how GPS has to correct for relativity

How I got here

Started with

Does GPS really need relativity?

Ended at

Atomic clock

The Trail

1. “gps relativity correction” (google.com)
2. Global Positioning System (en.wikipedia.org)
3. Error analysis for the Global Positioning System (en.wikipedia.org)
4. Gravitational time dilation (en.wikipedia.org)
5. Atomic clock (en.wikipedia.org)

What I came away with

Satellite clocks run fast by about 45 microseconds a day from weaker gravity and slow by about 7 from their speed, a net of roughly 38 microseconds. Uncorrected, position errors would build up by kilometers per day.

Keep going

• flights to Asia go over Alaska because the map is lying · Alistair Grant · 5 sources
• the 747 has a hump because everyone thought it would be obsolete · Alistair Grant · 5 sources
• a second is 9,192,631,770 wiggles of a cesium atom · Dev Malhotra · 5 sources
• the NASA space pen myth is backwards · Clara Novak · 4 sources