Time Dilation Throughout Space?

Grabitation and time dilution? It's like someone has changed the timelines. How often do typos sound so genuine and wordy??!

Grabitation sounds like it ought to be a real word and time dilution could be a website for wasting time.

a reply to: Phage

But the satellite clocks are indeed adjusted to account for time dilation.

I enjoyed your links which caused me to go haywire for hours reading about time dilution (now I have to do house chores!). Its an interesting topic that doesn't seem really settled. Some sources tell that relativistic offsets can be explained by sagnac effect which has been confirmed in earth based experiments.

Short answer - yes, with respect to us here on Earth, time is dilated all over the place in the universe. There's both the gravitational and relativisitic (due to relative speed) time dilation. In some places, their time is running faster than ours, in most others, slower.

As has been mentioned here before, to a person their own experience of time doesn't change. "Relative" is the key word here.

a reply to: glend
First you said that satellite clocks are not adjusted to account for relativistic effects and present as evidence a paper which says precisely the converse. Now you say that they are adjusted but for the wrong reason?

Some sources tell that relativistic offsets can be explained by sagnac effect which has been confirmed in earth based experiments.

Some sources say the Earth is flat. But your source does not say that the Sagnac effect explains the offset. I'll let you read it. As you should before posting. But what's the point of doing that? Right?

Do you think it is a coincidence that GPS satellite clocks are adjusted (before launch) just enough to work properly? Do you think it is a coincidence that the calculations which provide that adjustment value come from time dilation formulas?

The Sagnac effect is a factor but it is not a factor in the adjustment of the satellite clocks, it only comes into play on extremely accurate receivers, within the receiver itself, since there are many receivers, all moving in different ways.

During propagation of the signal from transmitter to receiver, the receiver most likely moves. Even if the receiver is at rest on earth’s surface, earth rotation will carry the receiver into a different position while the signal propagates to the receiver.

www.aapt.org...

An important point is that although time may progress at different relative speeds according to the frame of reference, it doesn't mean that the person experiences time moving at a different speed. I mean to say things don't go all slow motion for the person experiencing it.

I know it may seem like a silly point, but I just thought I would mention it.

a reply to: Phage

The sagnac effect isn't a belief of flat earthers, its been known by scientist for over 100 years!

One of the most confusing relativistic effects-the Sagnac effect-appears in rotating reference frames.? (See PHYSICS TODAY, October 1981, page 20.) The Sagnac effect is the basis of the ring-laser gyroscopes now commonly used in aircraft navigation. In the GPS, the Sagnac effect can produce discrepancies amounting to hundreds of nanoseconds.

Why the GPS clocks are adjusted before launch....

If the GPS orbits were perfectly circular, the corrections would include just a few constant contributions: for the gravitational
potential differences between the satellites and the ground, and for the second-order Doppler differences between the orbiting clocks and the reference clocks on the ground. Figure 4 shows how the relativistic frequency shift depends on the circular orbit's radius. At a radius of 9550 kIn, about 3000 km above the ground, the gravitational and Doppler effects cancel. Because the GPS orbits are higher than that, the gravitational blueshift is the largest contribution. So the net frequency correction for a GPS satellite is negative, amounting to 4.4645 parts per ten billion. Nowadays the rate of every orbiting GPS clock is adjusted by this "factory offset" before launch.
Link

So factory offset is carried out for gravitational blueshift and dopler effects not time dilution as you suggested.

Earth based gps receivers don't have atomic clocks to match the times of atomic clocks in space. Earth based gps receivers require an identical timestamp from each satellite to triangulate a position. So it doesn't matter if all satellite clocks run slow or fast only that their clocks are synchronized. link

a reply to: glend

So factory offset is carried out for gravitational blueshift and dopler effects not time dilution as you suggested.

I said time dilation, not dilution. But my goodness you like to cherry pick. Your very own source:

Relativistic coordinate time is deeply embedded in the GPS. Millions of receivers have software that applies relativistic corrections. Orbiting GPS clocks have been modified to more closely realize coordinate time. Ordinary users of the GPS, though they may not need to be aware of it, have thus become dependent on Einstein's conception of space and time.

So it doesn't matter if all satellite clocks run slow or fast only that their clocks are synchronized.

No. That is the reverse of the facts. The rate at which the clocks run is the only thing that matters. The receiver clock does not need to be synchronized to the same time of day as the satellite (though that is handy). The point that the writer misses is that the time delay is calculated relative to the other satellites, not the receiver. It doesn't really matter much if the clock is "right", what matters is the rate at which it runs. And without the adjustments to the satellite clock, they would be running at different rates. That synchronization occurs on the satellite before the satellite is launched.

Your other sources explain that, too bad you didn't read them.

a reply to: Phage

I said time dilation, not dilution

I know I am a poor speller so don't need reminding but if reminding me makes you feel bigger, go for it.

The point that the writer misses is that the time delay is calculated relative to the other satellites, not the receiver.

GPS receivers synchronize its quartz clock to the time it receives from GPS satellites. It also receives satellite position data (the ephemeris) so it can compute triangulation from the time delays from the source.

Banter all you want, time dilation is not an issue.

Your other sources explain that, too bad you didn't read them.

Not only did I read them, I checked their dates. If you had done so, you might have realized that receivers might have been advanced with the faster processors over the years.

a reply to: glend

GPS receivers synchronize its quartz clock to the time it receives from GPS satellites.

Which satellite? When the receiver gets a time value from a satellite, that value is subject to the travel time of the signal.

A satellite says, "the time now is 0.0" but when the receiver gets it the time actually 0.001 (for example) because of the time it takes for the signal to reach it.

But what about the satellite which is farther away? It says, "the time is now 0.0", but when the receiver gets the signal, it is now 0.0015.

See the problem? While you can get a time of day that's pretty good for getting somewhere on time, you cannot get enough accuracy for the positional calculations. That is why the clock time is not used for calculations. That is why the relative time differences between satellites is used, that is why the actual time of day is not necessary for the calculations.

If you had done so, you might have realized that receivers might have been advanced with the faster processors over the years.

Not relevant. While that allows for more satellites to be tracked at once, it does not change the methodology.

a reply to: Phage

It would be a problem if the satellite didn't also send precise information about its orbit (the ephemeris). The gps receiver needs 4 satellites to deduce its own co-ordinates from the delays in the signal. Only one local co-ordinate will give the same time for each satellite for the positions specified in the ephemeris. Which is why clocks on the satellites need be synchronized with one another. Its the only way it can be done without having synchronized clocks in the gps receivers as well.