If you hold an egg between your fingers and then release it, what will happen? Will it float up to the ceiling? Of course not! It'll fall to the ground and probably crack open. Why? That's right. It's all due to a little force we call gravity.
Thanks to gravity, we have our feet firmly on the ground. Without gravity, we might float right into outer space and never be seen again. Instead, Earth pulls us toward its center at all times, keeping us on the ground.
Every object with mass has a gravitational pull on the objects around it. That force depends upon the masses of the objects. Things with a lot of mass, such as Earth, exert a strong gravitational pull on the objects near it, such as you and me.
In addition to pulling objects toward it, Earth also accelerates those objects as they get closer to it. In other words, objects speed up as they approach Earth. More importantly, the laws of science tell us that all objects — regardless of their mass — gain velocity at the same rate as they fall.
But how can that be? It seems counterintuitive based upon our experience with the world around us. For example, if you hold a feather in one hand and a brick in the other and drop them at the same time, they won't hit the ground at the same time. Will they?
Which will hit first? If you said the brick, you're right! But why is that? If gravity causes objects to fall toward Earth at the same rate, then why will the brick hit the ground long before the feather?
The answer lies in another scientific concept: air resistance. Air is all around us. Those air molecules push against each other and other objects. They provide an upward force of friction against falling objects. Galileo also discovered that objects that are more dense are affected less by air resistance, while objects that are less dense will be slowed down more by air resistance.
This explains why a feather will fall to the ground very slowly when dropped. On the other hand, a brick will fall quickly to the ground as if there was no air around it. Scientists who have tested these theories will tell you that, if you drop a feather in a vacuum (a container with no air), it will fall at the same rate as the brick!