IM Egdall Posted September 19, 2010 Share Posted September 19, 2010 I agree that locking down the various frames of reference is key. May I suggest you consider the Earth and the other planet as stationary with respect to each other for simplicity. That way thay are in the same reference frame. So there are now two frames: 1) The Earth/other planet reference frame. and 2) The light (photon) reference frame. Say the Earth and the other planet are one lightyear apart (in the Earth/other planet frame). (And think of only sending a single photon, again for simplicity.) From the Earth/other planet reference frame, the photon (message) is emitted by us on Earth at time zero. One Earth year later, this photon is received by the other planet. Aliens on this other planet then send their return message (another photon) to Earth. One more Earth year later (year 2), the photon is received back on the Earth. Because the Earth and other planet are in the same reference frame, there is no time dilation or length contraction. (No relative motion so no shrinking of time or space). From the initial photon's reference frame, it is standing still and the Earth and other planet are moving at the speed of light. So the photon sees the ultimate time dilation and length contraction. From the photon's point of view, the distance between the Earth and the other planet has contracted to zero. From the photon's point of view, it travels from the Earth to the other planet instantaneously! Any photon going from place to place (in a vacuum) goes at the speed of light. Thus for it, time is frozen (it never ages) and all distances are contracted to zero. Link to comment Share on other sites More sharing options...
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