Isn't this similar to the view of Penrose?
A physicist who bets that gravity can’t be quantized
51–60 of 378 posts
Re: A physicist who bets that gravity can’t be quantized
#52Somewhat 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.…
The question of how can the Equivalence Principle work in the presence of gravitons comes up surprisingly often!
You will enjoy this discussion https://physics.stackexchange.com/questions/589074/why-can-t...
They go over several reasons why gravitons don't break the equivalence principle. In particular the answer about virtual particles is very important.
Re: A physicist who bets that gravity can’t be quantized
#53Earlier quoted context omitted.
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
if i have a crackpot theory and i’d like a real physicist to look it over and am willing to pay for their time where would i find one? asking for a friend
Sabine Hossenfelder apparently does this [1, 2] for $50/20min.
[1] http://backreaction.blogspot.com/p/talk-to-physicist_27.html
[2] https://aeon.co/ideas/what-i-learned-as-a-hired-consultant-f...
Re: A physicist who bets that gravity can’t be quantized
#54Somewhat 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.…
> 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.
No, this is completely false. Particle number is coordinate system and frame dependent.
Quantum particles aren't little billiard balls bouncing around, and it's really best to not think of them as 'particles' at all. They're just a calculational tool to describe excitations in quantum fields.
Re: A physicist who bets that gravity can’t be quantized
#55Somewhat 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.…
> General relativity says that you can't tell the difference between being unaccelerated, and being in free fall.
Just to be clear, GR only says this for a very specific case, and a very specific observer. In fact, one of the easier exercises when first learning how to work with metrics is to show how to measure the difference.
Re: A physicist who bets that gravity can’t be quantized
#56Isn't this similar to the view of Penrose?
My understanding is that Penrose does believe that gravity is fundamentally quantum in nature. But his proposal is that gravity is connected to the collapse of the wavefunction. In his view, it is the exchange of a graviton that precipitates the wavefunction collapse. But this is still a fundamentally quantum theory because it posits that the gravitational field is quantized (and hence gravitons exist).
Re: A physicist who bets that gravity can’t be quantized
#57Earlier quoted context omitted.
> 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.
If they are close enough to each other and far enough from everything else, then why not. The smallest objects for which we measured their gravitational interaction weighed just 90 mg ( https://arstechnica.com/science/2021/03/researchers-measure-... ). The biggest object put in quantum superposition weighed around 1 mcg ( https://physics.aps.org/articles/v16/s45 ).
So 90,000 times smaller. At first glance you made it look 90x smaller because I couldn't tell if "mcg" was a typo for "mg" or not (without clicking the link). I've never seen anyone use "mcg" to mean "microgram" before and I feel like it's misleading. Use "ug", or "μg" if you're feeling fancy.
Re: A physicist who bets that gravity can’t be quantized
#58Earlier quoted context omitted.
Genuine question here, when was the last time a total outsider made a significant contribution to physics?
Ask yourself; why are they outsiders in the first place? It's like asking why hasn't anyone who is not a player in major league baseball ever won a world series?
A better analogy is asking why someone who is bad at baseball isn't on an MLB team
Re: A physicist who bets that gravity can’t be quantized
#59Earlier quoted context omitted.
The word "probably" there is completely meaningless. There are many interpretations of QM and there is no compelling reason to choose one over the others. In particular the many worlds interpretation makes no testable predictions, it's just a story. There's absolutely nothing "elegant" about it. There's no math, no experiment, no explanation. A story like you read in some religious text or science fiction novel. It h…
Shut and calculate is putting your head in the sand and avoiding that physics should be telling us what the world is. 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.
> Shut and calculate is putting your head in the sand and avoiding that physics should be telling us what the world is.
It's how physics is done. PhD students don't sit in physics departments getting ideas from their interpretation of QM. The interpretations people have are so meaningless and useless they never appear in physics publications.
You don't like it, but it's what physics is.
> 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 the thing about most QM interpretations, and in particular the many worlds interpretation, and why they aren't science just stories: you're right, they add nothing. So they are untestable!
What does untestable mean? It means that they make no predictions about our world at all. They are stories. Their impact on physics or the universe we live in is the same as that of Winnie-the-Pooh. They're a waste of time.
> avoiding that physics should be telling us what the world is.
What can I say to "should"? I can only report what physics is in the real world. That's like saying, biologists "should" be working on building Jurassic Park because that's what you feel is the goal of the field. It's not. That's not what they do.
Re: A physicist who bets that gravity can’t be quantized
#60>> 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.
This sort of objection only arises because titles say baity things like "challenging orthodoxy". There's no information there—not in the bait and not in the objections the bait triggers.
The solution is to have a more substantive title. Fortunately the article supplies one of those in its HTML doc title, so we've switched to that (plus the s/the/a/ debaiting trick).
Let's focus on the article content now please.