Astronomy - General Relativity (14 of 17) Proof of Theory: Gravitational Time Dialation and GPS

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We will learn the proof of the theory of Gravitational Time Dilation and GPS. Both effects do not cancel out completely and must therefore be calculated and the results used in all timing and positioning calculations.

Next video in this series can be seen at:

[beardandflipflops]

Perfectly explained, efficient, right to the point and exactly wrong!

The proof is simple, get a USB GPS receiver (Which I have) plug it in.
Now change the time on your computer, it still works. Proving that GPS receiver software does not use GR calculation.

All that GPS receivers do is triangulate, that's why you need a minimum of three satellite signals.

[engineercliff]

Note that in ordered to get the 45 usec number, you have to take the difference between gravity effects at the earth and gravity effects at the satellite. Alternatively, you could use the formula for an orbiting body, sqrt(1-3GM/(rc2)), and get both special and general in one go.

[DroneMappingTools]

Geoids are used to correct for vertical inaccuracies due to differences in gravity. Do you have a video that demonstrates how gravity is affecting the accuracy of the vertical data, and how using a Geoid in processing fixes this error? I am having a very hard time understanding how the error occurs and how using a Geoid fixes it. Thank you for posting this video as it was also very helpful in furthering my understanding.

[pharaoh]

Perfectly explained, efficient and right to the point.

[dcfromthev]

I love how he has every color of dry erase marker, my kind of guy!

[zakirhussain-jsku]

Does gravitational time dilation result from backward motion of time due to decrease in entropy caused by gravity.

[hathay]

Your Golden easy minutes briefing hard chapters

[rudrashiva]

What will happen if you go through wormhole???? How time will effect????

[anthonygallant]

If we plot time on axis if the receiver is moving slower due to the gravity of the Earth and the satellite is moving faster due to its speed in time, when we do the summation of the special relativity and general relativity does that ever turn to the difference? Where the special relativity is in the positive time axis and the general relativity is in the negative.

[jy_decipherer_]

Sir, does the centrifugal force acted on the satellite affect any of the calculations? Since in the 8th video, it is shown experimentally that stronger gravitational field and centrifugal force both has the same time dilation effects

[anupambiswas]

Sir, is rotational movement of thr earth has an effect in this explanation??

[vgovind]

Great!.. can we derive this gravitational time dilation equation using some simple thought experiment, as we did for the time dilation equation in special relativity?

[tushardubey]

Sir are you a Professor.if yes then in which University

[achyuththouta]

But motion itself is relative so for the satellite, it's the earth that's actually revolving from the perspective of the satellite, so shouldn't satellite's point of view be the opposite or am I not understanding something

[davidgoldfield]

The equation for the time dialation on the satellite is NOT correct ! Special Relativity only applies to non accelerating moving objects. Since the gps satellite is in mid earth orbit, it is accelating at 9.8 m/S2, or g. Therefore, SR time dialation equation DO NOT apply !

[divvyyam]

If the clpcks on the satellite and at the Earth's surface change, one wrt to the other, then the receivers would indicate that change .
Is it not true that it is the PERCEPTION that the clocks have changed NOT that they really have changed ?
Only arsking !

[pablog]

This schoolbook computation of relativistic effects in the GPS system does not correspond to how the GPS really works ( GPS is not made of 1 receiver and 1 satellite but is made of a constellation of satellites in order to always have 4 over any point on earth surface). The schoolbook derivations for the 1 satellite-1 receiver system yields something around 11km inaccuracy shift in position per day ( -7us for the Special Relativity time dilation due to the velocity of the satellite and + 45us for the General Relativity gravitational time dilation due to the high altitude of the satellite resulting in 38us overall time drift which multiplied by the speed of light gives the 11 km figure). Is this the real expected time drift due to relativistic effects? No, it is not. The reason is that they are always 4 satellites over any point on Earth and all satellites have, in first approximation, same velocities and same altitudes: their clocks are thus synchronized ( they do not drift with respect to each other). This means than when a receiver receives 4 satellites navigation messages with their positions and times, it doesn’t matter how shifted their clocks are with respect to the receiver: 4 equations with 3 unknowns ( receiver x, y, z) allows to eliminate receiver t and compute x, y, z. Now the question is does the satellites always have same velocities and altitudes? the answer is again no, as satellites can slightly jump in their excentricities. But the shifts are small and introduce a small inaccuracy in position which varies between 0 and 10m within a period of 12h. Without knowing relativistic effects, the resulting GPS inaccuracy would be 10 m at max. Is that a big deal ? Not at all. For instance, ionospheric errors are up to several ten of meters during bad solar weather days. Moreover, base station on Earth regularly send signals to the satellites that contains their UTC time, allowing for synchronisation between their clocks times. Conclusion: Are there relativistic effects at play in the GPS? Yes. Is it of primordial importance to take them into account to have a working accuracy on a GPS system: not at all, as 10 m accuracy is better than good for most everyday use cases.

[tsoojbaterdene]

When a person presses A button in A circuit, light is off.When the person presses A button in B circuit, light is on.Why is that?Is it about position of the A button?Sir

[Bramon]

I’m just here tryin to figure out how to hit slo-mo irl while playing halo infinite

[quantumofspace]

Can you take a fresh look at the universe? PATENT KZ-33869 An easy-to-understand experiment is proposed to create and study super-powerful, stable gravitational waves, the signal of gravitational waves exceeds the noise, or the speed of light in a vacuum is not constant. The choice is yours.