How fast are you moving?
Geometry & Trigonometry
How fast is a point on Earth's surface moving, just from the planet's rotation? Build a model and compare it with the speeds a GPS app reports.
Introduction
GPS apps report your speed by tracking how your position changes over time, but there is also a hidden speed you always carry: the spin of the Earth. A point on the equator moves at over 1600 km/h from Earth's rotation alone, while a point at the poles barely moves at all. This exploration asks you to work out that speed for any point on Earth, then compare it with the speeds a GPS app reports for walking, cycling or driving.
Guiding Questions
- Pick a point on Earth's surface — how fast is it actually moving as the Earth spins?
- How does your speed depend on your latitude? Write it as a function and test it for cities around the world.
- The Earth also orbits the Sun. How do the two speeds compare, and how would you combine them?
- Could you extend this to the Moon, the International Space Station, or a point on a spinning wheel you measure yourself?