Article is 404 right now, for me at least.
Lose the V1 at the end of the URL.
A physicist who bets that gravity can’t be quantized
131–140 of 378 posts
Re: A physicist who bets that gravity can’t be quantized
#132Earlier quoted context omitted.
I think because of the abuse of "many worlds" in science fiction media (especially as of late) as a convenient plot device, people develop this idea that it's an unserious proposal wrt the foundations of physics. As far as I have read, it strikes me as perhaps the most parsimonious interpretation of QM out there. Genuinely curious, what do you mean by "but you didn't say it couldn't be this, nanananana...?" The Evere…
Assuming many worlds, and many here means: enormous amounts, far exceeding the number of particles in the universe, is everything but parsimonious. There happens to be a model that fits some data, but that's it. It's a grotesque assumption to avoid a conflict in a man-made theory. It's a funny thought, but no more than that. There's also nothing special about observing. Our consciousness isn't super-natural, so the i…
Many worlds just falls out of superposition and entanglement. Those happen in quantum systems, and we are made of quantum systems. To avoid that you have to stipulate something additional that avoids putting macroscopic objects like devices, cats and brains into superpositions.
Re: A physicist who bets that gravity can’t be quantized
#133Earlier quoted context omitted.
> You’re wrong about MWI in that it’s a more elegant interpretation because it adds nothing extra to the wave equation and treats the universe as fundamentally quantum with no arbitrary dividing lines for classically scaled objects. That's how it's often presented, but this is wrong. In fact, it does add something to the theory, and that's a measure of how many "worlds" there are after a quantum measurement, which he…
> the MWI has to somehow define a formal notion of an observer/a classical world Yes: in MWI, those things don't exist. The world is quantum all the way up and all the way down, observers are simply (other) quantum system that get to interact with the quantum system under the consideration. An observation, then, is simply an interaction between two quantum systems and follows all the usual rules so instead of the wav…
You're missing the point I was highlighting. Quantum mechanics makes very specific, very precise predictions about the probabilities of an observer seeing any of those states, which we have confirmed are correct to extraordinary precision.
The problem is explaining what is the relationship between these observed probabilities and the wave function amplitudes. If we say that all possible quantum states are realized in the universal wave function, we the need to explain why different states have different probabilities to an observer. The only way to do that in the deterministic world of MWI is to add a new postulate: one that says that for any state Xi, there are N observers in state Yi, where N = |psi(Xi)|, so that we can compute regular frequentist probabilities of an observer seeing a particular state over the amount of observers.
This is perfectly reasonable, but it is just as much an extra postulate as the measurement postulate.
Re: A physicist who bets that gravity can’t be quantized
#134> J. Oppenheim
I wonder what influenced him to become a physicist.
Re: A physicist who bets that gravity can’t be quantized
#135Earlier 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’m a quantum physicist and you wouldn’t believe how many people try and sell me on their theory that solves everything that is literally just an idea in their head and can’t even produce any quantitative predictions. The levels of self delusion that these people display is astounding and we need to mock it more openly imo
What do you intend to achieve by mocking these people?
Re: A physicist who bets that gravity can’t be quantized
#136The 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 wish any of you with the down vtes would at least have a conversation with me...
There is absolutely no evidence that the Planck length is anything like the smallest possible length or wavelength. Its "just" a length scale that pops out when you combine several physical constants. That combination of constants means that at the Planck scale quantum effects and gravitational effects are likely to both be relevant, which is cool, but other than that it doesn't really have any fundamental meaning.
Re: A physicist who bets that gravity can’t be quantized
#137Earlier quoted context omitted.
Why would anyone believe such a thing?
Because it’s very straightforward and has less assumptions and weird features than most other interpretations, and it has seen the most advancements in quantum fundamentals research
Complete layman here -- does that theory say that every time a quantum effect does or does not occur, in fact both possibilities happen but in different worlds?
The entire universe instantly splits up in two for every quantum event anywhere in it?
Edit: I read more comments and no, it's not literally that.
Re: A physicist who bets that gravity can’t be quantized
#138Earlier quoted context omitted.
No, Planck units have no intrinsic physical significance. They're just convenient to work in because they set the numeric values of several different physical constants to 1. The planck distance also happens to be roughly the length scale at which we expect quantum-gravitational effects to become significant, but roughly here means within a few orders of magnitude.
Oh, really? I totally misunderstood then. I thought I knew physics a little better than that! Thanks. EDIT: Hmm, so doesn't the fact that this particular value makes the math simplified not also imply some kind of meaning?
> Hmm, so doesn't the fact that this particular value makes the math simplified not also imply some kind of meaning?
No. There are plenty of other sets of constants you can choose to set to 1, inducing other length scales. Only dimensionless constants have physical meaning in isolation; dimensioned quantities are meaningful only with respect to each other.
Re: A physicist who bets that gravity can’t be quantized
#139Earlier quoted context omitted.
> You’re wrong about MWI in that it’s a more elegant interpretation because it adds nothing extra to the wave equation and treats the universe as fundamentally quantum with no arbitrary dividing lines for classically scaled objects. That's how it's often presented, but this is wrong. In fact, it does add something to the theory, and that's a measure of how many "worlds" there are after a quantum measurement, which he…
> That's how it's often presented, but this is wrong. In fact, it does add something to the theory, and that's a measure of how many "worlds" there are after a quantum measurement, which helps translate the wave function values into testable probabilities (the Born rule). The distribution of worlds/branches is determined by the wave function. A more likely outcome means there are many more worlds with that outcome. Y…
> A more likely outcome means there are many more worlds with that outcome. You can calculate the percentage of worlds that have that outcome.
First of all, this is a new postulate of QM, you can't derive it from the Schrodinger equation. It is perfectly equivalent with the measurement postulate.
> Measurement, observer and classical shouldn't be part of a physical theory. The answer as to why things appear that way to us is decoherence.
This contradicts the other part, where you were talking about a notion of worlds that can be counted. If they can be counted, they have to be defined as classical worlds. Decoherence only explains why worlds can't interact with each other, it doesn't help define what they are without appealing to measurements. Even the notion of "the environment" is somewhat ill defined if we go down to the philosophical level.
Re: A physicist who bets that gravity can’t be quantized
#140The 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 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.