5 ms·
> (we are not moving all that fast compared to the speed of light) From what I understand, no one ever moves (fast, slow, whatever) compared to the speed of li
by MichaelApproved 7y ago
> (we are not moving all that fast compared to the speed of light)
From what I understand, no one ever moves (fast, slow, whatever) compared to the speed of light from their own reference point.
The speed of light is always the same for all observers from their own reference point, so how do you reconcile those statements?
- cylon13 7y agoI don't move relative to my reference point, but you move relative to my reference point and vice versa. So from my point of view it makes sense to say you are moving at some fraction of the speed of light.
- antognini 7y agoYes, in your own reference frame you are stationary. So by definition all observers are at the same speed in their own reference frame, namely zero. What I was trying to say is that the velocity of the Earth relative to the Milky Way's SMBH is small compared to the speed of light.
- MichaelApproved 7y agoThanks for the clarification. This stuff can be clear and confusing at the same time.
- wokwokwok 7y agoIf we (sol / earth) were moving at a speed significantly closer to the (absolute) speed of light we would experience significant time dilation. This is significant for observing external events and correlating phase shifts to figure out distances. Eg. Things in the external universe may appear to happen extremely quickly. It’s actually very important. Regardless of how fast you appear to be moving in your own frame of reference, the speed you’re travelling in absolute terms affects what you observe externally (and specifically with regard to how fast you are moving compared to what you observing)
- roywiggins 7y agoThe thing we are at rest (ish) relative to is the cosmic microwave background. That's why we aren't moving that much relative to the rest of the universe, on average. Time dilation is relative between you and some other reference frame. All the "stuff" in the universe nearby is (fairly) static, so we can say we are not moving fast, but it's still relative to the stuff around is.
- mirimir 7y agoHuh. So could one use that as a standard frame of reference?
- roywiggins 7y agoMaybe, kinda. It's not obvious that it's more privileged than centering a reference frame on the Earth or the Sun. The CMB is maybe just an artifact of the Universe's history (like a Sun-centered one is an artifact of ours). If we didn't have any CMB radiation floating around to measure, everything would probably work exactly the same. Maybe you could measure all the motion of all the matter in the visible universe and measure the motion of the "center" relative to us.
- philipov 7y agoYes and no. The laws of physics do not pick out a preferred frame of reference, and they should be symmetrical under lorentz transformation, but the fact that we live in a cosmological universe starting with a big bang breaks that symmetry in practice. It's similar to how the laws of physics are symmetrical under translation and rotation, but the presence of matter around us means the surface of the earth is not the same as the surface of the sun. So, while we might use the CMB as a standard reference frame, the laws of physics should not.
- MichaelApproved 7y ago> the speed you’re travelling in absolute terms There is no such thing. You always have to compare your speed to something else. Speed is calculated relative to something else. Relativity.
- simonh 7y agoThat statement was very clearly talking about the difference between the reference frames of the Earth and the galactic core, and comparing that difference to the speed of light.