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Space Forum / Shuttle / July 2008Time on shuttle and ISS...
Hi, Are there any time sensitive instruments or experiments on the ISS that have to be adjusted for time dilation? If so, how often would they have to be adjusted? I imagine it wouldn't be until after many months? Or do they even need to worry about keeping the same time frame of reference as the Earth? > Hi, > [quoted text clipped - 6 lines] > Or do they even need to worry about keeping the same time frame of > reference as the Earth? On the ISS time display, they list GMT (Greenwich Mean Time) and AOBT (Adjusted On Board Time), which is usually a few seconds off. Someone else will have to explain whether that difference is due to relativistic effects, but that is the explanation I heard. They are going @ 0.002% of the speed of light, so some effects would be expected. Mike Ross > On the ISS time display, they list GMT (Greenwich Mean Time) and AOBT > (Adjusted On Board Time), which is usually a few seconds off. Someone > else > will have to explain whether that difference is due to relativistic > effects, but that is the explanation I heard. They are going @ 0.002% of > the speed of light, so some effects would be expected. I believe the lack of gravity has the bigger effect than the speed, as time dilates depending on gravity also. Interesting as of course you are in fact in free fall. Gravity is still there of course or you would simply be going in a straight line. Brian  SignatureBrian Gaff....Note, this account does not accept Bcc: email. graphics are great, but the blind can't hear them Email: briang1@blueyonder.co.uk ______________________________________________________________________________________________________________ >> On the ISS time display, they list GMT (Greenwich Mean Time) and AOBT >> (Adjusted On Board Time), which is usually a few seconds off. Someone [quoted text clipped - 5 lines] > I believe the lack of gravity has the bigger effect than the speed, as > time dilates depending on gravity also. >> On the ISS time display, they list GMT (Greenwich Mean Time) and AOBT >> (Adjusted On Board Time), which is usually a few seconds off. Someone [quoted text clipped - 5 lines] > I believe the lack of gravity has the bigger effect than the speed, as > time dilates depending on gravity also. Umm, what lack of gravity? You're moving in relation to the surface of the Earth, and you're in a gravity field, but you're not lacking gravity. SignatureGreg Moore SQL Server DBA Consulting Remote and Onsite available! Email: sql (at) greenms.com http://www.greenms.com/sqlserver.html In sci.space.shuttle message <BtydnTzBQ4-DC_vVnZ2dnUVZ_q3inZ2d@comcast.c om>, Sat, 28 Jun 2008 14:50:52, mike_l_rossREMOVE@REMOVEcomcast.net posted: >On the ISS time display, they list GMT (Greenwich Mean Time) and AOBT >(Adjusted On Board Time), which is usually a few seconds off. Someone else >will have to explain whether that difference is due to relativistic >effects, but that is the explanation I heard. They are going @ 0.002% of >the speed of light, so some effects would be expected. Nearer 0.003% of c, I believe. ISS is ten years old; relativity at that speed for 10 years should amount to well under a second. For the approximate speed : light would circle the Earth in 1/7 second, ISS takes 92 minutes. Signature(c) John Stockton, near London. *@merlyn.demon.co.uk/?.?.Stockton@physics.org Web <URL:http://www.merlyn.demon.co.uk/> - FAQish topics, acronyms, & links. Correct <= 4-line sig. separator as above, a line precisely "-- " (SoRFC1036) Do not Mail News to me. Before a reply, quote with ">" or "> " (SoRFC1036) > Hi, > > Are there any time sensitive instruments or experiments on the ISS > that have to be adjusted for time dilation? Per the subjectline, I don't think there's anything on the shuttle that sensitive, it uses MET for everything I believe. (well one could argue the GPS guidance system doesn't :-) > If so, how often would they have to be adjusted? I imagine it > wouldn't be until after many months? My guess is any experiments are pretty self-contained. (Though there was a relatively experiment planned for the outside of the ISS to test I believe frame dragging.) And in fact something like GPS has to take into both special relativity and general relativity. > Or do they even need to worry about keeping the same time frame of > reference as the Earth? SignatureGreg Moore SQL Server DBA Consulting Remote and Onsite available! Email: sql (at) greenms.com http://www.greenms.com/sqlserver.html On Sat, 28 Jun 2008 21:03:53 -0400, "Greg D. Moore \(Strider\)" <mooregr_deleteth1s@greenms.com> wrote: >Per the subjectline, I don't think there's anything on the shuttle that >sensitive, it uses MET for everything I believe. ...Well, like the ad says, "Get MET, it pays." OM Signature]=====================================[ ] OMBlog - http://www.io.com/~o_m/omworld [ ] Let's face it: Sometimes you *need* [ ] an obnoxious opinion in your day! [ ]=====================================[ Time dilation at a constant velocity just around the planet? Now that would be a heck of a long time to see a reasonable change I'd have thought. Brian SignatureBrian Gaff....Note, this account does not accept Bcc: email. graphics are great, but the blind can't hear them Email: briang1@blueyonder.co.uk ______________________________________________________________________________________________________________ > Hi, > [quoted text clipped - 6 lines] > Or do they even need to worry about keeping the same time frame of > reference as the Earth? Interesting comments. I have been following this thread. I have also gone on to read that the ISS's frame of reference for 24 hours is ~26 microseconds (plus or minus a few microseconds, depending on who's fuzzy math you are led to believe) slower than the Earth's 24 hour frame of reference. Time for the old twins again. If you have two twins that born at exactly the same time (C-section?) and one grows up to be, oh, say, a farmer while the other grows up to be an astronaut, the astronaut twin will be 260 microseconds younger than his farmer twin after spending ten days in orbit. Not exactly the fountain of youth, but it is pretty cool that the shuttle and ISS are "time machines" even though they aren't very efficient at it. > Interesting comments. I have been following this thread. > [quoted text clipped - 8 lines] > will be 260 microseconds younger than his farmer twin after spending > ten days in orbit. Personally I'd love to come back in about 100-150 years.... (there was a classic twilight zone episode that involved that). > Not exactly the fountain of youth, but it is pretty cool that the > shuttle and ISS are "time machines" even though they aren't very > efficient at it. SignatureGreg Moore SQL Server DBA Consulting Remote and Onsite available! Email: sql (at) greenms.com http://www.greenms.com/sqlserver.html |
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