On the Move!
Did you know that even while we stand still, we're moving. We humans have no sensation that we're moving through space, yet we are. Every day the earth rotates at about 1,000 miles an hour, at the equator. Because we are on the earth, we're moving too, right along with it. We're also moving with our earth as it revolves around the sun. The speed of that trip is about 18 miles a second. Why don't we have any sensation that we're going at these very fast speeds? The answer has to do with the fact that we only sense speed when we're accelerating or decelerating -- or speeding up or slowing down.
Think of what it feels like to be a passenger in a car. While the car is moving at a constant speed, let's say 30 miles per hour, we have no sensation that we're moving. But when the driver suddenly "steps on it" or accelerates quickly, we feel that. We feel the change in speed, even though we don't feel different sensations at differing speeds.
If you've travelled on an airplane, think about what it feels like during take-off. Take-off is hard to ignore! But once the plane is going at a more constant speed, even if it's 500 miles per hour, we don't sense that. The same thing is true about slowing down. When a car crashes -- or stops -- we feel it. So because the earth rotates and revolves around the sun at constant speeds, we don't feel these speeds. But we're moving just the same. We're also moving with our solar system around the center of the Milky Way galaxy. Why is our galaxy called the Milky Way? Because when we look at the night sky our galaxy looks like a splash of milk. It may not look to us that the Milky Way is moving, but that's because we're in it as it moves.