Level 8: Gravity and time

Space and time · level 8 of 8 · rough age 17 and beyond (a guide for parents; anyone can start anywhere)

Einstein's general relativity says gravity is not a force pulling through space, but the shape of space and time itself. This level follows the evidence: falling, clocks at different heights, the GPS satellites, starlight bent by the Sun, radio signals from Mars arriving late, and finally the clock a Mars base would need.

Lesson	You will be able to
The equivalence principle	Explain why gravity and acceleration cannot be told apart
Gravity slows clocks	Work out how much faster a higher clock runs
GPS and relativity	Add up both relativity effects on a GPS satellite clock
The bending of light	Find how far a star's light is bent passing the Sun
The Shapiro delay	Estimate how late signals passing the Sun arrive
A clock for Mars	Work out how fast a Mars clock gains on an Earth clock

Previous: Level 7: Special relativity · Space and time topic page · The companion level: Gravity and orbits, level 8