Long ago, it was believed that the gods ruled the weather, because it was a mystery to people. No one knew how to measure heat, cold, or wind. Galileo Galilei invented the thermometer in the 1500s. Soon after, the first barometer was invented to measure air pressure. In other countries, the Celsius scale is used, named after astronomer Anders Celsius. Today, meteorologists use newer tools like weather satellites and radar to make weather predictions.