theory of relativity -- time dilation? I read that time moves slower in a moving object than a static object?

Question

How is it determined which object is moving and which is static. Aren't they both moving relative to each other? In which case, how is it determined which time frame is moving faster -- and which is slower?

Answer 1

The beauty of Relativity is that no refference frame is the correct one. After all, it's all relative.
Let's say you are in a train, and another person is outside. The train starts moving. After a while they ask you who was moving, you say the other guy was moving. The other guy says, no the train was moving. Who is right? Both of you, because no refference frame is better than another one, they're all equal.

Answer 2

At speeds significantly less than the speed of light, it is acceleration and not velocity that makes time go wacky.
Einstein determined that acceleration had the exact same effect as increased gravity on the slowing of time. Time slows significantly on an object in a large gravitational field, an accelerated object and objects that approach an appreciable percentage of light speeds - at slower speeds, the time difference is negligible.
Interestingly enough, there are no "static" references - indeed, there are no objects that are truly at rest - yet every object can legitimately consider itself at rest when collecting data on the speeds and direction of other objects. Scientists on earth do it all the time. Steady state speed is undetectable - acceleration is easily detectable.
Comparing time frames can really only be done by comparing two objects at rest relative to one another - synchronizing their clocks - and accelerating one of the objects into space, turning it around and accelerating it back to the first object - the object which is sent into space will have "lost" time compared to the object that sent it out. Until we get a heck of a lot more technology, travel to a different planet with a synchrized clock with earth and, after discounting the accelleration and decelleration effects, we will be able to actually compare the time differences due to gravitational differences of planets - and I'll bet the farm that they exactly equal the results determined by Einstein's formulas. We already know that they will vary at the top of a mountain or in a high altitude plane verses at sea level due to the gravitational differences on earth.
And, as you probably know, each object will measure the speed of light as exactly the same - one object with a slower clock and shortened distances and the other with a "normal" clock and "normal" distances.
Great stuff, this physics, eh?

Answer 3

LeAnne's answer is a good one. Theory of relativity broke classic physic laws. In classic physic laws, everything can be determined exactly. Theory of relativity stated that not everything can be determined EXACTLY. It all depends on the frame of refference. If there are two or more people in the same frame of refference, than all of them would get the same result out of an experiment or a formula. If the frame of refference is different however, the result can and should be different. Although the results are different, both of them are right (assuming they did their job correctly). Most of the time the difference is soooo small, so the difference can be ignored, but when we're talking about speed or acceleration near the speed of light, we're talking a big difference, and the result can differ greatly. The time is different, the mass is different, and so on.
An example taken from the above answers, if you were to embark on a space ship leaving earth at speed near the speed of light to a planet far away and return, the time on your space ship would have slow down ACCORDING to the people of the earth. According to you, everything would be normal. This is because you have your own frame of refference, and the people of the earth have their own. Say according to you, you have been gone for 30 years, the people of the earth would say you have been gone for 150 years. You may have met your great grandson when you return! (just an example, I didn't really calculate the time with a formula). You insist that you've been gone just for 30 years, but the people of the earth insist that you've been gone for 150 years. Both of you are right. This is the basic foundation of the theoritical time machine. This theory requires you to think out of the box, the classic physic laws box, that is.

Answer 4

Hi. A complicated question, great! The time dilation is only noticeable at pretty high speeds, say of a spacecraft in orbit. Comparing two clocks with identical accuracy and precision show that the one in the spacecraft records time as being slower. But your question involves two different references for time. So let's say that the spaceship with one of the clocks is moving away from Earth. The time will still slow down but how do we compare them. Well we turn the ship around, obviously to get the clocks back together, right? But now the spaceship is moving SLOWER than the Earth against the backdrop of the universe, or at least in a different vector. So what happens when the two clocks are compared? You think about it.

Answer 5

Typically, the observer is in the stationary frame of reference. Things get a little tricky when acceleration is involved as well, since it is possible to determine which object is accelerating and which is stationary (or moving at a constant velocity). You see, it is actually the acceleration that results in time dilation.