Warp - any scientific take on it?

[KrazyHorse]

Originally posted by TCO


NO. C sends the signal to D, sure. But D already passed A.

No, the FTL transmission sends the message back in time for all observers in this example

Pay attention, would you?

[KrazyHorse]

Here are the transforms, in order (g stands for gamma, using little c as subscript and big C as speed of light)):

First leg (simple spatial displacement transform to right by d):

xa = xb+d
ta = tb

Second leg (boost by velocity v with gamma g):

xb = g(xc + vtc)
tb = g(tc + vxc/C^2)

Third leg (simple spatial displacement transform to left by d/g):

xc = xd - d/g
tc = td

Now, applying these transforms in order, we get the following transform between A and D:

xa = g(xd - d/g + vtd) + d = g(xd + vtd)
ta = g(td + v(xd - d/g)/C^2)

At td = 0, A and D pass each other (xa = gxd, so xd = 0 gives xa = 0)

As they pass each other, A's clock reads -vd/C^2, while D's clock reads 0


When A observes his own clock reading 0, he sends FTL to B. B observes his own clock reading 0.

Now, when tb = 0 at xb = 0, that means that xc = 0 and tc = 0. In other words, as B receives the signal, C passes him and both their clocks read 0.

Finally, C sends an FTL signal to D. tc = td, so both of their clocks read 0. BUT WE'VE ALREADY SHOWN THAT WHEN TD = 0, A AND D PASS EACH OTHER WITH A'S CLOCK READING -vd/C^2

A looks at D and sees him getting the signal A isn't going to send for another vd/C^2 seconds

OMG WTF THAT'S ****ING CRAZY

EDIT: 1 or two typos I just noticed.

[Lonestar]

The Warp, perhaps better known by it's official description the Immaterium, has been known for millions of years, since the War In Heaven between the C'tan and the Old Ones.

The Problem with Warp Travel is, of course, the very real danger of Warp Entities(i.e. Daemons) popping in and rasiing Hell on the transiting starship. There is also the limitation that, anything shorter than a a few light-years requires a point of reference. In the case of Humans, a thousand pyskers are sacrificed a day at the Astronomican, which, of course, is located on Holy Terra.

There are other FTL-methods besides Warp Travel, the Eldar use Webway Gates(think of them as Stargates) and the Necrontyr seem to have a FTL akin to the "Hyperspace" that the Galactic Empire uses to motor about it's Galaxy. Unfortunately, both of those require levels of technology generally unknown in the galaxy, and the lesser races have to make due with Warp Travel, and if your race does not have pyskers to navigate the warp, FTL travel is limited indeed.







Of course, all of the above is fictional, which makes it just as real as any warp the OP is talking about.

[DinoDoc]

Originally posted by Lonestar
The Problem with Warp Travel is, of course, the very real danger of Warp Entities(i.e. Daemons) popping in and rasiing Hell on the transiting starship.

I thought this was solved with the introduction of Gellar Fields which while not a perfect solution since it can fail does serve to mitigate the threat of daemonic possession of ships passing through the Warp.

[Lonestar]

Well, it can/ But the problem is that not all races have such a field on their Ship. For example, the Tau, being psychically neutral that they are, had no need for such a field (being effectively "invisible" to the Daemons of the Warp). This tended to blow up in their face when they were transporting auxiliaries that are psychically active, such as Kroot and Human. It took a while to figure out how to safely transport those auxiliaries, and even then they mostly travel on whatever race's ship they came from.

[KrazyHorse]

Stop ruining a perfectly interesting conversation.

[Kuciwalker]

Originally posted by KrazyHorse
No, it doesn't...

Same scenario. A sends message to B, B accelerates (and flies in a circle to get back to the same location, I guess), then sends it to A's past.

That's assuming the link actually transmits instantaneously in any frame of reference, instead of just one (in which case it would be essentially an infinite number of links between pairs of points in spacetime).

[KrazyHorse]

Originally posted by Kuciwalker


Same scenario. A sends message to B, B accelerates (and flies in a circle to get back to the same location, I guess), then sends it to A's past.

Errr....you're forgetting the general relativistic effect here...

[KrazyHorse]

You can have non-trivial space-time geometry without violating causality...

[Kuciwalker]

GR comes into this? We aren't talking about wormholes, but some magic that allows instantaneous transmission but only between regions limited in space but not in time. A wormhole is essentially an infinite set of links between a region limited in space and time - so if you enter the wormhole at A, come out at B, and then re-enter the wormhole at B you will always come out later at A than before, no matter how fast you start going.

[KrazyHorse]

What the **** are you on about? The conversation was about wormholes, not something completely equivalent to FTL radio.

Wormholes are gravitational distortions. They are non-trivial geometries. You can't have them without curvature...

[Kuciwalker]

Originally posted by Geronimo
Ok, So if in place of a worm hole A and B are connected by an instantaneous transmission closed circuit cable so that there is no ABCDA loop comparible to the causality wrecking one in the first example, there is no longer any way for any of the persons A, B, C, D to obtain information from their future?

I interpreted this as what you call FTL radio, rather than a wormhole that only lets information through.

[KrazyHorse]

Ah. I missed that post of Geronimo's. I thought we were still talking about "real" wormholes.

So yeah, this non-wormhole wormhole ****s up things just as bad at the ansible (duh)

[TCO]

Originally posted by KrazyHorse


No, the FTL transmission sends the message back in time for all observers in this example

Pay attention, would you?

NO! You're not paying attention to me. You're introducing something that was not in my example to show that what I hypothesize causes said effect. My "instant messager" doesn't work like that. It sends the info one minute later to A at the point where A is one minute later (which is past B). And if A IMs it to B, it's still one minute later. It did a more than 200 light year trip. But without going back in time. The forwarded message gets to B one minute after he sent it. so despite it's long travels. B did not get a message to go back to himself before he sent it.

[KrazyHorse]

Originally posted by TCO


NO! You're not paying attention to me. You're introducing something that was not in my example to show that what I hypothesize causes said effect. My "instant messager" doesn't work like that. It sends the info one minute later to A at the point where A is one minute later (which is past B). And if A IMs it to B, it's still one minute later. It did a more than 200 light year trip. But without going back in time. The forwarded message gets to B one minute after he sent it. so despite it's long travels. B did not get a message to go back to himself before he sent it.

You're the one not listening. How come your IM works between A and B but not C and D?