Given that earth travels through space at a rate of 67,000 miles per hour, why didn’t it move away from the Apollo 11 astronauts when they left earth orbit?

Question

Given that earth travels through space at a rate of 67,000 miles per hour, why didn’t it move away from the Apollo 11 astronauts when they left earth orbit?

In: Physics

Answer 1

Something that I don’t think the other answers have focused on enough is that things don’t just randomly slow down: there needs to be a force to change something’s speed. When you throw a ball out of a car, it stays moving forward at the same speed of the car *except* for the fact it is hitting otherwise-stationary air. By hitting the air, there is a force applied to the ball that slows it down.

In space, there is no air resistance, and no external forces that affect earth but not spacecraft. So, when on earth (or in earth’s atmosphere) you and everything around you is moving at that 67,000 MPH speed. When you leave the atmosphere, there is no mechanism to slow you down, so you are *still* travelling at that speed.