Time travelling twin paradox, 99% the speed of light?

Question

This is a rephrasing of a question I asked earlier with good answers but none that satisfied me.

Right, you are in a spacecraft and you are looking back at your twin on earth with a very large telescope.

Then you travel away from earth at 99% the speed of light. For a few years then come back.

According to relativity you will be younger than your twin. But while you are looking through the telescope you must at some point see your twin aging faster than you, therefore time speed up.

But everybody is telling me both twins are observing each other with time slowed down and I do not understand how.

Please help me.

Answer 1

There is no paradox. The outside observer sees time slow down (i.e., dilate) on the spaceship. The inside observer sees time speed up on Earth. Both observers are able to see the time effects because they are looking at the other observer's frame of reference (i.e., Earth or spaceship).

But both observers see time march on at the regular rate relative to their own frames of reference. There is a reason it is called the theory of relativity; that reason is because time is measured relative to one's own frame of reference (e.g., the Earth or the spaceship). When measuring other reference frames, time dilation is observable.

Although no one has observed time speeding up, they certainly have seen it slow down...in this case, the spaceship is a radioactive particle in a linear accelerator or collider. When such a particle is accelerated to near light speed, the rate of decay slows down because the passage of time on the particle (to the outside observer) slows down. [See the source for an easy reading explanation of time dilation.]

Answer 2

The time for the traveling twin actually slow down.
So, remember they have a different time reference.

However, the images seen (image aging) are different then the actual aging of the twins, as the images travel at the speed of light and are limited to this speed. What changes is the frequency of the images, depending on the direction of the traveling twin (moving away or coming back). The frequency of the images are slow (slow aging) when moving away and fast (fast aging) when coming back.

This is the relativistic doppler shift of the images observed.

Because of their difference in time reference, the shift from slow frequency to high frequency images will not happen after the same elapsed time. For the traveling twin the shift happens at the mid-point of the trip, while for the stationary twin (on earth), the shift happens fairly close to the end of the trip of the traveling twin.

You can find calculations and fairly comprehensive example of this at the link below.

Answer 3

What you have stated in your last statement IS the twin paradox; both twins come to different conclusions about how old they are, which is impossible. The reason for the paradox is that special relativity is an incomplete theory, and does not account for acceleration. Yet the "twin experiment" can't be actually performed without acceleration being involved.

Answer 4

Think of it like the doppler effect.
(reason why ambulances sound higher pitched approaching you and lower pitched when they've passed)

While going away, time would be slowed (like the slower rate of sound waves makes a siren lower pitched while leaving), but while approaching, time would be faster, just the one moving close to the speed of light would be less affected by the passing of time.