Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It only takes a minute to up. Connect and share knowledge within a single location that is structured and easy to search. I don't understand how time can be relative to different observers, and I think my confusion is around how I understand what time Time and relative. I have always been told and thought that time is basically a measurement we use to keep track of long it has been since an objects inception.
If that is even somewhat true, how can time be relative? If I have a rate of decay of X and you are somehow able to observe that such as watching me age how could I age at a different rate to 2 observers? If time slows Time and relative the faster you go, does that mean you age slower? Or do you age at the same rate, only it seems like it takes longer? If a second is currently defined as the duration of 9,, periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium atom at 0K, how can that change at higher speeds?
Assuming the temperature stays the same, shouldn't the measurement be the same? You must understand that in everyday life which fuels our intuition is pretty slow.
And that's a luxury for most, to Time and relative by a fast jet. That is a million times faster from anything we have today. Just because time seems to be relatively absolute pun intended from our standpoint because our stage is rather small, the time it takes light to propagate from one point to another is so small, it doesn't mean that time is indeed invariant.
The direction-of-motion parts of the interferometer contracted as they moved and thus prevented any relative motion or interference to be detected.
The two light als always came at the same time because of the length contraction in the direction of movement. Michelson couldn't accept this.
It went against his life's work. Lorentz did the mathematical foundation Time and relative an explanation to the problem, but he did little to analyze the result. Einstein came to the same equations by following a different train of thought, this time involving the nature of Galilei-Newton relativity which troubled himthe problem of light and all the evidence that was pointing that propagation through spacetime is constricted by a velocity limit.
So, Einstein "took the bone" nature was throwing him.
The speed of light is constant for ALL observers. No matter if they're sitting, falling, running, flying, sleeping. No matter how fast you're moving relative to others. If that is true, then something else must bend. From these simple postulates, which include the inability to differentiate intertial frames of reference, comes the death of simultaneity and of absolute time.
When it begins to move with someone, a second observer - you on the ground will notice that its path elongates relative to you. All the while, the man on the moving platform sees the light perfectly in sync, up and down, because he's moving with it.
That's Time and relative relativity, but the one who really experiences slower decay or the relativistic effects is the man who is accelerating. So, yeah, time is relative to protect the constancy of the speed of light. Hope it helps. And give it time. It has been proven many times over and a lot of scientific work today relies on relativistic effects of time dilation. It's exactly the repercussion of this.
Decay is the passage of time. Also, to every other observer the ship contracts. To the man onboard, he feels nothing. The passage of time is the same and the ship dimensions are the same. To protect relativity, he sees that others are slowed down in time and contracted. But he is the one who accelerated, therefore, he is experiencing the time Time and relative. And thus, time dilation implies slower time passage for the man onboard relative to other stationary observers. This has not yet been proven directly, but it is inferred from various experiments done by planes and atomic clocks and also the need to Time and relative up satellites after a while because of the gravitational differential.
Time goes slower, decay is dependent on time, slower decay. The final and most important point would be that time passes for everyone in the same manner you can't feel a change. But it is the relativity comparing to someone else which enables us to detect time passage differences. Just like you can't know how it feels to be a rabbit, because you've never had a chance to be one to make the comparison. A blunt, but accurate comparison. Just like you can't imagine a different kind of existence because you can't compare to an another Universe we've never been in it.
That's the gist of relativity. Everything we know is relative. That's "how" we know.
But the beauty of the human mind and the triumph of all science lies in the fact that we can contemplate this, our own limitations, our ways of thinking. And by doing so, we find a way to overcome them or to make the most of them.
You're "understanding of time" is perfectly okay.
What you are missing is the relation between space and time. If you an observer are sitting flying there, looking just at your clocks -- then you will never notice any time dilation. Relativistic effects appear when we have different observers in different points of space. Moving around, observing, sending als, e.
And when this observers try to make a coherent picture of their observations, they arrive at the conclusion that one cannot extend his local "understanding of time" to the "understanding of Time and relative for the whole space.
Actually space and time turn out to be very strongly interwoven, so we usually prefer to use the term spacetime. So, here's the deal. In order to make a solid step forward, Einstein and company basically needed to clarify what they were trying to say.
What they were trying to say looks something like this: "if you see a train passing by you, you're going to Time and relative things happen in slightly "fast motion" when it's at a distance coming toward you, and in slightly "slow motion" when it's at a distance moving away from you. This is no surprise; when you hear the train blow its horn it sounds higher-pitched as it approaches and lower-pitched as it leaves. As you can imagine, Time and relative effect is a little hard to observe! It really comes from "adding up" a lot of little effects that happened when the train accelerated to this massive speed.
That is, a wall that you used to think was a constant "5 feet away" in the x-direction is now going to start off being "5 feet away" but after a little time it might be "4 feet away", then "3 feet away", then "2 feet away", and so on.
Why time is relative, explained in under 3 minutes
This is very obvious and was known to Galileo and Newton. But there's a subtle effect, too, about time. But we can't ignore it so much these days, not with high-velocity particles that we have to calculate. Now it turns out that you have to break apart what's happening into little intervals of time when you're accelerating, but if you add this little change up, many times over, then it says both that stuff happening in your train appears to be in slow motion Time and relative to people outside the train, but also that stuff happening outside the train appears to be in slow motion relative to what's happening in the train.
So it's because time has this little "we start to disagree on the simultaneity of remote events" property, that we eventually build up a larger "we start to disagree on how big things are and how fast their clocks are ticking" discrepancy. And the great part about it is: you're both correct. Both of you have perfectly valid coordinates which perfectly describe the world. In fact, many contemporaries of Einstein thought that the newer "electrodynamics" science which was implying these things was fundamentally broken.
Before Einstein, people knew about these problems due to a guy named Lorentz, Time and relative didn't tend to take his work too seriously. Einstein's paper said, effectively, "we have to take him seriously. One reason that we can now appreciate is: we now know that the mathematics is totally self-consistent. Nobody ever disagrees on the order of events and nobody can use these weird "de-synching clock" effects to travel in time, unless they somehow find a way to move faster than the speed of light. So there's a real Zeno Paradox here guaranteeing that nobody can ever outrun light.
The most obvious paradox which turns out to not be a big deal is, "if I think that the people on the train are moving in slow motion, and they see me in slow motion, can't I just call one of them up and we'll Time and relative who's faster and who's slower on the phone call?. And the answer to that is, yes, if a phone could transmit information instantaneously, then nature would have to establish one of these people as correct and one of them as incorrect.
But, of course, real phones are also bound to transmit energy no faster than the speed of light -- and this gives the precise ambiguity that you need to make sure that both of them are perfectly correct and neither one can claim supremacy over the other. So that's what we mean by "time is relative": someone on the street, after correcting for Doppler effects, still thinks that people on the train are moving "in slow motion" and thus aging slower than people on the ground. People in the train of course see themselves just fine, but after correcting for Doppler effects think that people on the ground are moving "in slow motion" and thus aging slower than the people on the Time and relative.
Both groups have valid coordinates, and we cannot choose between them. Whenever you find an experiment which actually seems Time and relative test it, like "Well we'll stop the train and get out and check their ages," those coordinate shifts Time and relative balance everything out so that there is no paradox: usually the person who is accelerating becomes "wrong", so if we speed up to jump on the train we see the people on the train moving in fast-motion until they appear to be older than us, and it turns out that the "train was right"; but when the train slows down to check on the ages of the people on the ground, all those people move in fast-motion until they appear to be older than the people on the train, hence the "ground was right.
He makes this statement:. I think Domagoj's answer is excellent, but I disagree a little with this statement.