3 registered members (Ayumi, Akow, AndrewAMD),
1,505
guests, and 9
spiders. |
Key:
Admin,
Global Mod,
Mod
|
|
|
Re: Moving at the speed of light
[Re: Joey]
#356602
02/02/11 22:18
02/02/11 22:18
|
Joined: Oct 2004
Posts: 4,134 Netherlands
Joozey
Expert
|
Expert
Joined: Oct 2004
Posts: 4,134
Netherlands
|
That's correct (although the one traveling is the younger one in the end). The thing is that the one traveling away and then back changes his inertial system (e.g. by accelerating) which in the end cuts down his time consumption. The acceleration itself doesn't have an effect, though, as you're accelerating and decelerating. If you could change your inertial system without acceleration this would have the same effect.
This would allow us to build a time machine. *want* vec_set( player, vector(x,y,z) )? Since "inertial system" is just a fancy word for "we take this point as the origin of space", I could argue that space is just a made-up concept and our entire universe is defined by accelerations, thereby acceleration is the effect. But you could just as easily argue back your point of view . What interests me is when you take the cosmic background radiation as inertial system. Then the space in our universe shrinks inwards instead of extending outwards!
Click and join the 3dgs irc community! Room: #3dgs
|
|
|
Re: Moving at the speed of light
[Re: Joey]
#356620
02/02/11 23:04
02/02/11 23:04
|
Joined: Oct 2004
Posts: 4,134 Netherlands
Joozey
Expert
|
Expert
Joined: Oct 2004
Posts: 4,134
Netherlands
|
Yes I know that, but isn't "the change from one velocity to another" defined as "accelerating"? I think this is just a matter of definitions, a conceptual thing, but physically we mean to describe the same. That's what I try to say.
Then again maybe teleporting isn't describable by the true definition of acceleration, unless teleporting without acceleration is not physically possible.
Yes I agree change in velocity is a more general description than acceleration, and thus be the preferred term to use.
Last edited by Joozey; 02/02/11 23:11.
Click and join the 3dgs irc community! Room: #3dgs
|
|
|
Re: Moving at the speed of light
[Re: Joozey]
#356656
02/03/11 08:36
02/03/11 08:36
|
Joined: Jun 2006
Posts: 2,640 Earth
Germanunkol
Expert
|
Expert
Joined: Jun 2006
Posts: 2,640
Earth
|
Joey's question hasn't been answered yet, has it? Cause I always wondered the same thing... My Physics teacher tried to explain it to me, and I never got it...
All Movement is relative, as far as we know. So if I move away at the speed of light, I could also say YOU'RE moving away at the speed of light, so how does the universe "know" which one will have to age slower?
~"I never let school interfere with my education"~ -Mark Twain
|
|
|
Re: Moving at the speed of light
[Re: Germanunkol]
#356658
02/03/11 08:56
02/03/11 08:56
|
Joined: Feb 2008
Posts: 3,232 Australia
EvilSOB
Expert
|
Expert
Joined: Feb 2008
Posts: 3,232
Australia
|
I was under the belief that it was the "relative speed" that caused the dilation, not "change of velocity".
Someone mentioned that the space-shuttle clocks ned adjusting after a flight... I have also 'heard' that the clocks in the GPS-satellites also need adjusting occasionally, and they are not 'changing velocity' to my eye, but they are 'travelling' faster than us due to their greater distance from the center of the earth's axis.
"There is no fate but what WE make." - CEO Cyberdyne Systems Corp. A8.30.5 Commercial
|
|
|
Re: Moving at the speed of light
[Re: EvilSOB]
#356671
02/03/11 11:25
02/03/11 11:25
|
Joined: Jan 2003
Posts: 4,615 Cambridge
Joey
Expert
|
Expert
Joined: Jan 2003
Posts: 4,615
Cambridge
|
That's exactly the problem. Relativity itself does only tell you that if you're moving, your clock is slower. Then you tell me that I am moving, so my clock is slower. Of course both are right. The thing which causes a permanent "shift" of time, if you so will, is changing the inertial system (however that is done). That effect is hard to explain in few words but in principle that's the answer. That question is called "twin paradox" (see my link above).
edit: @evilsob: the problem with the gps satellites is not their greater speed but their constant acceleration; this is not a question of special relativity but of general relativity and much much harder.
Last edited by Joey; 02/03/11 11:27.
|
|
|
Re: Moving at the speed of light
[Re: Joozey]
#356714
02/03/11 16:34
02/03/11 16:34
|
Joined: Jun 2006
Posts: 2,640 Earth
Germanunkol
Expert
|
Expert
Joined: Jun 2006
Posts: 2,640
Earth
|
Joozey, I Don't get it. In my eyes, what you said doesn't answer my problem. If I drive away in a car, you'll say I'm accelerating. But then I tell you that relative to me, you're accelerating in the opposite direction. And, apart from the direction, your acceleration is exactly the same as mine. So we should both age slower, and both age "the same amount" slower.
Joey, I might find some time to look at the link, right now I'm in a rush...
~"I never let school interfere with my education"~ -Mark Twain
|
|
|
Re: Moving at the speed of light
[Re: Germanunkol]
#356736
02/03/11 17:31
02/03/11 17:31
|
Joined: Jul 2002
Posts: 3,208 Germany
Error014
Expert
|
Expert
Joined: Jul 2002
Posts: 3,208
Germany
|
One thing which always bothers me is the example you use and everyone else states. If you say that you move at a considerable fraction relative to earth, thus your clock moves slower, I (the one on earth) say that I am moving at a considerable fraction relative to you, thus my clock moves slower.
Anyone knows the solution? The standard reply you'll get when you ask people is that since you had to return to get back to earth, at that point you had to accelerate, and thus special relativity isn't valid anymore, and the problem has to be solved with general relativity. This, however, is not correct. The truth is that the equation for time dilation you are using is only valid for the above, simplified case of constant movement with no acceleration. So here's the short reply: When the twin is returning home, the inertial system you've been using CHANGES. It suddenly moves in a different direction - that's not something inertial systems generally do ;), and is the cause of the problem: In your calculation, you've been assuming that you're calculating stuff in a inertial system, but you're not. That false assumption leads to the wrong result. EDIT: because of the fact that time moves slower in space. Nebolous statements like that really don't help much, don't ya think? Relativity predicts TWO effects that change the "flow of time", if you will. One is described by special relativity - what is usually referred to as time dilation. It can be summarized as "Moving clocks go slower". The second effect is due to general relativity. Masses curve spacetime, in other words, it changes the geometry of it. The time you're measuring (the "proper time") is nothing but the length of your path through spacetime (disregarding units). Now, obviously, if masses curve spacetime, it only makes sense that the lengths of your paths change, too (and thus your measured proper time). Whats fascinating is that for satellites, bothe effects actually work in different ways: They're moving quiet fast relative to the earth, so that makes their clocks go SLOWER, yet at the same time, the mass of earth makes their clocks go FASTER compared to the one of someone on earth (the closer you are to masses, the slower your clocks go).
Perhaps this post will get me points for originality at least.
Check out Dungeon Deities! It's amazing and will make you happy, successful and almost certainly more attractive! It might be true!
|
|
|
|