As the planets congealed, gravitational forces and particle collisions created the high temperatures necessary to melt metals floating around in space, and minerals began their diversification.

ECONOMIST: Minerals

The problem becomes less acute once they've cleared the atmosphere, but the high speeds required to escape the Earth's gravitational field (more than 6.8 miles per second) necessitate an enormous amount of energy.

FORBES: Houston, We Have Problems

For GPS, this is an enormous issue because it turns out that the clocks on the satellites drift by almost 40, 000 nanoseconds per day relative to the clocks on the ground because they are high above the earth's surface (and therefore in a weaker gravitational field) and are moving fast relative to the ground.

BBC: Meet the world's director of time