How do scientists measure sea levels? It turns out that there are countless factors taken into account because the oceans aren't at the same level all around the world.

Thanks to different densities in the Earth's core, gravity's effect on the height of the oceans varies wildly around the world.

Minute Physics points out with the help of some map work by Ron Blakey that geodetic scientists had to create a highly detailed model of the Earth's gravitational field.

This allows them to calculate sea level to within a meter anywhere on Earth. Watch the video below: