Earlier quoted context omitted.
Planck.
Right, sorry.
[flagged]
A physicist who bets that gravity can’t be quantized
191–200 of 378 posts
Re: A physicist who bets that gravity can’t be quantized
#192Earlier quoted context omitted.
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 b…
> Will other large thermalised system (e.g. rocks) also experience observations that "look classical"?
The inner life of rocks is somewhat beyond our reach, I'm afraid. But they'll induce decoherence in the same way as a human, yes.
> Is there something special about "large thermalised systems" (and/or humans)?
Aside from being large and thermalized? No.
> How large have they to be to allow for "our observations"?
It's a continuum. The more internal degrees of freedom you have, and the more thoroughly they're mixed, the faster you'll decohere things.
> Where is the boundary between the thing being observed and the observing thing?
At the level of fundamental physics, there isn't one. "Observation" is an approximate and thermodynamic notion.
Re: A physicist who bets that gravity can’t be quantized
#193In 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…
> 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.
It was essentially a historical accident that the first systems where quantum mechanics was studied extensively (black-body radiation and atomic spectra) were ones in which quantum effects ended up discretizing something which was continuous in classical mechanics. Quantum mechanics does not generally impose, require or even match having things be discrete.
You can very easily have quantum systems where the relevant quantities are continuous, rather than discrete (wiki link: https://en.wikipedia.org/wiki/Continuous-variable_quantum_in...). Simple theoretical examples like the particle living on a 1d line or in 3d space are easy to understand, there are many (many many many) more complicated examples.
TLDR: there is no fundamental link between things being quantum-mechanical and things being discrete. Quantum mechanics makes some things discrete, but not everything.
Re: A physicist who bets that gravity can’t be quantized
#194> It’s become dogma. All the other fields in nature are quantized. There’s a sense that there’s nothing special about gravity — it’s just a field like any other — and therefore we should quantize it. I keep on citing Stephen Hawking here on HN, but it again seems very appropriate: > It would be rather boring if this were the case. Gravity would be just like any other field. But I believe it is distinctively different…
> it’s just a field like any other — and therefore we should quantize it.
So, trade dogma for tradition!
Re: A physicist who bets that gravity can’t be quantized
#195Earlier quoted context omitted.
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.
> I don’t know how someone is supposed to come up with evidence before a hypothesis
Sure, this is usually how science works. A good example is the famous Michelson–Morley experiment which was performed in 1887 and was a key piece of evidence directly inspiring Einstein's theory of special relativity in 1905.
The way science usually progresses is that there is some piece of evidence which current theories can't explain or deal with. That prompts the development of new theories, which make new predictions, which are then tested in further experiments.
Re: A physicist who bets that gravity can’t be quantized
#196Earlier quoted context omitted.
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 b…
> Will other large thermalised system (e.g. rocks) also experience observations that "look classical"? The inner life of rocks is somewhat beyond our reach, I'm afraid. But they'll induce decoherence in the same way as a human, yes. > Is there something special about "large thermalised systems" (and/or humans)? Aside from being large and thermalized? No. > How large have they to be to allow for "our observations"? It…
> 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.
Re: A physicist who bets that gravity can’t be quantized
#197(Not a quantum physicist. Please correct me if I am misunderstanding.) From what this article says, his assumption is that gravity is classical, but "fuzzy" or probabilistic: you can't precisely measure the gravitational field of a sufficiently small object. In the last years we've seen progressively bigger objects being put in quantum superposition. The theory from this article is incompatible with this process cont…
> possibly even without creating a particle accelerator the size of the solar system. Sure, you just need to entangle two objects big enough to exert a noticeable amount of gravity on one another but somehow do not interact gravitationally with the rest of the set up. Anyway, let's try a cat sized object first, then we'll finally know if Schroedinger had a point.
> somehow do not interact gravitationally with the rest of the set up.
And how would you do that?
If we had a way to shield a region of space from gravitational influence from something else we'd have a very useful technology
Re: A physicist who bets that gravity can’t be quantized
#198Earlier quoted context omitted.
> μg is too easily mistaken for mg Is that some joke about medical writing? Anyway, I just noticed that table doesn't have rules for nanogram. There is also no mega-anything. (On a serious parenthesis, I think I actually understand their rationale; but changing the abbreviation of only one of them is still confusing.)
Before Unicode, 'μ' was typically entered as an 'm' in a Greek font. This can go wrong in several ways, like if you converted the document to plain text, or if your laser printer didn't have the font and it substituted a regular font, you're suddenly off by a factor of 1000. 'mc' is ugly but safe.
Interesting. There's that too.
I assumed it was because of the phonetic similarity.
Re: A physicist who bets that gravity can’t be quantized
#199> It’s become dogma. All the other fields in nature are quantized. There’s a sense that there’s nothing special about gravity — it’s just a field like any other — and therefore we should quantize it. I keep on citing Stephen Hawking here on HN, but it again seems very appropriate: > It would be rather boring if this were the case. Gravity would be just like any other field. But I believe it is distinctively different…
Why would gravity behave different than Higgs field?
Re: A physicist who bets that gravity can’t be quantized
#200The 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…
I posted a response to this. It went through, but the board said I was posting too quickly. Bug dang about making it visible.