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endoself comments on Identity Isn't In Specific Atoms - Less Wrong

24 Post author: Eliezer_Yudkowsky 19 April 2008 04:55AM

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Comment author: endoself 29 May 2011 03:13:33AM 2 points [-]

Why did you not write this as a reply to me?

GR and QM are generally agreed to indeed be inconsistent.

[Citation needed]

I'll give you that loop-quantum gravity is "quantum mechnical" and "general realtivistic". But it isn't QM or GR.

Quantum mechanics is the theory that reality is described by the Schrodinger equation; loop quantum gravity includes the Schrodinger equation. Its proponents claim that it includes the general relativity field equations as a long distance limit; that is what we mean when we say that one theory is a quantization of another, just like quantum and classical electrodynamics.

And no, I don't read any popular literature. I hope the above helped explain my previous post a bit.

95% probability less than 10% of the physics you read is from journals/arXiv.

Comment author: PhilosophyFTW 29 May 2011 06:29:24AM -2 points [-]

Quantum mechanics is the theory that reality is described by the Schrodinger equation

You are insane.

95% probability less than 10% of the physics you read is from journals/arXiv.

Feel free to make further claims you have no evidence for. Here's an article from arXiv you might find interesting: http://arxiv.org/abs/0809.4144

I'm surprised that you put arXiv in the same class you put whatever it is you mean by journals. Maybe I should take the above article seriously? After all, arXiv makes it available. Get out of town.

Comment author: [deleted] 29 May 2011 06:32:10AM *  4 points [-]

You win two paper-machine points [1]: one for observing the true nature of arXiv, and the other for implicitly deriding those who argue the countability of the reals.

[1] Probably not redeemable for anything you'd want.

EDIT: Don't be too harsh on the mantra "QM says reality is described by Schrodinger". It's the noble lie they tell undergraduates -- or at least, what they told me when I was an undergraduate. In my opinion, it's slightly unfair to expect the average LW'er to have a better-than-undergraduate knowledge of QM.

Comment author: PhilosophyFTW 29 May 2011 06:40:51AM 1 point [-]

Thanks for the points. Yes, ArXiv frequently sucks. And people who argue that the set of real numbers has the same cardinality as the set of natural numbers are morons.. =)

Comment author: endoself 29 May 2011 07:34:58AM 1 point [-]

Don't be too harsh on the mantra "QM says reality is described by Schrodinger". It's the noble lie they tell undergraduates -- or at least, what they told me when I was an undergraduate.

Now I'm interested. In what way are "quantum mechanics" and "vector on a Hilbert space evolving according to Schrodinger's equation" not the same concept?

Comment author: [deleted] 29 May 2011 07:47:07AM 0 points [-]

They are. I guess the mantra I quoted should have been, "It is true that QM describes reality." That's what I assume the grandparent thought you were saying, anyway. It's not worth calling someone insane over a definition.

Comment author: endoself 29 May 2011 08:24:58AM 1 point [-]

I'm confused. Are you saying that I got called insane for saying that quantum mechanics is the theory that reality is described by quantum mechanics?

Comment author: [deleted] 29 May 2011 08:28:18AM 0 points [-]

No. I'm saying you got called insane for "saying" (though you didn't say this) that quantum mechanics describes reality.

But this is just my interpretation of things. I'm having trouble modelling PhilosophyFTW's beliefs.

Comment author: endoself 29 May 2011 07:30:52AM 2 points [-]
  1. I never stated that every paper on the arXiv was good.

  2. You have neither confirmed nor denied my actual statement.

QM and GR, if you stick them together, entail everything.

I'm not sure what your point is here. If you stick quantum mechanics and Maxwell's equations together, everything is entailed, but quantum electrodynamics did not give identity back to specific particles. It would be very unlikely for quantum gravity to do that either; certain parts of nature fit perfectly into a very rigid structure and the basic framework of quantum mechanics can be explained but will probably not be eliminated. You can't point to a specific part of a theory and say "the theory is wrong, so that result is wrong"; theories get improved, but they still have to have enough of the same structure to derive the results already tested by experiment.

Comment author: [deleted] 29 May 2011 06:37:47AM 0 points [-]

GR and QM are generally agreed to indeed be inconsistent

[Citation needed]

So I was somewhat surprised that Wikipedia claims that the above is a "popular claim", and goes on to cite some yoga involving the quantum mechanics of gravitons, whatever that means. I'm a mathematician, dammit Jim, not a theoretical physicist.

I think a more accurate version of what the grandparent meant is that one cannot merely take QM and GR, stick them together, and hope to get a coherent theory. One needs something more (for example, the above requires the existence of gravitons), and that's why people go hunting for unified theories.

Comment author: PhilosophyFTW 29 May 2011 07:05:09AM -1 points [-]

Relying upon Wikipedia is not advised here. QM and GR, if you stick them together, entail everything. (On the assumption that from a contradiction one can derive anything. Paraconsistent logical systems deny this assumption.) For some proposition, sentence, statement or utterance that P, QM entails P. GR entails not-P. Absent abandoning classical logic (and moving to something like paraconsistent logic), GR and QM are inconsistent.

Let's assume that a theory is false if the theory entails P and not-P (that is, let's ignore paraconsistent logical sytstems). Then sticking GR and QM together entails P and not-P. Any theory that entails both P and not-P is false. So sticking them together fails.

Almost all physicists are happy with the above claims, and so there is an ongoing search for theories that preserve what's supposedly right about QM with what's supposedly right about GR. Enter theories of quantum gravity. These theories might be in some respects "quantum mechanical". That is, they preserve some aspects of QM. These theories aren't QM or GR, however. They're attempts to preserve what's right (let's suppose) about QM and make that compatible with what's right (let's suppose) about GR.

We're utterly in the dark about which such theories might be true. Sadly, that's the state of the game. If you appeal to QM in defense of some interesting claim, you are failing to appeal to a theory you ought, as an intelligent and well-educated person, place a high degree of credence in. Here our favorite blogger is is screwing up.

Comment author: [deleted] 29 May 2011 07:17:51AM *  0 points [-]

Relying upon Wikipedia is not advised here. QM and GR, if you stick them together, entail everything.

I'm confused how you got this out of the above -- I didn't mean to imply that QM+GR was consistent. They need fixing, and the article supports this viewpoint. Grandparent asked for citations; the relevant article has several. I didn't see the earlier comments between you and endoself, because they're not in this thread, but in another, for some reason. For what it's worth, I think you're misinterpreting statements intended for poetic effect.

So while endoself is wrong when he claims QM isn't inconsistent with GR, you're equally wrong for believing EY supports QM over GR, when in fact it's incredibly likely (based on everything we know about EY's stance on updating) that for now EY supports QM when it talks about small things and GR when it talks about big things, and that if some better theory would come along that explained the evidence better, EY would update to follow that.

Of course, I can't speak for him, but I claim the above is a more reasonable interpretation of the state of affairs.

EDIT: So there's a simpler litmus test to apply here -- has EY directly said anything about GR? If so, what evidence is leading you to believe he denies it?

Comment author: wedrifid 29 May 2011 08:36:51AM *  1 point [-]

Grandparent asked for citations; the relevant article has several.

The source of your confusion is the meaning of the phrase 'Citation Needed'. It seldom has anything to do with wanting citations. Actually giving them to him is like answering a (bad) rhetorical question with a literal answer that effectively refutes the rhetorical point of asking it.

Comment author: [deleted] 29 May 2011 08:40:21AM 0 points [-]

What else does it mean?

Comment author: wedrifid 29 May 2011 10:42:47AM *  1 point [-]

What else does it mean?

  • "My beliefs are the default and privileged. You have the burden of justifying your beliefs to me."
  • "Get back in your place! Who do you think you are?"
  • "Your momma is inconsistent with General Relativity! But I'm saying it using an intellectual meme rather than the low brow meme."

Basically, if someone told me 'Citation Needed!' in the same conversation that they out of the blue told me I was insane then I would expect them to do whatever they could to find a way to sneer at or dismiss the citations I proceed to give them. I would expect them to feel like their grasp for dominance backfired and try to dig themselves out of what feels like a hole.

This isn't to say that 'citation needed' is never used literally or never appropriate. But I usually find that anyone who is actually interested in whether there are citations available tends to use different language in their reply.

Comment author: [deleted] 29 May 2011 11:07:15AM *  1 point [-]

Ah, I see.

Basically, if someone told me 'Citation Needed!' in the same conversation that they out of the blue told me I was insane

Those two things weren't done by the same person. endoself used [Citation Needed]; PhilosophyFTW called him insane in the followup, for a different reason.

Comment author: wedrifid 29 May 2011 11:17:41AM 0 points [-]

Those two things weren't done by the same person. endoself used [Citation Needed]; PhilosophyFTW called him insane in the followup, for a different reason.

Ahh. That changes the likely meaning somewhat (greater weight to the first bullet point, less to the last one).

Comment author: endoself 29 May 2011 08:50:30AM 0 points [-]

endoself is wrong when he claims QM isn't inconsistent with GR

I interpreted "QM is inconsistent with GR" as stating that GR cannot be quantized. This is usually what is mentioned in such discussions, as GR is much harder, maybe even impossible, to quantize as compared to other theories. There are very large advantages to only using the word 'consistent' in its precise mathematical definition, so I will do that from now on.