Suppose you are on board a spaceship that is passing the earth at 80% the speed of light. You see a clock on e

Question

Is it

a. 5 seconds-the same as on earth's clocks
b. less than 5 seconds if you are approaching earth, or more than five seconds if you are moving away
c. less than 5 seconds
d. more than 5 seconds

Suppose you are on board a spaceship that is passing the earth at 80% the speed of light. You see a clock on earth tick off five seconds. How much time elapsed on your clock while this was happening?

Answer 1

By Einsteins Theory

Time on Earth = (Time on board)/(1-((.8c)^2)/c^2) where c is the speed of light = 299 792 458 m / s

Time on board = 5 sec * (1-(299792458*.8)^2/(299 792 458)^2)

Time on board = 5 * (1-.64) = 1.8 sec

Answer will be less than 5 seconds

Answer 2

Are you asking what you would see or for the reality of time/space? Time space warps or special relativity actually deals with light. Unfortunately, it also says that light moves at the same speed whether you are traveling toward or away from the source. The light you would see, from the earth in relation to the clock would tick away slower than the one you have onboard. In reality they are the same. You can't actually change time, only your relationship to it.

Answer 3

C

According to Einstein's Special Theory of Relativity:

The closer and closer you get to travelling at the speed of light, the more time slows down...until when you reach the speed of light and time (supposedly) stops.

Also somewhat related, this is illustrated by theories that after astronauts go into space and return to Earth, they (supposedly) are actually younger than if they would have remained on Earth.

Answer 4

v = 0.8c
gamma = 1/SQRT(1 - v^2) = 1.666667 = 5/3

D(t) = D(t')*gamma = 5 * 5/3
=25/3 = 8.3333 s

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There is no preferred frame of reference. As far as you (and your clock) are concerned, everything is normal for you. It is the Earth (and its clock) that are moving (in reference to you) at 0.8 c. Therefore Earth time is dilated. Earth's clock will appear slow to you.

An observer on Earth will see you moving at 0.8c. As far as she is concerned, it is your clock that is slow. If she counted off 5 seconds on your clock, her clock would have moved 8.333 s also!

There is no paradox as the two clocks cannot be brought together (in special relativity) to be compared. If you stop the ship's clock to bring it to Earth's speed (or accelerate Earth to bring it alongside the ship), then acceleration is involved and special relativity no longer applies (you have graduated to general relativity where things really get weird).

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Time dilation:

The effect really has been observed (Mount Washington USA, 1962). Muons (sub-atomic particles) decay in a very precisely predicted manner. They have a half-life of 2.2 microseconds (millionths of seconds). Muons can be created in a lab at any speed, including very slow. That is why we know their "half-life" very precisely, according to their clock.

Half-life = the time it takes for half of them to decay. If you start with a whole bunch, after 2.2 micro-seconds half are gone. After the next 2.2 microseconds, half of the remaining half are gone. And so on (1/2, 1/4, 1/8, 1/16, 1/32...).

Very high energy cosmic rays crash into atoms at the top of our atmosphere. The collisions cause muons to 'rain' towards Earth at speeds of 0.992c (99.2% of the speed of light).

Even at that speed, half the muons should decay within a distance of approximately 650 metres (2.2 millionths of a second at 99.2% of the speed of light).

Yet, when measurements are taken at various altitudes, we find that it takes almost 5,200 metres for half the muons to disappear. At 0.992c, it takes almost 17.5 microseconds to cover 5,200 metres. That time period represents almost 8 "half-lives". There should be only 1/64 of the muons left.

This means that from our point of view, the muons' "clock" is going only 1/8 of the speed of our clock. When we will have measured 2.2 microseconds on the muons' clock, 17.5 seconds will have ticked on ours.

Length contraction:

Of course, if we could see things from the muons' point of view, we would see that the two detectors, which earthlings pretend they have placed 5200 metres apart, are only 650 metres apart, a distance which muons know they can cover, at 0.992c, in 2.2 microseconds...

Answer 5

Time is time, not influenced by speed, the thought that your speed will effect time, is neither been proven nor disproven, untill it has been proven correct, I'll stick with believeing what I know.

Answer 6

It is faster for you, b/c the journey mightbe a week for you and a decade for those on Earth.

Answer 7

c, isnt that einsteins theory on time travel?