Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Hannah LS on 14/01/2019 10:37:11
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Graham asks:
Given that the earth spins on its axis, which in turn spins within the solar system, which in turn spins within the Milky Way, which may spin within something else. Is it possible to calculate how fast the Earth is actually travelling?
What do you think?
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Graham asks:
Given that the earth spins on its axis, which in turn spins within the solar system, which in turn spins within the Milky Way, which may spin within something else. Is it possible to calculate how fast the Earth is actually travelling?
What do you think?
In each case, one is calculating the velocity relative to something (Earth's center, the sun, the center of the Milky Way itself, etc.). So for 'space', you would need to choose a reference that represent's 'stopped'. That frame is typically the one in which we're moving at the average velocity of everything we see, or the frame in which the cosmic microwave background is isotropic. These two frames are the same.
In that frame, the Milky Way is moving about 600 km/sec in one direction, but we're on the side spinning away from that, so subtract about 220 km/sec in somewhat the opposite direction. Net speed through 'space' is somewhere around 400 km/sec.
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No, not as far as I know. It's a observer dependent universe, and a 'frame dependent'. That meaning that when you define a 'speed' you must have another frame of reference you can define to be 'still'. With a car you use Earth, but Earth rotates and wobble, one doesn't take that into consideration and neither do one worry about how 'fast' Earth may 'move' through space.
It's the same with earths geodesic/'motion'. You need a frame of reference that you can call 'still' but we don't have any such that we know of. We have the cosmic background radiation but that one isn't a golden standard either, then we use what is called 'fixed stars', them being so far away from us that we can't define any motion to them. Or you do as Halc suggested and use any frame of reference you like to then define your 'motion' relative that.
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If, as Big Bang theory tell us, the Universe is not expanding through space; wouldn't it follow that the galaxy groups are "stationary" relative to space; if that has any real meaning?
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I should say it is "how fast the earth is travelling opposed to the gravity it experiences"
This encorporates all the mass in the universe, but at different distances and thus different forces. If you where the only mass in the universe you would be unable to tell if you where travelling at all, apparently even light (although this would need a source) would fit itself to you being stationary.
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Yes Bill, it should mean just that I think.
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Now let me just time reverse the Big Bang, playing the 'movie backwards.
How about that?
I'm at the exact point where it all started :)
No matter Earths, and my beds, 'relative motion'
As long as I'm the only one 'time reversing it' that is. If you do it too Bill, we will need two universes, as you too must be at the 'point of origin of that Big Bang'. Let's just hope it stays there..