Because of Gravity, Basically a force so strong it constantly pulls us to the earth with 1 G (Maybe 100 pounds of force constantly pulling us to the earth)
Light as a wave: Light can be described (modeled) as an electromagnetic wave. ... This changing magnetic field then creates a changing electric field and BOOM - you have light. Unlike many other waves (sound, water waves, waves in a football stadium), light does not need a medium to “wave” in.
Explanation:
A theromometer is the increase or decrease of earths atmospheric temperture, thats how you would measure the temperture of the air around you.