Topic awaiting preservation: space time (Page 1 of 1)

Right... so can some one explain this to me in english...

just minimal on the math.

I understand how gravity distorts space, and can bend light and such. That part of the gereral theory of realitivity is quite easy to understand... but I can not for the life of me, get my head around the time bits, and the um... paradoxes that can be produced from theroetical traveal at the speed of light.

For example how does a particle moves faster, but its time slowes down... and such.

What does that have to do with the particles reference frame? or... my reference frame. or... i am frazzled. Been readin about it and the general theory for some 12 hours or so.... Been writing a short paper on one bit of the general thory, but i decided to avoid this because i can not understand it.

Sorry to bust your bubble, but something like this pretty much is very hard to explain without math. I'll have a go anyways.

The faster something goes in space, the slower it goes in time. Therefore, if you were to fly at, say, 0.99999999999999% of the speed of light for a day, and then come back, two days would have passed for you, because of your increased velocity, but in normal space, years would have passed.

Don't ask me how it works, because I have no understanding of this kind of physics. This is just the basic layman's explanation.

Hope it helps.

I believe that concept is more a part of his Special Theory of Relativity....

Without the math.......

The faster something moves... The slower it's relative time gets. What that means, is that to it, time is still travelling as normal, but to the rest of the universe, time has slowed down for that object (so in the same period, more time has passed).

This has been proven, using atomic clocks. They took one atomic clock and left it stationary on earth, and took the other clock into a plane and flew it around for a long time.

The clock that was in the plane lost time compared to the one left on Earth.... (due to the low speeds and short distances, obviously it was a very minimal change... but definately a change...)

This theory also leads to the fact that you cannot go past the speed of light because time stops... and makes most space travel impractical until we figure out a way around it...

Imagine getting in your space craft to go to a nearby star, only to find out that the planet has already been inhabited by humans for a few hundred years.... Yet to you, only a few years have gone by.

I believe thats the basics of it... I haven't had to think about stuff like that for quite awhile now... If I remember more, I will add to it.

Jason

There is some stuff out there, currently pseudo-science, that says that time is actually a form of energy. Since energy can be converted to other forms of energy, is equatable, and can affect each other, it kind of makes sense that time and speed do affect each other. You know, indirectly proportionate or something. You know, like how mass and gravity are tied together. So is time and speed.

An interesting thing that kept popping up in my reading is that cx6 is possible. That is, traveling at six times the speed of light. If I remember correctly, this made a cameo in the movie K-PAX.

One of the coolest things I read about is that the event horizon affects time. A Russian scientist did experiments with rubber bands and clocks. The closer the rubber band got to snapping, the more time "stretched" or slowed down (sped up?).

If an event horizon does affect time, this means that consciousness can directly affect the flow of time. Now that's some wild stuff on more than one front. (Back in my karate days, I've seen some stuff that suggests this. I have even experienced first-hand it a few times. In the smallest of moments, you have all the time in the world.)

Man, I remember an article in Scientific American about tachyons. Scientists were baffled that a particle was dying before it was born. Not only that, but its path was "backwards". The sci-fi community jumped on this article in no time at all (pun!).

Hmmm... If I come across anything interesting to the non-math-minded lay, I'll post.

edit:
BTW, there is evidence to suggest that gravity travels at the speed of light. Not sure how valid the experiment is, though.


[This message has been edited by warjournal (edited 10-27-2003).]

Warjournal - The speed of gravity - yes, there has been an experiment about it recently - there are varying views - that it travels at the speed of light, slower, or instantly. Clearly, due to Eintein's theories, the last should be impossible. But hey - Im not a genius! I believe that the experiment (the curving of light around a planet - I believe Jupiter) showed that gravity moved at the speed of light. However, oter scientists called this into question saying that in fact the theoretical basis of their experiment were incorrect, that they were actually just indirectly measuring the speed of light - gravity did not enter into it.
There is one thing that they are certain appears to happen instantly - an electron moving between shells. Apparantly what actually happens is that the electron "cheats" - it goes back in time (Doesn't that create a positron though? Would this collide with one of the electron that was there and give off gamma rays? Im sort of in above my head here - any info would be very interesting!).
As for the moments in karate - I know what you're talking about. However, it has been proved that volition and consciousness are very separate - by the time you actually make the conscious decision, the action has already started, although the gap is very small, about 10 milliseconds I think. Couldn't the illusion of having extended time in these split seconds be just that - an illusion created by your mind? One way or another, your conscious isn't making the decision anyway. (Hey, isn't that the most brilliant argument when you get into trouble for doing something )

Wrayal

Go to kimber-ja.demon.co.uk and click on the link to the raytracer!

I'd suggest you get a copy of Hawking's The Universe in a Nutshell. He did a great job of simplifying some very complex concepts into a form I could understand.... If I can dig up my copy I'll try and find the section about space-time and tell you what it has to say about it. Its a great book though.

Ahh, the good old gravity, and this good old Descartes... lol. OK. During the XXth century, Einstein proved that gravity wasn't a force, but rather a deformation of the space-time continuum. 'Gravity' hasn't any speed. I don't know if I'm very clear so let's take an example. Imagine that you throw the ball on a flat ground. She will roll in a straight line. Unfortunately, you didn't notice there was a small hole on the ground. The ball rolls over it, and gets deviated. It's the same in space, but in three (or four) dimensions. The light is deviated by an invisible deformation of the space-time continuum.

Wrayal : To the best of my knowledge (but I may be wrong) electrons don't go back in time, I think you blended two different things : nuclear reactions and thermodynamics.

The Beta+ radioactivity consists in the disintegration of an atom into another one, which is lighter (to keep the number of elements constant, a positon is emitted during the process). The newly created atom is excited by the disintegration, and it must reach a normal state. Therefore, this atom emits gamma rays (these rays are the ones that cause cancers and such, they are the most dangerous ones).

And when a light source create two photons travelling in two different directions, if you alter the state of the first photon the second one is altered as well, at the same moment. As photons travel at the speed of the light, it is impossible that any information travelled between the two photons; in fact, they are bound differently, but don't ask me to explain the how and why, I haven't studied it yet.

Eyezaer : The way I see time paradoxes is simple : the closer you are from the speed of light, the closer you are from the speed of the informations (you can call that events), the more you gain time on events : in fact, the more events are slowed down next to you. But in fact, I don't understand completely this myself, so I won't pretend I do.

Im certain electrons can go back in time, and are seen (in the normal passage of time), as positrons (at least according to QED), but I was just not sure in this situation what would happen. I am also certain that electrons go back in time to flick between shells "instantly", although I must be getting something wrong somewhere - if the situation I depicted was correct you would start with an electron, but end up with an electron (albeit in a different shell) with the gamma rays of positron and one of the electrons annihilating each other. If this only happened when electrons go in shells, it might be understandable (lower shells -> less energy ->energy must be given off, in the form of the gamma rays), although this is clearly not what actually happens, because my idea would predict the same things when electrons go to shells further out.

BTW, when an electron goes in one shell, it gives out one quantum of energy. This is seen as light normally, yeah?

Wrayal

Go to kimber-ja.demon.co.uk and click on the link to the raytracer!

I fear you lost me It sounds very interesting though, but I can't help you at all about it. I'll try to ask my physics teacher after the autumn break about this.

BTW, when an electron goes in one shell, it gives out one quantum of energy. This is seen as light normally, yeah ?

Yes, that's right. There are a lot of different levels of energy in an atom, on which electrons are travelling. The closer they are from the core, the lower their energy is. The further they are from the core, the bigger their energy is. Now, when an atom is excited or receive any type of energy, some electrons move, and raise from one level. The atom is excited. However, the electrons aren't excited for a long time : they loose quickly their energy and come back to their original level. During this transition, they indeed emit a photon (also called a quantum of energy). To this photon corresponds indeed a radiation of light, characterized by its frequence. The energy of this photon follows this law (demonstrated by Max Planck) :

Ef - Ei = h * v

Ef and Ei being the energy levels concerned by the transition
h being the Planck's constant, h=6,62*10^(-34) J.s
v being the frequence of the radiation emited, in Hz

There are thousands of transitions that charaterize an atom. The disintegreations taking place in the sun excite hydrogen atoms, thus creating thousands of such radiations. All the radiations combined create almost a complete light spectrum (and yes, the light coming from the sun is not a complete melange of all the existing colours). On the contrary, a sodium lamp works by exciting sodium atoms, which emit a single type of radiation, a single ray in the visible spectrum. This radiation is orange.

Hope this helps

Oh, and sorry for hijacking your thread Eyezaer

[This message has been edited by Moon Shadow (edited 10-27-2003).]

Thanks for that, this sort of stuff is v interesting. Unfortunately, Im working from sort of incomplete knowlede - Iv not benn taught about quanta, let alone QED (im in year 10) so i learn stuff from reading eg QED from Feynman's lectures etc.
One other thing - in QED, Feynman says that a photon is its own anti-particle. How does that one work? If it is, then surely they would all annihilate each other. I can only guess that instead of giving off gamma rays, they give off photons. Im probably wrong, whats the real answer?

Wrayal

Go to kimber-ja.demon.co.uk and click on the link to the raytracer!

I see...

So can some one break down the math for simplified space time?

Okay, I'll take a shot here.. And I'll try and stick a load of math in there too, hopefully while still making some sense, and maybe my explanation can be a bit more detailed where others were lacking.

Okay, here goes. Typical situation of an earth observer looking at an astronaut flying by in his space ship. For explanations sake, I'll modify the atomic clock to be a light-pulse clock, more on that;

On earth and on the spaceship, we'll have a clock that emits a light pulse and receives it back again after bouncing off a mirror to denote a unit a time. To the astronaut who is moving along with the clock on his spaceship, the time interval required for that light pulse to go to and fro being 2d/c, c = speed of light (3x10^8 m/s) and d being the distance to the mirror. (This is just a velocity = distance/time formula slightly alge-bre-sized.) The earth people see their clock do the same, pretty much. (very very slightly different due to being on earth and all that, blabla.) However, lets say that the spaceship is going to go left to right, horizontally across an earthlings line of sight, sorta, and that the astronauts light clock shoots the beams up and bounces back off a mirror down to the clock. The earthlings see that the light beam bounces up and down just as the astronaut does, but at the same time, the astronauts move horizontally, and this would appear to give the light beam a diagonal path to the earthling. To the earthlings, the distance that the light travelled by the astronauts light clock travelled a greater distance than the astronaut sees it. But light still always travels at 3x10^8 m/s. With a greater distance to cover, the light will appear to take a longer time to complete it's mirror-circuit than the earthlings own light clock which takes the same amount of time it always did.

So, to sum up; The earth people see 1 tick of time go by on their clock, while the space ships clock takes 2.5 ticks to tick. But the astronaut, in his frame of reference, just sees one tick per tick. So the astronaut experiences time more slowly than it does for the earth people.

If you would like to determine the actual time difference, you can use pythagoreans theorem to determine the length of the diagonal that the light travels in 1 tick and such.. That math is a liiiittle beyond me at this point, but I know I'll learn about it soon. (I do know at least that the diagonal is d^2 + L^2 = diagonal^2, then just use v = d/t using c to figure out how long it takes for a light beam to travel that hypotenuses distance.)

I will cite my AP Physics book for the final alge-bre-sized formula;

delta-t = ti / sqrt(1-(v^2/c^2))

Hope that cleared some things up, though I doubt it.

-Xel