Q:

Does the Earth emit heat?

I'm reading my first book on physics "Seven brief lessons on physics" by Carlo Rovelli, and in his chapter on "Probability, time and heat of black holes", he mentions that Stephen Hawking showed that black holes are hot, they emit heat. My question is, does the earth emit heat? 

A:

Yes; but not for the same reason as a black hole.
Every object emits electromagnetic radiation with an energy corresponding to it's surface temperature.
Earth emits heat; but it also absorbs heat from radiation.  In the light of the sun for example, more radiation is absorbed by the planet than emitted, so it heats up; but the Earth is still emitting that thermal radiation.

