How Would You Navigate After Using a Warp Drive?

[aychamo]

Hey guys;

Say that yesterday someone invented a warp drive, that would allow you to shoot across our galaxy in an instant. Say we went up in space today and used it. When you appeared at what you would think would be the other side of the galaxy, how would you know where you are?

My point is: If such a technology even was invented, wouldn't you be all but lost when you got to your destination? Any "signals" coming from Earth to let you know where you are would take however many billion years to reach you. Would you effectivly be lost? Or would there be other mechanisms to locate yourself? (Star locations, etc)

 

[SpaceTiger]

My point is: If such a technology even was invented, wouldn't you be all but lost when you got to your destination? Any "signals" coming from Earth to let you know where you are would take however many billion years to reach you. Would you effectivly be lost? Or would there be other mechanisms to locate yourself? (Star locations, etc)

If such a technology existed, then locating yourself from the stars and galaxies would be a relatively trivial matter (particularly if you were smart enough to make a warp drive). However, current physics suggests that warp drive is not possible.

 

[Entropy]

Well, if the warp drive aloud you to go pass the speed of light and you knew how fast you were traveling and how long you traveled plus the direction you went in, they you could easily find your location.

Other than that, possibly by use of star charts you could locate yourself, but then again stars can look very different in different locations because stars will be in different locations not only because you moved but also because you are closer/further to them so you are seeing "younger" or "older" light coming from them.

 

[ohwilleke]

A guy who doesn't bring a map with him on a galactic length journey, and doesn't know which direction and distance he was traveling into start with, to give him a good hint about where he will be, deserves to be lost.

 

[misskitty]

He, or she, could use the Hitchhiker's Guide to the Universe. I agree with Ohwilleke, anybody who wouldn't bring a bloody map with them is daft.

SpaceTiger does have a point in stating current physics points out no such machine is possible.

 

[DaveC426913]

Actually, current physics does NOT make such a machine impossible.

It makes FTL drives impossible, but not warp drives.

FTL (faster-than-light) drives by definition exceed c.

Warp drives create or make use of wormholes to warp space, making the distance between 'there' and 'here' smaller and traversable without exceeding c.

Nothing in modern day physics says this can't be done. In fact, Einstein's equations predict it as a possibility. (Then again, they also predict that time travel is possible.)

 

[misskitty]

If anything were to exceed c wouldn't it just turn into energy?

 

[Phobos]

When you appeared at what you would think would be the other side of the galaxy,

The whole of the galaxy is made of the same stuff we see on this side...stars, nebulae, etc.

You may just not know the local layout of stuff (particularly on the other side of the galaxy where we don't have a clear view from here...the galactic center obscures our view of the other side).

how would you know where you are?

Presumably, you would target a specific location for your journey. Either you would know it beforehand through observations or you would map it out once you got there relative to areas you do know about. If you did a random shot, then although you might not have any idea about local conditions, you could still easily find the galactic plane and center merely by looking (and thereby orienting yourself) and then you could look outward toward other galaxies and figure out your new position relative to the view you had of those galaxies back on Earth.

Any "signals" coming from Earth to let you know where you are would take however many billion years to reach you.

The galaxy is about 100,000 light years across, so an EM signal would take at most, 100,000 light years (not much help, granted).

 

[ohwilleke]

Actually, current physics does NOT make such a machine impossible.

It makes FTL drives impossible, but not warp drives.

FTL (faster-than-light) drives by definition exceed c.

Warp drives create or make use of wormholes to warp space, making the distance between 'there' and 'here' smaller and traversable without exceeding c.

Nothing in modern day physics says this can't be done. In fact, Einstein's equations predict it as a possibility. (Then again, they also predict that time travel is possible.)

The trouble with wormholes is that the large scale structure of the universe is very close to topologically flat, as shown by the cosmic background radiation studies. A wormhole that would get you any place far away requires a universal that significantly not topologically flat.

 

[SpaceTiger]

Nothing in modern day physics says this can't be done.

Except for the fact that you'd need more than a galaxy's worth of energy to achieve it. I'd say that qualifies as "can't be done".

An interesting link on the subject:

http://www.nasa.gov/centers/glenn/research/warp/socanwe.html

 

[owl3951]

Well...

Except for the fact that you'd need more than a galaxy's worth of energy to achieve it. I'd say that qualifies as "can't be done".

An interesting link on the subject:

http://www.nasa.gov/centers/glenn/research/warp/socanwe.html

...if you want to get all technical...

 

[JesseM]

The trouble with wormholes is that the large scale structure of the universe is very close to topologically flat, as shown by the cosmic background radiation studies. A wormhole that would get you any place far away requires a universal that significantly not topologically flat.

Why do you say that? I think maybe you are taking the embedding diagrams too literally, wormholes don't require that two regions of space be "near" each other in some higher-dimensional space (in fact general relativity itself doesn't require any such higher-dimensional space for curved 3D space to be 'embedded' in).

 

[ohwilleke]

Don't they? The idea of a wormhole is that you avoid the need to travel at greater than c to get from here to there in a given time by connecting two points via some connection of a shorter length. I have a hard time seeing how that isn't equivalent either a higher dimensional space or a topologically non-flat space.

 

[JesseM]

Don't they? The idea of a wormhole is that you avoid the need to travel at greater than c to get from here to there in a given time by connecting two points via some connection of a shorter length. I have a hard time seeing how that isn't equivalent either a higher dimensional space or a topologically non-flat space.

What do you mean by "topologically non-flat"? I thought flatness referred only to curvature, and would be compatible with a range of topologies. For example, it's possible to have a flat universe with the topology of a torus, as discussed in this article.

 

[turbo]

The galaxy is about 100,000 light years across, so an EM signal would take at most, 100,000 light years (not much help, granted).

Darn! I was hoping to use my Magellen GPS receiver to find my way back. I'll be 99,970 (or so) years too old to do that. Unless the wormhole slowed MY time down so that I perceived only a brief passage while the entire external universe experienced 100,000 years of time. That way, a powerful enough beacon in Earth orbit might help me get back...although after about 200,000 years elapsed time on Earth, "catching up with old friends" might be a bit problematic.

 

[JesseM]

Darn! I was hoping to use my Magellen GPS receiver to find my way back. I'll be 99,970 (or so) years too old to do that. Unless the wormhole slowed MY time down so that I perceived only a brief passage while the entire external universe experienced 100,000 years of time. That way, a powerful enough beacon in Earth orbit might help me get back...although after about 200,000 years elapsed time on Earth, "catching up with old friends" might be a bit problematic.

You don't need a wormhole to get to the other end of the galaxy in a short subjective time, special relativity will work fine. From the point of view of observers at rest wrt the galaxy, although it will take you over a hundred thousand years to cross it, if you go fast enough your clock will slow down enough so that you have only aged a few years when you reach the other end...from your point of view, you are aging normally but the length of the galaxy has lorentz-contracted down to much less than a hundred thousand light years. You can look at http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html to see a table of how much onboard time it would take to reach various distant locations, like the Andromeda Galaxy, if you accelerated at 1G for the first half of the journey and then decelerated at 1G for the second half (for example, it'd take 20 years to reach the center of the galaxy, 28 years to reach the Andromeda galaxy). But like you said, when you return to Earth huge amounts of time will have passed according to earth-clocks.

 

[DaveC426913]

...the large scale structure of the universe is very close to topologically flat...

Yes, on average. Doesn't mean smaller areas are flat too.

 

[DaveC426913]

Except for the fact that you'd need more than a galaxy's worth of energy to achieve it. I'd say that qualifies as "can't be done".

You'd be wrong. That merely qualifies as "impractical". Before determining whether it is feasible, we must first determine if it is theoretically possible, which it is.

 

[SpaceTiger]

You'd be wrong. That merely qualifies as "impractical". Before determining whether it is feasible, we must first determine if it is theoretically possible, which it is.

No, it qualifies as "can't be done". You can't harness a galaxy's worth of energy to get across a galaxy. That's one of the most ridiculous things I've ever heard. At this point, we don't think it will be physically possible to perform this feat. I acknowledge that physics might change, but it simply can't be done with what we know.

 

[JesseM]

"more than a galaxy's worth of energy" to do what, exactly? To travel across the galaxy fast enough so that the journey only takes a few years of onboard time? To build a wormhole connection from one end of the galaxy to the other? To build an Alcubierre warp drive to get you there? I don't think it's been established that any of these things would require that much energy, although we won't know whether the last two are even physically possible until we have a theory of quantum gravity.

 

[DaveC426913]

No, it qualifies as "can't be done". You can't harness a galaxy's worth of energy to get across a galaxy. That's one of the most ridiculous things I've ever heard. At this point, we don't think it will be physically possible to perform this feat. I acknowledge that physics might change, but it simply can't be done with what we know.

1] Your "more than a galaxy of energy" line is pulled out of thin air. Because you say it takes that much energy, doesn't make it so.
2] I think it should have gone without saying, but apparently not: "it can't be done with current technology". I think the initial poster took that for granted, I don't know why you didn't. Becasue we can't do it today does not mean it can't be done in theory. We know of no reason why it can't be done.
3] For the purposes of labelling this as a serious proposition, as opposed to a "ridiculous" one, note that this type of civilization is actually already defined by Nocolai Kardashev. A type III civilization is defined as one that can harness an entire galaxy as a power source.

It only seems ridiculous because you haven't read up on the subject.

 

[SpaceTiger]

Actually, "more than a galaxy's worth of energy" is a quote from a professor in the department here. His name is J. Richard Gott. I suggest you do a little research on that yourself.

I can't write much now, but will expand later.

 

[JesseM]

Actually, "more than a galaxy's worth of energy" is a quote from a professor in the department here. His name is J. Richard Gott. I suggest you do a little research on that yourself.

What book/paper is it from? Can you give the page number? Gott is known for studying the subject of time travel, so he might have been talking about something like the energy needed to create a Gott loop out of cosmic strings that would allow you to travel back in time, not the energy needed to travel across the galaxy at close to the speed of light, or the energy needed to hold open a stable wormhole.

 

[ohwilleke]

Yes, on average. Doesn't mean smaller areas are flat too.

True, but the extent of non-flatness locally is well understood as a virtue of GR and still doesn't get you to a GR with useful wormholes given what we know about local mass distributions in anywhere we could ever get to.

 

[JesseM]

True, but the extent of non-flatness locally is well understood as a virtue of GR and still doesn't get you to a GR with useful wormholes given what we know about local mass distributions in anywhere we could ever get to.

The question of the large-scale curvature of the universe is irrelevant to wormholes as far as I know--again, it's possible for wormholes to connect distant regions even when an embedding diagram of the universe's large-scale curvature wouldn't show those regions 'close to each other' in the embedding space (the whole idea of an 'embedding space' is just a visual convenience, general relativity itself describes spacetime curvature in intrinsic terms, without the need for any embedding space). As for the local mass distribution, I don't think it's possible to create a wormhole from scratch by pushing matter/energy around into a certain configuration. When people talk about an advanced civilization creating a traversable wormhole, they usually handwave about expanding a wormhole that occurs naturally in the quantum foam that's suggested to exist at the Planck scale according to some ideas about quantum gravity.

 

[DaveC426913]

Actually, "more than a galaxy's worth of energy" is a quote from a professor in the department here. His name is J. Richard Gott. I suggest you do a little research on that yourself.

No, the onus is on you.

 

[SpaceTiger]

not the energy needed to travel across the galaxy at close to the speed of light

I'm not disputing that you could cross the galaxy in a lifetime with much smaller amounts of energy (exploiting SR, as you said), I'm talking about wormhole travel, as Dave was referring to. I promise to give more details and do more research as soon as I return to school. Unfortunately, I've been attending my grandfather's funeral and only have very small intervals of free time.

 

[AcEY]

surely even if we use a warp drive, we would still have the problem of time dilation?

 

[JeffL]

You could use distant galaxies and the center of the Milky Way to extrapolate your coordinates. Local star positions will change but not the more distant objects (at least not that much). So you can still use them to get your bearings. Definitely make sure you have an idea of how far and what direction that spacecraft should go before clicking on the warp drive. I think it's possible.

 

[DaveC426913]

surely even if we use a warp drive, we would still have the problem of time dilation?

Nope. Time dilation is related to acceleration and velocity. A wormhole bypasses them.

Though it has been shown that wormhole in fact can easily act as a time machine, by bringing the two ends near each other (I forget exactly how this works.)