#### Tim Alphabeaver

• 214
• That's no beaver
##### Re: Flat Earth Satellites
« Reply #40 on: January 27, 2020, 09:13:13 PM »
Helpful or not helpful isn't really a valid scientific or logical standard.
Well I think I can't argue with that.
**I move away from the infinite flat plane to breathe in

#### Tim Alphabeaver

• 214
• That's no beaver
##### Re: Flat Earth Satellites
« Reply #41 on: January 27, 2020, 09:19:14 PM »
As for pricelesspearl, I think it's safe to assume that his posts should fall under the "blatant troll" category by now - we shouldn't waste our time with them.
A 'blatant troll' is what you call a valid direct response to your post, with citations?
**I move away from the infinite flat plane to breathe in

#### Groit

##### Re: Flat Earth Satellites
« Reply #42 on: January 27, 2020, 10:43:29 PM »
Quote
At different positions in its orbit, a GPS satellite will have differing speeds relative to different GPS receivers. Given this, do we need to adjust the speed used in the equation for time dilation to account for this variation?

That’s because, the velocity is relative to the earth as a whole, not to any fixed point. The earth rotates slower at the poles than at the equator so the exact velocity of the receiver will vary depending on where it is.  Not to mention that more often than not the receiver itself will be moving.  The relative velocity between the receiver and the satellite changes because the velocity of the receiver changes depending on location and/or speed…not because the velocity of the satellite changes.

Hi Pricelesspearl

I think the effects of time dilation are the same for all receivers on the surface of the Earth (at sea level), as all clocks at sea level tick at the same rate regardless of their rotational speeds. For example an observer at the north pole will feel stronger gravity than an observer at the equator, so the north pole observers clock should tick slightly more slowly. However, the observer at the equator has a faster rotational speed which cancels the effects and thus both observers clocks tick at the same rate.

Obviously not everyone lives at sea level and not everyone travels in a vehicle at the same speed, but i think the effects of time dilation due to this is very, very small.

#### pricelesspearl

• 181
##### Re: Flat Earth Satellites
« Reply #43 on: January 27, 2020, 11:44:15 PM »
Quote
I think the effects of time dilation are the same for all receivers on the surface of the Earth (at sea level), as all clocks at sea level tick at the same rate regardless of their rotational speeds. For example an observer at the north pole will feel stronger gravity than an observer at the equator, so the north pole observers clock should tick slightly more slowly. However, the observer at the equator has a faster rotational speed which cancels the effects and thus both observers clocks tick at the same rate.

Obviously not everyone lives at sea level and not everyone travels in a vehicle at the same speed, but i think the effects of time dilation due to this is very, very small.

I don’t disagree with that.  I was just responding to Pete’s apparent understanding of the passage below and explaining why a GPS satellite will have differing speeds relative to different GPS receivers…because the receivers are accelerating, not the satellites
The response given makes it clear that although “in principle” the speed of the receiver changes the calculations; the difference is so minor it isn’t relevant.

Quote
Q - At different positions in its orbit, a GPS satellite will have differing speeds relative to different GPS receivers. Given this, do we need to adjust the speed used in the equation for time dilation to account for this variation?
A - In principle, we do need to use a different value for v in Equation 1 depending on the precise speed of a given satellite relative to a particular receiver. However, the speed of the satellites (3874 m/s) is much larger than the speed of a GPS receiver as it moves with Earth’s rotation (465 m/s at the equator). Differences in the values of the relative speed between a satellite and a receiver result in variations in the amount of time dilation of just 1% at most and so are insignificant for the current accuracy of the GPS.