A physicist who bets that gravity can’t be quantized • Hacker News Board

Re: A physicist who bets that gravity can’t be quantized

#341

Post by rvcdbn » Tue, Jul 11, 2023, 12:38 PM UTC

btilly wrote: post #225

rvcdbn wrote: post #18

Earlier quoted context omitted.

I’m a “believer” in the Everett Interpretation (on the grounds that it’s the simplest interpretation) but I can’t see how such an experiment could prove anything. This experiment seems to assume we can keep the whole apparatus including the Geiger counter and the mechanism to move the cannon ball from becoming entangled with the environment (decohering). This seems very far outside the realm of current technology.

It shows that when there is a superposition of quantum mechanical states, you also get a superposition of two different space-time structures. The reason why the Everett Interpretation is needed for the experiment to be valid is that according to it decoherence results is a superposition of quantum mechanical states, and not a collapse. If you believe in another interpretation, there has been a collapse, and so the e…

Once decoherence has occurred I don’t think it’s meaningful to say that the system exists in a superposition of states. The multiple decohered branches of the wave function can no longer interfere with each other and so there’s no way for them to affect each other, which is why we call them separate worlds. Within each decohered branch there’s an experimental apparatus and a human that sees one specific outcome. This was Everett’s main insight that each observer in each branch experiences what looks like a collapse but is really just their brain becoming entangled with one or other of the measurements.

Re: A physicist who bets that gravity can’t be quantized

#342

Post by fartsucker69 » Tue, Jul 11, 2023, 12:40 PM UTC

kromem wrote: post #185

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. 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…

all quantities in virtual worlds are always quantized.

Re: A physicist who bets that gravity can’t be quantized

#343

Post by mensetmanusman » Tue, Jul 11, 2023, 12:56 PM UTC

gerdesj wrote: post #230

skinner_ wrote: post #205

Earlier quoted context omitted.

I believe you are misparsing that sentence. The dogma and the tradition are the same thing.

Dogma and tradition are two very different concepts. Dogma is forced down from "above" and tradition is consensual. Tradition is "organic", dogma is proscribed. Tradition: "We chase a wheel of cheese down Coopers hill in Gloucestershire and invite severe injury, for a laugh" - won by a somewhat concussed Canadian lass this year, well done her. https://www.theguardian.com/food/2023/may/29/woman-wins-coop... Dogma: "Th…

Dogma is tradition formalized.

Re: A physicist who bets that gravity can’t be quantized

#344

Post by lgas » Tue, Jul 11, 2023, 1:38 PM UTC

ImHereToVote wrote: post #301

ethn wrote: post #300

Earlier quoted context omitted.

It's not relational. There's several rigorous proofs against Spinoza's relational theory. Namely that of Kant and Einstein: "even if space is composed of nothing but relations between observers and events, it would be conceptually possible for all observers to agree on their measurements, whereas relativity implies they will disagree" [0] 0: https://en.wikipedia.org/wiki/Relational_space

Unless one of the observers accelerates for some reason. Now his observation is privileged.

Doesn't relativity mean there's no difference between that observer accelerating in one direction and everything else accelerating in the opposite direction? So wouldn't everyone's observation be equally privileged? I'm asking honestly as am (obviously) not a physicist.

Re: A physicist who bets that gravity can’t be quantized

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Post by jfengel » Tue, Jul 11, 2023, 1:42 PM UTC

Gordonjcp wrote: post #236

jfengel wrote: post #171

Earlier quoted context omitted.

That's not what Planck's Constant is. Planck's Constant connects energy to length (in space or time). It's just a way of shifting units around. You're thinking of the Planck Length, which is the result of combining the Planck Constant with the speed of light. It also happens to be the wavelength of a photon so short that its energy makes it a black hole, connecting it to gravity. It's often presented as if it were th…

[flagged]

I'm afraid I don't get the joke, but that's on me. I apologize.

Re: A physicist who bets that gravity can’t be quantized

#346

Post by prometheus76 » Tue, Jul 11, 2023, 1:47 PM UTC

gerdesj wrote: post #230

skinner_ wrote: post #205

Earlier quoted context omitted.

I believe you are misparsing that sentence. The dogma and the tradition are the same thing.

Dogma and tradition are two very different concepts. Dogma is forced down from "above" and tradition is consensual. Tradition is "organic", dogma is proscribed. Tradition: "We chase a wheel of cheese down Coopers hill in Gloucestershire and invite severe injury, for a laugh" - won by a somewhat concussed Canadian lass this year, well done her. https://www.theguardian.com/food/2023/may/29/woman-wins-coop... Dogma: "Th…

I would offer a slight alteration to your definition of "dogma". It's a Greek word and it was the name of wooden cubes that served as the markers of the edge of someone's property. It's more accurate to think of dogma as "boundaries" than as proscriptions.

I am saying this as an Orthodox Christian, so this is probably a different view than the view of the Roman Catholic church that you are probably more familiar with. They have definitely gone more towards the "top-down" approach than the Orthodox Church since the Great Schism in 1054.

What I mean by this is that the Roman Catholic church has a LOT more dogmas and they are much more specific than the Orthodox Church. The Orthodox Church has very few dogmatic statements and a much different view of the canons of the church.

Re: A physicist who bets that gravity can’t be quantized

#347

Post by goatlover » Tue, Jul 11, 2023, 1:57 PM UTC

tsimionescu wrote: post #319

goatlover wrote: post #291

Earlier quoted context omitted.

Measurements are interactions that result in entanglement. Atoms radioactively decaying in your body are interactions. The environment is the entire universe as it becomes entangled with a quantum event.

Entanglement is not enough to give you the properties of measurements. While it is often presented as "when a spin-0 particle decays into two particles, one must have spin +1 and the other spin -1", that is not what the math actually says. What the math actually says is that the spin of each particle is a linear combination of |+1> and |-1>, and that their sum must be 0. For example, one of the entangled particles co…

Decoherence from entanglement with the environment interferes with the coherence of the supposition, so we only see the pure state as I understand Sean Carol's argument. At this point in the video below he goes over the spin states.

https://youtu.be/LGtimjuA5gA?t=2545

Re: A physicist who bets that gravity can’t be quantized

#348

Post by goatlover » Tue, Jul 11, 2023, 2:04 PM UTC

tsimionescu wrote: post #331

consilient wrote: post #118

Earlier quoted context omitted.

> 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). All interpretations need to induce a measure over observations ( not "worlds") to produce meaningful results. Without that all you have is an abstract mathematical object. > As you can see, the two interpretations require the same amount of extr…

> All interpretations need to induce a measure over observations (not "worlds") to produce meaningful results. Without that all you have is an abstract mathematical object. Agreed, but the MWI in particular does so by applying frequentist probabilities over all versions of an observer, the so-called worlds. The argument goes that there is an apparent non-deterministic process from the point of view of every individua…

It's not really anymore than tables and chairs not being part of fundamental physics means they're additional postulates to physics. Because table and chairs emerge from the underlying physics. Same thing with measurement, observers and probability in MWI. Or to put it another way, the baggage of classical physics being quantized misleads us into thinking measurement and probability need to be fundamental postulates.

Re: A physicist who bets that gravity can’t be quantized

#349

Post by btilly » Tue, Jul 11, 2023, 2:15 PM UTC

rvcdbn wrote: post #341

btilly wrote: post #225

Earlier quoted context omitted.

It shows that when there is a superposition of quantum mechanical states, you also get a superposition of two different space-time structures. The reason why the Everett Interpretation is needed for the experiment to be valid is that according to it decoherence results is a superposition of quantum mechanical states, and not a collapse. If you believe in another interpretation, there has been a collapse, and so the e…

Once decoherence has occurred I don’t think it’s meaningful to say that the system exists in a superposition of states. The multiple decohered branches of the wave function can no longer interfere with each other and so there’s no way for them to affect each other, which is why we call them separate worlds. Within each decohered branch there’s an experimental apparatus and a human that sees one specific outcome. This…

According to quantum mechanics, they can no longer interfere with each other.

But we are bringing gravity into the mix. Gravity works differently than the other forces. Do space-time structures also exist in a superposition of states? Or does QM work against an essentially classical gravitational space-time background?

Without a theory combining quantum mechanics and gravity, the answer is not obvious. The fact that the superpositions do NOT interfere gravitationally means that either there was no quantum mechanical superposition (collapse actually happened) or that gravity can also exist in superimposed states. If you believe in the Everett interpretation, then there must have been a quantum mechanical superposition, and this tells us something non-trivial about a quantum theory of gravity.

Re: A physicist who bets that gravity can’t be quantized

#350

Post by zmgsabst » Tue, Jul 11, 2023, 2:16 PM UTC

xmcqdpt2 wrote: post #332

zmgsabst wrote: post #271

Earlier quoted context omitted.

How is it a cop out? We know two things: - universe was small enough everything was tightly coupled - non-local phenomena occur Insisting that our beliefs reflect an ideology (eg, you can segregate off portions of reality to study in isolation) which seem contrary to observed reality (eg, the points above) is religion — not a scientific investigation of the universe.

Superdeterminism sidesteps interpretational questions by arguing against reductionism, which is pretty much the core of all physics. Where is this hidden information stored? What causes the specific outcomes in a destructive measurement? To say that QM is in fact a local hidden variable theory because everything was once touching billions of years ago, without positing any mechanism for it is a cop out. At least inst…

Not just because it was touching:

- because it was touching;

- and because we observe non-local information stored in braiding of the wave equation; even when we separate the constituent (quasi)particles.

The belief that you can reduce a system by decoupling a particle or system from outside influences is at odds with that second fact. We’re storing the hidden variables in those non-localities; when you measure a system where both particles are part of a non-local phenomenon, they’re coordinating through that non-locality.

What has literally no proposed mechanism is suggesting such non-local quasiparticles disappeared — by what specific mechanism did primordial anyons dissipate?