Going to the future

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Kow
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Going to the future

Postby Kow » Thu Nov 19, 2009 4:31 am UTC

I've been pondering lately and thought about how awesome it would be to go really fast (relativity speeds) away from earth and back again, much like the twin paradox, to "travel" forward in time. It'll be several years (or more) after you left and you'll effectively be in the future.

Does anyone see any flaws in my idea? Assuming one could get a ship that would be able to support a person for a while and accelerate the needed amounts and such.
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Re: Going to the future

Postby poxic » Thu Nov 19, 2009 4:40 am UTC

I have two major concerns:

1) We haven't yet figured out how to stop solar radiation from ripping apart your DNA within a few months of leaving Earth's protective atmosphere and radiation belt. It's a problem they're tussling with when planning Mars exploration by humans.

2) So you get back several years later, maybe lots of years later, than the time you spent actually travelling. So ... your friends are all much older and wiser than you, or dead. Your family has, over the years, adjusted to life without you, or they are dead. Technology and culture have progressed without you, and you're some sort of Rip Van Winkle, an old fogey before your time, unfamiliar and uncomfortable with the new things and the cultural changes they brought. You're a living anachronism. The skills you learned as a teen and young adult are now out of date. You'll have some fame as "the Anachronist" and can get on some talk shows, but what else?

So yeah, no. I'll choose (like I actually have a choice) to proceed into the future at the rate of one second per second, like everyone else.
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Re: Going to the future

Postby Kow » Thu Nov 19, 2009 4:45 am UTC

poxic wrote:I have two major concerns:

1) We haven't yet figured out how to stop solar radiation from ripping apart your DNA within a few months of leaving Earth's protective atmosphere and radiation belt. It's a problem they're tussling with when planning Mars exploration by humans.
How far out does that go? What sort of materials block solar radiation? Perhaps the vessel could generate an intense magnetic field to deflect said particles.

2) So you get back several years later, maybe lots of years later, than the time you spent actually travelling. So ... your friends are all much older and wiser than you, or dead. Your family has, over the years, adjusted to life without you, or they are dead. Technology and culture have progressed without you, and you're some sort of Rip Van Winkle, an old fogey before your time, unfamiliar and uncomfortable with the new things and the cultural changes they brought. You're a living anachronism. The skills you learned as a teen and young adult are now out of date. You'll have some fame as "the Anachronist" and can get on some talk shows, but what else?

So yeah, no. I'll choose (like I actually have a choice) to proceed into the future at the rate of one second per second, like everyone else.

I dunno. Personally, I think that would be really neat. People can learn new things right? I'd imagine it wouldn't be much different from moving to a foreign country. It reminds me of a Niven book, A World Out of Time, where this guy does that only for 3 million (or so) earth years. Now that I think about it, that''s probably where I got the idea.
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Re: Going to the future

Postby lulzfish » Thu Nov 19, 2009 5:10 am UTC

Kow wrote: the vessel could generate an intense magnetic field to deflect said particles.

From what, batteries?
And then if you don't like the future, you're stuck.
Even worse, you'd spend several years in space (Even if we could go partial light-speed, it would take some time to travel), bored out of your mind and with no human contact.

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Re: Going to the future

Postby Kow » Thu Nov 19, 2009 5:57 am UTC

lulzfish wrote:
Kow wrote: the vessel could generate an intense magnetic field to deflect said particles.

From what, batteries?
And then if you don't like the future, you're stuck.
Even worse, you'd spend several years in space (Even if we could go partial light-speed, it would take some time to travel), bored out of your mind and with no human contact.

I figured it was assumed the the method was available. Be it a ramjet style ship or whatever else. And obviously there would be plans for what to do if you don't like the future. Hell, humans might not even exist by the time you get back.
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Re: Going to the future

Postby poxic » Thu Nov 19, 2009 6:22 am UTC

Kow wrote:How far out does that go? What sort of materials block solar radiation? Perhaps the vessel could generate an intense magnetic field to deflect said particles.

At least as far as the edge of the solar system, or the edge of how far the Sun's radiation can push, which is much further than Pluto's orbit. Once you leave that area (note that Voyager 1 and 2 haven't really left there yet), you're into the radiation from the galaxy at large, which we don't know anything about. (We've never been there.)

NASA has looked at many options for shielding astronauts for Mars travel. One is a gigantic sphere filled with water, with the crew capsule in the centre. One is a magnetic thingamajig, but it's too complex/expensive for us to consider building (as is the gigantuan water sphere). In fact, of the many potential solutions, they haven't found a single one they like.

I just went googling for the article I first read about this, but instead found this somewhat informative article. A few people think they've found a smaller, more feasible magnetic solution, but we don't know yet if it will work. The article also specifies the danger a Mars-bound astronaut is likely to face: double the risk of a fatal cancer (40% chance) vs. normal population, plus an increased occurrence of cataracts (they say 39 astronauts now have cataracts, but not the relative risk).
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Re: Going to the future

Postby Twistar » Thu Nov 19, 2009 7:26 am UTC

Whenever I or someone around me is complaining about not having enough time to do homework I just tell them to go sit on the moon or something, send the earth away from you at relativistic speeds for a little then make it come back. In the meantime taking your time writing your massive research paper for a few months (at least as long as you SHOULD have been working on it while earth was here) and on earth only a few hours in the night it was due will have passed!

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Re: Going to the future

Postby gmalivuk » Thu Nov 19, 2009 4:52 pm UTC

I suspect that traveling to the future cryogenically will be a technological possibility long before we figure out how to travel safely at relativistic speeds.
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Re: Going to the future

Postby Random832 » Thu Nov 19, 2009 6:24 pm UTC

No problem at all with the idea in principle.

Or, as I always* say: Going to the future is easy; the trick is getting back.

*I actually came up with that just now. But I'm going to say it when/if the opportunity arises again, so there.

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Re: Going to the future

Postby Technical Ben » Thu Nov 19, 2009 11:03 pm UTC

By any chance were you watching "planet of the Apes" at the same time as I was?

Think of the dangers of returning:
You have no immunity to the simple cold, as it has a new strain your body does not know how to deal with. You die.
The language and culture and governments have changed so much they do not know who you are. Your imprisoned/shot down upon re-entry.
And that's before the Monkeys turn up. ;)
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Re: Going to the future

Postby Kow » Thu Nov 19, 2009 11:36 pm UTC

Technical Ben wrote:By any chance were you watching "planet of the Apes" at the same time as I was?

Think of the dangers of returning:
You have no immunity to the simple cold, as it has a new strain your body does not know how to deal with. You die.
The language and culture and governments have changed so much they do not know who you are. Your imprisoned/shot down upon re-entry.
And that's before the Monkeys turn up. ;)

I got nothing to counter the immune system probles likely to be faced.

Regarding too much of a change: return broadcasting a white flag message, or hell, brandish a white flag ( to cover language barriers).

Maybe Futurama-esque style time travel would be better. Not as cool though...
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Re: Going to the future

Postby Talith » Thu Nov 19, 2009 11:43 pm UTC

Depending on how far in to the future you want to travel I think you'd have to either accelerate so much that your body can't handle the G-forces in such a short time, or accelerate so slowly that by the time enough effective time dilation occurs, you'll be dead inside you space ship before it returns to earth. Either way doesn't look like a good idea so I don't think it's worth trying out until we find a way of humans putting up with tremendous G-forces. (P.S I haven't done the maths so I might be wrong about how long you'd have to apply an acceleration for to have a time difference).

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Re: Going to the future

Postby BlackSails » Fri Nov 20, 2009 12:03 am UTC

Technical Ben wrote:You have no immunity to the simple cold, as it has a new strain your body does not know how to deal with. You die.


You cant be sure of that. You might be the only man in the world who didnt have his immune system replaced with nanobots at birth, and so are completely immune to all modern diseases.

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Re: Going to the future

Postby n00bpwn3r » Fri Nov 20, 2009 12:32 am UTC

Twistar wrote:Whenever I or someone around me is complaining about not having enough time to do homework I just tell them to go sit on the moon or something, send the earth away from you at relativistic speeds for a little then make it come back. In the meantime taking your time writing your massive research paper for a few months (at least as long as you SHOULD have been working on it while earth was here) and on earth only a few hours in the night it was due will have passed!


Sorry, it doesn't work that way. When you get back, more time has actually passed for the Earth than for you (i.e. hours for you but months for the Earth). You'd have missed all your other assignments as well!

Speaking of which, time to get back on my research paper due tomorrow...
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Re: Going to the future

Postby Talith » Fri Nov 20, 2009 12:45 am UTC

n00bpwn3r wrote:
Twistar wrote:Whenever I or someone around me is complaining about not having enough time to do homework I just tell them to go sit on the moon or something, send the earth away from you at relativistic speeds for a little then make it come back. In the meantime taking your time writing your massive research paper for a few months (at least as long as you SHOULD have been working on it while earth was here) and on earth only a few hours in the night it was due will have passed!


Sorry, it doesn't work that way. When you get back, more time has actually passed for the Earth than for you (i.e. hours for you but months for the Earth). You'd have missed all your other assignments as well!

Speaking of which, time to get back on my research paper due tomorrow...

Actually Twistar was right, if the earth is the object being accelerated with respect to your reference frame, time will have progressed less on earth than it has for you. (It's equivalent to you accelerating away on a spaceship and then back again, just replace 'you' with 'the earth')

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Re: Going to the future

Postby Izawwlgood » Fri Nov 20, 2009 12:53 am UTC

poxic wrote:1) We haven't yet figured out how to stop solar radiation from ripping apart your DNA within a few months of leaving Earth's protective atmosphere and radiation belt. It's a problem they're tussling with when planning Mars exploration by humans.

You may be interested to read that NASAs Radiobiology Program has found that humans may be more resistant to low levels of ionizing radiation than we previously assumed.
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Re: Going to the future

Postby gmalivuk » Fri Nov 20, 2009 12:58 am UTC

Talith wrote:Depending on how far in to the future you want to travel I think you'd have to either accelerate so much that your body can't handle the G-forces in such a short time, or accelerate so slowly that by the time enough effective time dilation occurs, you'll be dead inside you space ship before it returns to earth.

Nope.

If I go at 1g for 12.76 years, then turn around and accelerate the other direction at 1g for twice that (so I stop and then start back towards Earth), and then turn around again and decelerate for the last 12.76 years, I'll still be alive and a million years will have passed on Earth.

I don't know offhand how to do the calculations, but if I do a high-speed loop, so I'm going fastest at the farthest point, instead of slowing to a complete stop at the far end of my trip, I can skip a million years on Earth even quicker from my perspective.
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Re: Going to the future

Postby Talith » Fri Nov 20, 2009 1:06 am UTC

gmalivuk wrote:
Talith wrote:Depending on how far in to the future you want to travel I think you'd have to either accelerate so much that your body can't handle the G-forces in such a short time, or accelerate so slowly that by the time enough effective time dilation occurs, you'll be dead inside you space ship before it returns to earth.

Nope.

If I go at 1g for 12.76 years, then turn around and accelerate the other direction at 1g for twice that (so I stop and then start back towards Earth), and then turn around again and decelerate for the last 12.76 years, I'll still be alive and a million years will have passed on Earth.

I don't know offhand how to do the calculations, but if I do a high-speed loop, so I'm going fastest at the farthest point, instead of slowing to a complete stop at the far end of my trip, I can skip a million years on Earth even quicker from my perspective.


Thanks for the maths, I guess it is possible, and quite comfortably, without any of that nasty muscle deterioration from <1 G environments.

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Re: Going to the future

Postby PM 2Ring » Fri Nov 20, 2009 3:48 am UTC

http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html

All these figures are for a journey accelerating at 1g.

Code: Select all

    T          t         d          v                γ
    1 year    1.19 yrs  0.56 lyrs  0.77c                 1.58 
    2         3.75      2.90       0.97                  3.99
    5        83.7      82.7        0.99993              86.2
    8     1,840     1,839          0.9999998         1,895
   12   113,243   113,242          0.99999999996   116,641

So in theory you can travel across the galaxy in just 12 years of your own time.  If you want to arrive at your destination and stop then you will have to turn your rocket around half way and decelerate at 1g.  In that case it will take nearly twice as long in terms of proper time T for the longer journeys; the Earth time t will be only a little longer, since in both cases the rocket is spending most of its time at a speed near that of light.  (We can still use the above equations to work this out, since although the acceleration is now negative, we can "run the film backwards" to reason that they still must apply.)

Here are some of the times you will age when journeying to a few well known space marks, arriving at low speed:

4.3 ly        nearest star            3.6 years
27 ly         Vega                    6.6 years
30,000 ly     Center of our galaxy     20 years
2,000,000 ly  Andromeda galaxy         28 years
n ly          anywhere, but see next paragraph     1.94 arccosh (n/1.94 + 1) years

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Re: Going to the future

Postby gmalivuk » Fri Nov 20, 2009 3:53 am UTC

Yes, and that's what I used for the previous figures.

However, if you go straight out at 1g for awhile, then thrust at 1g perpendicular to your velocity (rotating so your path curves around in a circular arc) until you're heading back towards Earth, and then decelerating at 1g, I *think* a 29-year journey on the ship gives you about 950,000 years for Earth.
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Re: Going to the future

Postby meat.paste » Fri Nov 20, 2009 3:38 pm UTC

You could circumvent the difficulties of interstellar travel my making a black hole at the L3 point of the Earth/Sun orbit (it shouldn't affect the Earth much in the near term). Then just skim near the event horizon without being torn apart by the tidal forces. Easy-peasy. Bonus: you can adjust the time shift by simply varying the altitude you pass above the event horizon.
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Re: Going to the future

Postby JWalker » Fri Nov 20, 2009 4:08 pm UTC

gmalivuk wrote:Yes, and that's what I used for the previous figures.

However, if you go straight out at 1g for awhile, then thrust at 1g perpendicular to your velocity (rotating so your path curves around in a circular arc) until you're heading back towards Earth, and then decelerating at 1g, I *think* a 29-year journey on the ship gives you about 950,000 years for Earth.


What do you mean by perpendicular? Do you just mean thrust in a direction such that you will put yourself on a trajectory that returns to earth, or something else? I'm not sure if it would work if it was simply perpendicular, as if you are moving at relativistic speeds you can't decouple parallel and perpendicular the way you can usually, but of course you could be right as I haven't calculated anything.

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Re: Going to the future

Postby gmalivuk » Fri Nov 20, 2009 4:20 pm UTC

I mean perpendicular to your direction of motion. The thing I included in the calculation was time dilation, so what feels to you to be 1g perpendicular to your direction of travel if gamma=10 looks from the outside to be 1/10 g, as far as how your motion is going to change. I readily admit that I may have missed some important bits, as it was pretty late at night.

But the relativistic rocket page mentioned before does say specifically that a faster way to get to and from a distant object, if you don't need to stop there, is to head out at an angle (not directly toward it), then turn until you pass it midway through your circular arc, which you continue until you're heading back toward Earth. Unfortunately there aren't any equations for this motion given on the site, though, so I don't know if I got them right.
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Re: Going to the future

Postby Woofsie » Fri Nov 20, 2009 8:45 pm UTC

Technical Ben wrote:The language and culture and governments have changed so much they do not know who you are. Your imprisoned/shot down upon re-entry.


Surely you could remain in radio communication with earth during your trip. Ideally you could arrange to have some kind of super-condensed news feed sent to you, so that every morning when you wake up you can read about what happened during the last year on earth.

This would be a great way to avoid getting bored too. Imagine a constant stream of blockbusters, each one having been written and produced while you were asleep, as well as being able to watch the latest scientific theories unfold and progress at massive speed.

Then when you want to return you let the folks back on earth know and they can take whatever medical precautions they need to.

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Re: Going to the future

Postby gmalivuk » Fri Nov 20, 2009 9:09 pm UTC

Woofsie wrote:Surely you could remain in radio communication with earth during your trip.

Not under constant acceleration you couldn't.
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Re: Going to the future

Postby Random832 » Fri Nov 20, 2009 9:34 pm UTC

gmalivuk wrote:Not under constant acceleration you couldn't.


I'm not sure I follow your logic here.

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Re: Going to the future

Postby meat.paste » Fri Nov 20, 2009 9:41 pm UTC

I would presume that the redshift would be so extreme that the Earth would have to be broadcasting in extreme gamma rays for the spacecraft to receiving radio. To send a couple of gigabytes of data a day would require an assload of power. The receiving antenna on the space craft would have to be efficient at an astounding range of frequencies (it would get the data in the gamma ray band for the first year or so, then x-rays, UV, visible, IR, microwaves, then radio waves at about spaceship year 5.)

Of course, the energy required to speed a ship to that velocity is pretty damn astounding, too. So, I suppose it would be possible given the technical hurdles on energy production would have been fixed to start the mission anyway.
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Re: Going to the future

Postby Charlie! » Fri Nov 20, 2009 10:51 pm UTC

meat.paste wrote:I would presume that the redshift would be so extreme that the Earth would have to be broadcasting in extreme gamma rays for the spacecraft to receiving radio. To send a couple of gigabytes of data a day would require an assload of power. The receiving antenna on the space craft would have to be efficient at an astounding range of frequencies (it would get the data in the gamma ray band for the first year or so, then x-rays, UV, visible, IR, microwaves, then radio waves at about spaceship year 5.)

Of course, the energy required to speed a ship to that velocity is pretty damn astounding, too. So, I suppose it would be possible given the technical hurdles on energy production would have been fixed to start the mission anyway.

*nit-pick* "X-rays" is the part of the spectrum. Gamma rays are a specific phenomenon in radioactivity.

To conserve energy and receiving antennae (though making things a little tougher on transmitters), maybe better to always receive RF but change what frequency everybody broadcasts in to account for redshift?

Besides, it can't be THAT bad... Relativistic redshift for year 5 there (0.99993 c) is "only" 168 times. You could broadcast in UFH and they'd receive in HF :P Okay, so admittedly by year 12 you'd have to be broadcasting near or in the infrared (not possible with current technology), but that's probably the least of your problems by that point.
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Re: Going to the future

Postby andyisagod » Fri Nov 20, 2009 11:09 pm UTC

Charlie! wrote:*nit-pick* "X-rays" is the part of the spectrum. Gamma rays are a specific phenomenon in radioactivity.


Umm no, gamma rays are part of the EM spectrum, I guess the problem would be that we don't have the technology to create a gamma ray radio broadcast but I think a larger problem with comunication would be the time dilation. In the classic twin parradox setup with constant velocity on the way out and back in with a bit of acceleration to turn around, you have observe the earth time dilated on both legs of the journey so the amount of information you recieve is going to be limited by the bandwidth (as in the howfast can you send it sense) of the output from earth. Of course in that setup you get a massive amount of information when you turn around but not as much the rest of the time. For a constant acceleration model I guess the time on earth will allways appear fast so for receieving information you are pretty well off but would have to adapt to recieve/transmit the data red/blue shifted.

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Re: Going to the future

Postby Charlie! » Fri Nov 20, 2009 11:40 pm UTC

andyisagod wrote:
Charlie! wrote:*nit-pick* "X-rays" is the part of the spectrum. Gamma rays are a specific phenomenon in radioactivity.


Umm no, gamma rays are part of the EM spectrum

Oh, whups, a quick search shows that to be mostly true. Gamma rays are *also* a blanket term for stuff that comes from excited nuclei, but I didn't know before that x-rays had an upper limit on their frequency.
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Re: Going to the future

Postby gmalivuk » Sat Nov 21, 2009 2:04 am UTC

Random832 wrote:
gmalivuk wrote:Not under constant acceleration you couldn't.

I'm not sure I follow your logic here.

I was thinking in terms of the apparent horizon that's formed in an accelerating reference frame: As long as you're accelerating away from Earth at 1g (1.03 ly/y^2), you'll never receive *anything* sent from earth even one year after you left. And in fact the universe behind you will begin slowing down from the moment you start accelerating.

Of course, if you plan to return to Earth then you will eventually stop accelerating away from it, and eventually start coming back, which means you'll make up for the period of no messages with huge bursts of information on your return trip.
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Re: Going to the future

Postby makc » Sat Nov 21, 2009 5:38 pm UTC

gmalivuk wrote:you'll never receive *anything* sent from earth even one year after you left.
Why? (c) terminator

as long as your own speed is less than c you will receive signals.

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Re: Going to the future

Postby gmalivuk » Sat Nov 21, 2009 5:46 pm UTC

No, not if you keep accelerating. As soon as you stop accelerating, sure, then you get signals at the rate they were sent. And if you start accelerating back in the other direction, you'll get them much faster than they were sent out. But if you're accelerating away from Earth at a ly/y^2, there will be an apparent horizon behind you at 1/a. Which means that if you're accelerating at 1.03, you won't see anything that happens at or after 1/1.03 years, or 354.4 days, after you left.

http://en.wikipedia.org/wiki/Hyperbolic ... ativity%29
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Re: Going to the future

Postby Izawwlgood » Sat Nov 21, 2009 7:15 pm UTC

I know this is basic relativity, but I figure I'll ask here anyway as it seems to be mentioned;
If you are constantly accelerating, but still below the speed of light, you will send and receive signals as normal, but doppler shifted? And what happens when you are >c, or is that all theory and thus moot?
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Re: Going to the future

Postby gmalivuk » Sat Nov 21, 2009 7:22 pm UTC

Send and receive signals to/from where? As I said, if you're accelerating, it will look to you like time back where you started is slowing down (and everything's red-shifting), asymptotically approaching a time 1/a after you left.

And you never go faster than c, so I'm not sure what you mean by that.

(I'm talking about acceleration as the apparent acceleration in the frame of the ship. The acceleration observed by outsiders obviously decreases over time, because it can't remain constant indefinitely while still remaining below lightspeed.)
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Re: Going to the future

Postby Izawwlgood » Sat Nov 21, 2009 7:38 pm UTC

gmalivuk wrote:Send and receive signals to/from where? As I said, if you're accelerating, it will look to you like time back where you started is slowing down (and everything's red-shifting), asymptotically approaching a time 1/a after you left.

Does the doppler shift result because of the speed traveling, or the acceleration? If you're going .9c but not accelerating...?
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Re: Going to the future

Postby gmalivuk » Sat Nov 21, 2009 7:46 pm UTC

There will be doppler shift simply because you're going fast. But the shift will increase over time if you're accelerating, which is why there's an apparent horizon.
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Re: Going to the future

Postby SQL Dave » Sun Nov 22, 2009 5:51 am UTC

Steven Wright (I think) said... "I time traveled last week. I laid down on my bed and closed my eyes. When I opened them I was several hours in the future"

Perhaps not germane or helpful, but I found it funny.


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