How do you keep a Moon base from baking and freezing?

Have you ever touched a metal slide that sat in the sunshine all afternoon? It feels hot enough to make you pull your hand back. Now picture a place where the ground gets far hotter than that, and later far colder than snow.

That place is the Moon. No one lives there yet, but people dream of building a Moon base, a small home with rooms for astronauts. So how do you keep a Moon base from baking and freezing?

On the Moon, one day of sunshine lasts about two whole weeks. All that time, the sun beats down without a single cloud. The ground grows hotter than boiling water.

Then night comes, and it lasts about two weeks too. The Moon has no air to hold the warmth in, so the heat slips away into space. The ground turns colder than the coldest freezer on Earth.

A Moon base needs a thick blanket of its own, one that slows the heat going in and coming out. A giant blanket from Earth would be much too heavy for a rocket to carry. So what could astronauts use that the Moon already has in heaps, all around them?

They can use the Moon's own ground. The Moon is covered in regolith, which means loose gray dust and broken bits of rock. It lies over the whole Moon like a deep layer of gray powder.

Astronauts will drive digging machines to scoop up regolith and pile it over the base. They make the pile thicker than a grown-up is tall. Under that heavy coat, the rooms sit snug, like a seed tucked under the soil.

Heat moves very slowly through a thick pile of regolith. So the hot daytime sun cannot push its heat down to the rooms, and the night cold cannot pull warmth out of them. Under the pile, the temperature stays steady, day and night.

Steady is good, but under the pile it is still chilly, like a winter day. So the astronauts switch on heaters inside the base. The heaters warm the air until it feels like a cozy room at home.

Heaters need power to keep running. During the long sunny day, astronauts set solar panels beside the base to catch sunlight and power the heaters. Through the long dark night, they run the heaters on a small power station they bring from Earth.

Here is our word: regolith. Astronauts pile a thick coat of regolith over a Moon base, so heat moves through too slowly to bake or freeze the rooms, and heaters keep the air cozy inside.

Rest snug and warm tonight, little Moon builder, tucked inside your own cozy home.