by Chris Peterson » Mon Feb 22, 2010 6:51 pm
mark swain wrote:If I could not see outside our galaxy, How could i tell it was spinning? Even the dark Matter spins with us. At 100,000 Light years across, its hardly noticeable.
We do not need to see outside the galaxy to tell we are spinning. Since we are in a non-inertial frame, there are forces present that can be measured. It is true that the forces may be too small to detect with current technology, but that's a different issue. Consider that we can easily determine that the Earth is spinning (and how fast it is spinning) from inside an enclosed and isolated lab, using pretty simple equipment. It's harder with the galaxy, since the angular velocity is so small. But certainly not impossible.
If the universe was spinning, And you could somehow see outside, I doubt you would notice any movement in a billion years.
Again, you don't have to see outside (in fact, it is impossible to see outside the Universe). Although the effects of the Universe spinning in some higher dimension are going to be different from ordinary motion in three dimensions inside the Universe, we are still presumably talking about a kind of non-inertial frame that should produce effects that are, at least theoretically, observable. Theory predicts what those effects should be, and observations have failed to show them, which places an upper bound on the rotation rate- assuming the theories used are correct. But there are a lot of conflicting ideas about the geometry of the Universe, so I'd hesitate to say with any certainty whether or not it is rotating.
[quote="mark swain"]If I could not see outside our galaxy, How could i tell it was spinning? Even the dark Matter spins with us. At 100,000 Light years across, its hardly noticeable.[/quote]
We do not need to see outside the galaxy to tell we are spinning. Since we are in a non-inertial frame, there are forces present that can be measured. It is true that the forces may be too small to detect with current technology, but that's a different issue. Consider that we can easily determine that the Earth is spinning (and how fast it is spinning) from inside an enclosed and isolated lab, using pretty simple equipment. It's harder with the galaxy, since the angular velocity is so small. But certainly not impossible.
[quote]If the universe was spinning, And you could somehow see outside, I doubt you would notice any movement in a billion years.[/quote]
Again, you don't have to see outside (in fact, it is impossible to see outside the Universe). Although the effects of the Universe spinning in some higher dimension are going to be different from ordinary motion in three dimensions inside the Universe, we are still presumably talking about a kind of non-inertial frame that should produce effects that are, at least theoretically, observable. Theory predicts what those effects should be, and observations have failed to show them, which places an upper bound on the rotation rate- assuming the theories used are correct. But there are a lot of conflicting ideas about the geometry of the Universe, so I'd hesitate to say with any certainty whether or not it is rotating.