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New theory claims to unite Einstein's gravity with quantum mechanics

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Re: New theory claims to unite Einstein's gravity with quantum mechanics

#181

Post by maaaaattttt »

jerf wrote: post #125
maaaaattttt wrote: post #28

This is a question I've been asking myself (probably due to a lack of understanding and knowledge) and this theory seems to hint at something similar: why do we assume spacetime to be homogenous in its nature? Here they seem to say that on some quantum level spacetime could vary drastically. Couldn't then dark matter be explained by some variations on a large scale? Like giant "wrinkles" in spacetime? They would then…

"Here they seem to say that on some quantum level spacetime could vary drastically." This is not a result of this theory. Our best current theories say this too: https://en.wikipedia.org/wiki/Quantum_foam Spacetime getting distinctly different at very small scales is a vital part of all modern theories and I doubt it's going away. Even if spacetime is shown to be continuous itself, which I tend to personally doubt [1…

Thank you for the link to cosmic strings! This is actually exactly what I had in mind when, as you quoted, I was mentioning wrinkles and “black trenches”.

So, you don’t think structures like galaxy superclusters are a second hand visualization of the existence of cosmic strings? I know these formations could be explained by the effect of gravity of just visible matter. But maybe it’s both. Like a valley could exist because of a river and a river could exist because of a valley.

Since this concept has been around for so long I have some reading to do to understand why cosmic strings are not a possible explanation for dark matter. To me high density and invisible fit the bill for dark matter quite well.

Edit: never mind, continued reading the article and saw this

> in the past it was thought that their gravity could have been responsible for the original clumping of matter into galactic superclusters. It is now calculated that their contribution to the structure formation in the universe is less than 10%.

Re: New theory claims to unite Einstein's gravity with quantum mechanics

#182

Post by layer8 »

a_cardboard_box wrote: post #147
Timeroot wrote: post #123

Earlier quoted context omitted.

(I went to a talk by Oppenheim author a couple weeks ago on this topic.) The idea is that gravity, as a force, only operates classically. More precisely: there is a classical state describing the curvature of space time, and then a quantum state describing the configuration of particles on that spacetime. But then, that quantum state needs to affect the classical state again (mass bends space), which would usually le…

If this hypothesis is true, would it give us a way to distinguish many-worlds vs. wave function collapse? If the many "worlds" are all interacting with a single classical spacetime, we should be able to measure the gravity of other worlds, right? I'm not a physicist, but that sounds a lot like dark matter to me.

There is no implication that the classical spacetime wouldn’t still split into branches, possibly with different variations in the stochastic effect from each other.

Re: New theory claims to unite Einstein's gravity with quantum mechanics

#183

Post by selfmodruntime »

mr_mitm wrote: post #65
szundi wrote: post #19

Earlier quoted context omitted.

Untestable theories are not theories - I mean, for what purpose and why care?

Some theories are only untestable for practical reasons, like needing a particle accelerator the size of the solar system. That doesn't make them unscientific or "not theories". That is not the kind of falsifiability that Karl Popper had in mind.

Do you have any examples? I‘d to read up!

Re: New theory claims to unite Einstein's gravity with quantum mechanics

#184

Post by nabakin »

bjornsing wrote: post #138
yathaid wrote: post #33

The article mentions the 5000:1 odds bet, but reading the text of the bet itself is hilarious: >>> Whereas Carlo Rovelli and Geoff Penington firmly believe that gravity is better described by a quantum theory. >>> And whereas Jonathan Oppenheim is more sympathetic to other possibilities (i.e. doesn’t have a clue) ... [1] - https://www.ucl.ac.uk/oppenheim/pub/quantum_vs_classical_bet...

Interesting that three so obviously intelligent people could get the odds of the bet wrong: it’s not a 1:5000 bet, it’s a 2:5000 bet a.k.a. a 1:2500 bet.

I don't think so. It's 5000 from each loser and there are two potential losers so 5000*2=10000 and 2:10000 is the same as 1:5000.

Re: New theory claims to unite Einstein's gravity with quantum mechanics

#186

Post by a_cardboard_box »

a_cardboard_box wrote: post #147
Timeroot wrote: post #123

Earlier quoted context omitted.

(I went to a talk by Oppenheim author a couple weeks ago on this topic.) The idea is that gravity, as a force, only operates classically. More precisely: there is a classical state describing the curvature of space time, and then a quantum state describing the configuration of particles on that spacetime. But then, that quantum state needs to affect the classical state again (mass bends space), which would usually le…

If this hypothesis is true, would it give us a way to distinguish many-worlds vs. wave function collapse? If the many "worlds" are all interacting with a single classical spacetime, we should be able to measure the gravity of other worlds, right? I'm not a physicist, but that sounds a lot like dark matter to me.

Answering my own question based on Oppenheim's lecture[1]: In his theory, the stochastic interaction between quantum and classical states necessarily causes the wave function to collapse, so it is not compatible with many-worlds. Being able to measure the gravity of other quantum worlds is something predicted by semiclassical gravity, which Oppenheim calls "complete nonsense".

[1] https://www.youtube.com/watch?v=sde7k3jJp5E

Re: New theory claims to unite Einstein's gravity with quantum mechanics

#187

Post by thfuran »

edgefield wrote: post #160
nojvek wrote: post #143

Earlier quoted context omitted.

Love that there is a test. Some of the theories like gravity waves and Higgs boson took almost half a century to be confirmed by experimentation. The hard part about this is building tools that can precisely measure mass fluctuations with extremely low error bars at picosecond timescales. Because we need to both validate the theory and that the device is correctly measuring. So much of science became only possible be…

I’m not a physicist much less an astrophysicist and so take what I’m about to say with a hefty grain of salt. But I wonder if this new approach can also explain observations of distant galaxies. Distant galaxies either redshift because they’re moving away faster over time due to dark energy or redshift because their mass is changing. Can this new theory help explain why older galaxies might lose increasing mass over…

>redshift because their mass is changing.

Why would that cause red shift?

Re: New theory claims to unite Einstein's gravity with quantum mechanics

#188

Post by thfuran »

jakubmazanec wrote: post #176
nojvek wrote: post #143

Earlier quoted context omitted.

Love that there is a test. Some of the theories like gravity waves and Higgs boson took almost half a century to be confirmed by experimentation. The hard part about this is building tools that can precisely measure mass fluctuations with extremely low error bars at picosecond timescales. Because we need to both validate the theory and that the device is correctly measuring. So much of science became only possible be…

> So much of science became only possible because of better instruments. I would argue a stronger claim: experimental confirmation of theories and better measurements must always bootstrap each other. The history of temperature has many examples [1]. [1] https://psychology.okstate.edu/faculty/jgrice/psyc4333/Therm...

Surely someone has at some point come up with a theory that was testable with then-current equipment.

Re: New theory claims to unite Einstein's gravity with quantum mechanics

#189

Post by slim »

edgefield wrote: post #160
nojvek wrote: post #143

Earlier quoted context omitted.

Love that there is a test. Some of the theories like gravity waves and Higgs boson took almost half a century to be confirmed by experimentation. The hard part about this is building tools that can precisely measure mass fluctuations with extremely low error bars at picosecond timescales. Because we need to both validate the theory and that the device is correctly measuring. So much of science became only possible be…

I’m not a physicist much less an astrophysicist and so take what I’m about to say with a hefty grain of salt. But I wonder if this new approach can also explain observations of distant galaxies. Distant galaxies either redshift because they’re moving away faster over time due to dark energy or redshift because their mass is changing. Can this new theory help explain why older galaxies might lose increasing mass over…

I thougt the red shift is due to Doppler effect and the universe expansion (planets are running away from any observer in the universe)

Re: New theory claims to unite Einstein's gravity with quantum mechanics

#190

Post by tycho-newman »

thfuran wrote: post #187
edgefield wrote: post #160

Earlier quoted context omitted.

I’m not a physicist much less an astrophysicist and so take what I’m about to say with a hefty grain of salt. But I wonder if this new approach can also explain observations of distant galaxies. Distant galaxies either redshift because they’re moving away faster over time due to dark energy or redshift because their mass is changing. Can this new theory help explain why older galaxies might lose increasing mass over…

>redshift because their mass is changing. Why would that cause red shift?

Losing energy shifts the frequency of your emissions towards red.

Basically, cooling down is the same thing as moving farther away from an inertial reference point.

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