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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

#21

Post by MattPalmer1086 »

treeman79 wrote: post #4
btilly wrote: post #2

If you believe in the Everett Interpretation, then he is wrong. The Everett Interpretation, aka Many Worlds, holds that both observer and observed are quantum mechanical systems. From this it follows that the act of observation does not produce a "collapse", but it does separate the observer into multiple observers that can't interact with each other again. So Schrödinger's cat is in a superposition of alive and dead…

Where would energy come from for creating each universe?

Why would it necessarily require any energy?

Energy is what we have to expend to effect change within a universe. There may be no requirement for energy to split into a branching multiverse.

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

#22

Post by CraftingLinks »

edgyquant wrote: post #12
btilly wrote: post #2

If you believe in the Everett Interpretation, then he is wrong. The Everett Interpretation, aka Many Worlds, holds that both observer and observed are quantum mechanical systems. From this it follows that the act of observation does not produce a "collapse", but it does separate the observer into multiple observers that can't interact with each other again. So Schrödinger's cat is in a superposition of alive and dead…

Why would anyone believe such a thing?

Because that's what quantum mechanics in it's purest form tells us. Avoiding the many worlds requires tagging on extra stuff not in the equations.

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

#23

Post by AnimalMuppet »

Somewhat off topic, and somewhat related: I don't think there actually is such a particle as a graviton.

General relativity says that you can't tell the difference between being unaccelerated, and being in free fall. But in one case you have no gravitons coming in, and in the other you have gravitons. I can change whether gravitons are there or not by a (general) relativistic transformation.

But that's not possible. Either the gravitons are there, or they aren't. There's not two sets of reality of what particles exist for two different coordinate systems.

Therefore gravitons don't exist. The bending of spacetime is what's really going on, and there is no quantum version of the gravitational field. (Except possibly that the bending of spacetime could be quantized, but that's not what we mean by a graviton.)

I am very open to being shown to be wrong here. Can anyone do so?

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

#24

Post by sandworm101 »

outlace wrote: post #6
sandworm101 wrote: post #3

>> Jonathan Oppenheim, who runs a program exploring post-quantum alternatives at University College London, suspects that’s because gravity simply can’t be squeezed into a quantum box. So... he is still part of the Orthodoxy. He is challenging ideas, but as an employee of University College London he is hardly any sort of outsider to the physics community.

Genuine question here, when was the last time a total outsider made a significant contribution to physics?

https://en.wikipedia.org/wiki/STEVE

https://en.wikipedia.org/wiki/Subauroral_ion_drift

Not exactly the discovery of a new quark, but it triggered realworld research into the cause of the phenomena. That qualifies as contribution imho.

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

#25

Post by lavelganzu »

treeman79 wrote: post #4
btilly wrote: post #2

If you believe in the Everett Interpretation, then he is wrong. The Everett Interpretation, aka Many Worlds, holds that both observer and observed are quantum mechanical systems. From this it follows that the act of observation does not produce a "collapse", but it does separate the observer into multiple observers that can't interact with each other again. So Schrödinger's cat is in a superposition of alive and dead…

Where would energy come from for creating each universe?

The question is a misunderstanding. In the pure wave (Everett) interpretation, there are no universes being created when the wave function branches. Rather, different regions of the wave function become separated (decohered) from each other. https://physics.stackexchange.com/questions/41588/many-world...

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

#26

Post by srejk »

weatherlight wrote: post #13
srejk wrote: post #7

Earlier quoted context omitted.

You have to be trained in physics to theorize about it. Thinking otherwise is the realm of the crackpot. https://www.youtube.com/watch?v=11lPhMSulSU

I love Dr. Collier's videos. Her method of story telling/video essay is extremely unconventional but very effective.

Me too bestie, I haven't taken physics since undergrad but I appreciate that it's a layer of understanding above popular science (that never covers any of the math) while remaining accessible.

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

#27

Post by captainclam »

treeman79 wrote: post #4
btilly wrote: post #2

If you believe in the Everett Interpretation, then he is wrong. The Everett Interpretation, aka Many Worlds, holds that both observer and observed are quantum mechanical systems. From this it follows that the act of observation does not produce a "collapse", but it does separate the observer into multiple observers that can't interact with each other again. So Schrödinger's cat is in a superposition of alive and dead…

Where would energy come from for creating each universe?

I think this question stems from a fundamental misunderstanding of the Everett interpretation...the idea of "many worlds" (a phrase I do not favor specifically because of this very misunderstanding!) evokes this imagery of an entirely new universe BURSTING forth dramatically upon the collapse of the wave function, and as an entirely new universe is "created," the amount of extent energy is literally doubled (or multiplied by many times more). Indeed, where does this energy come from?

What the Everett interpretation suggests is that in the same way you are comfortable with the function f(x)=y having (infinitely) many values (you don't HAVE TO choose an x, ie the function doesn't collapse), the wavefunction simply is what it is and doesn't collapse either. What we observe as the collapse of a function is simply an artifact of being a conscious being that can only observe one value of the of the wavefunction at any particular moment.

None of these unique values (observables) of the wave function can interact with each other (in the same way the value of x=2 doesn't "interact" with the value of x=8 for f(x)=y), so energy cannot be gathered or duplicated at any particular point of the wave function, so this energy creation/duplication is no issue.

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

#28

Post by slowmovintarget »

btilly wrote: post #2

If you believe in the Everett Interpretation, then he is wrong. The Everett Interpretation, aka Many Worlds, holds that both observer and observed are quantum mechanical systems. From this it follows that the act of observation does not produce a "collapse", but it does separate the observer into multiple observers that can't interact with each other again. So Schrödinger's cat is in a superposition of alive and dead…

In Everettian Mechanics, decoherence occurs long before the box is opened. The photons in the box interact with the cat. That entanglement with the environment which causes the branching of the wave function occurs then.

The observer that opens the box is already either in a branch where the cat is asleep (to borrow from Sean Carroll) or awake.

The interesting thing to come to understand is that probability doesn't actually seem to exist as a real feature in the universe. Rather, probability is a measure of what observers believe they will or are seeing. Probability, in Everettian Mechanics, is about perception of the universe, not a feature of the universe itself.

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

#29

Post by FollowingTheDao »

The basic misunderstanding is that "things" exist as particles, and the Planck limit, IMHO, proves that everything is a wave and the Planck length is the smallest wavelength, or resolution, that any particle (certainty) can exist.

Fundamentally, all matter is uncertain.

The problem physicists have is that they are trying to align classical psychics with quantum physics when it is quantum physics all the way down. You cannot use quantum physics to describe classical physics because classical physics is only our minds collapsing the quantum universe so we can, well, exist.

To me, gravity is a side effect of quantifying. A byproduct of our brains collapsing wave functions.

A wave is a probability of a particle. Our minds create certainty out of a probability, that is, our minds collapse the wave function. We need to be certain of gravity, since it is a risk to our survival is we do not.

Space-time itself is a collapse of the quantum field and it is through this collapse that gravity is "observed" or "felt". With out particles, no gravity, with out wave collapse, no particles. Therefor wave collapse creates gravity.

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