The difficulty of interstellar travel

[taper]

Assuming we ever figure out faster than light travel, how the heck are we going to navigate? We can't just use the 3D position of stars seen from Earth, because we're moving beyond the light cone observed by Earth. In other words, the traveler would see stars at radically different points in time and space than someone back home.

If Earth were the center of a clock face, and you went to, say, the rim of the face at 9 o'clock, a star at 8 would appear much older, and a star at 2 would appear younger, and both may be in different positions.

Even if we could plot their positions in 4D space, it won't do us much good. If we pop out of FTL at an unknown location, we'll see a bunch of points in the sky, but even the fastest computer can't do anything until it decides what star is what. The problem here is you need to see how the stars travel relative to each other, which can take days to years depending on the distance. Not very practical, and there's too much randomness in stellar evolution and travel to make a true 4D model.

I've done a fair amount of "hard" scifi reading, but I don't remember anyone ever mentioning this before. Or is this just small beans compared to actually getting FTL?

 

[GoodSarmatian]

Set a course to a position about halfway to the star, then stop, adjust your position and direcion and start again. Repeat until you're almost there.
And hope nothing get's in the way.

 

[peter grimes]

Set a course to a position about halfway to the star, then stop, adjust your position and direcion and start again. Repeat until you're almost there.

If you do that, you'll never get there!
-Zeno

 

[History_Buff]

If you do that, you'll never get there!
-Zeno

Ah, but the last couple events will involve you moving over infinitessimal distance, and there for take 0 time, allowing you to reach your destination.



As for OP, it might be possible to plot everything in a 4D scale, and then identify stars based on their (presumably unique) emmission spectrum. Set up a computer program to locate 2, and check to 2 more based on the star catalogue, thus allowing you to establish a 4D position. Thats what I came up with after 30 seconds of thought. I'm sure an astronomer could do better.

 

[Mise]

It doesn't matter if you're travelling faster than light or slower than light -- the stream of light from star X is simply a trail of breadcrumbs that you can follow. At every infinitesimal moment, the star will change position (as you say), so at each infinitesimal moment, you can see where the star is now, and head towards it.

Incidentally, we know fairly well where stars will be in, say, 200 years time, based on our model of the galaxy. So if we were travelling at 100 light-years an hour, we'd know which direction to head in.

 

[taper]

I suppose keeping track of how the stars change while traveling in real space could be done, but what about non real space? If we end up using some sort of wormhole or other dimension travel, you can't do this. Short hops could work, but might not be feasible. Since we haven't worked out the math yet, I can suppose whatever I want, right? What if the energy required to create the wormhole is independent on the distance traveled? 100 short hops instead of one big one might take too much energy to be carried on board. There's still the problem of what happens if you get lost. Maybe we'll create a massive mapping survey to record how space looks at many points throughout the galaxy, and create a usable 4D map from that.

 

[Fetus4188]

I see no reason to assume that at such a time that we have the technical capability to travel to the stars that we would not also have the (far less involved) ability to use current data to extrapolate the positions of stellar objects.

 

[GoodSarmatian]

If you do that, you'll never get there!
-Zeno

I knew some smartass will come with that reply, that's why I wrote almost there .

 

[Perfection]

I don't see the big fuss is. I mean, first off you don't need to worry about steller evolution or much proper motion, because trip times are small compared to these events. Also, in most cases, you'e going to know what star is where because presumably you have some clue how to control your starship. But let's say there's a worst case scenario where your starship is lost somewhere within a known region of scace (but unkown within it) traveling at an unkown speed, there's plenty of stuff around that can help. There's local stars, by which one's position can be measured if you know the locations of the stars, their spectra and thier intensity, there's also landmarks such as other galaxies, pulsars, and high intensity or unusual stars, and star clusters.

Compared to the impossibility of FTL, navigation is a mere afterthought.

 

[Perfection]

I suppose keeping track of how the stars change while traveling in real space could be done, but what about non real space? If we end up using some sort of wormhole or other dimension travel, you can't do this. Short hops could work, but might not be feasible. Since we haven't worked out the math yet, I can suppose whatever I want, right? What if the energy required to create the wormhole is independent on the distance traveled? 100 short hops instead of one big one might take too much energy to be carried on board. There's still the problem of what happens if you get lost. Maybe we'll create a massive mapping survey to record how space looks at many points throughout the galaxy, and create a usable 4D map from that.

It's not to hard really, you go "look Andromeda", "look the galactic core", look "xx nebula" and "yy cluster" then get progressively more local.

 

[civ_king]

failure... if you are moving faster than light you can't see those stars, and what happens if you go through a nebula cloud at that speed, thats a LOT!!!!! of friction

 

[History_Buff]

failure... if you are moving faster than light you can't see those stars, and what happens if you go through a nebula cloud at that speed, thats a LOT!!!!! of friction

Go watch BSG

Everyone knows that in the world of imaginary (the whole dicussion is pretty rediculous) FTL travel, you calculate your path first, THEN jump.


And why exactly wouldn't you be able to see things at FTL?

 

[warpus]

Assuming we ever figure out faster than light travel, how the heck are we going to navigate? We can't just use the 3D position of stars seen from Earth, because we're moving beyond the light cone observed by Earth. In other words, the traveler would see stars at radically different points in time and space than someone back home.

Send out FTL navigational beacons all over the place and use them to triangulate your position.

 

[Perfection]

Send out FTL navigational beacons all over the place and use them to triangulate your position.

Why bother? We got billions of natural ones already.

 

[warpus]

Why bother? We got billions of natural ones already.

But we can't send signals to them and get data back.

I'm not even sure if what is written in the OP is a real problem.. but if it was, beacons should do it.

 

[Perfection]

Who cares! You'd need a lot of time to send and recieve signals anyways (if they were STL or light-speed). Look at some pulsars, triangulate your position and get on with it!

 

[warpus]

Who cares! You'd need a lot of time to send and recieve signals anyways (if they were STL or light-speed). Look at some pulsars, triangulate your position and get on with it!

That would work - you could figure out which pulsars are which by spectral analysis.. probably? maybe?

Actually, that would probably work. You stop every once in a while, get your bearings, and move on.

 

[Perfection]

well pulsars pulse at a specific frequency. Of course, you gotta worry about relativistic effects and blah blah but that crap can be worked out.

 

[warpus]

Or you could just use bacon.

 

[Perfection]

bacon should only be used for culinary purposes, any other use is a waste of bacon.