Relativity

[Lightbender]

Just a quick ponderation of sorts (is that a word?). If our good friend Einstein was correct in his theory which is based on the two postulates. That the speed of light in a vacuum is constant and independent of the source or observer. And that the mathematical forms of the laws of physics are invariant in all inertial systems.

(takes a breath) if his theory is correct, then is it possible to decrease ones velocity to an extent that one would achieve the exact opposite? Let me know if I'm going out on a limb here...

-Ted

[Tormod]

Ponderation sounds like a good word ot me...especially on a Sunday.

But I must admit I don't understand the question. What opposite is it you want to achieve?

Do you mean decreasing your velocity so that you are completely still, in regards to every possible observer frame and time system?

If so, I think it would be a tough task since, considering the expansion of the Universe, you'd be hard pressed to find aby spot in the Universe which is absolutely still. And if you try to decrease your velocity by matching the velocity of the expansion, you are merely moving along with it. If you try to go slower than it, you are simply moving away form the center of the source of expansion at a slower rate - in order to move towards it you will have to accelerate to a speed faster than the rate of expansion.

Gödel postulated that if the Universe is rotating, there could be time loops. But even here I don't think the point was that one could come to a complete stand-still, you will *always* be moving in reference to something.

(And let's not even start thinking about the Multiverse theory where our Universe is just one of many...)

But I am merely rambling here...maybe you could rephrase your question? Opposite to what?

[Tormod]

Please ignore this posting - I am just checking that users receive mail for subscriptions.

[Lightbender]

By opposite I mean, the inverse of time dilation. But I supposed I know now that the "slowest" you could move would be the rate at which the universe is expanding.

[T.J.]

Mr. "Lightbender" why can you only go as fast as the rste the universe is expanding. Why does Einstien say that it is not posible to travel faster than the speed of light? is it because it would take infinate energey and the universe can't do that? Pardon my "simple" questions im only 13 but highly intrigued.

[Tormod]

TJ,

I think you mistook my input for Lightbender's.

The issue here is whether you can actually inverse time dilution (ie, the slowing of time as you accelerate an object) by trying to decelerate insted of accelerate.

My response to that was that while you can accelerate towards the speed of light and therefore gradually see a time dilution effect, the opposite is not so simple because you can't *not* move at all. No matter where you are in the Universe, you will always be moving in reference to somehing (for instance, the expansive force of the Universe). So any attempt to try to reduce time dilation by deceleration is simply an act of moving in a different way than before.

I would like to point out that of course, if you happen to be travelling *Very* fast, you can easily decelerate and inverse the time dilution - but not to a point where it starts going backwards in time.

As regards your question why nothing can move faster than the speed of light, it is simply one of the most basic constituents of Einstein's theory of realtivity. Nothing can move faster than light, because as an object approaches the speed of light, it has to spend so much energy to keep accelerating taht the object itself turns into pure energy. That is what the formula e=mc2 says. A mass moving at the speed of light equals the square of the energy it contains.

While it is easy to assume that things can move faster than light, in theory it is impossible.

This probably sounds like a jumble of strange ideas...I'll give it a think and see if I can come up with a better answer.

[michaelchang]

TJ,

Here is a site which may help you help. You might find it a bit challenging (considering your age of course), but try n pick up as much as u can. This is a book which Einstein wrote himself explaining the theory of relativity including the process of deducing the theory. I personally find this the easiest book 2 understand on relativity.

http://www.bartleby.com/173/

As for your question regarding the speed of light as the speed limit. This can be explained by one of Einstein's questions, the most famous E=mc^2. One interpretation of this equation is that mass and energy are equivalent.

As an object moves at a certain speed, it has a certain amount of (kinetic) energy. The faster the object is moving, the larger the amount of energy it has. From this equation, E=mc^2, it can be seen that the mass of the object would increase. At close to the speed of light, the object has a lot of energy and hence a large mass, and needing a large amount of energy to accelerate any further. The energy (hence mass) rapidly increases as u close in on the speed of light and you will need an infinite amount of energy to accerlerate the object anymore because at that speed, its mass is infinite.

Lightbender, the opposite of time dilation is time moving faster for your frame of reference relative to the other frames. To achieve this, u will need to accelerate all the frames of reference so that they are moving very fast relative to you. Then THEIR time will be dilated and hence it will seem that your time has been moving faster. The same effect can be achieved by being at rest (or slower than) all other frames of reference.

[michaelchang]

How did i do with the post above?

[James]

this may be a spectacular coincidence>>>but do you hava daughter with a name that starts with c?

[Wannabe Genius]

I aint sure if I am on the right track with this, but by decelleration, you are effectivly halving your velocity at rate x, however, you can never achieve absolute zero by halving, there is always a fraction smaller, just like there is always a bigger fish etc (tacky star wars quote I know).

the only way to acieve the exact opposite, is to apply negative accelleration, which is not the same as decelleration. Negative accelleration I think is the same as applying positive accelleration in the opposite direction, in which case you get the same result. Its like saying you can never go backwards, you are always moving forwards in another direction. I get the feeling what you're asking is essentially the same question as "can time move backwards" the answer to that, as I explained in my post on universal contraction, is no. The end result is always the same. possitive accelleration in a different direction.

Hope this helps

Martin.

Quicky to test your brains - science tells us that nothing can move faster than light.......in which case, how can science also tell us that light deccellerates over time? If nothing can move faster than light, then surely light cant either? and if light is deccellerating, would it not eventually get to a point where anything can move faster than it? assuming that the universe is around long enough for it to reach such a point.

Answers on a postcard please.