4 ms·

A drunk awakens in a void and finds his arms, legs, in fact all extremities are bing pulled outward by some reverse gravity. It is quite unpleasant. By some st

A drunk awakens in a void and finds his arms, legs, in fact all extremities are bing pulled outward by some reverse gravity. It is quite unpleasant. By some strange mechanism he is able to make himself start spinning. At first it is worse: in one direction the reverse gravity increases in effect! So he reverses and is relieved to find that in the other it slowly abates. Though the sweet relief is strange. Because if he goes too far in that direction, he finds that the expulsatory force begins to increase again. But eventually he finds the sweet spot and stays there, relieved, to find himself not being pulled apart. "This", he says to himself, "I shall call an inertial reference frame. It is so much more relaxing than the others."

taneq 9y ago
Sounds like a first year physics question. "Consider a spherical drunk in a frictionless vacuum..."
- madaxe_again 9y ago
  A perfect spherical drunk, in fact.
  - deleted 9y ago
    [deleted]
  - noonespecial 9y ago
    ...of uniform density. Although, for us, it was always a spherical chicken.
    - QAPereo 9y ago
      ...Alone in a universe.
eru 9y ago
And interesting enough, the universe does have a unique privileged inertial reference frame: that which makes the background radiation look isotropic.
- Ari_Rahikkala 9y ago
  Only locally, though. The next galaxy cluster over has a uniquely privileged inertial reference frame, too, but it's in motion (and accelerating!) relative to ours.
  - danbruc 9y ago
    I think you are wrong, observers in different galaxies will agree on the inertial reference frame in which the background radiation is isotropic. The relative velocity between different galaxies will show up as different dipole components in the measured background radiation, but if you compensate for that, you should get the same inertial reference frame no matter from which galaxy you measured.
    - Ari_Rahikkala 9y ago
      I'll admit to not being a physicist and to being easily confused by the subject, so I'll just use a silly little metaphor to check whether I'm thinking straight, and try to avoid terminology I don't fully understand (which, since I don't have a particularly strong understanding of even special relativity, means not using relativity terms at all): Think of the universe as a rubber sheet over a table, being stretched in all directions. My understanding is that cosmic background radiation is on the rubber, stretching and moving with it just like all the matter is. If background radiation were on the table instead, there would be exactly one spot on the rubber that saw no motion relative to it, while spots very far away from that spot would see a huge amount of motion. If you went out far enough, you'd be seeing hard radiation from half the sky. Or, as another view, though I find this one harder to think about, since here the expansion of the universe seems to confuse rather than clarify things: The background radiation you see at any given point is simply the photons radiated inward from a sphere of a very large radius centered on that point. Every point has its own such sphere, and if an observer sees a dipole component in its background radiation, it means that that observer is in motion relative to the average motion of the matter that those photons originally came out of.
empath75 9y ago
would it be possible for a drunk in a void to change his rotation?
- dmikalova 9y ago
  You could blow in one direction or the other, at an angle. The air you push away will push you the other way.
  - philipov 9y ago
    If you're suspended in a fluid or gas, you're not in a void.
    - madaxe_again 9y ago
      Well, if he had a lungful if air, blowing would work - after all, rockets do work in a vacuum. That said, he’s drunk, so the answer is to piss into the luminiferous aether.
- scatters 9y ago
  No, because angular momentum is conserved, assuming flat space. It is possible to change one's orientation, however.
- CydeWeys 9y ago
  The story is phrased in a way that is delicately subtle, and thus elides the mechanism whereby the drunk can change his rotation. Here's a hint: It's relevant that the person is drunk. Another hint: Newton's third law.
  - madaxe_again 9y ago
    I call it my inbuilt vectoring urea reaction engine.
    - Simon_says 9y ago

taneq 9y ago

Sounds like a first year physics question. "Consider a spherical drunk in a frictionless vacuum..."

madaxe_again 9y ago
A perfect spherical drunk, in fact.
- deleted 9y ago
  [deleted]
- noonespecial 9y ago
  ...of uniform density. Although, for us, it was always a spherical chicken.
  - QAPereo 9y ago
    ...Alone in a universe.

eru 9y ago

And interesting enough, the universe does have a unique privileged inertial reference frame: that which makes the background radiation look isotropic.

Ari_Rahikkala 9y ago
Only locally, though. The next galaxy cluster over has a uniquely privileged inertial reference frame, too, but it's in motion (and accelerating!) relative to ours.
- danbruc 9y ago
  I think you are wrong, observers in different galaxies will agree on the inertial reference frame in which the background radiation is isotropic. The relative velocity between different galaxies will show up as different dipole components in the measured background radiation, but if you compensate for that, you should get the same inertial reference frame no matter from which galaxy you measured.
  - Ari_Rahikkala 9y ago
    I'll admit to not being a physicist and to being easily confused by the subject, so I'll just use a silly little metaphor to check whether I'm thinking straight, and try to avoid terminology I don't fully understand (which, since I don't have a particularly strong understanding of even special relativity, means not using relativity terms at all): Think of the universe as a rubber sheet over a table, being stretched in all directions. My understanding is that cosmic background radiation is on the rubber, stretching and moving with it just like all the matter is. If background radiation were on the table instead, there would be exactly one spot on the rubber that saw no motion relative to it, while spots very far away from that spot would see a huge amount of motion. If you went out far enough, you'd be seeing hard radiation from half the sky. Or, as another view, though I find this one harder to think about, since here the expansion of the universe seems to confuse rather than clarify things: The background radiation you see at any given point is simply the photons radiated inward from a sphere of a very large radius centered on that point. Every point has its own such sphere, and if an observer sees a dipole component in its background radiation, it means that that observer is in motion relative to the average motion of the matter that those photons originally came out of.

empath75 9y ago

would it be possible for a drunk in a void to change his rotation?

dmikalova 9y ago
You could blow in one direction or the other, at an angle. The air you push away will push you the other way.
- philipov 9y ago
  If you're suspended in a fluid or gas, you're not in a void.
  - madaxe_again 9y ago
    Well, if he had a lungful if air, blowing would work - after all, rockets do work in a vacuum. That said, he’s drunk, so the answer is to piss into the luminiferous aether.
scatters 9y ago
No, because angular momentum is conserved, assuming flat space. It is possible to change one's orientation, however.
CydeWeys 9y ago
The story is phrased in a way that is delicately subtle, and thus elides the mechanism whereby the drunk can change his rotation. Here's a hint: It's relevant that the person is drunk. Another hint: Newton's third law.
- madaxe_again 9y ago
  I call it my inbuilt vectoring urea reaction engine.
  - Simon_says 9y ago