Question on the Theory of Relativity: Time Slowing?

Question

Let's say I get in a spacecraft and travel close to the speed of light. By the theory of relativity, I may come back having aged only one year while the Earth aged 100 years.

The part that confuses me is: Why can't the opposite be true, i.e. I age 100 years while the Earth ages 1 year? By my frame of reference, I am standing still while the Earth is moving close to the speed of light. Whose frame of reference determines how fast time is moving?

Answer 1

This is why it's called the Twin PARADOX, originally thought up to "refute" the theory of special relativity. The Lorentz-Fitzgerald transform is symmetric between any two uniformly moving frames, but this symmetry is broken if either one of them is not moving uniformly. The travelling twin has to turn around in order to come back, so he's the one with the non-uniform moving frame.

Special relatiivty is usually graphed in hyperbolic space, in which proper time of the travelling spaceship can be hard to discern. There's an alternate graphical representation of special relativity that shows the time of the twin at rest to be equal to the path length of the travelling twin, while the proper time of the travelling twin is shown to be the vertical line x = 0. I know this sounds very confusing, but bear with me. Let the spacetime path of both twins to begin at (x,t) = (0,0), so that the vertical path (0,t') is the proper time of the travelling twin, while the path length of the travelling twin is the time t of the stationary twin. Then a moment's thought will show that regardless of the path the travelling twin takes, the length of the path will always be longer than the change in the vertical, or t'. Thus, it's the stationary twin that has aged more than his travelling twin. There is no symmetrical counterpart to this representation, where the twins reverse roles. There is no linear transform to reverse them, it depends on the path the travelling twin makes.

Answer 2

every thing depends on the frame of reference. If you are static and the earth is moving close to speed of light, the age of earth will very less compared with your age with respect your frame of reference. If there is some thing which is moving faster than earth then that object will be "younger" than earth compared to earth's frame of reference.

Again if you are on earth, then it doesnt matter how fast the earth is moving, relative to earth your speed will be zero so both will age at the same rate...

Answer 3

well taking from a an episode of star trek voyager, there was a planet was an very high rotation rate. like every second was a full day. in the show the people that lived there aged 1 day for every second. so basically if the earth is spinning near the speed of light, we are living on that planet and therefore we would age a lot faster compare to the rest of the universe, very interesting question, i really have no idea about this.

Answer 4

It's the twin paradox. Well, all the answers above are a bit confusing. No frame of reference is the preferred frame. You have left the earth in spaceship and you can be fully convinced that it is the earth which is moving with the speed near that of light and people at earth should be younger.

BUT THERE IS ONE PREFERRED FRAME OF REFERENCE WHICH IS UNACCELERATED WITH RESPECT TO MASS AND ENERGY OF THE UNIVERSE. EARTH IS SUPPOSED TO LIE IN THAT FRAME AND WHOEVER LEAVES THAT FRAME,TIME SLOWS DOWN FOR HIM.

Answer 5

No, it is not the same thing. You were the one experiencing the acceleration, not the earth. The frame of reference (FOR) is change if acceleration is applied to one observer.

The key thing is that you started in the FOR of the earth and then proceeded to change yours. So when your journey began you were progressing at the same rate of time as earth, and then modified your speed (and therefor your time). Once you had reached the speed of light your aging would be near 0 compared with the FOR you started at. If the earth had been accelerated to light speed the reverse would have been true. Their rate of time is not effected by your leaving and accelerating like crazy, but would be if they had left you and accelerated like crazy. So think of acceleration (or deceleration of course) as the force which changes your FOR and your rate of time.

It is a lot more complicated when you start out with 2 people in 2 different FORs, but for them to meet and interact they have to assume the same FOR. I don't have time for all that!

Answer 6

the closer you get to the speed of light the slower time will flow and if you reach the speed of light time would stop. if you travel for 100 years at, let's say 99% the speed of light you would probably be just a few hours older.

Answer 7

Earth itself might ahve aged 1 year, but you are at rest so you will age normally. The object moving at the speed of light (itself) would age slower...I think.

Answer 8

It would be possible if you could manage to be able to accelerate the earth to near the speed of light. But does that really sound feasible?

Answer 9

Motion through time * motion through space = c. [c, of course, means the speed of light (in a vacuum).]

The more energy you put in moving through space, the less energy you put into moving through time. This goes for anything and everything. By moving at close to c, you're using up a lot of your energy in motion through space and very litle energy is used for moving through time. The earth moving along very very slowly, comparatively, is still using lots of its energy for motion through time as well as space.

Answer 10

Because it was your frame of reference that experienced the accelertaion, not that of the Earth. It was -you- who were pushed back in your chair, not me. This is what actually causes your clock to 'slow down' WRT mine.


Doug