A query on time dilation to nearby star systems

I saw the article about the new planet found in the Libra constellation today, and I was thinking about the possibilities of life on that planet.

So lets say that sometime in the near future a pulse drive is perfected that allows humans the ability to travel at the speed of light (It takes about 33 days at a constant 1G acceleration to get there).

Near the speed of light we know that time dilation is going to be a factor for the person on board, but how exactly will it work. The planet 581c is approximately 20 light years away.

Time dilation only occurs with any real significance near the speed of light, so lets say we could travel there at roughly .95 times the speed of light, or at least enought to create time dilation effects of around 6X.

For us on earth, does that mean that it would still take 20 years earth time to get there, but only 3.33 years for the person on board? Or the other way around?

Just curious.

reply to post by docpoco


20 years would still be 20 years for us left behind on Earth. Not sure of the exact ratio but time for those travelling at near-c would experience less realtive time. It's still twenty years objective for the rest of us not travelling at near c velocities. In fact, 20 years still "passed" for those on board our theoretical spaceship; it's just that they only experienced some fraction thereof subjectively.
Also, remember to take into account the time spent accelerating to near-c and then de-celerating to a stop at the end. That'll make a difference in calculating exactly how much time passes for those aboard any vehicle approaching c.

Originally posted by docpoco
Time dilation only occurs with any real significance near the speed of light, so lets say we could travel there at roughly .95 times the speed of light, or at least enought to create time dilation effects of around 6X.

For us on earth, does that mean that it would still take 20 years earth time to get there, but only 3.33 years for the person on board? Or the other way around?

Who told you that going at 95% of the speed of light results in a time dilation of around 6x?

According to Wikipedia it's more like 3.3x at 0.95c relative velocity:
en.wikipedia.org...

Going at 95% the speed of light, c, and not counting the speed of the Earth which isn't too fast relative to c, it would take about 21 Earth years to travel 20 light years, and the astronauts would age more slowly by a factor of about 3.3 or about 6 years during the voyage.

reply to post by Arbitrageur


Nobody told me that. I said roughly .95 or whatever it takes to get to 6x. It was just a rough number. I was looking at a graph in a magazine and of course things start to bunch up exponentially the closer you get to c.

Either way, the point was, how would this affect long travel times?

If the astronaut experience significantly less time, then I suppose it would make sense that it would be not only possible but likely that one travelling that fast could travel extremely large distances in less relative time. It would just take a long long time to get the information back to us.

Originally posted by 35Foxtrot
reply to post by docpoco

 

20 years would still be 20 years for us left behind on Earth. Not sure of the exact ratio but time for those travelling at near-c would experience less realtive time. It's still twenty years objective for the rest of us not travelling at near c velocities. In fact, 20 years still "passed" for those on board our theoretical spaceship; it's just that they only experienced some fraction thereof subjectively.
Also, remember to take into account the time spent accelerating to near-c and then de-celerating to a stop at the end. That'll make a difference in calculating exactly how much time passes for those aboard any vehicle approaching c.

I kinda answered my own question when I was typing, but I still wanted to get some input.

So theoretically, if one could travel at 99.999999% the speed of light, then you could travel EXTREMELY vast distances in your own lifetime, correct?

Like when I calculated time dilation at .9999999 I got something like a factor of 232000x time dilation.

So in theory, one could travel to across the entire milky way galaxy in about 5 months.

Cool.It seems that if one could get close enough to c, you could travel almost anywhere in your lifetime, just millions of years would pass on earth. That part sucks.

Originally posted by docpoco
So theoretically, if one could travel at 99.999999% the speed of light, then you could travel EXTREMELY vast distances in your own lifetime, correct?

That's true, however you can calculate how much energy it takes to accelerate to that speed and the result will suggest that accelerating a spaceship to that speed will take vast amounts of energy. Just to accelerate one single proton to that speed takes a lot of energy. That's because while time is slowing down, the apparent or relativistic mass is increasing toward infinity as you approach the speed of light.

We could build a ship that would go perhaps 10% of the speed of light (see Project Orion in Wikipedia), but that's about the limit of our current technology, we think. We never built it (at least not publicly) but we think we could.

Originally posted by docpoco
Like when I calculated time dilation at .9999999 I got something like a factor of 232000x time dilation.

Well again I'm not sure how you're doing your dilation calculations but they seem to be off significantly, though you have the right basic idea.

Here are some figures already calculated:

www.xs4all.nl...

At 0.9999998c the time dilation factor is only 1,895
At 0.99999999996c the time dilation factor is 116,641 so your calculation is too large. But theoretically if you could go that fast you could cross the 100,000 light year milky way in less than a lifetime. In reality, we don't know of any way to accelerate a person or a spaceship to such high velocities. I think the electric bill for the particle accelerators that just accelerate tiny electrons and protons to such velocities is over a million dollars a month. Figure out how many protons are in a spaceship and you get some idea of the massive energy requirements to accelerate a spaceship to those velocities.

Cool . Thanks for the info.

Clearly some type of yet undiscovered or unharnessed energy would be required. Perhaps some type of dark matter or anti-matter energy system could do it.

Again, the calculations were rough and clearly no anything scientific.

I was doing them here: www.1728.com...

Thanks for the input!

Originally posted by docpoco
Like when I calculated time dilation at .9999999 I got something like a factor of 232000x time dilation.

Originally posted by docpoco
Again, the calculations were rough and clearly no anything scientific.

I was doing them here: www.1728.com...

Thanks for the input!

You're welcome. Here's an example of how to use that site:

[atsimg]http://files.abovetopsecret.com/images/member/0dfc77edfd44.png[/atsimg]

Type in the .9999999 and then click the 3rd button, as you can see the dilation factor is 2236, not 232000.

The 2236 looks about right.

Yes it would take some type of energy source and propulsion method we haven't thought of yet to go that fast, if it's possible.

www.abovetopsecret.com...

For anyone who needs a laugh, check out this thread also on this same board.

And honestly, if anyone wants to jump in and help this guy out it would be nice.