How Does Time Dilation Affect Measurements of Earth's Size from Satellites?

Click For Summary
SUMMARY

The discussion centers on the effects of time dilation on measurements of Earth's size from GPS satellites. It is established that GPS satellites' clocks run faster than those on Earth's surface due to gravitational time dilation as predicted by Einstein’s General Theory of Relativity (GTR). The conversation explores the implications of this time difference, specifically how it affects the measurement of light travel time between two points on Earth, suggesting that distances may appear larger from the satellite's perspective. The assumption that the speed of light remains constant regardless of gravitational strength is critically examined.

PREREQUISITES
  • Understanding of General Theory of Relativity (GTR)
  • Familiarity with GPS technology and satellite mechanics
  • Knowledge of time dilation and its effects on measurements
  • Basic principles of light propagation in varying gravitational fields
NEXT STEPS
  • Research the implications of gravitational time dilation on GPS accuracy
  • Study the concept of coordinate systems in General Relativity
  • Learn about the synchronization processes of satellite clocks
  • Explore the effects of spacetime curvature on light speed measurements
USEFUL FOR

This discussion is beneficial for physicists, aerospace engineers, and anyone involved in satellite technology or the application of General Relativity in practical scenarios.

Zman
Messages
96
Reaction score
0
The GPS satellites in stationary orbit around the Earth have clocks that run a little faster than the clocks on the surface of the earth. This is predicted in Einstein’s GTR.
Because of this the satellite clocks have to be synchronised on a regular basis with those on the earth.

Assuming that the speed of light is constant regardless of the strength of the gravitational field. Can I assume this?

And for the sake of argument let the satellite clock run 10% faster than the clocks on earth.
If the satellite measures the time taken for light to go between two points on the earth, it will measure the time as 10% bigger than Earth based observers.
Because distances are all effectively defined by the speed of light does the Earth then seem 10% bigger from the satellite?
 
Physics news on Phys.org
Zman said:
Assuming that the speed of light is constant regardless of the strength of the gravitational field. Can I assume this?
This is true in a local sense, so if you construct a coordinate system using freefalling rulers and clocks in a small region of spacetime where the curvature is negligible, the speed of light will be c as measured in this coordinate system. But over a larger region where the curvature of spacetime is significant, then depending on what coordinate system you use in this region (and in GR you can use basically any coordinate system you want), the coordinate speed of light may not be constant.
 

Similar threads

  • · Replies 103 ·
4
Replies
103
Views
8K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 70 ·
3
Replies
70
Views
7K
  • · Replies 101 ·
4
Replies
101
Views
10K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 26 ·
Replies
26
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 12 ·
Replies
12
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 88 ·
3
Replies
88
Views
8K