1. May 21, 2004

### energia

Time Dilation Q&A

The following questions explore the mechanics behind the theory of relativistic time dilation

NOTE* this is not a topic for questioning the validity of time dilation -
replies are expected to provide logical solutions based on relativistic principles

it is also not a podium for Philosophiae Doctors (PhD's) to present lectures

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The Questions

1. Special Relativity predicts that time on a clock in motion slows down relative to a stationary clock - and slows proportionately relative to it's speed - up to the speed of light where the clock in relative motion would completely stop

(1.) explain in simple terms what causes this phenomenon

2. a stationary clock on the earth moves faster relative to a clock on a satellite in geosynchronous orbit - since the satellite is travelling at thousands of meters per second - although it seems to stand still above a point on the earth

(2.) True/False (and why)

3. multiple choice: A. a clock on the earth moves faster relative to a clock on a spacecraft travelling away from the earth at 30000 m/s

B. the clock onboard the space craft moves faster relative to the clock on the earth

C. both move faster relative to one another

(3.) A, B, or C (and why)

4. if the spacecraft were stationary in space... the earth would move away from it at 30000 m/s in it's orbit around the sun

is there a difference between the earth moving away at 30000 m/s and the spacecraft moving away at 30000 m/s ?

(4.) Yes/No (and why)

5. if a spacecraft is travelling along earth's orbit in the opposite direction
at 299763458 m/s it is travelling away from earth at 299793458 m/s
(1000 m/s faster than lightspeed) does this violate Special relativity?

(5.) Yes/No (and why)

6. do the clocks stop onboard the above mentioned spaceship and then move backward in time relative to stationary clocks on the earth?

(6.) Yes/No (and why)

Last edited: May 21, 2004
2. May 21, 2004

### Staff: Mentor

1. Its a biproduct of the constancy of the speed of light. Beyond that, "why" or "what" gets kinda philosophical.

2. Doesn't make a whole lot of sense (grammar is a little iffy - could you reword?). But maybe I can clarify: a geostationary satellite travels at about 3km/s relative to a fixed (non-rotating) earth. Or when you say "moves" are you talking about the time it is reading? That's a little more complicated: due to both SR and GR, the net result is time passes faster for the satellite.

3. Again, what do you mean by "moves"? If you mean the rate of the passage of time, a clock on a spaceship at 30,000 m/s experiences both SR and GR time dilation and its clock has a net rate increase relative to a stationary earth clock.

4. Yes: acceleration.

5. No. You can't add velocities that way when they are that high. Neither an observer on the ship, nor one on earth will see the other moving at >C.

6. No. See 5.

These questions are the basics of SR/GR. You may want to pick up a book and learn that way - it may allow you to avoid going through this question/answer process.

3. May 21, 2004

### energia

if you would, please post the philsophical perspective on this byproduct of the consitancy of lightspeed in a way that anyone reading this topic can comprehend it.. this will help those new to relativity to come to terms with the concept

please tell me which parts of the text are grammatically unclear
and i will try to reword them in a more clear and concise way

correct

when i say move, im refering to the rate at which time passes
(for example: 1 s/s = 0% time dilation)

correct

however please don't be reluctant to use more philosophical explanations

this question and answer process is the best way for many to comprehend concepts that are not so easy for most people to come to terms with

since you have a good understanding of the concepts
try to explain them as you would to a person who has never heard of relativity
and is unlikely to spend their days reading ~ Relativity - The Special and General Theory by Albert Einstein from cover to cover

4. May 25, 2004

### wisp

A simple explanation can be given in terms of the mechanics of the moving clock. But this can only be posted in the theory development forum. If you like I can post you details there under "the mechanics of time dilation" etc...

wisp

"particles of nothingness"