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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

#141

Post by Guvante »

dataflow wrote: post #10
mvdtnz wrote: post #6

Earlier quoted context omitted.

The fact that you, a random internet guy, knows this makes me believe that the world's top experts on measuring this exact thing probably thought of it, and if there is a mysterious divergence this probably doesn't account for it.

I figure as much, but that's kinda why I'm asking what made it mysterious. I actually hadn't heard of it being seen as mysterious until today - that comment is the first time I've seen that. Until today I thought it had been was unsurprising for scientists.

50 ug over 130 years is way too fast

> The reason for this drift has eluded physicists who have dedicated their careers to the SI unit of mass. No plausible mechanism has been proposed to explain either a steady decrease in the mass of the IPK, or an increase in that of its replicas dispersed throughout the world

https://en.m.wikipedia.org/wiki/International_Prototype_of_t...

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

#142

Post by cnity »

lordnacho wrote: post #137
cnity wrote: post #102

Earlier quoted context omitted.

Isn't it more like: "exploitation of a market inefficiency renders the market efficient over time", or something to that effect? Or rather, (others) making money from trading is what makes it hard (for you) to make money from trading.

Sure, depends on how you encounter it. Most often on forums someone will show up wanting to hear about how to write a strategy, and they are rebuffed with "nobody would ever publish that".

I love encountering nay-sayers because it means either:

1. I am wrong and could learn something new.

2. They are wrong and their opposition fills me with defiant determination.

The difficulty comes when you view something as case 2 but it is actually case 1 and you embarrass yourself. I do this all the time.

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

#143

Post by nojvek »

hn_throwaway_99 wrote: post #2

> A second paper, published simultaneously in Nature Communications and led by Professor Oppenheim's former Ph.D. students, looks at some of the consequences of the theory, and proposes an experiment to test it: to measure a mass very precisely to see if its weight appears to fluctuate over time. Definitely don't know enough to comment about the overall proposal, but given how many grand physics theories over the pas…

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 because of better instruments. Be it microscopes to see the tiniest phenomena or telescopes to observe the furthest phenomena.

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

#144

Post by jessriedel »

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 mean clearly if it's a mistake this is a matter of terminology not intelligence, but could you explain how it's wrong?

If A wins, B pays A $1. If B wins, A pays B $N. For the bet to be fair (zero expectation value), the probability that A wins needs to be p=N/(N+1) and that B wins needs to be 1-p=1/(N+1). My understanding of what "odds" are is the ratio of the outcome probabilities: p:(1-p) = p/(1-p) = N/1 = N:1. (This is why the "log odds" are log(p/(1-p)).)

Do they use a different notion of "odds" in sports gambling?

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

#145

Post by bjornsing »

jessriedel wrote: post #144
bjornsing wrote: post #138

Earlier quoted context omitted.

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 mean clearly if it's a mistake this is a matter of terminology not intelligence, but could you explain how it's wrong? If A wins, B pays A $1. If B wins, A pays B $N. For the bet to be fair (zero expectation value), the probability that A wins needs to be p=N/(N+1) and that B wins needs to be 1-p=1/(N+1). My understanding of what "odds" are is the ratio of the outcome probabilities: p:(1-p) = p/(1-p) = N/1 = N:1. (…

Turns out the only interesting thing is how sloppy my reading is (and how quick I am to blame others for that sloppiness…).

I simply missed the second “each” below:

> Should space-time be shown to be quantum, the loser will give to each of the winners, one ITEM of their choice. If the alternative hypothesis is deemed to be correct, the losers will each give 5,000 ITEMS to the winner.

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

#147

Post by a_cardboard_box »

Timeroot wrote: post #123
maho wrote: post #99

After skimming the second paper, I still don't understand how precision mass measurements come into play here. They mention Cavendish-type measurements, but they are used for measuring the gravitational constant. Of course, you can turn the formula around, plug an unknown mass into the apparatus and then call it a mass measurement, but it's going to be a very imprecise measurement. A Penning trap can give you 11 to 1…

(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.

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

#148

Post by seeknotfind »

bjornsing wrote: post #145
jessriedel wrote: post #144

Earlier quoted context omitted.

I mean clearly if it's a mistake this is a matter of terminology not intelligence, but could you explain how it's wrong? If A wins, B pays A $1. If B wins, A pays B $N. For the bet to be fair (zero expectation value), the probability that A wins needs to be p=N/(N+1) and that B wins needs to be 1-p=1/(N+1). My understanding of what "odds" are is the ratio of the outcome probabilities: p:(1-p) = p/(1-p) = N/1 = N:1. (…

Turns out the only interesting thing is how sloppy my reading is (and how quick I am to blame others for that sloppiness…). I simply missed the second “each” below: > Should space-time be shown to be quantum, the loser will give to each of the winners, one ITEM of their choice. If the alternative hypothesis is deemed to be correct, the losers will each give 5,000 ITEMS to the winner.

Given this each, I'm surprised the headline isn't 10,000:1 bet.

Also, who wants 10,000 <$20 items? It's a cool payout, but if I wanted to spend ~$200,000, I wouldn't do it in 10,000 pieces.

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

#149

Post by naasking »

Timeroot wrote: post #126
throwaway4PP wrote: post #122

Exciting times! Any physicist here aware of how these two papers would impact the applicability or validity of Modified Newtonian Dynamics (MOND)? background: my lay understanding of MOND is that it modifies the gravitational interaction parameter over cosmological distances. the force exerted on objects due to gravity is currently accepted to scale with distance in a certain manner (ex. 1/distance^2) while MOND post…

It's of no relevance to MOND, at least none that I can see. MOND gives a different scaling relation, and is therefore contradicting general relativity. Its goal is to explain the effects we associate with dark matter, without the need for dark matter. General relativity is (we are pretty sure) inconsistent with quantum field theory. String theory tries to fix the issue by replacing the particles in field theory with…

> The Bullet Cluster is a particular instance where we can actually "see" the dark matter flying around, in a way MOND couldn't hope to explain

This is not correct. In fact, LCDM can't even explain the Bullet Cluster [1]. The evidence is not so favourable to LCDM over MOND [2] when taken as a whole.

More recent observations on wide binary stars disfavour MOND more strongly, but the classic reasons you cite are not valid reasons.

[1] https://arxiv.org/abs/0704.0381

[2] https://arxiv.org/abs/2110.06936

Edit: See for instance what Milgrom said about the Bullet Cluster back in 2006:

http://astroweb.case.edu/ssm/mond/moti_bullet.html

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

#150

Post by zehaeva »

throwaway4PP wrote: post #122

Exciting times! Any physicist here aware of how these two papers would impact the applicability or validity of Modified Newtonian Dynamics (MOND)? background: my lay understanding of MOND is that it modifies the gravitational interaction parameter over cosmological distances. the force exerted on objects due to gravity is currently accepted to scale with distance in a certain manner (ex. 1/distance^2) while MOND post…

I am pretty sure that MOND has been completely ruled out[0] given some recent evidence. And by more than 5 sigma.

[0]https://bigthink.com/hard-science/dark-matter-alternative-mo...

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