Does the twin paradox introduce a paradox?

Question

Some postings in other groups insist that during certain periods of acceleration during his trip a traveller insists that his twin sister is physically ageing at faster or slower rates than she was before he commenced his trip on the basis that this is what he determines on the basis of his calculations based on the Lorentz equations.

I am trying to find out if this concept is 'conventional wisdom' in the scientific world?

Answer 1

The period of acceleration is not relevant, per say. This is a common and ingrained misunderstanding (I predict thumbs downs). The relative aging rate difference occurs during the coasting period too, and the Lorentz Tranformations used to calculate the effect need not consider the acceleration period. The Lorentz contraction of the trajectory (the length of the galaxy, say) causes the astronaut to only travel a short distance in his reference frame, so he ages less. That's the key concept. In principle, you could transport a la Star Trek to an already moving ship as it passes earth (or radio a signal to start a clock on board if you want to be more realistic), transport to an already earth bound ship you pass at the far end of the trip, then transport back to earth as that ship passes earth. You'd get the same result - young astronaut, old earth twin.

Answer 2

I would say that it is "conventional wisdom". It has even been shown by having someone take an atomic clock (these clocks are very very precise) on a plane and then comparing it with one that had not been moved. The one on the plane had lost some very small amount of time (planes might seem to travel fast but it is like standing still when compared to the speed of light).

As far as the twin thing, what happens is you have two people and one jumps in a spaceship and accelerates to near the speed of light and then flies out several light years and then returns to earth. It is the periods of acceleration and stopping that are crucial. It is these periods that allow one to deterine that the person on the spaceship will have aged less than the person on earth. Now while the spaceship is coasting around, his clock will appear to be running slow to the person on the earth and the reverse will also be true. The person on the spaceship will see the clock on the earth running slow. This is explained in special relativity as each observer should see the same thing. But these observations are only apparent and caused by the lorentz contraction and time dilation as applied to two coordinate systems in relative motion. But because the spacship person has undergone those periods of acceleration and stopping it is their time that will have actually slowed down. I should perhaps point out that it is not the acceleration that causes the person to age slower it is traveling at some speed near the speed of light. The longer you do this (move at a constant speed near the speed of light) the bigger the age deifference between spaceship person and earth person.

Answer 3

It's not only 'conventional wisdom' but the phenomenon has been proven to actually exist. Two identical atomic clocks were tightly synchronized. One stayed behind while the other was flown around for several hours aboard a high-speed jet. When the two clocks were brought back together, the two clocks no longer showed the same time.

Answer 4

This concept was first introduced by Einstein concerning the limits of accelleration in Space-Time when approaching the speed of light, and later expounded upon by Carl Sagan in his wonderous series Cosmos.

Answer 5

It is a fact, a body in motion, especially at high speeds ages slower than a body at a rest.