", not all hope.
| pnpnp wrote:
| Was this really its best hope? I still have my fingers crossed
| for an Alcubierre drive using antimatter as an energy source.
|
| Hasn't work been done in this area recently? I remember seeing an
| article saying it might technically be possible with a
| hilariously large energy source, but I don't know if that has
| been disproven.
| aardvark179 wrote:
| So what's going to provide your negative energy density, given
| it isn't going to be antimatter now, and that was our best
| candidate?
| gs17 wrote:
| >Also dying with this measurement is another sci-fi hope:
| artificial gravity that works without rotation or acceleration.
| If antimatter truly anti-gravitated, then simply by building a
| spacecraft's floor out of normal matter and its ceiling out of
| antimatter, we could create a spacecraft that had its own built-
| in, automatic system for artificial gravity.
|
| I've never heard this idea, but that sounds hilariously
| dangerous.
| thereddaikon wrote:
| I have never heard of antimatter being used in that way, even
| in the most off the wall, science illiterate speculation.
| Usually its as a power source.
| andrewflnr wrote:
| Yeah, because the idea of antimatter being anti-gravitational
| is so obscure and silly that not even scifi authors use it.
| db48x wrote:
| The idea was mostly limited to really bad science fiction, the
| kind that is really a fantasy with science-fictional set
| dressing.
| LeifCarrotson wrote:
| Doesn't that proposal merely ~halve the amount of mass
| required?
|
| I'm in an office right now that has a ceiling made out of
| normal matter (gypsum, fiberglass, steel, and tar, probably a
| couple thousand kg overhead) and a floor also made out of
| normal matter (carpet, concrete, iron, silicon, oxygen, and a
| bunch of other stuff adding up to 6x10^24 kg), which generates
| artificial gravity at 1g. It happens to be rotating at 1/1440
| RPM, but that's only a 0.2% reduction in the acceleration.
|
| Sure, if antimatter caused anti-gravitational forces, you could
| have achieved the same gravitational acceleration I experience
| in my office using one 3x10^24 kg sphere of antimatter overhead
| and one 3x10^24 kg sphere of matter beneath, but that's still
| not a Starship Enterprise, much less an X-wing, with artificial
| gravity generators. You're still stuck at: F
| = G x m_matter / r^2 + G x m_antimatter / r^2 F =
| 4 x pi / 3 x G x density x radius_matter + 4 x pi / 3 x G x
| density x radius_antimatter
|
| with planet-sized masses and radii for both.
|
| And I'm not sure that "hilariously" is a sufficient modifier
| for the danger level when standing in a 3m gap between planet-
| sized spheres of matter and antimatter.
| izzydata wrote:
| What about building a circular ship around a micro black hole?
| Or is that just real gravity and not anti-gravity?
| Cthulhu_ wrote:
| Note: armchair reply, I don't know enough astro whatnots to
| substantiate this take:
|
| That implies that you can actually move the black hole; a
| black hole producing 1G requires it to be as heavy (or, to
| have as much attraction) as the earth itself. It would be a
| lot more compact - a black hole as heavy as the earth is
| about the size of a ping pong ball - but if my intuition is
| correct, would require as much force to move as it would to
| move the earth.
| db48x wrote:
| Yep, F=ma. For a given force, if mass is big then the
| acceleration must be small.
|
| Also, I feel compelled to mention that to get an Earth-like
| gravitational field near the event horizon of a non-
| spinning black hole, it needs to mass more than the whole
| galaxy. It would be about a light-year across, iirc, and if
| you built a shell around it (which would not be easy) then
| the surface area would be so large as to beggar
| description.
|
| Small black holes are not very earth-like because of the
| extreme tidal forces. Trying to stand on that ping-pong
| ball would be extremely uncomfortable.
| User23 wrote:
| If it's an antimatter black hole you can dump normal
| matter into it to release energy, assuming some way
| exists to turn that into useful acceleration.
| nyssos wrote:
| An "antimatter black hole" is just a black hole. There
| might still be something behind the event horizon to
| annihilate with, there might not, the question might be
| meaningless, but in any case you're not getting anything
| back out again.
| User23 wrote:
| Don't have to get anything out just need to accelerate
| the singularity.
| ben_w wrote:
| It doesn't, at least not within currently understood
| physics:
|
| https://www.youtube.com/watch?v=cFslUSyfZPc
|
| You'll push the black hole with precisely the same
| momentum (in the opposite direction) as you yourself got
| from whatever device was pushing the matter towards the
| black hole.
| aetherson wrote:
| And hilariously useless even if you wave away the costs and
| catastrophic dangers. Yes, you can have a floor of normal
| matter and a ceiling of antimatter and produce... like... maybe
| 0.00001 m/s^2 of gravity?
| thsksbd wrote:
| And ludicrously energetically expensive.
|
| But that's science proposal writing, isn't it? Propose
| something that would be ludicrous even if it were physical.
| mr_mitm wrote:
| Ludicrous barely begins to describe the idea. It would have
| to be a mass on the order of magnitude of a moon that you
| would have to a) create and b) carry with you so that you
| would feel some gravity. Why not just build a rotating ring
| instead? No one in scifi was even entertaining this idea
| afaik.
| thsksbd wrote:
| "It would have to be a mass on the order of magnitude of a
| moon"
|
| Here I am overcomplicating things in terms of E=mc2, and
| you come and point out the obvious.
| Izkata wrote:
| > No one in scifi was even entertaining this idea afaik.
|
| Yeah, this is the first I've heard of it too. If it's not
| rotation it's usually left unexplained, and when it's not
| it's usually something along the lines of an artificial
| gravity generator that pulls things towards it, like in
| Star Trek the floors contain "gravity plating" that does
| that on a small scale.
| mr_mitm wrote:
| It's never wrong to confirm by experiment, but there was never
| really any doubt among professional physicists that antimatter
| falls down. Similar doubts are expressed about the feasibility of
| the warp drive by Alcubierre himself:
| https://twitter.com/malcubierre/status/362011821277839360
| OhNoNotAgain_99 wrote:
| [dead]
| marcosdumay wrote:
| I don't think anybody expects a wrap driver to be possible.
| It's just one of those odd things where the math says
| something, and it's well work looking at just in case. (Just
| like negative mass matter is something that nobody expects to
| exist, but likes to appear on equations here and there.)
|
| That said, I don't follow it closely, but didn't somebody
| recently worked out one that works without negative mass
| matter?
| distract8901 wrote:
| >That said, I don't follow it closely, but didn't somebody
| recently worked out one that works without negative mass
| matter?
|
| Yes. There was recently a few papers published showing that a
| static warp field is mathematically possible without negative
| energy. However, the field doesn't move or impart
| acceleration on its own. The best you can do is drag the warp
| field behind your ship with normal thrusters. Such a field
| seems to be pretty useless right now, but maybe that research
| will lead to something else in a few years
| stouset wrote:
| What exactly _is_ this "warp field", then?
| nathan_compton wrote:
| spacetime.
| lawlessone wrote:
| >The best you can do is drag the warp field behind your
| ship with normal thrusters. Ok we can build a warp
| trebuchet.
| distract8901 wrote:
| The static warp field doesn't allow you to go faster than
| light because it doesn't move relative to the generator.
| You can drag the field around at sublight speeds but
| that's about it.
|
| Though IIRC they played around with some different
| geometries that did move, but the energy required was
| many times more than the entire universe contains.
| I_Am_Nous wrote:
| Perhaps not useless, but definitely not as convenient as we
| hope warp technology will be someday. Could such a device
| be used as a way to improve thruster efficiency? If you can
| drag a large enough warp bubble with conventional
| thrusters, and it "slopes" space in front of you, could it
| make moving in the direction of the slope easier so you use
| less fuel?
| delecti wrote:
| It always seemed like a reasonable, but still big, assumption
| that antimatter behaved the same way under gravity. Anti-
| particles have opposite charge, so maybe it could have made
| sense that they have opposite "gravitational charge"? But also
| gravity doesn't _have_ "charge".
|
| So yeah, agreed. A good thing to confirm, even if (especially
| if) they expected the result to be unexciting.
| NoGravitas wrote:
| Even among people who hold out hope that a warp drive is
| physically possible (as opposed to merely mathematically
| possible), I don't think _anyone_ ever suggested that
| antimatter was a candidate for the negative mass required by
| the equations. It 's always been some kind of unobtainium.
| mst wrote:
| Agreed, though also I really appreciate this sort of "obvious"
| experiment, because the incentives really aren't set up to
| encourage it and we've been surprised often enough over the
| centuries that Actually Double Checking is probably something
| we should do more of.
|
| (there's a parallel here to 'more negative results' and 'more
| replications')
| mr_mitm wrote:
| Yes, nobody expected to find a positive cosmological constant
| either. Well except Steven Weinberg kinda.
| netbioserror wrote:
| Why would anti-matter be theorized to produce anti-gravity? I
| thought the "anti" part only amounted to charge or spin, with
| mass still being positive?
| Khoth wrote:
| I don't think anyone really expected antimatter to produce
| antigravity, but it had never been tested before so it was
| worth doing the experiment.
| raattgift wrote:
| One of the questions in physical cosmology is, "why is there so
| little antimatter/matter mixing in the cosmos?". We can measure
| the mixing by looking for the annihilation spectrum (e.g. e+ e-
| -> 511 keV/c^2, which for distant extragalactic sources should
| redshift with the expansion of space). We can produce lots of
| e+ (positrons) and other antimatter here in laboratories, and
| so have a fair chunk of the total annihilation spectrum. We
| also have the spectra of lots and lots of galactic objects
| (stars, neutron stars, and so forth) and spectra from
| extragalactic events large (neutral hydrogen clouds) to small
| (supernovae). There is essentially no sign of known matter-
| antimatter interaction.
|
| Our galaxy and other members of its cluster are, to high
| confidence, made essentially entirely of matter.
|
| We have not yet totally precluded distant isolated galaxy
| clusters made essentially of antimatter, but the cosmic ray
| spectrum (we see lots of particles that originate at
| cosmological distances) puts increasingly strong constraints on
| the distribution and density of such galaxies: there aren't
| many in total, there's no dense blob of them. The oldest
| galaxies that we can obtain spectra are also closer together,
| and each non-observation of annihilation spectral lines puts
| ever-tighter constraints on other old galaxies'
| antimatter/matter mix. It is fairly safe to bet that there is
| simply no significant blob of antimatter in the observable
| universe, and that what antimatter there is comes from nuclear
| decays and high-energy astrophysical processes, and all of this
| antimatter quickly annihilates spatially near where it's
| produced.
|
| However, that raises a trio of questions. (1) Did some process
| strongly disfavour the production of antimatter in the early
| universe, when hydrogen and helium was being produced in
| abundance? (2) if (1) is true, what is the nature of that
| process, and how could we see it experimentally? (3) if (1) is
| not true, where did all the antimatter go? There is an
| inversion of (3) as well: why didn't the disappearing
| antimatter take all the matter with it too?
|
| The above is the essence of "the missing antimatter problem" or
| "the matter-antimatter asymmetry problem" or "baryon asymmetry"
| <https://en.wikipedia.org/wiki/Baryon_asymmetry> (that last
| name is for technical reasons, including that there are lots of
| antineutrinos, anti-photons (which are just photons), and
| (somewhat complicatedly) anti-gluons and antiquarks [endnote 1]
| in our universe) and there is a substantial academic literature
| by experimentalists and theorists.
|
| A family of that literature explores the idea of _segregation_
| : matter and antimatter had similar abundances but were driven
| apart by some process in the early universe. The result is that
| there will be large (observable-universe-size-or-bigger)
| regions dominated by antimatter, and large regions (like ours)
| dominated by matter. But what is the nature of the process?
|
| A subfamily exploring that last question considers the
| possibility that the segregating interaction is gravitational;
| a sub-sub-family considers that a change of sign of quantum
| spin can generate a gravitational difference. One approach to
| this is to treat quantum spin as a generator of the spin tensor
| in a modification of General Relativity in which the spin
| tensor generates the torsion tensor. In General Relativity
| there is no spacetime torsion at all, so in "semiclassical
| gravity" where one adds quantum fields to General Relativity
| (e.g. as in Stephen Hawking's famous 1974 "Black hole
| explosions?") matter and antimatter gravitate identically.
| Introducing non-vanishing spacetime torsion can change the
| nature of black holes enough that black hole evaporation could
| be very different. And if one couples particle spin to torsion,
| one could distinguish a black hole created by significant
| antimatter from a black hole created by practically no
| antimatter, and we would expect that to show up in the spectra
| of active galactic nuclei (generated by supermassive black
| holes) and in the gravitational wave detections of black hole
| mergers and black hole-neutron star collsions.
|
| Apart from the lack of observational support (which one could
| sidestep by saying that there is basically no antimatter
| available to large black holes because it was all chased out of
| the observable universe by spacetime torsion effects), this
| quantum spin = spacetime torsion approach runs into a number of
| theoretical problems. The anti-hydrogen experiment that's the
| subject here adds a further problem that would need solving.
| Why would antimatter-matter gravitation today work differently
| from antimatter-matter gravitation in the early universe? If
| they work the same, then this experiment makes it unlikely that
| gravitational repulsin from torsion could solve the missing
| antimatter problem via _early segregation_.
|
| This antihydrogen result also imperils proposals for theories
| of quantum gravity wherein quantum spin (other than that of the
| graviton or its string equivalent) is gravitationally relevant
| (but not necessarily arising in that family of string theories
| especially to solve the missing antimatter problem, i.e., "our
| theory has a gravitational spin-antispin term in the action
| which we don't mind because maybe it's too small to matter or
| maybe if it's big at high energies (like in the hot dense early
| universe) it can solve a big problem like the missing
| antimatter problem", essentially).
|
| Finally, wikipedia has a so-so page which is at least
| reasonably accessible and equipped with a good references
| section:
| https://en.wikipedia.org/wiki/Gravitational_interaction_of_a...
|
| - --
|
| [1] https://profmattstrassler.com/articles-and-
| posts/largehadron...
|
| "The standard shorthand, "the proton is made from two up quarks
| and one down quark", is really a statement that the proton has
| two more up quarks than up antiquarks, and one more down quark
| than down antiquarks. To make the glib shorthand correct you
| need to add the phrase "plus zillions of gluons and zillions of
| quark-antiquark pairs." Without this phrase, one's view of the
| proton is so simplistic that it is not possible to understand
| the LHC at all." (for which see a later followup,
| <https://profmattstrassler.com/articles-and-
| posts/largehadron...>)
| Filligree wrote:
| People have tossed the idea around, and it makes sense to
| check, but I'm not aware of anyone who seriously thought it
| might have negative mass.
| pmarreck wrote:
| This has long been one of my justifications for the "maybe
| intelligent extraterrestrial pilot" theory of UFO's; now that
| theory is weakened...
| thsksbd wrote:
| Why did they think it would have negative gravitational
| attraction? I always thought it would be attractive mass and
| didn't realize that was to be proven.
|
| EDIT: now that I think about it, what are the implications for
| the "arrow of time" arguments?
| nyssos wrote:
| > Why did they think it would have negative gravitational
| attraction?
|
| They didn't. There are very strong theoretical reasons (among
| them, CPT symmetry) to expect antimatter to gravitate normally.
| But it's still good to actually check.
| mst wrote:
| > our greatest science-fiction hope for achieving warp drive has
| completely evaporated
|
| Damnit, "was completely annihilated" was Right. There.
| lend000 wrote:
| Take the following with a huge grain of salt:
|
| The controversial scientist Bob Lazar, the guy who made Area 51 a
| household name, put out a video when he first went public that,
| regardless of whether you think he's full of shit or not, is
| pretty interesting and better than most sci-fi in terms of
| explaining how an advanced vehicle might travel without
| propulsion and not be limited by the speed of light [0].
|
| His premise is that the strong nuclear force is a purely
| attractive sub-force of gravity that affects spacetime in the
| same way, and that there are heavier elements that were created
| in star systems with much more energy than our sun and its
| predecessors. These stable, high atomic weight elements
| (specifically element 115, which was synthesized and added to the
| periodic table much later) have large nuclei past a certain size
| threshold, in which the strong (gravitational) force reaches
| nonlinearly beyond the nucleus and can be amplified and focused
| (somehow?) into a gravitational wave that distorts spacetime. He
| claims that antimatter annihilation, also fueled by the same
| element, is the source of power for that amplification.
|
| [0] https://www.youtube.com/watch?v=b_Lre3B6SUQ
| empath-nirvana wrote:
| Wouldn't it be more interesting to learn real physics instead
| of made up stuff?
| ben_w wrote:
| Real physics requires ten simultaneous partial differential
| equations for the gravity, and 17 space filling complex-
| valued fields for the particles in the standard model, and
| they don't even work right with each other.
|
| Interesting to me, sure, but I'm enough of a nerd than in the
| team building exercise today where we all had to write a one-
| word summary of ourselves on a post-it note in secret, then
| guess which post-it corresponded to which person, even though
| we were all nerds and I wrote "nerd" on my post-it, everyone
| else immediately knew it was mine without any debate.
| withinboredom wrote:
| I enjoy fantasy physics more than regular physics by a pretty
| large margin.
| lend000 wrote:
| It's not like you or I are actually going to do anything
| based on our limited understandings of particle physics, so
| fortunately it's irrelevant. But I'm not one of those people
| who says every year that we understand everything (until next
| year when some updates come out and they reiterate their
| position).
|
| Contemplating why anything exists at all is much more
| interesting than inaccessible and incomplete particle physics
| anyway.
| moffkalast wrote:
| The only thing that real physics is good for is telling
| enthusiastic people that "ackchyually that's not possible
| because of these equations I won't bother explaining, trust
| me bro". Made up stuff wins every time.
| [deleted]
| DonnyV wrote:
| No warp drive, no artificial gravity. You really want to kill my
| morning. :-(
| FridgeSeal wrote:
| We truly live in the universe with most boring set of physical
| laws.
|
| Hard light speed cap, no anti-gravity, entanglement can't be an
| information channel, no warp drives. It's like we got stuck on
| the "no fun" setting hahaha.
| charred_patina wrote:
| If you like sci-fi, you should read the Three Body Problem
| series. I won't post any spoilers but the "no fun" setting is
| a plot point.
| asah wrote:
| Wait until you hear about the situation in the middle east...
| :-(
| tomrod wrote:
| I mourn that the sectoral conflict has resulted in yet more
| violence. People can live pluralistically -- it's been proven
| many times over to work well and in the best interest of all
| people involved.
|
| That said, it's pretty far removed from a conversation on
| antimatter.
| fabulous265 wrote:
| Even mathematically it doesn't make any sense: we would need to
| go to a causally disconnected region of spacetime to be able to
| go faster than the speed of light, but that's just not feasible.
| Once you go to that causally disconnected region of spacetime,
| the only outcome is to go to a singular point in space (even
| though you can go back and forth in time, theoretically at least)
| : if that sounds familiar to you, it's because it is well
| represented into the movie <<interstellar>> and indeed he goes to
| a region causally disconnected to ours: a black hole.
| jameshart wrote:
| If its intention was to illustrate realistic causal
| disconnection, _Interstellar_ does a pretty poor job.
|
| What with the causal loops and so on.
| outworlder wrote:
| So you don't think it's realistic that 'love transcends
| dimensions of space and time'? :)
| jameshart wrote:
| Or that the only thing standing between humanity and the
| ability to build space craft capable of colonizing other
| planets is getting the right numbers to plug into a
| 'gravity equation'?
|
| Having been sold on the movie by people telling me the
| science was "realistic"... the reality was disappointing.
| lordfrito wrote:
| > getting the right numbers to plug into a 'gravity
| equation'
|
| Those are what I like to call "load-bearing" numbers. :)
|
| There's so much science _daydreaming_ in what passes for
| the science press that people think all of our problems
| will be solved once the smart people (or quantum
| computers) find the magic formula and those elusive load-
| bearing numbers.
|
| Half the people here understand physics, and the sheer
| impossibility of the task due to the relative magnitudes
| involved, and have resigned themselves to "we better
| learn to live on this ball together as it's all we're
| ever going to have". The other half daydream about
| magical solutions that marvel movies tell us exist, we're
| just waiting for an Elon Musk or Tony Stark to discover
| it and then humanity enters a golden age.
| perihelions wrote:
| Related thread:
|
| https://news.ycombinator.com/item?id=37679584 ( _" Observation of
| the effect of gravity on the motion of antimatter (nature.com)"_;
| 68 comments)
| moomoo11 wrote:
| We should just build spaceships that are "tied" to a small planet
| or moon. Then just yeet that over massive distances.
|
| Imagine being an alien species and humans roll up pulling a small
| star or something.
| eppp wrote:
| Where do you get the energy to move that amount of mass?
| Xymist wrote:
| Start with a big planet. Orbit a gas giant, burn most of it
| for fuel to get up to sufficient speed that your relativistic
| mass exceeds that of what is left (and to stop yourself
| zooming off in the meantime) and then pull the remainder
| along with you.
| jackcosgrove wrote:
| I know there are a lot of hopes for warp travel, but doesn't it
| make more sense to decouple (most of) space travel from moving
| matter?
|
| To do this you need to decouple consciousness from bodies, which
| isn't possible with humans given that our consciousness grows
| along with our brains and everyone's structures are unique. But
| it is possible with artificial intelligence. Once consciousness
| has been digitized, you can beam it at the speed of light to a
| receiver.
|
| You still need to physically install the receiver somewhere,
| which is why I said only most of space travel could be non-
| physical. But once that receiver is in place, you can beam
| information to it and construct bodies onsite at minimal cost.
|
| This just seems like the kind of space travel the universe
| _prefers_ , since it minimizes action. Energy is for travel, and
| matter is for staying put.
|
| The stupendous amounts of energy required for warp travel just
| seem wasteful, when instead of adapting the universe to life we
| could adapt life to the universe.
| jvanderbot wrote:
| We need to let go of the "Ship full of brave men" meme of space
| exploration.
|
| It'll have to be robots, probably very small robots, some kind
| of solar sail / exogenous energy source (or maaaaaybe fusion?),
| and probably either a copy of some human's consciousness in a
| machine, or a bunch of fertilized frozen embryos, or both.
|
| And even then only after a lot of gene / tree bombing of the
| target planet to have any hope of making it liveable.
| Cthulhu_ wrote:
| A very believable theory is that this is how life on earth
| started - another ancient civilization shooting the building
| blocks of life everywhere and hoping something sticks.
| (panspermia?)
|
| But while this is cute, given the inexorable passage of time
| and entropy, any evidence that life was planted by ancient
| aliens has long gone. If it was e.g. a spaceship or meteor,
| it's been swallowed up by the earth and into the mantle by
| now.
|
| Unless there's a new source - like aliens making contact - it
| will remain unknowable.
| Maken wrote:
| You are essentially describing Clarke's Rama spaceship.
| jvanderbot wrote:
| Yeah - I don't think it's so clever that nobody has thought
| of it. It just seems obvious when you look enough into how
| hard inter-stellar travel will be.
|
| But making machines that operate for 100 years seems doable
| if we try.
| zzzeek wrote:
| how are you so sure that anyone else besides you is actually
| conscious ? you might be the only conscious being in the
| universe. the whole universe is yours. you've already traveled
| the entire thing.
|
| I'm conscious too but that's in my own universe, running in
| parallel to yours.
|
| the "once consciousness has been digitized" step would have
| many hurdles of similar complexity to meet before simplistic
| 21st century manipulation techniques would ever apply.
| tomrod wrote:
| > how are you so sure that anyone else besides you is
| actually conscious ? you might be the only conscious being in
| the universe. the whole universe is yours. you've already
| traveled the entire thing.
|
| Because other's express things that I in my wildest dreams
| couldn't have imagined.
|
| I think solipsism dies when epistemic humility comes into the
| picture.
| zzzeek wrote:
| i never really get the notion people sometimes have that
| consciousness arises from a specific, physically
| identifiable structure in the brain, where a person
| actually seems to have a "self", looking out of their eyes
| from inside their heads, and furthermore is "atomic" in
| that sense; it can't be split in half (because which half
| would the "self" be present in then?), yet there can exist
| no structure that produces the same output without the
| "they are looking out of their eyes from inside their
| heads" part.
|
| "self looking outside of my head" strikes me as so
| completely paradoxical that explanations such as each
| consciousness is its own universe seem just as plausible as
| any other. it does not mean the person you are talking to
| is not conscious, just that their consciousness is playing
| out in a parallel copied universe.
| I_Am_Nous wrote:
| In the past, this was understood to be the soul and you
| are correct when you describe it as atomic, though
| depending on which tradition is describing the soul it
| can have further attributes. My username is based on such
| a tradition -- the Nous (pronounced like noose) is
| considered the eye of the soul. Extrapolating that
| further, we focus the eye of our soul on whatever we want
| to, which can be ourselves, worldly aspirations, or
| spiritual aspirations.
|
| This would be considered the free will we are given at
| the basest level - we get to choose what we focus our
| soul on, and that can be changed at any moment. Such a
| tradition would say that since we are a body/soul
| composite, whatever we focus our soul on, our body
| willingly and immediately focuses on as well, for good or
| ill.
| tomrod wrote:
| I actually really enjoyed some of Sam Harris' "Waking Up"
| meditation series for this. Not a usual activity for me.
| However, I greatly enjoyed reflecting on the notion of
| "there is no self."
|
| [0] https://www.youtube.com/watch?v=CN-_zzHpcdM
| zzzeek wrote:
| Yes the "self" is an illusion, but at least for me,
| there's an _emergent_ illusion /whatever of "hey im
| inside this head looking out", which we claim arises from
| a physical brain structure. if this structure were
| divided in some way, does my current "self" vanish and
| two new consciousnesses arise? do those new
| consciousnesses have memory, so one is on one side of the
| room, the other is on the other ? at what point is my
| current "self" no longer viable such that it vanishes?
|
| edit: looks like HN is throttling me again. hmm but not
| edits. well that's fun
| tomrod wrote:
| Weird. Your comment came through just fine.
|
| I see your thought on emergence of self. Almost like self
| is equivalent to consciousness. Without a notion of self,
| you are part of a larger system with will.
|
| Stemming the claim that there is no free will, I know the
| argument, but don't agree to it as what we observe (that
| people make choices at least some of the time) goes
| against claimed theory (that our choices are random
| chemistry-driven outcomes based on state of the world).
| I'm not terribly deep in the area, though, and welcome
| correction or thoughts.
| dghughes wrote:
| Sounds like The Egg by Andy Weir
| http://www.galactanet.com/oneoff/theegg_mod.html
| bloopernova wrote:
| Never read that before, thank you for sharing, it's a great
| little story!
| dghughes wrote:
| Yeah it's a blast goes well with Isaac Asimov's The Last
| Question.
|
| Andy Weir also wrote The Martian.
| bloopernova wrote:
| I've just recently been reading Project Hail Mary, and
| enjoyed so much I'm on my 2nd re-read!
|
| The Martian is also great.
| qingcharles wrote:
| Two of my favorite sci-fi books of all time.
|
| Just found out Project Hail Mary movie is in pre-
| production...
| eternityforest wrote:
| We don't know for sure that AI would be conscious. Teleporting
| super intelligent zombies around isn't all that interesting.
| I_Am_Nous wrote:
| Here's the existentialism I was looking for :)
|
| I'm not sure how we can verify that empirically. Current LLM
| AI will hallucinate about the feelings it "has" and argue why
| it is a person, but only because it was trained on human
| language. The more human we make something seem, the more we
| blur the line until we might have a day where people upload
| their consciousness permanently without knowing if "they"
| will wake up inside the computer or just some copy of
| themselves that answers all the "don't kill me, I'm a real
| person" questions will wake up in the computer.
|
| Human software is still intrinsically tied to human hardware,
| so this seems like it would be far easier to create zombies
| than true humans, even if the checksum matches after an
| interstellar transmission.
| bluecheese452 wrote:
| Having my consciousness be trapped in a computer sounds
| terrifying. Like being completely paralyzed but still
| conscious.
| I_Am_Nous wrote:
| From a "future harm" perspective, if I have a full,
| functional backup of me somewhere, who's to say someone
| doesn't hack it down the line and torture copies of me?
| What's stopping an AI from torturing my backup because I
| didn't help fund AI research?
|
| Me never getting uploaded in the first place - that's
| what's stopping it :)
| moffkalast wrote:
| Well can you prove you're conscious? I'm just gonna assume
| you're not otherwise. That's the kind of benefit of the doubt
| we'll be giving AI apparently.
| leereeves wrote:
| > and construct bodies onsite at minimal cost.
|
| Once established, perhaps, but microchips aren't easy to build.
| You'd have to send a lot of infrastructure before you could
| create AI brains on another planet.
| zaptrem wrote:
| This is how interstellar travel worked in Altered Carbon.
| salawat wrote:
| I was a Traveller once, then I suffered a qbit flip in
| transmission the checksums couldn't compensate for. Now, I
| just love Coca-Cola brand Mango Fantastic soda, and hunting
| indigents for sport!
| jfengel wrote:
| A lot of people seem weirdly aggrieved by the limit of the
| speed of light. It's not really the reason we can't go to space
| -- if you had magic energy density you could go to the stars in
| as little time as you wish, due to relativity. (Weird stuff
| happens when you try to come back, but nobody ever seems to
| care about that anyway.)
|
| I think people hear "Einstein said you can't go faster than the
| speed of light" and think, "Surely I can figure out how to be
| smarter than Einstein". It appears to be parallel to the ones
| who get cranky when being told that Newton says you can't make
| a perpetual motion machine.
|
| I suspect that they don't spend as much time thinking about the
| brain-in-a-box version is that it opens up too many scenarios
| that are hard to think about. If you decouple consciousness
| from bodies, who are you? Why not make multiple copies? Why go
| anywhere at all, when you could just stick the sensors there?
|
| People really want the cowboys in space, and get aggrieved that
| somebody told them they can't. So they focus on overcoming a
| limit that seems like it can be solved just by thinking really
| hard, and leave the engineering details to the peons with
| calculators.
| api wrote:
| Agreed. Thing is we can still have our cowboys in space. The
| solar system is insanely huge and can be traversed in human
| time scales with technology based on known physics. The
| baseline world of The Expanse (minus the alien stuff) is
| entirely feasible.
|
| Interstellar travel is entirely possible too as long as you
| are okay with it being effectively a one way trip. Suspended
| animation is probably possible; we can do it to some animals
| and individual organs. So you go to sleep for a very long
| time and wake up in another star system. It would make the
| most sense to send a bunch of robots to build yourself a
| settlement first. Or alternatively send sentient AI which
| would find it much easier than humans to simply turn itself
| off for the duration of the trip.
| tgv wrote:
| Why would you put an AI on another planet? It's easier to
| transfer images and other data back here for everyone and
| everything to perceive.
|
| > construct bodies onsite at minimal cost
|
| That requires a bit more than a receiver. You'd have to build a
| robot factory, which requires energy production which requires
| mining which requires heavy machinery, which etc.
| btilly wrote:
| Reaction time and autonomy.
|
| Driving on Mars is incredibly slow in part because the signal
| has to get to and from us for every decision. And if
| communication is blocked for any reasons, the vehicle is
| stuck.
|
| AI on Mars fixes both problems.
| lloeki wrote:
| > the signal has to get to and from us for every decision.
| And if communication is blocked for any reasons, the
| vehicle is stuck
|
| Curiosity and Perseverance have a limited form of autonomy
| to work around that, as both can AutoNav: the former
| alternating standstill thinking and movement, the latter
| "thinking while driving".
|
| https://mars.nasa.gov/news/8980/nasas-self-driving-
| persevera...
| moffkalast wrote:
| That by itself isn't all that clever, since any half
| versed roboticist can do the same with some trial and
| error.
|
| What's seriously impressive about it is that it works in
| real time on an absolute brick of a 233 MHz PowerPC from
| the 90s. Like, an ESP32 probably outperforms it.
| ptha wrote:
| Apparently the Perseverance Mars Rover has some self-
| driving capability:
|
| _With the help of special 3D glasses, rover drivers on
| Earth plan routes with specific stops, but increasingly
| allow the rover to "take the wheel" and choose how it gets
| to those stops. Perseverance's auto-navigation system,
| known as AutoNav, makes 3D maps of the terrain ahead,
| identifies hazards, and plans a route around any obstacles
| without additional direction from controllers back on
| Earth._ [1]
|
| The mission has used AI not just for driving the rover, but
| also landing and targeting instruments. [2]
|
| [1] https://phys.org/news/2022-04-nasa-self-driving-
| perseverance... [2]
| https://www.enterpriseai.news/2021/02/19/perseverance-
| rover-...
| salawat wrote:
| >Perseverance's auto-navigation system, known as AutoNav,
| makes 3D maps of the terrain ahead, identifies hazards,
| and plans a route around any obstacles without additional
| direction from controllers back on Earth.
|
| ...in spite of this autonomy, Perseverence has a few
| major problems. It is famous for the severity of it's
| road rage and intolerance for human drivers, bicyclists,
| parked emergency vehicles, and pedestrians. Tests show a
| disturbing tendency toward "eliminating the human
| element" from it's driving environment to simplify route
| planning. The lengths the system will go to to achieve
| this were a major frustrator in early development, and
| initially attracting the interest of [REDACTION] for
| [REDACTION] due to [REDACTION] with an effective [THE
| REDACTION MACHINE IS BROKEN, FURTHER INQUIRIES SHOULD BE
| ROUTED THROUGH TOM].
|
| Mission planners at NASA found the risk involved with
| deployment to the Red Planet agreeable, but note that any
| ongoing colonization efforts will involve having to put
| the system down for the safety of any eventual colonists.
| ptha wrote:
| That's a slightly extreme route planning optimisation,
| but reminded me of UPS removing _left turns_ (in Right
| Hand Side driving countries like US) from their route
| planning to save fuel, lives, C02 emissions [1]
|
| [1] https://edition.cnn.com/2017/02/16/world/ups-trucks-
| no-left-...
| idiotsecant wrote:
| Our local system has a definite cap on processing power.
| Eventually it would be necessary to find more power to do
| more thinking.
| breuleux wrote:
| > But it is possible with artificial intelligence. Once
| consciousness has been digitized, you can beam it at the speed
| of light to a receiver.
|
| That may not remain true. The ability to serialize
| consciousness does not come for free, it requires extra wiring
| to carry all information out of the system or to stream it in,
| which is an intrinsic inefficiency. All other things kept
| equal, a brain's performance ceiling is higher if you only
| locally connect the units/neurons that need to be connected and
| nothing else, but in doing so you give up digitizability. It is
| entirely possible that future AI, in order to be performant
| enough, will lose the ability to be transmitted in the way that
| you describe.
| quickthrower2 wrote:
| Speed of light limit is a big problem though. How do you
| explore the universe if you can't catch up with it? Even with a
| Googol of human lifeforms running as AI spread out across it in
| a mesh, it is still expanding too fast!
| Udo wrote:
| This is a good argument for transhumanism. People seem to have
| a problem with the speed of light since without FTL, unmodified
| humans cannot meaningfully travel interstellar distances - and
| pop culture entertainment has surreptitiously sold us on this,
| if only because otherwise the timeframes and types of bodies
| involved would not be "relatable" anymore for the common types
| of drama we consume.
|
| _> Once consciousness has been digitized, you can beam it at
| the speed of light to a receiver._
|
| In principle yes, however, the energy required is still
| dramatic and bandwidth would probably still be a problem. It
| seems to me the default option would be to physically send non-
| aging transhumans, or virtualized/uploaded brains, or people in
| stasis (or a combination of these) using non-relativistic
| speeds.
| jackcosgrove wrote:
| > virtualized/uploaded brains
|
| That's a good point. Something about "never underestimate the
| bandwidth of a U-Haul carrying a bunch of tape drives."
| distract8901 wrote:
| It's been really weird seeing all these warp drive and
| antigravity people crawling out of the woodwork in response to
| this result.
|
| I have _never_ heard of antimatter proposed for _anything_ other
| than an energy source /storage. Not even in the oldest SciFi
| stories. Where did this idea even come from? It seems to have
| just appeared from nowhere as a way to feel bad about an
| otherwise inconsequential result.
|
| Very strange
| scionthefly wrote:
| Theoretical warp physics -- the real kind, like Alcubierre, not
| the Wesley Crusher kind -- proposes that a source of negative
| mass would be critical to the creation of a warp field.
|
| Antimatter as part of an energy storage system for propulsion
| is still a good idea. They'll just have to look elsewhere for
| that property, or modify the theory to work on different
| principles. Eric Lentz is working in that direction and doesn't
| think negative mass/energy is needed.
| empath-nirvana wrote:
| But we've seen anti matter and we already _know_ it doesn't
| have negative mass.
| distract8901 wrote:
| >Theoretical warp physics -- the real kind, like Alcubierre,
| not the Wesley Crusher kind -- proposes that a source of
| negative mass would be critical to the creation of a warp
| field.
|
| Well, yes, that's always been the crucial missing component
| from Alcubierre's design, but I've never seen anyone suggest
| antimatter would have negative mass or energy before now. The
| talk has always been about some hypothetical exotic matter
| jillesvangurp wrote:
| Not weird, just irrational. If warp drives were possible,
| aliens might be traveling to us before we'd invent them. That
| doesn't seem to be the case. There are a lot of explanations
| for that, including a few that involve conspiracy theories
| where this did in fact happen but we are being kept in the dark
| about it. But the easiest one would be that it hasn't happened
| because it isn't possible. Faster than light travel not being
| possible, it's unlikely for there to be a coincidence of any
| other intelligent species to exist within tens/hundreds of
| light years of our tiny little corner of the universe exactly
| at the moment where we hit enlightenment, steam machines, and
| rocketry in the time frame of about 250 years. Never say never
| of course but it does sound astronomically unlikely when you
| put it like that.
|
| In the absence of any nearby aliens to travel to, what exactly
| is the value of traveling at warp speed to some desolate bit of
| universe? We'd get nowhere a lot faster is about the most
| positive thing you could say about that. Most sci-fi is
| premised on the notion that we're not alone and that there is
| this wealth of interactions (good and epically bad) to be had
| on the far side of any worm hole that we travel through at warp
| speed. But we have zero proof of that nor a way to travel in
| such a fashion. Or even the confirmation of the possibility of
| being able to do so. Fantasy and reality are not really aligned
| here.
| deafpolygon wrote:
| Looks like we're gonna have to bet on Spore drives.
| timbit42 wrote:
| What about jump drives in Battlestar Galactica?
| pelorat wrote:
| Well, yeah, anti-matter is not negative matter, it's more like
| mirror-matter. Negative energy and negative matter probably
| doesn't exist in our universe. Negative matter would require an
| anti-photon that could in theory cause energy to be destroyed if
| it interacted with a regular photon.
|
| There are four types of matter, of which two are theoretical:
| positive-matter, positive-anti-matter, negative-matter, negative-
| anti-matter. Only the first two exist in our universe as far as
| we know.
| dghughes wrote:
| >the only requirement was something that anti-gravitated:
| something like "negative energy"
|
| A bit more than that. Didn't it also require the energy
| equivalent to the output of a small star?
| pmarreck wrote:
| Honestly, this does sound like an intimidatingly high amount of
| energy, but look at the progress of computational power since,
| say, 1973, 50 years ago. If the same advances in physical
| control of energy had taken place, who knows where we'd be
| today
| ben_w wrote:
| I'm not sure how many USD/GFLOPS you could get in '73, but in
| '84 they were Cray X-MP/48 costing $15,000,000 / 0.8 GFLOPS
| (inflation adjusted $600B/TFLOP); today we get RX 7600
| costing $269/21.5 TFLOPS ($12.51/TFLOP).
|
| If energy prices changed that much while spending per year
| remained constant, your usage would go up by a factor of
| about 48 billion. This might happen if we develop Von Neumann
| probes and disassemble a planet to turn it into energy
| collecting satellites, and some not-even-crazy estimates
| suggest this is indeed possible over 50 years.
| WJW wrote:
| The problem with that comparison is that we are not even
| close to the theoretical limits for computational density,
| while we are quite close to the limits for efficiency in
| things like turbines.
| arethuza wrote:
| The Tsar Bomba (5.3YW) managed about 2% of the power output of
| the Sun (384YW) - admittedly not for very long though...
|
| So Teller's _Sundial_ design was aimed at 10Gt so ~200 times
| more than the Tsar Bomba as tested.
|
| So Sundial's peak power output would perhaps have been roughly
| 1RW?
|
| Edit: Maybe you power the Warp drive with a sequence of
| Sundials.... in a sort of Orion like approach? :-)
|
| Edit2: So about a billion Sundials a second and you're good to
| go?
|
| Edit3: Usual upper limit of yield per mass is about 6Mt per t -
| so a Sundial would be about 1500t. So that would be burning
| about 1.5 Tt of bombs a second?
| api wrote:
| > The Tsar Bomba (5.3YW) managed about 2% of the power output
| of the Sun (384YW)
|
| TIL
|
| You know what's even more amazing/frightening? There is no
| power limit for hydrogen bombs. You could take a bomb like
| the Tsar Bomba or Castle Bravo and _use that as a blasting
| cap to trigger an even larger fusion stage_. ... and on, and
| on, in a vast nested turducken of kaboom.
|
| One of the ideas to deflect a planet killer asteroid would,
| if we had time, be to land there and build a base and
| assemble such a mega-bomb deep underground.
| arethuza wrote:
| "There is no power limit for hydrogen bombs"
|
| Edward Teller (who else) got there first!
|
| https://blog.nuclearsecrecy.com/2012/09/12/in-search-of-a-
| bi...
|
| A 1Gt primary (Gnomon) igniting Sundial to give 10Gt.
| NoMoreNicksLeft wrote:
| Can you only bump it an order of magnitude per stage
| though? Seems inefficient.
|
| Sounds like one of the defense contractor MBAs got ahold
| of the plan.
| arethuza wrote:
| I suspect that limit might be because a Sundial would be
| physically huge - 1500t or so.
| lttlrck wrote:
| "turducken" never heard of it and what a perfect word in
| this context LOL!
|
| https://en.m.wikipedia.org/wiki/Turducken
| dboreham wrote:
| The 3D version of turtles.
| CamperBob2 wrote:
| _One of the ideas to deflect a planet killer asteroid
| would, if we had time, be to land there and build a base
| and assemble such a mega-bomb deep underground._
|
| Problem: Giant-sized asteroid on collision course with
| Earth
|
| Solution: Build giant bomb and nuke it
|
| Problem: 843 medium-sized radioactive asteroids on
| collision course with Earth
| ben_w wrote:
| Hawking wrote in A Brief History of Time:
|
| > John Wheeler once calculated that if one took all the
| heavy water in all the oceans of the world, one could build
| a hydrogen bomb that would compress matter at the center so
| much that a black hole would be created
| ben_w wrote:
| Depending on the model, anything from the mass-energy of a few
| tons to several times the universe.
|
| Apparently a few models work with positive mass, but I'm
| reading headlines for that, I can't follow field equations.
| NoMoreNicksLeft wrote:
| That's just a scaling issue.
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