Chapter 04 of 5
Einstein in Orbit
The relativity corrections that keep your blue dot on the right street.
- The Problem
Clocks Disagree
Clocks on GPS satellites don't tick at quite the same rate as clocks on the ground.
- Reason One
Moving Clocks Run Slow
Special relativity says fast-moving clocks run slow. The satellites move at about 3.9 kilometers a second, so their clocks lose about 7 millionths of a second a day.
- Reason Two
High Clocks Run Fast
General relativity says clocks run faster where gravity is weaker. At orbit height, satellite clocks gain about 45 millionths of a second a day.
17 more cards in this chapter
Could you answer this?
Why do GPS satellite clocks need relativity corrections?
🛰️ Why Your Phone Needs Einstein
- 01Beeps From SpaceHow listening to Sputnik led to satellite navigation.
- 02Four Satellites and a StopwatchHow a phone works out where it is by timing radio signals.
- 03A Billionth of a SecondWhy GPS depends on atomic clocks and timing measured in nanoseconds.
- 04Einstein in OrbitThe relativity corrections that keep your blue dot on the right street.
- 05Lost in the CityUrban canyons, jamming and how your phone fills the gaps.