I read an article somewhere (i think american scientific)which said you could theorically travel into the future by going (for example) 50% the speed of light for a few years (in your time frame) and returning back to earth. Then you would notice that a much longer time has passed on earth, than the time you experienced during your journey.

The clocks on GPS satellites falls behind a bit ( a few milliseconds?) because of its speed around the earth...

My question is ...knowing that the ISS crew are probably the fastest humans constantly rotating the earth... how many seconds does their clocks fall behind after like 1 year in space? are they really considered to be travelling into the future?

Please be gentle with answering...

__________________
P.S. This is what part of the alphabet would look like if Q and R were eliminated.

-- Mitch Hedberg

Nothing theoretical about it.
Everybody travels into the future.
Some just faster then others.

I unsure whether the ISS travels fast enough to
produce a measurable time dilation.

__________________
Join the Illuminati

well they do orbit the earth every 90 minutes and are up there for months... is it possible to calculate the time dilation?

Imagine one of the crew had an atomic wrist watch on the moment they entered the ISS, and that watch was synchronized with another atomic clock on earth... When the crew returns home after 6 months and they check the two atomic clocks, how much would they be different?

Is my understanding of time dilation right? something I have misunderstood?
explanations would be appreciated

btw, Halcyan Dayz, You got 1001 posts

__________________
P.S. This is what part of the alphabet would look like if Q and R were eliminated.

-- Mitch Hedberg

For what it's worth, in a few years they are planning to send up an extremely accurate atomic clock to the ISS, to get a precise bead on the time dilation they experience, and of course to perform yet another test of general relativity--this may be the first really useful experiment they've done there. Check out the latest Scientific American special issue on time for more details.

__________________
"He fell for her like his heart was a mob informant and she was the East River."

--Anonymous

The order of any relativistic effect is (v/c)^2, and the v/c for the ISS is about 8/300,000, so (v/c)^2 is of the order of one part in 100 billion,which is close to the accuracy level of an atomic clock but I think measurable. In a 6 month mission, we are talking about a time difference on the scale of a fraction of a millisecond.

Here's an unrelated thought-- a human lifetime is about two to three billion seconds. Doesn't that sound like a long wait?

Thanks Ken G.

so we could say they are travelling micro seconds into the future... thats cool!

__________________
P.S. This is what part of the alphabet would look like if Q and R were eliminated.

-- Mitch Hedberg

They aren't in the future in the sense that they are in the same time frame as we are. It's just that they spent less time getting here than we did.

AFAIK, yes. You would need to know the speed at which the ISS is travelling, which you can get from the circumference of its orbit divided by its orbit period.

__________________
My message board, now more fun than ever - Text effects - Sky photos - Element spectra
Remember I before E except after C, or be seized by your weird neighbors who have had too much caffeine.

This is probably the best description of time dilation I've ever read. I must remember this one next time I get asked about it. Well done that man!

If I understand the equation given by Ken, the North and South poles are about 12 minutes younger than the equator.

((6378000*2*pi)/86400)/299792000^2*4.5e9*365.25*1440

Radius of Earth (m) * 2pi / seconds per day / c^2 * 4.5 billion years * days per year * minutes per day

The astronauts are experiencing two relativistic effects. Compared to an observer's clock on earth, their clock runs faster since they are in a weaker gravitational field, but slower due to their high velocity. I don't know which effect dominates in the ISS, but in GPS satellites (higher altitude/lower velocity) the gravity field effect does.

Remember that the earth is oblate, so that points on the equator are in a weaker gravitational field and are moving at a high velocity compared to the poles. Incredibly, the effects cancel (they don't have to) so they are both the same age. No twin paradox here.

__________________
There's room for all God's little creatures -
right next to the mashed potatoes

Won't somebody think of the children

Sending atomic clocks with all that radio activity, what if something should happen.

Does anyone else think the eco-lobby will scream about this

Especially after the fuss about NH.

__________________
Van Rijn's original Invisible Elf was running for the North Carolina Senate, but dropped out of the contest after the paparazzi snapped him with a cute pixie just outside Disney World in Florida. Now he has settled down with her as they await their first child, writing his biography of life in Van Rijn's backyard, - Now you prove me wrong

All what radioactivity?

__________________
"I have a cunning plan that cannot fail."
S. Baldrick

According to this it's about 7 msec (slow, i.e. they've aged less; the kinematic term dominates) for a six-month stay.


NASA isn't anymore, though. I'm pretty sure RACE and PARCS had their funding pulled, and probably SUMO. ACES is an ESA mission, so that is probably still on.

__________________
"I have a cunning plan that cannot fail."
S. Baldrick

You know, atomic clocks! It must have green glowing radiation, don't you ever watch movies?

Correct me if I'm wrong (as I frequently seem to be) but all the GPS satellites have atomic clocks on-board already. They broadcast a very precise and accurate time signal. That's how a GPS receiver triangulates its position, by comparing the difference in the time signals from the satellites it can hear, the positions of which are extremely accurately known.

clop

Yes, that's right, except they quadrangulate: you need four satellites to determine your position, since x,y,z and t are unknowns.

__________________
"I have a cunning plan that cannot fail."
S. Baldrick

My handheld GPS gives me a result with 3 satellites. But its error is a few hundred yards. With the addition of the 4th satellite, it improves to a few feet.

Is this because it is guessing at t, perhaps based on its own internal clock?

Is this just a huge coincidence? Would the same be true for Mars or Venus?