What goes up must come down, but have you ever wondered why? The answer is gravity. Gravity is an invisible force that pulls one object toward another. Anything that has mass – including humans – has gravity. The more mass an object has, the stronger its gravitational pull. We can’t feel gravity, but we know it’s there. When we jump, we come down.
- Even though the idea of gravity is pretty obvious, scientists didn’t have a word for it or a real understanding of it until 1687, when Sir Isaac Newton published his theories on the Three Laws of Motion.
- Mass determines how much gravity something has, but proximity (closeness) plays a part too. The Earth’s and the Moon’s gravity affect each other more than say, Earth and Jupiter because the Earth and Moon are closer to each other.
- Mass is different than weight. Mass is measured in grams. Basically, mass is how much of something there is. Weight is caused by gravity’s pull. If you visited another planet, you might weigh less or more, depending on the force of gravity on the planet. Your mass never changes.
- Gravity pulls falling objects down at the same speed, no matter what their weight is. So a ball weighing 5 pounds would fall just as fast as a ball weighing 10 pounds. Air resistance slows some objects down.
- Gravity: a magnetic force that any object with mass has. This force pulls two objects together.
- Proximity: distance and location something is in relation to something else
Q and A
Question: What causes tides?
Answer: Tides are caused by the Moon’s gravitational force on oceans, seas, and even lakes and rivers to a lesser degree. As the Moon rotates around the Earth, its gravitational force pulls the water inland. As the Moon continues its path around the Earth, the water recedes. Tides occur about every 12 hours.
Visit Idaho Public Radio to learn more about the force of gravity.