General > Discussion

Wormhole travel vs. FTL engines

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keybounce:

--- Quote from: GopherLemming on March 10, 2009, 05:56:56 pm ---I wasn't going to post again since I would probably just be repeating myself, but I felt the need to correct several points.


--- Quote ---but one of Einstein's assumptions was that the speed of light was constant from (almost any) reference frame.
--- End quote ---
Actually Einstein theorized that the speed of light through a vacuum was an average. Some photons travel slower then c and some travel faster but dividing the photon count by the net speed will always result in 186,282.4 miles per second (rounded up).
--- End quote ---
This doesn't agree with anything that I learned in special relativity, and I can't say that I know G.R. inside and out.

What I do know is that S.R. makes two assumptions:
1. The speed of light in a vacuum is constant in any inertial reference frame
2. The laws of physics are constant in any inertial reference frame

No average; no "some photons go faster and some slower". Absolute constants.

G.R. relaxes the constraints from inertial reference frame (no acceleration) to "Gaussian".


--- Quote ---
--- Quote ---That, along with the assumption that the laws of physics are the same churns out a bunch of odd results that match experimentations.
--- End quote ---
Some ideas are hard to picture but the vast majority of experiment results make complete sense in physics. Try to imagine the problem in an abstract way, without applying assumptions that we formulate in everyday life.
--- End quote ---

You get such odd results as "F = GMm/r^2" being hard to even state. Mass as seen by who? Distance as seen by who? Different observers will see different speeds, and different distances. It isn't even clear that this law can be stated under G.R.

You get such odd results that we now take as a given -- for example, if two people are walking towards each other, they have different concepts of "now" across the universe. You might even find that many many light years away, a planet blows up, and to one person that event is in the past, while to the other person it is in the future.

You get the "Light cone", which has "Elsewhere, but cannot say past or future"; you get "Past" (or "future"), but cannot say if here or not here, etc.

You get the whole "No, our satellites do not have the same clocks as the GPS receivers that listen to them".

Heck, you get "Sorry, the top floor's clocks aren't synched with the ground floor's clocks".

You get "Sure, if you're on a train, and you throw a baseball, the baseball goes as fast as both the pitch and the train. As long as the train isn't really really fast".

We grew up with these oddities, but they are oddities.


--- Quote ---
--- Quote ---"Cannot travel faster than light" is NOT one of the conclusions.
"Cannot accelerate up to the speed of light" is.

Space itself can, and does, "move" faster than light -- see the superluminal expansion of space itself.
--- End quote ---
Woah. Stop right there. Cannot travel faster then light IS a conclusion of special relativity. If you can't accelerate to c how would you get faster then c?
--- End quote ---
An object moving slower than light cannot accelerate faster than light.
An object moving faster than light cannot decelerate below light speed.

An object moving at the speed of light itself has an oddity. Light moving in the same direction (parallel to itself) moves at the same speed as light heading in the opposite direction. The only way this can happen is if photons takes zero time to move from emitter to absorber.


--- Quote ---
--- Quote ---The idea that you can move a bubble of space around faster than light, while nothing in that bubble has to move "fast" (don't ask relative to what) is both theoretically possible under G.R., and under (or at least was) research.
--- End quote ---
Ha ha! Good ol' warp drive eh? In theory it is possible. Manipulate space-time to contract ahead of an object and expand behind it. The travel time / distance would resolve as a speed higher then c while local speed never approached even relativistic velocities.

But our mate special relativity still plays a part. An observer outside the bubble would see the object going at a lower speed then c and the object would see the universe traveling at a speed of less then c yet the D/T= >c so it's a paradox right? Well no it isn't, but it's a little hard to explain so I'll give an analogy. If two people, named A and B could see each other and started walking in opposite directions, A sees B getting smaller and B sees A getting smaller. An apparent paradox that makes perfect sense in everyday situations.

In practice this warp is impossible though. The "bow-wave" would have to be created with very dense matter or energy and this matter or energy cannot exceed c so the bubble behind it is limited to c as well, meaning it isn't FTL travel.
--- End quote ---
So this idea has been disproven? Thank you; I was not aware of that.


--- Quote ---The other theory for this uses S-T disturbing objects, such as a quickly rotating singularity to distort space time to propel the object. This would require a network of these S-T disturbing objects in the same fashion as a train requires track. The track would be placed by a slower then c ship meaning the initial journey would be at normal speeds. Oh, and each track object would need it's own star for power.
--- End quote ---
So you need to build your road network, and once built, travel within your empire along the roads is fast. That doesn't sound any different than existing historical systems.

Note that it still permits FTL travel. Just not FTL expansion.

vedrit:
And, if I recall correctly (Simply awed, and stupefied by the spacial theory talk), the game didnt exactly say they PROVED that the aliens were traveling at FTL speeds, only it SEEMED to be so.

The only scientific addition I can add is that the only time light photons have been slowed was when passed through Bose-Einstein condensate. (I could be wrong, but Im fairly sure)

GopherLemming:
Please stop using the term "assume." Theory is a preferred word. Assumptions aren't based on any fact. Facts are purely based on fact. Theories cover anything between.


--- Quote from: keybounce on March 11, 2009, 04:03:13 am ---No average; no "some photons go faster and some slower". Absolute constants.
--- End quote ---

Light does vary in speed by a lot. I think the normal measured variation is 0.00000000000001 percent c. It is a considered a constant because net speed / photon count will ALWAYS equal c. Hence that calculation's answer is a constant.


--- Quote from: keybounce on March 11, 2009, 04:03:13 am ---You get such odd results... We grew up with these oddities, but they are oddities.
--- End quote ---

Your opinion of what is odd is obviously different to mine. Psychology isn't a subject I know much about (though I have my opinions) but from what I can see the reason you think of these as odd is because of the laws you formulated for yourself while growing up. Try seeing physics in a different way to how you see everyday life. I don't consider those situations odd because I understand them, can picture them in my mind and they are very well tested.


--- Quote from: keybounce on March 11, 2009, 04:03:13 am ---An object moving slower than light cannot accelerate faster than light.
An object moving faster than light cannot decelerate below light speed.
--- End quote ---

"Object" is the wrong word. Mass and information cannot reach or exceed c. Theoretical particles that travel faster then c could also never reach c. But because of that we can't interact with them, they can't be used to transmit information, they are very unstable (cannot be expressed as "existing" in the classic sense). You are right that FTL particles couldn't reach or drop below c, but I find you correcting me patronizing since I wasn't referring to them as they are completely out of context for this discussion!

Mass can't reach c. Mass and information can't exceed c.


--- Quote from: keybounce on March 11, 2009, 04:03:13 am ---So you need to build your road network, and once built, travel within your empire along the roads is fast. That doesn't sound any different than existing historical systems.
--- End quote ---

Indeed. Though I obviously didn't make the point well. Power is a problem. Destroying a hundred solar systems for a journey to a nearby star isn't that practical. I think the ratio is a ton of matter needs to be annihilated into energy for every atom that you send through the network but I can't be completely accurate off the top of my head.

keybounce:

--- Quote ---Light does vary in speed by a lot. I think the normal measured variation is 0.00000000000001 percent c.
--- End quote ---
Wow. I was not aware of that; thank you.


--- Quote ---Your opinion of what is odd is obviously different to mine. Psychology isn't a subject I know much about (though I have my opinions) but from what I can see the reason you think of these as odd is because of the laws you formulated for yourself while growing up.
--- End quote ---
Fair enough; my personal idea of "odd" is different than probably 95% of the population.

When I call something "odd" in this respect I'm referring to what most (>66%) of the population regard as "odd" based on normal activities and observations in every day life.

For about 20 years now, we've grown up with G.R. as a given, with adults having learned enough of it in this country that they understand it does strange things in strange situations. In other countries that level of learning isn't there, and the concept of "odd" differs.


--- Quote ---... but I find you correcting me patronizing since I wasn't referring to them as they are completely out of context for this discussion!
--- End quote ---
Fair enough. I was not trying to be patronizing, and I apologize for it.


--- Quote ---Mass can't reach c. Mass and information can't exceed c.
--- End quote ---
Right. One of the big surprises for me in physics was that light can travel faster than C, and relatively easily. Apparently (if I remember correctly), in a wave guide you can get the light waves to twice the speed of C if the information carried by those waves drops to half C; apparently the actual constant is C squared, not C itself.

The point was that while you cannot exceed C while staying in normal space, nothing prevents you from doing odd things with space. Warping space was one of the things that I had read of; you indicated that it turned out not to work. Massive spinning objects (hello rotating super massive black holes) was another; you just indicated that the power consumption is ZPM-level (sigh, no stargates.) Wormholes are an often discussed idea, but what I've read indicates that the current belief is that they are probably either ultra-rare, unstable, self-collapsing, or just plain "untravel-able" by anything bigger than a photon (so at best they can transmit information, not matter).

So the only thing left may be an M-space bridge, but it would have to be portable and able to run both ways.


--- Quote --- Please stop using the term "assume." Theory is a preferred word.
--- End quote ---
Now we're into nitpicking. "Assumptions", to me, are what you place at the start of any theory. Given those assumptions, the theory states what is predicted.

S.R. and G.R. each made two assumptions; then, based on those assumptions being true, some things come out to be true. The assumptions of S.R. are untestable -- you cannot get a true inertial reference frame, but it turns out that the predictions of S.R. match local observations for non-accelerating reference frames. G.R., on the other hand, DOES match predictions to observations, so the presumption is that the two assumptions made by G.R. are in fact true.

(as a side note: S.R. is not the only theory that manages to match observation and prediction. Lorenz, if I recall correctly, came up with a different set of assumptions that also match, and turns out to be 100% equivalent to S.R., but has very different assumptions about why and what's happening than S.R. does. For example, does an object only appear to change size with speed, because the observer cannot see identical instants at different locations, or is there in fact a true reference frame, and objects really do change in size, but since your rulers also change, you cannot tell.)

That is what the term "assume"/"assumption" means to me. If it has a different meaning to you, then lets agree to disagree.

odie:
Oh Oh OOOOooooooooooooooooo..... how could i have missed such an exciting theory discussion!? OMG.

I love sci fi stuff!

And to help us understand that FTL (Faster than Light) is theoretically possible in the real world (at least in theory), check out this wonderful piece of paper published closed to a decade ago... came across it during my diploma years......
Warning ahead though, its uber intellectual and so brace urself.....
FTL Discussions

And something on DISCOVERY that seemed plausible for design here perhaps? Lol.
Discovery stuff

More? Lol.
See This
and
THIS!

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