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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

#181

Post by FollowingTheDao »

eigenket wrote: post #159
FollowingTheDao wrote: post #153

Earlier quoted context omitted.

I’m giving you a hypothesis about the reason why the Planck length exists as a constant. Below Planck length there is no length, time, mass, or temperature. All of those things are given “reality” by our mental process.

That is certainly a hypothesis, but there is no evidence for it.

Hey, I’m no Einstein, but even he had hypothesis that took decades to be shown evidence to prove they were true.

I don’t know how someone is supposed to come up with evidence before a hypothesis, but if you have a new understanding of the scientific process Please let me know.

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

#182

Post by nocoolnametom »

bowsamic wrote: post #46
phkahler wrote: post #35

Earlier quoted context omitted.

>> It’s already obvious that a quantum theory of gravity is needed because we need a way to talk about superpositions of spacetime curvatures. Is that because of things like the double slit experiment they mention? A particles could be monitored via its gravitational effect on spacetime to determine which slit it went through. What if the particles mass behaves as a mass distribution in such an experiment? Does that…

The problem is that it doesn't act like a mass distribution, it acts as two non spatially overlapping possibilities. I think that the only way to save classical gravity would be superdeterminism. If quantum states correspond to anything other than our ignorance, i.e. if superposition states are actual physical states of reality, then gravity will need to be quantum.

When you say superdeterminism are you referring to something like Pilot Wave theory, where what appear to our measurements as probabilistic yet random interactions are merely expressions of a more complex yet non-random underlying system that we cannot, as yet, measure? (I don't even know if that's the proper description of the hypothesis.)

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

#183

Post by eigenket »

consilient wrote: post #163
eigenket wrote: post #146

Earlier quoted context omitted.

I attended a talk by Jonathan Oppenheim a while back on this subject, and my understanding based on that is that in his model something (very) roughly like this happens. You put your massive object in superposition, it interacts with space-time and "tries" to put space-time in superposition but since space-time is fundamentally classical (in his model) what happens is space-time ends up in a probabalistic mixture of…

Seems like this would show up as an equivalence principle violation, no?

That isn't obvious to me - the equivalence principle works fine in classical GR, I'm not sure why it would break in Jonathan's model, but I'm very far from qualified to speak authoratively about his work!

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

#184

Post by kgwgk »

consilient wrote: post #155
kgwgk wrote: post #144

Earlier quoted context omitted.

Is it possible to observe anything at all in MWI? If yes, what does it mean to "observe something" in MWI? If not, is there any physical content in MWI?

Observations in MWI are just ordinary physical interactions. Specifically they're perturbative-regime interactions between the thing being observed and large thermalized systems (e.g. humans). From the perspective of the thermal bath, you get exponential suppression of everything but the eigenstates of the interaction Hamiltonian, which is why our observations "look classical".

Will other large thermalised system (e.g. rocks) also experience observations that "look classical"?

Another MWI proponent here is talking about how the "look classical" thing is "simply an artifact of being a conscious being that can only observe one value".

Is there something special about "large thermalised systems" (and/or humans)? How large have they to be to allow for "our observations"? Where is the boundary between the thing being observed and the observing thing?

MWI seems to still face most of the difficult questions - it not all.

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

#185

Post by kromem »

In the decades since the establishment of these theories, both the continuous (classical) spacetime of general relativity and discrete matter of quantum mechanics, the world has changed in rather significant ways.

One of those has brought forth advances in technology which led to creating virtual world geometry with continuous function derivation which then gets converted into discrete voxels in order to track state around free agent interactions.

Often, to save memory these systems only convert to voxels when the free agent is observing or has interacted with the relevant geometry.

We sit in a massive universe that we can observe but cannot interact with over 99% of because it's expanding away from us faster than the speed limit of local information from us to it.

Within the local area where we can interact with things, they behave as if continuous until free agents interact with them when they appear to collapse to discrete units, but if the information relating to those interactions is erased, they go back to behaving as if continuous.

Maybe the relationship between apparently continuous spacetime and quantized matter is much simpler than it seems to those ignoring what's currently being built within the world they are studying so closely.

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

#186

Post by consilient »

FollowingTheDao wrote: post #180
consilient wrote: post #173

Earlier quoted context omitted.

It's not a constant, any more than the meter or the foot. It's just part of a unit system that happens to be convenient for carrying out certain calculations.

I have questions about your understanding. Or maybe it is a problem with my communication. There is a planck constant. https://en.m.wikipedia.org/wiki/Planck_constant

Planck's constant is not the Planck length.

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

#187

Post by TeMPOraL »

jacquesm wrote: post #179
brianpan wrote: post #172

Earlier quoted context omitted.

I think if it's point sized, you're allowed to imagine any shape of cat. :D

For a uniform gravity field it is essential that the cat is spherical.

It's also crucial that the point-sized spherical cat is not spinning, because that's a quick way to get a ring-shaped cat.

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

#188

Post by eigenket »

FollowingTheDao wrote: post #180
consilient wrote: post #173

Earlier quoted context omitted.

It's not a constant, any more than the meter or the foot. It's just part of a unit system that happens to be convenient for carrying out certain calculations.

I have questions about your understanding. Or maybe it is a problem with my communication. There is a planck constant. https://en.m.wikipedia.org/wiki/Planck_constant

The Planck length and Planck's constans are both named after Max Planck. That doesn't mean they're the same thing. The Max Planck Institutes are also named after Planck, but they are neither lengths nor constants.

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

#189

Post by amelius »

javajosh wrote: post #81
amelius wrote: post #74

Earlier quoted context omitted.

Refraction is well understood. It is caused by interactions of the incoming wave and electron clouds of atoms. https://en.wikipedia.org/wiki/Ewald%E2%80%93Oseen_extinction...

Ah, perhaps you are inclined to stop reading when you come across open parenthesis?

Ok, I confess that I didn't read the entire comment. But you have a second problem, as you should explain why the conventional explanation does not hold or is canceled by your theory.

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

#190

Post by kromem »

317070 wrote: post #140
FollowingTheDao wrote: post #113

Earlier quoted context omitted.

I wish any of you with the down vtes would at least have a conversation with me...

> our minds collapse the wave function While I know there are many sources available of people saying this exact thing, this is a common misunderstanding of the Copenhagen interpretation of quantum physics. There is nothing special about our minds.

I'm curious why you think the commenter is interpreting according to the Copenhagen interpretation?

It sounds more like they are working within a view similar to the Von Neumann–Wigner interpretation.

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