Answer:
when the ground is very hot and the air is cool.
Explanation:
The hot earth warms a layer of air right above the ground. Light is refracted as it passes through the cool air and onto the hot air sheet (bent). A coating of very warm air near the earth bends the light from the sky almost into a U-shaped bend.
<span> changing its shape
changing its mass
or changing its volume</span>
Krypton ... symbol Kr ... is an element. It's element number 36, because
there are 36 protons in the nucleus of every atom of Krypton.
Krypton has nothing to do with Superman, except that about 75 years ago,
the creators of Superman thought it was a cool-sounding scientific word,
so they chose it for the name of his home planet.