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Given the speed of light is 299,792,458 meters per second and that it is constant through out the universe, (i.e a person who measures the speed of light while standing still will get the same result as a person moving through space in a rocket)

My question is: if I'm standing still, what is the speed of me moving through the universe? Compared to the speed of light?

The following variables should be taken into consideration

  1. the speed at which the earth is rotating,

  2. The speed at which the earth is moving around the sun,

  3. The speed at which out solar system is moving around our galaxy,

  4. The speed at which our galaxy is moving in our universe.

bobie
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Tien Dinh
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  • There is a 5th option: none of the options 1 to 4. There is no absolute speed. – Sofia Dec 21 '14 at 22:31
  • Speed of light is constant across all inertial frames according to the SI definition at http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/speed_of_light.html. What i'm after is the my velocity relative to light within the universe. – Tien Dinh Dec 21 '14 at 23:19
  • Your speed relative light is $c$. No matter what your speed is relative anything else is. That is what it means for everyone to measure the same speed of light. – dmckee --- ex-moderator kitten Dec 22 '14 at 03:27

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In relativity there is no absolute speed because there is no notion of absolute space or time--your speed can only be measured relative to some reference frame (a coordinate system which assigns a position coordinate to each object at each time coordinate), usually an inertial frame (the speed of a light ray is the same regardless of which inertial frame you choose, for a numerical example showing how this works see my answer here). So you can be "standing still" relative to the Earth, or relative to the Sun, but no physical meaning can be assigned to "standing still" in a non-relative sense.

Community
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Hypnosifl
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    This answer is misleading. The fact that speed doesn't matter is not at all equivalent to an absolute space-time, but to the fact that there exists no privileged inertial frame of reference. The inertial structure is actually absolute in physics : to accelerate is something you can be sure of, while to have some velocity with respect to "some supposely absolute space-time" doesn't matter. – sure Dec 21 '14 at 22:51
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    Let me add that in general relativity, the inertial structure is a consequence of matter distribution and not an a priori. It's important to notice the difference. – sure Dec 21 '14 at 22:54
  • @sure - Not sure what you mean, an "empty" spacetime with no matter anywhere, i.e. a flat SR spacetime, is a valid solution to the Einstein field equations in GR, and all solutions possess local inertial frames at every point regardless of the specific matter distribution. I also don't know what you mean when you say the "fact that speed doesn't matter is not at all equivalent to an absolute space-time"--I said "absolute space and time", two terms which had a specific meaning for Newton as explained in the link, not "absolute space-time" which is not a phrase I've ever seen used before. – Hypnosifl Dec 22 '14 at 04:13
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    But there is an inertial frame that is "better" than the others: the one where the CMB has no dipole moment, i.e. where we are standing still relative to the CMB. That would be the most logical frame to use when answering the question. – Thriveth Dec 22 '14 at 22:55
  • @Triveth - When physicists say there is no preferred frame, they are talking specifically about the basic equations of physics working the same in each inertial frame, even if one frame may be easier to work with for reasons relating to the particular matter distribution. If you are in a sealed windowless lab moving inertially with nothing external to refer to, and you do some experiments to find the correct equations for the laws of physics in a coordinate system inside the lab, you will end up with the same equations regardless of whether the lab is at rest or moving relative to the CMBR. – Hypnosifl Dec 22 '14 at 22:59