If there is no absolute motion, why should one of the "twins" be entitled to a privileged point of reference?

Answer 1

Special relativity is only useful for situations in which the reference point is inertial. For a spaceship to leave Earth and return, there must be a huge amount of acceleration (even if it leaves Earth already moving quickly) when it turns around to come back. Because Earth is close to inertial, its reference frame is the correct one.

One cannot compare the ages of the twins before the return journey because Einstein also states that simultaneity is not absolute.

Answer 2

The point of privledge does not exist other than in an illustration. When we live in our present universe we all have equal time in order to perform certain events, eating, sleeping, education and so forth. The person moving near the speed of light can do none of these things. The person is "frozen" into a particular value of time that is not the same as the twin at home. While the twin at home has an interesting job, marries his sweet wife, and raises a delightful family, the twin would be locked into a time condition where none of these things could happen.

Were one of the twins to leave earth, instantly moving at the speed of light, and were that twin to have a hot cup of coffee with them when they started, it would still be warm 20 years later when they reached their destination, were they to actually move at the speed of light.

There are writings reative to this at http://360.yahoo.com/noddarc and
http://timebones.blogspot.com You might check out "The Problem and Repair of Relativity".

Answer 3

I assume that you are talking about the twin paradox in time travel discussions. Well, when we compare the twin moving in light speed or near light speed to the twin on earth, it doesnt mean the twin on earth is on a privileged point of reference. We are simply taking a slow moving reference (in this case earth) as point of reference compared to the fast moving (near light speed) target. More like comparing a slow moving entity to the fast moving entity. Both are moving alright, but not at same speeds. Hope that helps.