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A physicist who bets that gravity can’t be quantized

quantamagazine.org

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Re: A physicist who bets that gravity can’t be quantized

#301

Post by ImHereToVote »

ethn wrote: post #300
hughesjj wrote: post #175

Earlier quoted context omitted.

I'm definitely into the "it's an emergent phenomena" camp. I think it's inherently relational, as that's a more efficient way to encode geometry rather than space itself being a quantized "thing". Afaik this theory is the "leading"/imho most promising theory of "quantum gravity", that being the "gravity = entanglement" conjecture and the related ideas of "Complexity= action/volume/whatever" that susskind and many oth…

It's not relational. There's several rigorous proofs against Spinoza's relational theory. Namely that of Kant and Einstein: "even if space is composed of nothing but relations between observers and events, it would be conceptually possible for all observers to agree on their measurements, whereas relativity implies they will disagree" [0] 0: https://en.wikipedia.org/wiki/Relational_space

Unless one of the observers accelerates for some reason. Now his observation is privileged.

Re: A physicist who bets that gravity can’t be quantized

#302

Post by zmgsabst »

drdeca wrote: post #275
zmgsabst wrote: post #271

Earlier quoted context omitted.

How is it a cop out? We know two things: - universe was small enough everything was tightly coupled - non-local phenomena occur Insisting that our beliefs reflect an ideology (eg, you can segregate off portions of reality to study in isolation) which seem contrary to observed reality (eg, the points above) is religion — not a scientific investigation of the universe.

First, as a religious person: no, contrary to what you seem to be saying, dismissing superdeterminism isn't "religion". Second, dismissing superdeterminism is not, as you seem to say, "contrary to observed reality". The belief that one is capable of forming ideas that bear any resemblance to reality, is justified on account of, in order for one's beliefs or lack-thereof to have any use, it would have to be true. Thin…

Except that, we know such macro correlations exist — for the two reasons I outlined.

We know that the universe was once highly correlated, due to its size, and we know that such correlations form super-macro structures, from galaxies to filaments. We further know that knots in the wave equation are a non-local phenomena, such as with anyons. The minimal assumption is that any particle we encounter is part of such a non-local phenomenon.

To assume that we can isolated regions of reality uncorrelated to those two phenomena is to assume an ideological belief, unsupported by evidence.

That you didn’t discuss my actual objection to dismiss it with generalities is very telling.

Re: A physicist who bets that gravity can’t be quantized

#303

Post by _a_a_a_ »

lamontcg wrote: post #209
_a_a_a_ wrote: post #67

Earlier quoted context omitted.

90 mg... that is beyond gobsmacking

I honestly can't tell if you're impressed we've measured the gravitational interaction of something that small, or staggered by our inability to measure a feature of things so large that you can easily hold them in your hand.

"The current best estimate for the mass of Earth is M⊕ = 5.9722 × 10^24 kg" (wiki) so ~6 × 10^27 grammes, so 90mg ~ 28 orders of magnitude smaller. So very, very much the former.

Re: A physicist who bets that gravity can’t be quantized

#304

Post by kgwgk »

consilient wrote: post #221
kgwgk wrote: post #196

Earlier quoted context omitted.

> But they'll induce decoherence in the same way as a human, yes. From the perspective (?) of the (non-human) thermal bath, will that decoherence result in a single (diagonal, mixture) state or in a particular state of those N separate states that would "look classical"? Decoherence doesn't make things "look classical" by itself - at least until you define what "looking" is.

Depends on whether you're talking about the "perspective" of the whole joint |Rock>|Interaction Eigenstate 1> + |Rock>|Interaction Eigenstate 2> ... system or just one of its components. > Decoherence doesn't make things "look classical" by itself - at least until you define what "looking" is. Of course; but that's true of every scientific theory. Decoherence solves the preferred basis problem, not the hard problem o…

> Decoherence solves the preferred basis problem, not the hard problem of consciousness.

Ok, I guess I misunderstood the scope of "There's also nothing special about observing."

It's not clear to me if you (MWI) would say that rocks had defined positions when nobody was observing them - or whether the question of things having definite positions (and the very existence of those things) wouldn't even make sense in the absence of consciousness.

Re: A physicist who bets that gravity can’t be quantized

#305

Post by eigenspace »

scrubs wrote: post #288
eigenspace wrote: post #98

Earlier quoted context omitted.

It's pretty general. Just draw the worldlines for some particles bouncing off eachother, and then perform a Lorentz boost, which means choosing a new tilted spatial surface to intersect the worldlines. If you perform a boost, then the spatial surface intersect fewer or more worldlines, and worldlines which were for particles in one frame can become antiparticles in another. Consider an electron absorbing a photon at…

That example I think is tangential. The better example is free fall in a gravity well v. being accelerated up like in an elevator in space far, far away from gravitational sources

They asked for an example with Lorentz boosts, so only inertial frames.

Re: A physicist who bets that gravity can’t be quantized

#306

Post by SpaceManNabs »

HardlyCurious wrote: post #253
mr_toad wrote: post #246

Earlier quoted context omitted.

General relativity requires singularities, QM prohibits them. It’s a puzzle.

Singularities aren't believed to be real by physicists to my understanding. Which if true, would mean the existence of them in GR is an error of the formulation or an error of comprehension. If you look at the tangent lines facing toward the middle of the torus they would point to a single middle point, a singularity. But if you follow those lines around the surface they would never get to that extrapolated point of…

Singularities arent real in what sense? You can deal with some with penrose diagrams and other tools is what you mean?

Re: A physicist who bets that gravity can’t be quantized

#307

Post by guerrilla »

consilient wrote: post #129
guerrilla wrote: post #102

Earlier quoted context omitted.

I was told that this is exactly what the Bekenstein bound ultimately means. It seems reasonable to me, but then why is that not conclusive? Also if anyone who knows wants to explain why the Bekenstein bound is even a thing, I'd love to hear that too.

Exceeding the Bekenstein bound would mean having less-than-equilibrium free energy. See https://arxiv.org/abs/1802.07184

Hmm so that would be a system being out of equilibrium but in a "negative" direction, which is nonsense since any amount of non-equilibrium is a positive amount of free energy.

So, I don't understand any of the math in that paper but is there any easy/intuitive way to explain why a higher information density would require negative free energy?

I guess I need to understand the relationship between information density and free energy first. Hmm.

Re: A physicist who bets that gravity can’t be quantized

#308

Post by SpaceManNabs »

richardw wrote: post #259
XorNot wrote: post #248

Earlier quoted context omitted.

Keep in mind in GR singularities don't really make sense either: i.e. when you pass the event horizon of a black hole, under GR the rules say that you must always been traveling towards the singularity. But the corollary of this is that it's not actually possible - mathematically - to arrive at the singularity (because then you'd be moving parallel with it rather then towards it). So while we can define what happens…

Can they reach the center? And how long would that take? I ask because time will slow down for them as they accelerate towards the center.

Time doesnt slow down for them. They reach the center in their time as normal. We never see them reach the center.

You can use kruskal coordinates and other tools to understand this.

Re: A physicist who bets that gravity can’t be quantized

#309

Post by astrange »

naasking wrote: post #281
astrange wrote: post #274

Earlier quoted context omitted.

That would be very fine indeed since the CMB doesn't eg seem to be pixelated and we don't observe numeric instability anywhere.

I wouldn't even assume that discrete theories must have a resolution that can be detected.

Any amount of quantization should have very noticeable indirect effects somewhere. Try implementing game physics and you'll see it.

Re: A physicist who bets that gravity can’t be quantized

#310

Post by GoblinSlayer »

mr_toad wrote: post #246
chownie wrote: post #229

Earlier quoted context omitted.

Is that not what it does?

General relativity requires singularities, QM prohibits them. It’s a puzzle.

General relativity requires infinite time for singularities to form. Fully formed singularity is a mathematical construct which is assumed into existence, it doesn't correspond to anything physical.
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