[QUOTE=JohnnyMo1;44081079]No, because for any signal which signal which gets somewhere faster than a light beam, we can find a reference frame of an observer who sees that signal going backwards in time.[/QUOTE]
Where is this frame? Like where word someone be seeing it go back in time.
[QUOTE=Mingebox;44081396]Where is this frame?[/QUOTE]
Usually between the sofa cushions
[editline]28th February 2014[/editline]
[QUOTE=Mingebox;44081396]Where is this frame? Like where word someone be seeing it go back in time.[/QUOTE]
It's not really a question of where, it's a question of your state of motion. Here's a little thought experiment: Two countries are signing a peace treaty, they want to sign it at the same time so that it's fair, so they place a light exactly between them on the table which will turn on, and when they see the light they will each sign their page immediately. The light turns on, they sign when they see it, a referee standing by the table sees them sign at the same time. Hooray!
But a car was driving by, heading from the country A side to the country B side, and the driver witnessed the signing. Light travels at the same speed in all reference frames, so from his perspective, this light pulse from the light bulb in a sphere, the same as the people as the table see. BUT, he sees the delegate from country B heading towards the wave front, so he sees the light first, and signs the treaty first. If he was traveling in the other direction, he would have seen the delegate from country A signing first.
The treaty signings by each country are separated by a [I]spacelike interval[/I], since they happen close enough together that a light beam cannot travel between them. The light from the light bulb makes it to them at the same time (in some reference frame) because it's traveling both directions at once, but a laser pointer shined from the country A delegate as he signs to the country B delegate wouldn't make it before he signs in any reference frame.
So the point of this is, because the treaty signings are separated by a spacelike interval, depending on our state of motion, we can find that signing A happens before signing B, or vice versa, and no one actually has claim to have the "correct" viewpoint. They're all equally valid. The same goes for a spaceship leaving planet A to get to planet B faster than light. Since leaving and arriving are spacelike separated events, we can find a reference frame in which the ship arrives before it leaves, and this reference frame is perfectly valid.
[editline]28th February 2014[/editline]
And that's why FTL travel is fucked up.
warp theory is more likely possible and also achievable by human reachable energy sources to generate the field
so ST was close
also some year ago some egyptian student found out nice propulsion tech
which reminds me on impulse propulsion la ST
;)
I know this question is gonna make a lot of physics people in this thread angry at me, but are wormholes possible? Wormholes as a means of transportation, I mean.
[QUOTE=Ardosos;44082376]I know this question is gonna make a lot of physics people in this thread angry at me, but are wormholes possible? Wormholes as a means of transportation, I mean.[/QUOTE]
Probably not. They appear in valid solutions to the Einstein field equations, but like the Alcubierre drive, they require exotic matter to keep them from collapsing.
[QUOTE=JohnnyMo1;44081406]Usually between the sofa cushions
[editline]28th February 2014[/editline]
It's not really a question of where, it's a question of your state of motion. Here's a little thought experiment: Two countries are signing a peace treaty, they want to sign it at the same time so that it's fair, so they place a light exactly between them on the table which will turn on, and when they see the light they will each sign their page immediately. The light turns on, they sign when they see it, a referee standing by the table sees them sign at the same time. Hooray!
But a car was driving by, heading from the country A side to the country B side, and the driver witnessed the signing. Light travels at the same speed in all reference frames, so from his perspective, this light pulse from the light bulb in a sphere, the same as the people as the table see. BUT, he sees the delegate from country B heading towards the wave front, so he sees the light first, and signs the treaty first. If he was traveling in the other direction, he would have seen the delegate from country A signing first.
The treaty signings by each country are separated by a [I]spacelike interval[/I], since they happen close enough together that a light beam cannot travel between them. The light from the light bulb makes it to them at the same time (in some reference frame) because it's traveling both directions at once, but a laser pointer shined from the country A delegate as he signs to the country B delegate wouldn't make it before he signs in any reference frame.
So the point of this is, because the treaty signings are separated by a spacelike interval, depending on our state of motion, we can find that signing A happens before signing B, or vice versa, and no one actually has claim to have the "correct" viewpoint. They're all equally valid. The same goes for a spaceship leaving planet A to get to planet B faster than light. Since leaving and arriving are spacelike separated events, we can find a reference frame in which the ship arrives before it leaves, and this reference frame is perfectly valid.
[editline]28th February 2014[/editline]
And that's why FTL travel is fucked up.[/QUOTE]
I'm still not clear on this whole reference thing. Does matter what is observed? What if nobody's even looking? Is it just the observations that are paradoxical, or can predestination thing occur?
[QUOTE=Mingebox;44082676]I'm still not clear on this whole reference thing. Does matter what is observed? What if nobody's even looking? Is it just the observations that are paradoxical, or can predestination thing occur?[/QUOTE]
No, it doesn't actually matter if anything is observing, and it's not just the observations that are paradoxical. A "reference frame," the stuff a given observer sees, is actually just a relateable way of talking about changes of coordinates in spacetime. I may be making things even harder to understand by adding more abstraction here, but the thrust of it is that the question, "Did event A occur first, or did event B occur first?" doesn't have coordinate-independent meaning when we talk about spacelike-separated events. If we were working on a problem, we'd say it depends on how we measure. From a more physical standpoint if we were observing an event, though, it depends on who is measuring an how they are moving, because that determines how coordinates will work.
So, I'm grasping here, what you're saying FTL would make it so one would simultaneously see two frames that since, still seperate in their own relative spacetime, can't interact in a logical manner because you don't know what belongs when?
[QUOTE=Falubii;44069336]It's hard to design a vehicle in which nothing will go wrong in a 20 year trip.[/QUOTE]
20? lets try for a few more zeros in there
[QUOTE=Mingebox;44082996]So, I'm grasping here, what you're saying FTL would make it so one would simultaneously see two frames that since, still seperate in their own relative spacetime, can't interact in a logical manner because you don't know what belongs when?[/QUOTE]
I think so, If I'm interpreting your post right. You'll have frames where effect precedes cause. Should be pretty obvious why that's bad.
[QUOTE=JohnnyMo1;44084289]I think so, If I'm interpreting your post right. You'll have frames where effect precedes cause. Should be pretty obvious why that's bad.[/QUOTE]
Is that from the perspective of the cause/effect, or from an external view? Also, what if we pretend wormholes exist? What would be the difference between a wormhole between two planets, and those planets being next to each other
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