[Scotty]

They travel at the speed of light.  Just like every other electromagnetic wave.

Exactly, slow.

Nothing is faster.  Fast.

[Colonol Dekker]

They travel at the speed of light.  Just like every other electromagnetic wave.

Exactly, slow.

Nothing is faster.  Fast.

Only one thing is faster. Here's video proof.

[Shivan Hunter]

I'm sure this is all totally related to Fermi's Paradox and everything.

'Fast' and 'slow' are relative terms. If you want to compare c to the speed of anything else, obviously it's fast. But on an astronomic scale, it's quite slow (takes 100000 years just to cross our galaxy, doesn't it?). Really, once you start dealing with magnitudes this large, 'fast' and 'slow' really don't mean much until they hold some relevance to the matter at hand.

Wait, why are we talking about this, again? :/

[Scotty]

Because Kosh was calling radio waves slow in relation to some as yet undisclosed or undetected signal we're supposed to be detecting.

[watsisname]

Well I get his point that they're slow when you consider the size of large scale structures in the universe.  Ie, the speed of light makes for a woefully slow journey (or communication) between stars... let alone galaxies.

Neumanns do not (always) colonize, do not (always) terraform, and do not have anything to do with the life that created them.

Look up what a von Neumann probe is, as well as the berserker and seeder subsets.

True, I didn't consider that.

Dekker: 

[General Battuta]

For the moment there's absolutely nothing faster than C that doesn't involve causality violation, so lightspeed's all we've got.

Regardless, even at sublight speed, a single Neumann replicating at feasible speeds should have been able to hit every star in the galaxy by now.

[Colonol Dekker]

Assumig their creators would have developed intelligence, and applied it to building said machines instead of... i dunno a giant theme park or some sort of soup recepie.

[Bobboau]

For the moment there's absolutely nothing faster than C that doesn't involve causality violation, so lightspeed's all we've got.

Regardless, even at sublight speed, a single Neumann replicating at feasible speeds should have been able to hit every star in the galaxy by now.

just because we haven't figured out a way around this doesn't mean some other intelligence hasn't, the fact that we have no idea where to even begin thinking about how to do this just shows that if someone else is using a technology like this then we would have not the slightest hope of detecting it.

[Wobble73]

Because Kosh was calling radio waves slow in relation to some as yet undisclosed or undetected signal we're supposed to be detecting.

Exactly, there could be something out there we have yet to even discover, beyond our current perception or understanding!

[Aardwolf]

For the moment there's absolutely nothing faster than C that doesn't involve causality violation, so lightspeed's all we've got.

This is something I've never quite understood. What is this 'causality' that is somehow violated if something goes faster than light? Does this just mean that if something goes faster than light, that it just 'happens' without any visible cause?

Because if that's all 'causality' means, then "violating causality" doesn't seem like it would really mean anything. I mean, how is it different from how a supersonic jet isn't audible until the sound cone passes you (and if you were blind, you wouldn't be to tell it was coming)? It's not like it's going back in time.

@Wobble73: Fhtagn?

[General Battuta]

For the moment there's absolutely nothing faster than C that doesn't involve causality violation, so lightspeed's all we've got.

This is something I've never quite understood. What is this 'causality' that is somehow violated if something goes faster than light? Does this just mean that if something goes faster than light, that it just 'happens' without any visible cause?

Because if that's all 'causality' means, then "violating causality" doesn't seem like it would really mean anything. I mean, how is it different from how a supersonic jet isn't audible until the sound cone passes you (and if you were blind, you wouldn't be to tell it was coming)? It's not like it's going back in time.

Indeed, you clearly have never quite understood this.

Causality violations occur when effect precedes cause.

Objects that move faster than light move backwards in time.

This would allow a faster-than-light ship to destroy itself while it was still being constructed.

[Aardwolf]

What I don't get is how moving faster than light is the same as moving back in time.

Something to do with the whole (1-v²/c²)^0.5 ?

Waiiiiiiit... diagramming it. I'll get back to you

[Wobble73]

For the moment there's absolutely nothing faster than C that doesn't involve causality violation, so lightspeed's all we've got.

This is something I've never quite understood. What is this 'causality' that is somehow violated if something goes faster than light? Does this just mean that if something goes faster than light, that it just 'happens' without any visible cause?

Because if that's all 'causality' means, then "violating causality" doesn't seem like it would really mean anything. I mean, how is it different from how a supersonic jet isn't audible until the sound cone passes you (and if you were blind, you wouldn't be to tell it was coming)? It's not like it's going back in time.

Indeed, you clearly have never quite understood this.

Causality violations occur when effect precedes cause.

Objects that move faster than light move backwards in time.

This would allow a  ship to destroy itself while it was still being constructed.

And if it destroyed itself so that it couldn't be constructed then it couldn't destroy itself! There's the crux! It couldn't destroy itself therefore it wouldn't. It would have to exist outside it's own space-time continuum, once it had travelled faster than c. Then it wouldn't be able to ever get near it's past self.


Scuze me, I have been drinking Brandy and realise I really shouldn't be posting! LOL!

[Wobble73]

What I don't get is how moving faster than light is the same as moving back in time.

Something to do with the whole (1-v²/c²)^0.5 ?

Waiiiiiiit... diagramming it. I'll get back to you

If you are travelling faster than light you are doing things before anyone can perceive it, therefore you would be in the future when people in your present would be in the past.



Does remind of the joke that all Australians are actually 1 day ahead (nearly) than us in the UK! Therefore they are from the future! LOL!


EDIT** Sorry for the double post!

[General Battuta]

What I don't get is how moving faster than light is the same as moving back in time.

Something to do with the whole (1-v²/c²)^0.5 ?

Waiiiiiiit... diagramming it. I'll get back to you

You need to take a course on special relativity.

[The E]

Okay, it's like this.

At location A at time 0, an event happens. The effects of that event are transmitted to the rest of the universe at a maximum speed of c outward from A. An observer at location B can only know about the event after a time equal to the distance between A and B divided by c has passed.

If we now assume that the event is accompanied by an FTL pulse that B can detect, then B will know about the event before the light of the event has reached him. That means that B will be changed by the event before the event has happened in his context (context being defined as what B can observe using light speed methods only). As such, to someone observing B, it looks as if B reacts to the event before the event has happened, thus causality has been violated, as the effect comes before the cause.

[Wobble73]

Another way is... it takes what 30-45 secs for transmissions from the moon to reach earth, thus the time lag in communication between Houston and a moon mission! If we could transmit and receive transmissions faster than light. Then that lag would disappear or at least become negligible.

[General Battuta]

When the spacetime interval between two events is space-like (which characterizes events along an 'FTL' world-line), two different inertial reference frames may disagree not only on the time between the events (as they would in a timelike worldline), but also the order of the events.

This stands in contrast to two IRFs observing a normal, timelike worldline, wherein they may disagree on the time between two events, but never on the order of the events.

In a spacelike FTL worldline situation, IRF A may claim event 1 happened before event 2, but IRF B will claim that event 2 happened before event 1. Remember that both IRFs are equally valid.

The consequences of this are very problematic. To quote Wikipedia:

In the case of a hypothetical signal moving faster than light, there would always be some frames in which the signal was received before it was sent, so that the signal could be said to have moved backwards in time. And since one of the two fundamental postulates of special relativity says that the laws of physics should work the same way in every inertial frame, then if it is possible for signals to move backwards in time in any one frame, it must be possible in all frames. This means that if observer A sends a signal to observer B which moves FTL (faster than light) in A's frame but backwards in time in B's frame, and then B sends a reply which moves FTL in B's frame but backwards in time in A's frame, it could work out that A receives the reply before sending the original signal, a clear violation of causality in every frame.

To summarize: for a FTL (spacelike) worldline, there will always exist some IRFs which interpret the worldline as an object moving back in time. This leads to paradoxes which cannot occur, like signals being received before they are sent.

For an illustration of why this is bad, imagine that you have a radio signal you will send to detonate a bomb under your chair. You send the signal down a spacelike geometry, and it is received before it is sent, detonating the bomb and killing you. 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hurk

[Aardwolf]

@The E: Yeah I get that much. But to me, that suggests that it doesn't matter if causality is violated. There's no paradoxes to be had.

Diagram I was making:


X = position (1-dimensional instead of 3, but whatever), Y = time (up is later)

Basically, to an observer (at the head of the light cone), the FTL object looks as though it has appeared and then split into two parts, moving in opposite directions. The one moving 'backwards' appears to be at positions that are getting farther away at a rate faster than the speed of light. The one moving 'forward' appears to be moving at the same speed (I think).

So what am I doing wrong? (And don't just say "not taking a course on it"; if there isn't a flaw in my logic, then whether or not I've taken a course on it is irrelevant).

[General Battuta]

Reread my last post. Your logic is faulty.

Because you've never had any courses on the topic, you made the mistake of assuming that there existed a 'visibility cone', rather than understanding - as any SR graduate would - that the light cone represents a fundamental causal horizon.