|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Is there a deeper time?
Now I know that relativity tells us that going faster than light would
mean travelling backwards in time. And one of the examples they often give is that looking at stars and galaxies means we're looking back in time. Okay that's all pretty easy to understand, it took the light some time to travel from the star or galaxy to our eyes (or instruments). We're seeing an image that started travelling to us several years ago. But to me that just means we're seeing an image from an earlier time, how is that supposed to be time travel? As an example, we can hear a thunderclap several seconds after we can see it. The sound took a certain amount of time to travel to us; it's an image of a sound produced earlier but just now getting to us. However, if I go supersonic and try to catch up with the sound earlier, I don't consider myself to have travelled backwards in time to hear the sound earlier. Yet in relativity, going *at* the speed of light means time stops entirely for you. Yet, in our normal world, we see events where photons crash into objects all of the time, but from the photon's own perspective, there is nothing that's happening? The photon experiences no events because time has stopped for it? That's why I'm asking if there is a "deeper" time at the heart of the universe, one which records events happening even at the speed of light, when what we normally call time stops? Yousuf Khan |
#2
|
|||
|
|||
I'm fairly sure of this, but I wouldn't bet the farm, because then we'd
have no pecans to sell. |
#3
|
|||
|
|||
Yousuf Khan wrote:
Now I know that relativity tells us that going faster than light would mean travelling backwards in time. No--the premise in relativity is that the speed of light cannot even be attained by particles with rest mass as is empirically born out. |
#4
|
|||
|
|||
Yousuf Khan wrote: Now I know that relativity tells us that going faster than light would mean travelling backwards in time. And one of the examples they often give is that looking at stars and galaxies means we're looking back in time. Okay that's all pretty easy to understand, it took the light some time to travel from the star or galaxy to our eyes (or instruments). We're seeing an image that started travelling to us several years ago. But to me that just means we're seeing an image from an earlier time, how is that supposed to be time travel? As an example, we can hear a thunderclap several seconds after we can see it. The sound took a certain amount of time to travel to us; it's an image of a sound produced earlier but just now getting to us. However, if I go supersonic and try to catch up with the sound earlier, I don't consider myself to have travelled backwards in time to hear the sound earlier. Yet in relativity, going *at* the speed of light means time stops entirely for you. Yet, in our normal world, we see events where photons crash into objects all of the time, but from the photon's own perspective, there is nothing that's happening? The photon experiences no events because time has stopped for it? That's why I'm asking if there is a "deeper" time at the heart of the universe, one which records events happening even at the speed of light, when what we normally call time stops? Yousuf Khan So IOW you want to know how special relativity plus FTL signaling equals causality violation and backward time travel? http://www.faqs.org/faqs/star-trek/r...ity_FTL/part4/ Richard Perry |
#5
|
|||
|
|||
Yousuf Khan wrote:
Now I know that relativity tells us that going faster than light would mean travelling backwards in time. Actually it doesn't. Relativity does not and cannot say anything about travelling forward or backward in time. It doesn't distinguish the two directions in any way. One can make an argument that faster-than-light travel plus the principle of relativity would imply time travel, but I think it's a weak argument. The arrow of time is usually explained by saying that time symmetry is broken by the big bang. The principle of relativity is also broken by the big bang, and I see no reason why this same mechanism couldn't also prevent communication into the past using tachyons. And one of the examples they often give is that looking at stars and galaxies means we're looking back in time. [...] But to me that just means we're seeing an image from an earlier time, how is that supposed to be time travel? You're right, they're wrong about there being a connection to time travel. Yet in relativity, going *at* the speed of light means time stops entirely for you. Yet, in our normal world, we see events where photons crash into objects all of the time, but from the photon's own perspective, there is nothing that's happening? This is tricky. Basically, light can't change internally, because there's no time scale on which the change can happen. For example, particles which travel slower than light -- like muons and atoms -- can be unstable and decay, but light can't. However, that doesn't prevent light from being changed by an external influence, like a collision with something else. -- Ben |
#6
|
|||
|
|||
Yousuf Khan wrote:
Now I know that relativity tells us that going faster than light would mean travelling backwards in time. Really, really bad start. And one of the examples they often give is that looking at stars and galaxies means we're looking back in time. Getting worse. Okay that's all pretty easy to understand, it took the light some time to travel from the star or galaxy to our eyes (or instruments). We're seeing an image that started travelling to us several years ago. But to me that just means we're seeing an image from an earlier time, how is that supposed to be time travel? As an example, we can hear a thunderclap several seconds after we can see it. The sound took a certain amount of time to travel to us; it's an image of a sound produced earlier but just now getting to us. However, if I go supersonic and try to catch up with the sound earlier, I don't consider myself to have travelled backwards in time to hear the sound earlier. Every child left behind. Yet in relativity, going *at* the speed of light means time stops entirely for you. Why don't you calcualte gamma for v=c? Yet, in our normal world, we see events where photons crash into objects all of the time, but from the photon's own perspective, there is nothing that's happening? Photon POV is not an inertial reference frame. The photon experiences no events because time has stopped for it? That's why I'm asking if there is a "deeper" time at the heart of the universe, one which records events happening even at the speed of light, when what we normally call time stops? Wouldn't you rather be in management? http://www.dilbert.com/ -- Uncle Al http://www.mazepath.com/uncleal/ (Toxic URL! Unsafe for children and most mammals) http://www.mazepath.com/uncleal/qz.pdf |
#7
|
|||
|
|||
Sam Wormley wrote:
Yousuf Khan wrote: Now I know that relativity tells us that going faster than light would mean travelling backwards in time. No--the premise in relativity is that the speed of light cannot even be attained by particles with rest mass as is empirically born out. That's not really an answer, is it? It's just a diversion of the subject. Don't let this subject get hijacked by the newsgroup kooks trying to push their own little pet theories, it's a serious question. Explain why lightspeed travel is time stopped, and why FTL is backwards time travel, never mind whether you think it's practical or not. Pretend that I'm an intelligent photon, now why has time stopped for me, and why are no events happening to me? And why is it that the rest of the slower-than-me world sees me doing all kinds of things, like vibrating and racing past them headed towards some object to smack into it and maybe bounce off or get absorbed by it, when I, myself, am completely unaware of all that? Yousuf Khan |
#8
|
|||
|
|||
Yousuf Khan wrote: Sam Wormley wrote: Yousuf Khan wrote: Now I know that relativity tells us that going faster than light would mean travelling backwards in time. No--the premise in relativity is that the speed of light cannot even be attained by particles with rest mass as is empirically born out. That's not really an answer, is it? It's just a diversion of the subject. Don't let this subject get hijacked by the newsgroup kooks trying to push their own little pet theories, it's a serious question. In relativity theory, a massive particle travelling slower than lightspeed cannot accelerate past the lightspeed barrier since it would require infinite energy. It is therefore impossible to start below light speed and end up faster than light speed. This is what Sam was referring to. What Sam failed to realize was that this does not prevent a particle from having been created with faster than light speed. Such theoretical particles are called tachyons. In Quantum Field Theory, a tachyon could explain the spontaneous violation of the electroweak symmetry, and various other phenomenon. A fundamental problem for tachyons though is that since they can posses negative energy they violate spacetime supersymmetry (since energy must be the square of the supercharge, roughyl speaking). One should note that spacetime supersymmetry is empirically false. The existence of FTL particles is still something unclear. Explain why lightspeed travel is time stopped, and why FTL is backwards time travel, never mind whether you think it's practical or not. Pretend that I'm an intelligent photon, now why has time stopped for me, and why are no events happening to me? And why is it that the rest of the slower-than-me world sees me doing all kinds of things, like vibrating and racing past them headed towards some object to smack into it and maybe bounce off or get absorbed by it, when I, myself, am completely unaware of all that? Those questions can be answered by finding/reading wikipedia special relativity articles. Yousuf Khan |
#9
|
|||
|
|||
"Yousuf Khan" wrote in message ... That's not really an answer, is it? It's just a diversion of the subject. Don't let this subject get hijacked by the newsgroup kooks trying to push their own little pet theories, it's a serious question. If you are serious then there are resource that will help and some people have already suggested places you can start. The thing is that you can't just pick up an understanding of relativity in a few usenet posts, you need to study the subject. It took me a few months to learn enough to understand why time travel would be a consequence of FTL motion. Explain why lightspeed travel is time stopped, and why FTL is backwards time travel, never mind whether you think it's practical or not. Time and space are ways of describing the 4D universe we live in, but to an extent they are interchangeable just as a vector can be split into x and y components in more than one way. However, those components are always related by Pythagoras Theorem to the length of the vector. A similar relationship occurs between space and time but the sign of the time component is negated. The consequence is that the time it takes to get anywhere as measured on a spaceship is less than the time measured by someone left behind watching, at as you approach the speed of light, the shipboard time approaches zero. If you could travel faster than light (as measured here) to some distant planet which is moving away from us, then return faster than light as measured from that planet, you would arrive back here before you left. The obvious conclusion is that, if you think getting back before you left is impossible, then so is FTL motion. BTW, the shipboard time for each leg of the journey would be imaginary! Pretend that I'm an intelligent photon, now why has time stopped for me, and why are no events happening to me? And why is it that the rest of the slower-than-me world sees me doing all kinds of things, like vibrating and racing past them headed towards some object to smack into it and maybe bounce off or get absorbed by it, when I, myself, am completely unaware of all that? From your point of view, there is no distance or time between your creation and destruction. You are unaware of everything, even your own existence. It doesn't really help much to try thinking that way. Get a decent introductory textbook from the library. The one I usually recommend is "Spacetime Physics" by Taylor and Wheeler but you'll find other book lists on many web sites: http://www.amazon.com/exec/obidos/tg...544736-5476764 HTH George |
#10
|
|||
|
|||
Yousuf Khan wrote:
Sam Wormley wrote: Yousuf Khan wrote: Now I know that relativity tells us that going faster than light would mean travelling backwards in time. No--the premise in relativity is that the speed of light cannot even be attained by particles with rest mass as is empirically born out. That's not really an answer, is it? It's just a diversion of the subject. Don't let this subject get hijacked by the newsgroup kooks trying to push their own little pet theories, it's a serious question. Explain why lightspeed travel is time stopped, and why FTL is backwards time travel, never mind whether you think it's practical or not. o since clock can't attain c, time is not stopped. o since one cannot travel FTL, your question make no sense. Are There Any Good Books on Relativity Theory? http://math.ucr.edu/home/baez/physic..._booklist.html |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
The case against time travel | persian ram | Misc | 0 | June 21st 05 09:30 PM |
Can't get out of the universe "My crew will blow it up"!!!!!!!!!!! | zetasum | Space Shuttle | 0 | February 4th 05 11:11 PM |
All technology outdated | betalimit | Policy | 0 | September 20th 04 03:41 PM |
All technology outdated | betalimit | Policy | 0 | September 20th 04 03:41 PM |