space travel

You're "against" faster than light travel? Has it been proven to hurt the environment or something? (Subtle ST:TNG jab.)

I think maybe what you're talking about is wormholes?

If we're just speculating...

We know that time dilates as the speed of light approaches. So at 99.9% of the speed of light, a traveler could go between two close stars at a very reasonable 30 or so years. The problem, both for story tellers and travelers, is that everyone they know at the planet is going to experience a vastly increased number of years while he is gone.

But we don't really know what happens at 100% of the speed of light, since it effectively acts as a barrier which we can never exceed. It is, in my mind, sort of like an asymptote where a line may never touch.

But what happens at 101% of light speed? Since it is all speculation, you could say that, even though your speed is still increasing, time begins to dilate in the reverse direction. So intrepid scientists could find an exact speed, or speeds, above LS that maintains the progression of time we're used to.

Another option you could explore is man-made white-holes. As these only exist in theory (the opposite of black holes, they push things away, rather than sucking them in). Perhaps they bend space in the opposite way that black holes do, and would render the time dilation of FTLS travel moot. So space ships would create smallish white holes and then somehow contain them, and use them to shove themselves around at incredible speeds, without feeling the chronic consequences.

Well it depends on "whose" time you're speaking about.

Is it a person on the ship, or a person on earth?

If it's on the ship, then just traveling close to the speed of light will do the trick. Time will dilate, and the time the astronaut experiences will be less than that of the guy on earth. Look up the Twin Pardox, and it will explain this in more detail.

If you're asking about less time passing on earth while the ship is hauling ass somewhere, then I think you're in a physics pickle with no way out short of some kind of "worm hole" or warp drive type deal.

Dommo said:

If you're asking about less time passing on earth while the ship is hauling ass somewhere, then I think you're in a physics pickle with no way out short of some kind of "worm hole" or warp drive type deal.

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Magic, yep. But it has to sound like science-y magic.

Most people are willing to suspend their disbelief with travelling at the speed of light, being as the scientific community seems to unanimously say "probably not going to happen, ever."

You can get away with FTL drives, folding space, folding time, and people will generally allow it.

Here, try this for ideas:

http://en.wikipedia.org/wiki/Faster-than-light

KC36 said:

Let's say my space travelers are gone for four months their time traveling at the speed of light. How many months will pass by on Earth? I need an estimate on this for my story, so I need some help on that.

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I don't know the answer to this one. I expect the answer is a lot longer than four months, though.

I have another question: Say that they are twenty light years away. How fast (or slowly.... or maybe just fast because this is in the 2400s and they can make things travel faster) does an email or video message send that far away? Or at least an estimate. (I'm bad with these things) Also keep in mind that in my story world, the whole Universe is connected with an intergalactic database, so the message would send quickly to the nearest resource center and send to the spaceship. So I'd say maybe under ten minutes? Maybe less?

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The fastest messages can travel is at the speed of light (unless you inject some bolognium that supercedes that limit) so if they are 20 light years away, a message sent by radio (or laser or x-ray or whatever) would arrive at the destination in 20 years. Radio, visible light, x-rays and gamma radiation are all "light" and the waves of all of them travel at the speed of light (C).

There is a popular trick in SF to send messages faster than light: the ansible as coined by Ursula K. LeGuin and subsequently used by several other authors. There is also the idea of using "quantum entanglement" where simply you take two particles that share the same state and separate them (requires sub-luminal transport) then when the state of one particle is changed, the other changes simultaneously, regardless of the distance between them. Extrapolate that, and you have instant e-mail.

http://home.att.net/~srschmitt/script_starship.html

That's a relativity calculator. It's pretty self explanatory and fairly realistic in the time estimates, as it takes into account both the time needed to accelerate, and decelerate.

It then tells you how time is experienced for a person on the ship, and a person on earth.

In my case, I wanted my ship to go 20 light years, while accelerating at 1g(so my ship had gravity ). To make that journey, the travelers on the ship experienced about 6 years, while the people on earth experienced about 21 years. That should kind of give you the idea of what would happen in real life interstellar travel.

Assuming you can get a high enough fraction of the speed of light, a traveler might only experience a few years, while millenia might pass on earth. Definitely some interesting stuff.

http://www.1728.com/reltivty.htm?b0=.99 This calculator gives you the time multiplier for the people outside of the ship. This can be used for saying that I'm traveling at say .95 C (speed of light), and you can directly correlate that to a certain time distortion. Also remember that both the mass of a something, and the dimensions of something also change when you are reaching near light speeds. Your mass increases, and the length of your ship in the direction of travel, decreases.

For example I put in .5 C in the calculator, which is half the speed of light. At that speed, time goes passes at about 86% as fast on the ship as it does on earth.

900,000,000,000,000 light years
.03 Earth G's
2000 years on board the ship

I guess .03 earth G's is not too healthy. Too bad there isn't a calculator where you plug the amount of time wanted on board the ship. Surely there are some better numbers than this. Or am I just going to have to make something up?

.03 g's is hardly ANYTHING. Let me put it this way, it's approximately .3 m/s^2 so in 10 seconds you'd be going 3 m/s which is what a person walking does. In 24 hours, you'd be going 25,000 m/s, which is pretty quick, but still minuscule compared to the speed of light. Just to get close to lightspeed, your looking at 12,000 days and that's not factoring in the decreased speed gains you get as the ship starts to gain mass due to reaching relativistic velocities.

Let me do a quick run down to help you out.
(c is the speed of light, and I'm giving a percentage and telling you the time dilation effect)

10% c = time is a .5% slower on the ship
20% c = time is 2% slower on the ship
30% c = time is 4.8% slower
40% c = time is 9.1% slower
50% c = 15.4%
90% c = 67 % slower
99% c = 86 % slower
99.99% c = 98.6% slower(1 year on ship = almost 1 century on earth)

So can you kind of see what I'm getting at? Every little bet closer to the speed of light has a HUGE impact on the time experienced on the ship. It's basically an exponential increase that asymptotes at the speed of light.

I researched this exact quetion for a novel I'm writing. Here's what I found out:

1. In the book Contact, Sagan had Dr. Kip Thorne review the Einstein-Rosen Bridge (wormhole) concept used to send his traveller (Jodie Foster in the movie) across the universe. Kip OK'd the theory. Given that some physicists see him as a superior scientist when compared to Hawking, I trust his opinion! If you recall, Jodie Foster made an interstellar trip in a matter of seconds (?) Earth time, 17 hours from her frame of reference.

2. Instantaneous communication is impossible with current theories. Neutrinos are nice because there are essentially no ways to interfere with them (unlike radio), but collecting (i.e., receiving) is a problem with today's science. Other massless (is that a word?) subatomic particles may also show promise. THe idea is that E=MC^2 says that you can't go faster than light. The speed of light is consant. So the more energy you use to go faster, it actually starts to convert to increased mass. But, if you have a massless object (e.g., tachyon, etc.), you can't increase its mass - so they can go FAST. But again, you have to account for some way of receiving them.

On the other hand, writers have gotten around these issues with magic-like solutions. A good example is Scott-Card's ansible for instantaneous communication. It all depends on whether you want to write hard sci fi or "soft" sci-fi.

I'm not a physicist - so someone may want to review this post to see if I got it right.

That's a good point, but I still take it with a grain of salt. Relativity has been experimentally validated.

Neutrinos are definitely the way to go for interstellar communication. In fact that's how a lot of scientists are leaning towards the idea that the earth is nuclear powered(neutrino emissions from fission), and why we are still geologically active when other planets like mars are pretty much dead.


I definitely think it's possible for instantaneous communication through quirks of physics like quantum entanglement. However I've yet to see anything that would indicate that it's a real possibility for any form of faster than light travel. That's not to say that it isn't, it's just that I've not seen any experimental information that would suggest that it is. BUT, there are a few quirks in a couple of different physics theories that make wormholes and such possible.

JoNightshade said:

You're "against" faster than light travel? Has it been proven to hurt the environment or something? (Subtle ST:TNG jab.)

I think maybe what you're talking about is wormholes?

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Wasn't "pollution" one of the the "problems" in the DS9 series? I really enjoyed that two-hour premier episode (insert baseball reference here), but the regular series episodes didn't live up to the premier.

And wormholes are a bit weaselly for me...

Bartholomew said:

Magic, yep. But it has to sound like science-y magic.

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Such "magic" has specific names in different fictional universes - it's "Warp Speed" in Star Trek, then there was that movie that had "Ludicrous Speed"...

KC36 said:

Sorry Jo, I never thought of it that way.

And to what Dommo said, I never realized time would pass by differently on Earth when the space travelers are gone.

Let's say my space travelers are gone for four months their time traveling at the speed of light. How many months will pass by on Earth? I need an estimate on this for my story, so I need some help on that.

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If they're traveling AT the speed of light (well, more practically, at 99.999 percent of the speed of light) then four months on the ship could be thousands, even millions of years for objects (such as Earth and the rest of the Galaxy) that aren't in the 'accelerated' frame of reference.

A somewhat more practical idea (referencing your next question) is have the ship accelerate to something like 95 percent of the speed of light (, where four months on the ship is equivalent to maybe 21 years on Earth, and in that time they go 20 light-years away from Earth.

To check this I went to that calculation website, put 20 years in distance, and 1 g in acceleration (so those on the ship experience Earth-normal gravity), and it told me 21.8 years Earth time, 6 years ship time. To get the ship time down to 4 months (about .33 year) requires 40 g's, which is WAY too much acceleration for a human to take. You can add an "inertial damper" (I've heard that term used in Star Trek) to the ship to compensate, but that's a pretty much fictional device, and if it EVER fails while they're under high acceleration, everyone on board will be squshed flat and killed almost instantly (but this could add extra drama to the story if the inertial damper output varies slightly - everyone will fell like they're on an elevator goiing up and down, and they're hoping it doesn't hit bottom).

KC36 said:

I have another question: Say that they are twenty light years away. How fast (or slowly.... or maybe just fast because this is in the 2400s and they can make things travel faster) does an email or video message send that far away? Or at least an estimate. (I'm bad with these things) Also keep in mind that in my story world, the whole Universe is connected with an intergalactic database, so the message would send quickly to the nearest resource center and send to the spaceship. So I'd say maybe under ten minutes? Maybe less?

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With the "quantum entanglement" thing that Pthom mentioned (and with news stories I've read in recent years, this is becoming more science and less fiction [!]), such emails could travel galaxy-wide in microseconds. The bad news is it could get stuck and delayed for hours or even be lost, due to the intergalactic email server being overloaded with spam...

KC36 said:

Sorry for all these questions. I just want to get everything straight before I get to the actual space traveling part in my novel. Thats probably 6 chapters away.

Thanks for the answers so far.

-Karla

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Hey, Karla.
Have you read Speaker For the Dead and the subsequent volumes of Ender's Saga? Card has space travel similar to what you describe. Ender ends up being three thousand years old in objective (universe) time, but something about only thirty in subjective (his physical age) time, because he travels a lot near the speed of time. At one point I think he also mentioned that every minute on the ship meant sixteen hours of time out there.

One of Larry Niven's stories (I forget the title, maybe someone else can remind me) has a MC who flies a Bussard Ramjet (a fancy but plauslble "space drive" design) through the Galaxy at near lightspeed, which takes thousands of years in "real time" to do, but his "ship time" was about 30 years. I recall that the MC does get back to Earth, but of course there's been a lot more than 30 years' worth of changes...

For a more direct non-fiction treatment of this topic, I strongly recommend "The Road To The Stars" by Ian Nicolson:
http://www.amazon.com/dp/0688033369/?tag=absolutewritedm-20

Another detail not mentioned so far is that in these relativistic trips, the rocket engine is running ALL THE TIME - for the first half of the trip, it is speeding you up. At the midway point you turn the ship around so the rocket's exhaust is pointing TOWARD your destination, and you're SLOWING DOWN for the second half of the trip. So there's substantial amounts of time (especially for a 'short' 20-light-year trip) at the beginning and end of your trip where you're NOT going at a relativistic speed, and you're not getting a significant amout of the time difference. "The Road To The Stars" explains all this in plain English, as well as going through the mathematical equations and calculations to get the time (both "ship" and "everywhere else") to do various places. It also goes into how big your fuel tank will need to be, which is another huge "detail."

KC36 said:

Bartholomew's idea of white holes pushing the space ship seems okay for me to use. I'm just not 100% sure at this time.

I just don't want too much time to pass by on Earth, because I only want them gone for at the most 8 months. I never realized things could get so complicated.

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It's amazing how complicated things get - just that thing they launch from Florida, the Space Shuttle, not only takes people 100+ miles up, but also gets them moving horizontally at seven miles PER SECOND. And in re-entry and landing, slows them down and stops them without splatting them against the inside walls. And look at it sitting on the launch pad - I think most of the launch weight is fuel.

The furthest reasonable sublight-speed trip from Eath in 8 momths might be to Pluto, formerly known as one of the planets. The nearest star is four light-years away, so you'd absolutely need FTL travel to get there and back within 8 months.

KC36 said:

I talked to my physics teacher earlier and he mentioned something about white holes and black holes connected together to form a universal high way. Humans just have to discover where they are. Say I use that and they just use the paths to reach their destinations quicker. Is that okay? Will they get back to Earth without too much time passing by?

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Yes, that's the 'wormhole' idea, but I find it "dodgy" and not really good "hard SF." I suggest an idea of going throgh a 'transporter' that converts you and/or your spaceship to subatomic particles and THEN sends those particles through the 'wormhole', and on the other end have something that converts the particles back into people or space ships or whatever. Whatever object you send through a wormhole is surely gonna get converted into its consitituent particles anyway, so it might be better to send things through in a way that you can convert them back.

The "Road to the stars" book also discusses faster-than-light travel, but overall how and if we could do it is much more speculative than going to the stars at sub-light speeds.

KC36 said:

I wish this could be soo much easier. Can't I just ignore relativity?

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Well, yeah, a lot of good, published stories do...some just don't mention it, others use HandWavium to push it aside.

benbradley said:

Another detail not mentioned so far is that in these relativistic trips, the rocket engine is running ALL THE TIME - for the first half of the trip, it is speeding you up. At the midway point you turn the ship around so the rocket's exhaust is pointing TOWARD your destination, and you're SLOWING DOWN for the second half of the trip. So there's substantial amounts of time (especially for a 'short' 20-light-year trip) at the beginning and end of your trip where you're NOT going at a relativistic speed, and you're not getting a significant amout of the time difference. "The Road To The Stars" explains all this in plain English, as well as going through the mathematical equations and calculations to get the time (both "ship" and "everywhere else") to do various places. It also goes into how big your fuel tank will need to be, which is another huge "detail."

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Actually, unless your ship uses some sort of massless fuel (surely that is bolognium!) then you may accelerate for quite a bit longer than the midpoint of your journey. This is because as you burn fuel, your ship becomes lighter and therefore goes faster, but now has less mass and needs much less time to slow down. This assumes, of course that the ship doesn't need to carry enough fuel with which to return home. They DO have rocket fuel that works in your ship at your destination, don't they?

Pthom, that is a good point actually.

I recommend reading "Discovery at Roswell" by Terry Deary.

IIRC, it dealt with a reasonably plausible method that involved using something so heavy that it bent space across so you could move (more or less) straight to where you wanted. Sort of like if you stood at one end of a plank of wood and the other end curved around so you could step straight there instead of walking the length of the plank.

Something like that, anyway.

I kind of like Ben's idea of a transporter that converts people and spacecraft into particles. That can definitely work. I'm guessing that's been used, but does that mean I can't use it?

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But particles still can't travel faster than light (and even particles, if they have any mass at all, will attain near-infinite mass as they approach lightspeed. Making a single mass-atom go lightspeed is as problematic as making a starship do it, from that pov. (I'm thinking, but I suppose there are bigger sizes of infinite mass, hey?)

The problem with distance is only the space in between. A lot of SF simply does what others have suggested: come up with a viable technology which allows the reader to suspend disbelief and don't explain it too much so your physics readers can't be given mind-seizures.

Me, I put my money on the infinite energy source of the vacuum. It is the spontaneous creation of empty space (well, realistically, it's only "empty" to us because we cannot see what's beyond.)

Folks ask where the energy to spin off multiverses comes from with each quantum "choice" and that's it: Universes are created because there is infinite energy in nothingness.

Given infinite energy to pour into a system, you can simply remove your starship from one point in space/time and re-insert it into any other point in space/time.

Your readers will appreciate the infinite possibilities (unless your story depends on the finiteness and consequences of limitations, in which case ... 'bang the rocks together')

Hey, who you gonna believe, me or wikipedia?!

In cosmology, the zero-point energy offers an intriguing possibility for explaining the speculative positive values of the proposed cosmological constant. In brief, if the energy is "really there", then it should exert a gravitational force. In general relativity, mass and energy are equivalent; both produce a gravitational field.
One obvious difficulty with this association is that the zero-point energy of the vacuum is absurdly large. Naively, it is infinite,
but one must argue that new physics takes over at the Planck scale, and so its growth is cut off at that point. Even so, what remains is so large that it would visibly bend space, and thus, there seems to be a contradiction. There is no easy way out, and reconciling the seemingly huge zero-point energy of space with the observed zero or small cosmological constant has become one of the important problems in theoretical physics, and has become a criterion by which to judge a candidate Theory of Everything.
http://en.wikipedia.org/wiki/Zero-point_energy

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