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harrylin
#39
Mar30-11, 06:00 AM
P: 3,187
In addition:
Quote Quote by Max™ View Post
[..]
Yes, in your frame, you'd only experience/age/observe 2~ years, and claim your laser beam only crossed 2 light years.
Again: not in "your frame" but in the inertial frame in which you happen to be in rest at that time. That may sound picky but it becomes essential in a continuation of discussion, as now happened:
If you then turned around and fired a reply laser while going fast enough that you again measure the beam traveling for only 2 years as it crossed 2 light years, you would return 1280+ years after you left, roughly 4 years older. [..]
From the experience of the traveler, indeed this will be the case, and he may have difficulty in explaining - based on that experience - why the stay-at home aged so much. You may next want to argue that this proves that the inertial frame of the Earth is something like a True Rest frame - but that's wrong. In relativity all inertial frames are equally valid in the sense that no such frame can be identified from observations.
Here you switched from using one inertial frame to another for one observer. For a reality-like description that is not allowed; in that sense, the class of inertial frames is preferred in special relativity.

For "twin-paradox" scenarios in which one observer switches inertial frames (or in which he uses a non-inertial frame), only* the description of the other observer who does not switch frames provides a consistent and realistic explanation in SR (loosely said: "frame-hopping" leads to inconsistent or unreal descriptions).

Cheers,
Harald

*Einstein tried to get rid of that with GR, but most people nowadays don't appreciate the reality of "induced gravitational fields".