steven

Karma: 527

steven May 24, 2008, 9:22 AM
1 point
on: Mach’s Principle: Anti-Epiphenomenal Physics
Also, I think where you say “centripetal force” you mean “centrifugal force”; they go in opposite directions, the centrifugal (pseudo)force is the one pulling things apart, the centripetal force is the one keeping things together.

steven May 24, 2008, 9:11 AM
10 points
on: Mach’s Principle: Anti-Epiphenomenal Physics
Warning: Mach’s Principle is not experimentally proven, though it is widely considered to be credible.

I don’t see what experiments have to do with anything so long as we all agree GR is true. Apparently there are a lot of different things that people have called “Mach’s principle” and GR obeys some of them but not others: http://arxiv.org/PS_cache/gr-qc/pdf/9607/9607009v1.pdf . For example, it seems like you want to claim “Mach7” from this paper (“If you take away all matter, there is no more space”), which is false. It also seems like you want to claim “Mach10”, which is meaningless in GR. There’s a thing called “Goedel’s rotating universe”, so clearly there’s something subtle going on.
What links here?
- wnewman's comment on Open Thread June 2010, Part 3 by Kevin (Jun 16, 2010, 9:41 PM; 0 points)

steven May 6, 2008, 12:15 PM
1 point
on: Decoherence is Simple
If the expansion of the universe continues, as current cosmology holds it should, there will come some future point where—according to your model of reality—you don’t expect to be able to interact with the spaceship even in principle; it has gone over the cosmological horizon relative to you, and photons leaving it will not be able to outrace the expansion of the universe.

IIRC for this to be true the universe’s expansion has to accelerate, and the acceleration has to stay bounded above zero forever. (IIRC this is still considered the most probable case.)

steven May 1, 2008, 11:05 AM
5 points
on: The Born Probabilities
You wouldn’t have to stand off beside the mathematical structure of the universe, and say, “Okay, now that you’re finished computing all the mere numbers, I’m furthermore telling you that the squared modulus is the ‘degree of existence’.”

Instead, you’d have to stand off beside the mathematical structure of the universe, and say, “Okay, now that you’re finished computing all the mere numbers, I’m furthermore telling you that the world count is the ‘degree of existence’.”

steven Apr 28, 2008, 11:35 AM
0 points
on: The Conscious Sorites Paradox
(even if it could have been, but isn’t, the case that the latter possibility did tell me what to do)

steven Apr 28, 2008, 11:32 AM
0 points
on: The Conscious Sorites Paradox
Eliezer, I agree that it looks like you shouldn’t be able to get the Born rule a priori, but I don’t think you’re acknowledging that the same is true of the “equal probability for all worlds” rule. You need some way to translate a third-person physical view into subjective anticipations, and I don’t see how this could use anything other than a priori reasoning at some point.

Also—if I’m unsure whether my utility function says I should care about worlds in proportion to their Born measure or equally independent of their Born measure, and the latter possibility doesn’t tell me what to do, then for practical purposes it drops out and I can pretend it’s just the former.

steven Apr 27, 2008, 2:22 PM
0 points
on: On Being Decoherent
Quantum suicide is a good way to ensure that your next experience will be the trivial “experience” of being a corpse with no brain activity.

steven Apr 27, 2008, 2:20 PM
2 points
on: On Being Decoherent
Eliezer, I think your usage of “Standard Model” is different from that of physicists.

steven Apr 27, 2008, 11:47 AM
1 point
on: Where Experience Confuses Physicists
Anytime you start looking for things that resemble bridging laws, you should suspect that you’re on a zombie track. What you need are identity laws.

I don’t think bridging vs identity laws makes much of a difference; might it not be possible to say something like, “the mind is identical to a structure in the physical world, and the degree to which a structure A exists in a structure B is proportional to the probability that a random program with input B puts out A”?

steven Apr 26, 2008, 2:53 PM
2 points
on: Where Experience Confuses Physicists
Sorry for the triple-post, but I’m hoping to make my position a bit clearer --

I don’t see why probabilities in many-worlds QM should produce any new mysteries that were not already present in ordinary functionalist philosophy. In functionalism, to turn a third-person view of the world into subjective anticipations, you need a criterion to determine whether the world implements a mind, and how many minds it implements, and/or to what degree. Once you have such a criterion, it should be straightforward to apply it to a branching quantum universe, and it doesn’t seem obvious a priori that this criterion would say the branching quantum universe implements the same number of minds for every one of the structures that we happen to call a “world” (if there’s even a reasonable way to decide when to call something one world and when to call something two worlds).

Mitchell Porter, I think, would say that the same problems of vagueness of existence/implementation/etc kill both functionalism and the MWI. I would say that the solution to these problems for functionalism will show us the way to a solution for the same problems in MWI, one that shows that we have to assign probabilities the Born way to begin with and not equally across worlds.

steven Apr 26, 2008, 12:53 PM
2 points
on: Where Experience Confuses Physicists
How come no one has yet investigated whether or not Ha’ro’s suggestion can be proven or disproven from first principles?

As far as I know it has been disproven from first principles. If we should put an equal probability on all non-mangled worlds, then we should expect to find ourselves in a high-entropy world, unless I’ve misunderstood and the number of non-mangled worlds stays exactly constant under entropy increase.

I think it would be possible to prove that if you made a monkey type out a random program with the universe as input, it would output your mind with a probability proportional to the squared amplitude of your world. I think if you studied the orthodox Deutsch/Wallace/Greaves decision-theoretical account of probabilities in MWI, you would understand how to do this proof, even though they don’t put it in these terms. But I’m not sure.

cheerleads for orthodoxy

steven Apr 26, 2008, 12:40 PM
2 points
on: Where Experience Confuses Physicists
Rot13:

V guvax Qr’qn vf Qnivq Qrhgfpu.

steven Apr 25, 2008, 3:15 PM
−1 points
on: Where Physics Meets Experience
Caledonian, ordinarily that would be true, but the point is that in the MWI the number of worlds increases exponentially as a function of entropy, so very soon high-entropy worlds outnumber low-entropy worlds by a factor of (if I’m not mistaken) ten-to-the-power-avogadrillions. As just one example, there should be a lot more Everett worlds where we used up all the fossil fuels than where we didn’t. AFAIK that’s still true if you consider only non-mangled worlds, but maybe I misunderstood the model and the number of non-mangled worlds actually stays constant under entropy increase.

steven Apr 25, 2008, 1:53 PM
0 points
on: Where Physics Meets Experience
In today’s post I would like to see De’da and/or Wa’da ask Ha’ro, if worlds are equiprobable, 1) why we’re not in a near-maximum-entropy universe, and 2) if we can win the lottery by burning stuff afterward. (Maybe there are legitimate answers, I don’t know.)

steven Mar 14, 2008, 6:57 PM
0 points
on: Qualitatively Confused
If a coin has certain gross physical features such that a rational agent who knows those features (but NOT any details about how the coin is thrown) is forced to assign a probability p to the coin landing on “heads”, then it seems reasonable to me to speak of discovering an “objective chance” or “propensity” or whatever. These would be “emergent” in the non-buzzword sense. For example, if a coin has two headses, then I don’t see how it’s problematic to say the objective chance of heads is 1.

steven Mar 12, 2008, 9:02 PM
2 points
on: Probability is in the Mind
Standard reply from MWIers is that MWI keeps realism and locality by throwing away a different hidden assumption called “counterfactual definiteness”.

steven Mar 12, 2008, 8:52 PM
3 points
on: Probability is in the Mind
I think there’s still room for a concept of objective probability—you’d define it as anything that obeys David Lewis’s “Principal Principle” which this page tries to explain (with respect to some natural distinction between “admissible” and “inadmissible” information).

steven Feb 27, 2008, 5:38 PM
0 points
on: Leave a Line of Retreat
(Of course as long as we’re under these weird assumptions then not discussing tactics could be a fatal mistake too, etc etc)

steven Feb 27, 2008, 5:17 PM
0 points
on: Leave a Line of Retreat
Heh, so how do you know that it is not the case that this hypothetical JCG reads overcomingbias but not people’s private thoughts?

steven Feb 27, 2008, 2:05 PM
0 points
on: Leave a Line of Retreat
I’ve considered how to kill or rewrite a Judeo-Christian type God

Obligatory Pascal: Ah, but what if there’s a tiny chance that He’s reading along to figure out our tactics?