Spacesuits

How did the astronauts survive in the heat of the lunar day?

The astronaut's spacesuits weren't white just because it looked smart, white reflects the most heat radiation, thereby minimising the amount absorbed.

The suits were also cooled using a system not unlike your refrigerator in your kitchen. It worked because water sprayed into a vacuum experiences a very rapid drop in pressure and consequently temperature.

The same thing happens to aerosol sprays. Why is it that spray-on deodorant is so cold? It is due to the sudden drop in pressure between the can and outside air.

So, when a small amount of water was sprayed onto a cooling element on the rear of the spacesuit its temperature dropped so much that it would freeze over it. The cooling water of the spacesuit is then pumped through this element. The heat of the water melts the ice which rapidly boils off (the boiling point of water being very low in a vacuum) into space taking the unwanted heat with it.