satt comments on Justifiable Erroneous Scientific Pessimism - Less Wrong

14 Post author: Eliezer_Yudkowsky 08 May 2013 08:37PM

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Comment author: satt 10 May 2013 10:05:09PM 0 points [-]

[EY quote on the covariance of physical law for a spinning body]

Edit: You are correct from a classical physics standpoint that if you are in a windowless room on a merry-go-round, you can tell whether the merry-go-round is standing still versus spinning at a constant speed.

As far as I can tell, what I'm saying holds even for non-spinning accelerating objects, and under quantum physics. According to QFT, a sufficiently sensitive thermometer accelerating through a vacuum detects a higher temperature than a non-accelerating thermometer would. This appears to be a way for a thermometer to tell whether it's accelerating without having to "look" at distant stars & such.

Comment author: nonplussed 14 May 2013 09:52:02PM 0 points [-]

Hm, I'm not sure the thermometer can conclude that it's accelerating from seeing the black body radiation. I think it's equivalent to there being an event horizon behind it emitting hawking radiation (this happens when you accelerate at a constant rate). The thermometer can't tell if it's next to a black hole or if it's accelerating. Could be wrong though, but I vaguely remember something along these lines.

Comment author: satt 15 May 2013 02:25:23AM 0 points [-]

I don't see anything incorrect in what you say. (Sounds to me like a direct consequence of the equivalence principle, although I'm no GR expert.) But I'm assuming away the possibility of rogue black holes in this hypothetical, since I'm wondering whether a sufficiently sensitive sensor could detect its own acceleration even inside an otherwise empty universe (or at least without reference to the rest of the cosmos).

Comment author: arundelo 10 May 2013 10:22:11PM 0 points [-]

I think I misunderstood what you and Silas were talking about. (Note though that my train thought experiment was about a train with a constant velocity. The billiard ball technique works to detect acceleration of the train even if no rotation is involved.)

Comment author: shminux 10 May 2013 10:16:46PM *  0 points [-]

Yes, all acceleration is absolute, not relative. You don't need hypothetical esoteric effects to detect it, a usual weighing scale will do. Gravity throws a bit of a quirk in it, of course.

Comment author: satt 10 May 2013 10:39:36PM *  0 points [-]

I'm simultaneously reassured (that my intuition's correct) & confused (about SilasBarta & Eliezer's remarks, since they read to me like they contradict my intuition). Maybe I should post a comment on the Sequences post rather than continuing to press the point here, though.

[Edit: originally linked the wrong Sequences post, fixed that.]

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