I know something about it, but is there a more or less simplified explination somewhere on the “net” I could read. Or someone explain it here. I know you can’t really “simply” explain something that complex but can someone help?
AltaVista: Simple Query “The Theory of Relativity”
That should get you started.
–Kalél
(The Original EnigmaOne)
Common ¢ for all ages.
OK, here’s the shortest I can explain a part of the theory of relativity:
Item 1: Speed of light
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Light moves at an absolute velocity. The velocity of light in a vacuum is a constant.
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Speed=distance divided by time, or v=d/t.
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In a function like v=d/t, variables behave in a similar manner (a strange way of putting it, but trying to stay non-mathematical). Thus, if v has a maximum limit, then as v approaches that limit, d must become infinitely large, and t infinitely small to compensate.
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Thus, when it comes to traveling in the universe, since at some point velocity becomes constant, the rate at which time passes as you approach that maximum speed becomes smaller and the distance between where you are and where you are going becomes smaller.
Item 2: Non-identifiabilty of moving source
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There is no way to tell, when two objects move past one another, which is moving and which is standing still.
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Look at item 1, #4 again. As you approach the velocity of light, your time speeds up and distances become smaller, so light always appears to be moving the same speed regardless of what your absolute velocity is.
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Since the only constant velocity is that of light, and no matter what speed you are moving “light speed” is always the same for you, you have no way of telling if you are really moving, or if everything else is moving instead.
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Thus all motion is * relative * and there can be no defined absolute motion.
Item #3) “Infinte” speed of energy
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Pure energy, in a “frictionless” environment, travels at maximum speed, the speed of light.
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Think of a line of soldiers marching. If the all take a step with their right foot at the same instant, the whole line can move forward at once, with the back person moving at the same time as the front one. This is an “ideal” situation.
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Energy is the same way. Imagine a pulse of energy like the soldier at the front of the line. As soon as he starts his step, everyone else is starting their step, and so there is no time difference between when the first soldier steps and the last soldier steps. The time it took this “energy” to travel down the line was zero (since the whole line moved at once) so the velocity was infinite (or light speed, the maximum velocity).
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Now, imagine your average untrained people in a line. The first person takes a step. The second person realizes that they have taken a step, and themselves take a step, and so on down the line. This is a “real” situation.
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Eneregy that has to travel through matter is like this too. Since not everyone steps at once, it takes time for everyone to move forward a step. The last guy moves forward some time after the first guy finished his step. This is what happens to energy when it has to travel through matter. Thus, light, “pure energy” travels at its maximum in a vacuum. If there’s any matter in the way, it behaves like the second line of people, and it takes time for light to travel from point a to point b, and so light in a non-vacuum travels slower than the speed of light.
Item 4) E=mc^2
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The calculus for this is really astronomical, so please forgive me.
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See point #1. This is not what really complete, but it may help you keep this straight, and it’s almost close to the truth.
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Since energy could move along at the speed of light if it wasn’t for matter getting in the way, we can look at matter as a sort of “slowed down” energy; if we could travel at the speed of light we wouldn’t be getting in the way of the rest of the energy, we’d actually “be” that energy. So really, matter is energy, and energy is matter. Energy is merely the “limiting case” of matter, or if you prefer, matter is merely the “general case” of what energy is. They’re the same thing, just behaving in a different way.
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We need a mathematical way to relate these things. Since matter and energy are the same thing, there should be a direct, linear relationship between the mass of something (how much stuff is there) and its energy if it were traveling the speed of light (since at that point it would be pure energy). A linear relationship is always in the form y=ax+b, where a and b are constant. Let Energy(E)=y and mass(m)=x. E=am+b. Since at zero mass, there is no possible energy, (plug zero into the above equation for both m and E) then b must also equal 0. So now we’ve got E=am, or energy is equivalent to mass times some constant. Einstein, in an elaborate proof that is quite above even my head, showed that indeed, a=the velocity of light squared. We use “c” to represent the velocity of light. So E=mc^2.
All of this is a part of Einstein’s theory of “special relativity” Just as he tackled the speed of light in “special relativity” he tackles gravity and a whole other bunch of stuff in “special” relativity, when he proved, among other things, that it is impossible to determine whether the source of an acceleration is due to gravity or thrust (i.e. if something is falling or is being pushed or pulled).
Jason R Remy
“One pill makes you taller, and one pill makes you small, but the ones that mother gives you don’t do anything at all”
– Jefferson Airplane * White Rabbit * (Slick, G. 1966)
Oops, the gravity and thrust stuff is in, as I should have said, the theory of “general relativity” which extends special relativity to accelerating objects as well as constantly moving ones. Remember: constant speed = special relativity. All motion, including acceleration = general relativity.
Jason R Remy
“One pill makes you taller, and one pill makes you small, but the ones that mother gives you don’t do anything at all”
– Jefferson Airplane * White Rabbit * (Slick, G. 1966)
Relatively simple stuff.
Easy for you to say.
Alternate Theory of Relativity:
If your parents didn’t have any children, there’s a good chance you won’t either.
It’s only a theory
In other words, not a law.
In other words, always trying to be dis-proven.
Whew. No use trying to memorize theories, shoot, I have enuff to do with just the truth.
The TRUTH? You can’t HANDLE the truth!
Urgh, once again educating the minds of people who refuse to listen…
Theories are no less truthful than laws. The two serve different purposes, and are entirely different ways of explaining the world. Theories don’t become laws when they are “proven,” theories aren’t just guess waiting to be proven or disproven. No one is trying to disprove relativity. They may be disagreeing on why the things relativity is describing happen, but that doesn’t mean that what relativity describes doesn’t really happen. Theories don’t have less “facts” to back them up than laws do, theories are different from laws… Read the thread Evolutionists are wrong! The earth is young.
Theories are supported by every bit of evidence that points to them. Both time contraction and distance contraction, things predicted by relativity, are readily observable, as well as energy-mass equivalency (atomic bomb, the sun, etc. etc.) and gravitational effects on light. Theories don’t become accepted theories unless they are completely supported by evidence. Now, that also doesn’t mean that everything that Einstein said is still accepted as correct (he once said of quantum mechanics “God soesn’t play dice with the universe.” but later himself recanted and came to accept QM as a valid means of explaining some very bizzare behaviors) but the general ideas of what the theory tells us (about energy and matter, etc. etc.) are still observably accurate.
Jason R Remy
“One pill makes you taller, and one pill makes you small, but the ones that mother gives you don’t do anything at all”
– Jefferson Airplane White Rabbit (Slick, G. 1966)
I’d like to commend jayron 32 for his bravery in trying to summarize that so concisely. It an ain’t easy task to do that. 
Yeah, and it’s only a theory that the universe exists too.
Relavitity is a very well established, well proven concept. At a future date, it my be updated and improved (in the same way that Einstein updated Newton’s ideas), but it isn’t going to be shown to be “wrong”. All of the effects associated with special relativity have been observed over and over again. Most of the effects of general relativity have also been observed frequently.
Let me clarify this by saying that light moves at the exact same velocity in a vacuum for all observers regardless of their motion. That was the initial assumption that led Einstien to all of the cool fireworks in special relativity.
But you actually do make this point later on.
I know you are simplifiying, but I just felt the need to say that there ain’t no such animal as “absolute velocity”. There is only velocity relative to something else. But again, you do make this same point later on in the summary.
Thank you Jayron 32. IT was most helpful. So was the other alta vista link.
I guess the thing that I’m now wondering is if you were to get into some kind of, for lack of better word, spaceship, and travel near the speed of light. And come back to earth your body would age X years but everybody on earth would age Y years. Thus you’d in effect put yourself in some sort of time machine, putting yourself in what now looks like to you the future.
Also on another note, if you could, somehow disprove the speed of light is a constant, you’d pretty much destroy all the physics we now know, right?
Causation of Big Bang-someone or something reaching the speed of light. Possible?
Yes, this effect can happen. It’s commonly called the “twins paradox”. The validity of this idea has been demonstrated by radioactive materials in cosmic rays and particle accelerators, which end up having an extended half-life due to fast motion.
Well, I’m assuming that you are specifically referring to the speed of light in a vacuum.
It probably would not destroy existing physics. It would need to be some bizarrely unusual case that allowed for the change, because in all of our observations of the universe, we have yet to see such a case. Such an idea would probably “update” our current view rather than destroy it.
Two probs with that.
First of all, reaching the speed of light really is impossible for a massive body. Conceptually, to the traveller, reaching the speed of light would be like reaching infinite speed. It is just as impossible.
Second, it is hard to talk about causes to the big bang, as cause implies the prior existence of an event, and the big bang is literally the beginning of time.
Time being an abstract thing. The big bang would be the beggining of time as we know it. How do we know that the universe, or matter that came from the big band didn’t exist for millions of years prior to the big bang?
Secondly, you can probably guess where my next question is going…
It seems we could theoretically, use relativity to explain a form of time travel into the future. Is there anything on a parallel note that would let us, theoretically travel back in time.
Thanks for the answers guys. You have not only explained this stuff simple but you make it interesting too.
Well, time isn’t that abstract. It is just as quantifiable as distance. As the big bang story goes, time and space were created as part of the big bang, so it’s kinda hard to say “prior” when there is no time to be prior in.
With relativity, travel forwards in time is a clear possibility. As far as travelling backwards in time, there are is a very unlikely senario involving a rapidly moving wormhole, but that assumes that wormholes really exist, and that it is possible to travel trough one. Surviving a trip through a wormhole looks about as likely as surviving the decent into a blak hole.
Of course then there is the problem of causality violation (the whole killing-your-parents-before-you-were-born thing), which leads most physicists to believe that travel backwards in time is almost certainly impossible, even if we have yet to prove it impossible.
Ok please explain what a wormhole is?
I heard the time travel problem explained as You could, but you won’t cause you didn’t. In other words you could kill your mother, but you won’t kill your mother because you didn’t kill your mother. Kinda a life is predestined thing.
Or another explains it as parallel universes. Or the second you kill your mother you would cease to exist
Jayron,
Kudos for your compressed version of realitivity. It has been some time since I have seen someone put it in laymans terms so succintcly. FYI for all your trouble it seems that mark is yanking your chain. Advise him to open a book.
Simplified Theory of Relativity: Time move slower when you’re with your relatives.