# Fast then light experiment

jaiii
Hi,

I would like to ask for such a theoretical case:

spacecraft moves in space and time and should be curved spacetime around the ship but is produced by gravity, which
would compensate for the curvature to zero and light and gravitational waves would have curved around the ship.
Ship could overcome the speed of light.

zhermes
You can't overcome the speed of light.

John232
If the universe was expanding FTL then wouldn't we already be traveling FTL relative to other galaxies? The universe traveling FTL seems to be an accepted TV theory already...

zhermes
TV theory?!

Traveling 'faster than light' relative to something else, from another observer's reference frame is not an issue---and is accepted as you suggest, for instance, we observe quasars at the opposite ends of the visible universe to be moving FTL relative to each-other. Again, that's not an issue.

You can not travel faster than light relative to any local space-time.

John232
Hey, the people saying it work at universities...

They say there is no problem with space itself expanding FTL, but the objects moveing with the expansion (galaxies) would then end up traveling FTL relative to each other.

Most of what I have read on the forums as to the reason galaxies on the opposite end of the universe do not travel FTL is because of the addition of velocities. But, if space can allow galaxies to travel FTL relative to each other then the addition formula would never be able to give their true velocity since they can travel FTL relative to each other and the formula itself by its own design would prevent that mathmatical result. So then wouldn't applying addition of velocity to galaxies traveling with the expansion of space just be wrong?

zhermes
So then wouldn't applying addition of velocity to galaxies traveling with the expansion of space just be wrong?
Yes. That's definitely very accurate. But it is also only one way of 'thinking about it' / 'describing it.' You're right, and it is the mathematically correct way of describing it.
Another way of *thinking about it* however, is that these two hypothetical galaxies are forever outside of causal connection with eachother. They will never see eachother, never know the other exists. A laser traveling from one towards the other will never reach its destination... thus in this respect, they are distancing themselves at a rate FTL.

John232
Also, the galaxies on the edge of the visable universe traveling close to the speed of light wouldn't even be able to observe a galaxy on the opposite end of our visable universe. They would observe us to be on the edge of their own visable universe and the other galaxies out beyond ours in complete darkness.

John232
So then the addition formula isn't being used on galaxies already? I have had a hard time getting a quick responce or finding an older one on this topic.

I think the reason for the edge of the visable universe is more of being a problem with the age of the universe. Light would not have had time to travel that distance since its birth. That was Einsteins reasoning but back then we didn't have the telescopes we have now to determine the actual size. But, I don't think we can not see them because they are traveling FTL. The velocity of a photon is unaffected by the velocity of the object it comes from, unless it was only a great enough distance that it lost its wavelike properties by being streatched out from the expansion of space itself from going over that distance.

jaiii
But scientists acknowledge that warp drive is In line with scientific knowledge and also exceeds the speed of light.