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## Main Question or Discussion Point

I've studied SR previously and, after a lot of work, grew to understand it. Now I have to re-work through it using a different textbook and can't figure out the deal with time dillation.

I derived the equation

T = T

With relative ease. In this equation, T

At this point, my textbook states that this means that the observer at rest observes time slowing down for the moving person. I don't understand this.

Say a spaceship was passing by Earth. I'm laying in the grass, looking up. In my frame, I'm at rest. The spaceship passes over, quickly. I measure the time I can see it. Since I'm at rest in my own frame, this time is T

The same chain of events could be measured from the spaceship. Staying in my frame, my equation tells me that the spaceship measures a higher time. Perhaps I measured 4 seconds, while the spaceship measured 8!

In other words, more time passed for the ship. Doesn't that mean that I observe a spaceship where time is moving much faster! After all, I "saw" twice as much as time passing on their clocks than on mine!

I derived the equation

T = T

_{0}γWith relative ease. In this equation, T

_{0}is measured by a person at rest (in his own frame) while T is measured by a person moving (in the rest frame of the first observer. Due to the nature of γ, T will always be larger than T_{0}.At this point, my textbook states that this means that the observer at rest observes time slowing down for the moving person. I don't understand this.

Say a spaceship was passing by Earth. I'm laying in the grass, looking up. In my frame, I'm at rest. The spaceship passes over, quickly. I measure the time I can see it. Since I'm at rest in my own frame, this time is T

_{0}.The same chain of events could be measured from the spaceship. Staying in my frame, my equation tells me that the spaceship measures a higher time. Perhaps I measured 4 seconds, while the spaceship measured 8!

In other words, more time passed for the ship. Doesn't that mean that I observe a spaceship where time is moving much faster! After all, I "saw" twice as much as time passing on their clocks than on mine!