Physics

The source of up to half of the Earth’s internal heat is completely unknown – here’s how to hunt for it

The source of up to half of the Earth’s internal heat is completely unknown – here’s how to hunt for it

It may not be obvious while lying in the sun on a hot summer’s day, but a considerable amount of heat is also coming from below you – emanating from deep within the Earth. This heat is equivalent to more than three times the total power consumption of the entire world and drives important geological processes, such as the movement of tectonic plates and the flow of magma near the surface of the Earth. But despite this, where exactly up to half of this heat actually comes from is a mystery.

Physicists control electrons at femtosecond timescales - Results may help improve efficiency of solar cells, energy-harvesting devices.

Physicists control electrons at femtosecond timescales - Results may help improve efficiency of solar cells, energy-harvesting devices.

When you shine a light on a conducting surface like silicon or graphene, that light jump-starts certain electrons into high-energy states and kicks off a cascade of interactions that happens faster than the blink of an eye. Within just a few femtoseconds — a thousand trillionth of a second — these energized electrons can scatter among other electrons like balls on a billiard table, quickly dissipating energy in an ultrafast process known as thermalization.