Originally posted by KellyJay
Time differs or the different conditions caused either the observer, or
devices being used to measure time to become altered? Can we say
that an exact point in time like "now" for example is the same
throughout all of the universe? If we were to freeze all of the universe
at a single point in time would it all stop at once, is there a now
everywhere at the same moment?
Kelly
If you could do that in fact, there would be a spectrum of time hacks where for instance, inside a black hole, the time flow might put that time hack 1 million years ahead of the same time hack on someone on Earth.
Likewise if you sliced all the time up at once in the universe, the time hack on someone on the surface of the Earth would be different from someone sitting on Mars, which has about 1/3 Earth gravity.
A very tiny difference in that case but in fact measurable. That is why they have to have atomic clocks inside each GPS satellite, time flows slightly differently 300 miles up in space for several reasons, one being you are simply in a lower gravitational field, like if you were on the surface of the Earth and you weighed 100 Kg and you had a building that was about 4000 miles high, you would be at 2 radii from the center of the Earth, so the inverse square law says you would weigh 1/4 of your surface weight or 25 Kg.
Because you are in a lower gravitational attraction field up there your time would run slightly faster, certainly not at a 4 to 1 ratio but the difference is enough to ruin the calculations of position based on GPS readings which effected by variable gravitational fields and also by velocity.
Even though at 18,000 odd miles per hour which is an average velocity of satellites, that does not come even close to the speed of light where relativistic effects get serious.
Even so, the effects are enough to ruin position estimates on the earth, by serious amounts, some say GPS readings would be off as much as 5 kilometers if all of those time flow and velocity changes were not incorporated into the calculations of when a pulse leaving the satellite actually arrives at the GPS radio.
That is due to the fact that at the speed of light, even a tiny change in arrival times which is what GPS is ultimately based on, the changes are enough to seriously screw up your position measurement.
That is a very real world class of phenomena that can be easily measured. You can measure the difference in time flow of atomic clocks where one sits on the ground and a second clocked starting off totally synced to the first one now goes on an aircraft and simply by being say, 10,000 feet up, thus in a slightly lower gravitational field, the change can be measured which follows Einsteins equation as exactly as we can presently measure them.
All of that is proven science and you cannot make a usable GPS without taking that into account. But there are experiments ongoing to the fundamental question of whether time flowed at a different rate now V 13 billion years ago.
Most of the experiments done on say, lower frequency radiation coming off a nova V higher frequency stuff so far has shown no difference in arrival times which says something about the overall flow of time, saying that 13 billion years ago a second was a second here and there back in time.
That does not mean someone will show some small change that will still shake up the core of science and lead us in new directions. News at 11.
If you had two atomic clocks totally synced and put one on a 10,000 foot mountain it would run a tiny bit faster than the synced at ground level so the time hacks would all be different even at that level if you could freeze the universe at some point in time. You would have a graph where my time hack would not be in the same 'place' as the time hack on the mountain or the time hack of a spacecraft going half the speed of light or someone sitting on Mars, their time hacks would all be in different places on a time hack scale. It would be like taking a shotgun and putting a ruler on the ground where the pellets come back to earth, the ruler would show some of them coming at say, 1000 feet and others at 1200 feet and so forth, the ruler in this case being a time hack ruler in say nanoseconds per division or whatever.
If you froze the universe, I would be at one point on the ruler but my astronaut buddy would be at another point on the time ruler when time froze.
Is time a constant?
30 Jan '10 07:412 edits
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