Free Fall

What is gravity? A force that pulls us in to Earth, and keeps us grounded, whether we are standing on “top” of the Earth or on the “bottom.” We could dive into to Einstein’s Theory of Relativity or Newton’s Theory of Gravitation, and really get into what gravity is, but for now we will stick with a simplistic answer—when two objects are attracted to one another.

I want to discuss a fallacy with gravity, with the promise that one day I will deliver an in depth gravity discussion. I hope you are sitting for this one, because what I’m about to tell you may come as a shock. Are you ready? Here is goes, you have been lied to your whole life! Yes, it’s true, I know, okay, okay—enough! Let’s go! Pick yourself up off the floor, because I’m going to tell you what fallacy has wronged you all these years. Have you ever heard of the term “zero” gravity? Read or heard discussions on our astronauts in “zero” gravity, the way things “float” inside the International Space Station, the idea that you basically look as though your swimming under water in space—in “zero” gravity. One problem, if gravity is two objects attracted to one another, and the Earth’s gravity keeps the Moon in place, and the Moon’s gravity can cause tidal waves in the oceans, then the space between the Earth and Moon must experience, some type of gravitational effect—right? Right! There is no such thing as “zero” gravity, the idea of “zero” gravity is a fallacy, I know your hurt, and feel lied too. Lucky for you, I’m here to set the record straight.

If zero gravity is not a real thing, then why are our astronauts “swimming” out in space. Believe it or not the orbit of objects including the ISS, who orbits around Earth every 90-minutes, are in free fall. Simply explained, satellites, space stations, and space crafts and all the other “stuff” in orbit, is suspended in permanent free fall, they are falling back to Earth and “missing it” every time. Where the ISS sits in low-Earth orbit, the pull of gravity is only 8% weaker than that at the ground where we are. So these objects are still falling under the influence of gravity. Free fall is the feeling you get when you’re riding a roller coaster and drop down what seems to be a 90-degree angle, and you feel yourself lift-up from your seat, or if you ever been on the Tower of Terror in Disney, or the feeling of sky diving as you plunge towards Earth and hit your terminal velocity—meaning you maxed out your falling speed, you can only fall so fast.

So how are these free-falling objects, never falling and reaching the surface? Each object has enough horizontal velocity to maintain its orbit and free-fall. Imagine throwing a baseball, it travels some-certain amount of horizontal distance before it hits the ground. Instead, now imagine the baseball field is wrapped around a sphere, with its own gravitational pull, you are on the pitcher’s mound at the top of the sphere. You pitch the ball, and it travels some-certain amount of distance before falling—wait it won’t fall to the ground, because you are on a sphere and the ball is falling not to a flat ground, but from the balls perspective a ground that is consistently getting “deeper” causing it to maintain its horizontal velocity as it orbits around the sphere, coming back to where it started and hitting you in the back of the head, where you are still standing on the pitcher’s mound. This is the same effect the objects in orbit experience. Between their horizontal velocity and Earth’s curvature—which is approximated to be for every 8km the Earth curves 5m down—objects remain in free-fall causing the misnomer of “zero” gravity.

So, next time you hear the term “zero” gravity, laugh at them, and explain how they couldn’t be more wrong!

Dedicated to Jenn–Congratulations on your accomplishment today this one is for you!