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Astronauts come back to Earth younger than they would have been had they stayed on Earth for that same period of time. They are traveling so fast relative to the Earth that time slows down for them. Does that mean that the astronaut interacted with time? Does time interact with speed? And if so, does that mean time is made up of some kind of fundamental particles, like gravity has the graviton? What does time have?

Qmechanic
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zack opilis
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  • This sounds like relativity. (Or some form of it). I'm not sure what you mean by "interacted with time". Could you clarify what you're trying to say? – Andrew Gies Sep 30 '14 at 06:17
  • Zack, the question I've linked as a duplicate explains what time dilation is and why it happens. A search of this site for time dilation will find you lots more related questions. – John Rennie Sep 30 '14 at 06:26
  • The downvote seems harsh. Zack is basically asking what the mechanism of time dilation is, and I suspect that's a question that has puzzled most of us at some point. – John Rennie Sep 30 '14 at 06:28
  • i read the question that was linked too, still dont understand how time can be relative, is it just that mathematically the astronaut is suppose to come back younger than everyone else but doesnt, or does he actually come back younger than everyone else? – zack opilis Sep 30 '14 at 06:40
  • i guess ime not qualified to ask such questions ill go back to playing video games sorry guys – zack opilis Sep 30 '14 at 06:42
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    Zach, that mathematical description of relativity really has been experimentally verified. Take another look at the question @JohnRennie linked. The top answer is quite good and will probably help you. Time is a positional thing, just like space. Our perception that it "flows" in one direction is actually not well understood at all. – DanielSank Sep 30 '14 at 06:56
  • Zack, it's a good question, but it can't be answered in any useful way without getting into the maths. I dont know of any non-mathematical explanation that isn't ultimately misleading. – John Rennie Sep 30 '14 at 07:27

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You don't have to be an astronaut traveling at near the speed of light to experience this effect. It can be measured quite precisely here on Earth and it has been measured both on elementary particles in accelerators and by flying atomic clocks around the world in planes.

Humans are simply not used to it because the differences between the flow of time in different coordinate systems are too small to be felt by our biological perception of time. Our internal clocks are just not precise enough to experience the world as it really is (the same is true for most of quantum mechanics). Instead, we are experiencing a simplified version of it, in which having one crude clock that is independent of motion is "good enough".

Thankfully we can visualize on our computers what the world would really look like if we had the right kind of senses to detect the actual details of a relativistic world. Look up MIT's "A Slower Speed of Light" game, if you want to get an idea of what's "behind the curtain"!

And while all of this may sound very strange, it's no different from what people had to deal with when we invented the microscope. Suddenly there were all these bacteria and single cell organism and all these details on common objects that we could never see before! Or think about the changes in our ideas when we suddenly had telescopes. It opened up a new world. Even a small telescope can make you see tall mountains on the Moon, and Jupiter has moons of its own, Saturn has a ring, Mars has all kinds of structures on it that nobody had ever seen before and there were new planets and millions of new stars, that the naked eye can't see.

Relativity is no different, except that the "microscopes" that allow us to see its workings are better clocks and particle accelerators.

CuriousOne
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As for "why", that is either simple or complex! The simple answer is that it is a consequence of the speed of light being constant for all observers. That means when travelling relative to each other they both measure time differently. This site provides a simple math explanation

OTOH, time is measured differently in different gravitational fields, and that is a lot more complex - General Relativity