Sunday, January 22, 2006 - 09:04 pm, by: Dave Hart(Davyboy)
How many have a working GPS in their car? Did you know that part of the electronics uses Einstein's 'Theory of Relativity'? Apparently when the US brass were told of this they didn't believe it and had it switched off until they found that their subs were getting out of position by increasing amounts every day until they switched it back on. Just heard of this on the radio today.
Sunday, January 22, 2006 - 11:18 pm, by: Clayton Webb(Clackers)
Because an observer on the ground sees the satellites in motion relative to them, Special Relativity predicts that we should see their clocks ticking more slowly (see Lecture 32). Special Relativity predicts that the on-board atomic clocks on the satellites should fall behind clocks on the ground by about 7 microseconds per day because of the slower ticking rate due to the time dilation effect of their relative motion Can anyone explain this in LAMENS terms??
Monday, January 23, 2006 - 12:11 am, by: Dave Hart(Davyboy)
Sorry Jef, as I said I just heard it on the radio and missed the beginning which identified this professor. It was a very good talk and being not long after Christmas it was a repeat of the previous years highlights which I also missed. Another item in his talk was space travel to planets in other solar systems. His example was of someone of 25yrs setting off from earth to the centre of the Milky Way. His craft would accelerate for 10yrs (I presume to light speed) then decelerate for 10yrs, turn round and repeat the process back to earth. He would then be 65yrs old but the earth would have aged more than 48000yrs. He then talked about matter/anti matter, the Big Bang theory, dark energy etc.
Monday, January 23, 2006 - 12:16 am, by: Adam Parisi(Kooks)
I'll give it a shot though. Say you are in a rocket moving at 1/2 the speed of light, and another rocket with a massive digital clock (so you could see it) passes you moving at 3/4 of the speed of light. Because it is moving away from you, the light has further and further to travel, which means that the clock appears to be going slower relative to whatever clock you have in your rocket. This is time dilation. Now, satellites orbit the earth, at a different speed relative to you standing on the earth. The data being transmitted from the satellite (moving at the speed of light) will be taking longer and longer to reach you, hence the time dilation between the satellite and surface. I guess they measured it to that amount. I hope that I got it right in my understanding, but if not, can a wiser head fix me up?
Monday, January 23, 2006 - 12:51 am, by: Peter Nitschke(Pen)
Suggest replace "accelerating" with "moving" as the speeds are constant unless the rockets are accelerating.
The problem with applying this to satellites, is that they may be moving closer towards you or further away as it orbits. They aren't moving away from you all the time (or else they wouldn't be in orbit, but heading out to space).
Monday, January 23, 2006 - 01:46 am, by: Dave Hart(Davyboy)
It doesn't matter if the satellites or coming towards or away it all comes down to the difference in velocity between those satellites and the ships. I say velocity and not speed because the satellites are in a constant change of direction.
Monday, January 23, 2006 - 01:47 am, by: Adam Parisi(Kooks)
Hokay, replaced accelerating with moving...good point. I can see the problem you have pointed out, and I have to agree, but I think it has to do with the period of the satellite's orbit, which in that article says it's 12 hrs. So that would mean that it's angular velocity is higher (relatively) than at any given point on the earth's surface, which may explain that time they give. But they gon on to say that due to gravity's effect on timespace, that the reverse is true, and that clocks on the earths surface appear slower to the satellite by a much larger factor. So, at the end of it all, I can proudly stand up and say "It's got me buggered what it's all about!"
Monday, January 23, 2006 - 04:18 am, by: Dan McColl(Hoon)
Now it's time to start on string theory....
BTW the sattellites would appear to get closer and the time would speed up between when they cross the horizon till they are directly above you, Then would get farther away and the time would slow down from when it was above you till it gets below the other horizon.
Monday, January 23, 2006 - 07:24 am, by: David Vaughan(Davidv)
They are not geostationary so far as I know. My GPS shows which satellites should be in the sky at any moment and how far above the horizon, and they move about compared with my location.
Monday, January 23, 2006 - 09:27 am, by: Matthew Sharpe(Madmatt)
So, when you get stopped by the cops for speeding, just tell them you are trying to stay young by moving reletively faster than everything else around you...
Previous
