This is a picture of O-zone depletion. The o-zone is going down about 4% every decade. Although that doesn't seem like a lot, it is. This depletion occurs when CFCs and other chemicals are released into the air. The O-zone is very important, it helps keep the plants, animals and people alive.

This is a thermometer. A thermometer measures temperature or gradient. There is mercury in the device that will physically change with the temperature.