According to Relativity Theory, which is over 100 years old now and tested ad infinitum: If we are both in spaceships and pass each other, we can each measure the rate that time is passing for the other. You, in ship A, run your sensors and see that my clocks are running more slowly than yours, just as Einstein predicts with his time dilation equations and based on our relative velocity. I, in ship B, run my sensors and see that your clocks are running more slowly than my clocks, just as Einstein predicts with his time dilation equations and based on our relative velocity. . So whose clocks are really running more slowly?
Another interesting thing most people may not know, that's also how electromagnetism works. You see, electrons are very lightweight particles and so approach close to the speed of light in an electric current. When you have two electrons moving parallel to each other in the same direction, the rate of electric force they exert on each other, relative to an outside observer, is less. So with the electrons repelling each other less, that no means there's an overall net attraction between both conductors that are carrying current. The positively charged nuclei from one wire attracts towards the electrons in the other wire. Imagine the point of view from the perspective of the two electrons. To them everything seems completely normal. But to an outside observer, time has slowed to a near standstill for these two electrons. That means rate of force pushing them apart decreases, from the perspective of an outside observer. Now if the current is moving in opposite directions, that enhances the repulsion. Because of relativity, we have to view the situation from the electron's point of view. If the electron was standing still (from its perspective), then the oncoming electron would have to be going nearly twice the speed of light, which isn't possible even from the perspective of an observer moving at close to the speed of light. Instead the electron just appears to be emitting a higher rate of electromagnetic force.
Actually, the electrons in a wire travel at about the speed that you walk. The signal travels at about half the speed of light. But the actual speed of the electrons, known as the drift velocity, is just a meter or a few per second in a typical circuit. And it was a question. Whose clocks are running more slowly? Please read the post.
Time Is Moi. And Moi is now. What some hypothetical observer witnesses is so much, He Said / She Said we witness as gospel truth today. Questions?
You're right. Guess it has more to do with frames of reference than any time dilation. (or maybe even tiny degrees of time dilation can end up having big effects)
You'd have to use a third point as a reference say the Milky Way galaxy or Earth itself. Both rotate at a "relative" rate but one can can call standard time. Measure ship's clocks to that. For the curious: the formula -- http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/tdil.html Second set down. It does the calculation for you.
Nope. But nice try! One of the core principles from Special Relativity: There is no preferred observer. This means that there is no absolute frame of reference - no true state of being motionless. It is all relative - what is your velocity compared to me?
I can make the assumption that I am at rest and the rest of the universe is moving around me, and it would be an entirely valid assumption - that is to say I wouldn't find any violations of the laws of physics. Keep in mind that this all ignores gravity fields and accelerations [General Relativity]. This is all out in free space and moving with constant velocities.
As a corollary: The classic twin paradox and how it applies here. We have identical twins, young men, and send one off in a spaceship at near the speed of light for a year his time, When he returns, he is only a year older, but his twin might be an old man. If time is relative, when the twin is travelling off at near the speed of light, he looks back and measures clocks on earth running slowly compared to his. But when he returns, in fact he is young and his twin is old, so his clocks were really running more slowly on the spaceship. If the solution to the original paradox was that it depends on the observer... how do we know which twin gets old?
I am certainly no relativity expert, but concerning the twin paradox, the difference is that one of the twins experiences acceleration and deceleration in order to leave and then return to the other twin. The twin who stayed at home remained in an inertial system while the twin who left did not remain in an inertial system. The "non-inertial" twin would be younger. I don't pretend to understand why the above holds true. I do know that all inertial time frames are equivalent, but acceleration and deceleration introduces non-inertial forces into a system and that system can no longer be considered inertial. I do wish someone with an understanding of the original question would chime in.
Concerning the original post and the question: The following quote is from http://www.physicsoftheuniverse.com/topics_relativity_special.html "In a nutshell, the Special Theory of Relativity tells us that ... moving clocks run more slowly as their velocity increases until, at the speed of light, they stop running altogether." My question is "velocity measured in respect to what?" The center of the universe or something? But I thought it was relative? With any two inertial frames, A and B, that are moving with respect to each other, can't we view one of them as being stationary and one of them as moving? And vice versa? So which inertial frame is considered as moving?
Great answer! And physics tells us what, not why. So you're doing fine. Note that due to the acceleration and deceleration, there is additional time dilation - clocks run slowly in gravity fields. So it gets much more complicated to calculate the actual age of the returning astronaut. It requires General Relativity.
It is relative to an observer you define to be at rest. First you have to pick a reference frame that you define to be at rest, and then everything is calculated against that. Yes And that is the point - it depends on who you define to be at rest. It is arbitrary. That is what is meant by the expression, there is no preferred observer. ... provided nobody accelerates.
So it still doesn't make sense. I can choose A to be at rest or B to be at rest. So that would change the outcome of the clocks. But there can be only one truth. If A is at reat, B's clock is slower. If B is at rest, A's clock is slower. So which is it?
Oh yes, we can get as close to the speed of light as we wish, but we can never reach it. It is a critically important distinction to understand. V can never be equal to C, so to say what Relativity tells us IF V = C, has no meaning. We can only talk about the limit as we get very close. If you were to reach V = C, Relativity would appear to say we would have infinite mass, no length, and we would exist at all point in space simultaneously - the entire universe would have zero length to the traveler.
It depends on the observer. Both frames of reference are valid. We think we can sit back and see both realities but really we cant. Ultimately it comes down to what each observer measures. In that frame of reference, that IS reality. In another frame of reference, one might measure a different reality. But we can only exist in one or the other. And whatever is your frame of reference, what you measure is real. All of the seeming contradictions go away in any real-world problem. No matter how you try to twist things and find a violation, everything always works out correctly. No two observers are able to identify a contradiction in the laws of physics. It is one of the greatest mind fks of all time! That's why I love it.
There IS only one truth for you - the one in your frame of reference. But I'm afraid you don't have an exclusive.
The answer is each are depending on your relative position. Its like when star trek says "all stop" while in space. Well there is no stop in space, your position and speed are relative to something else. If you are travelling next to an asteroid that is moving at 10miles per sec relative to earth, to you the asteroid isnt moving at all. To earth its a cataclysmic speed. We are all experiencing a similar thing at this moment. We are sitting in front of a screen relatively not moving at all, but in reality you are travelling 70000 mph right now.
