Helping Aubie this week is Dr. Ruel A. (Tony) Overfelt, Professor of Mechanical Engineering, with AU’s Samuel Ginn College of Engineering

Dear Mrs. Reynolds’ class,

Actually, there is gravity everywhere. It gives shape to the orbits of the planets, the solar system and even galaxies. Gravity from the Sun reaches throughout the solar system and beyond, keeping the planets in their orbits. For example, gravity from Earth keeps the Moon in orbit.      
In fact, gravity is a very important force. Every object in space exerts a gravitational pull on every other, and so gravity influences the paths taken by everything traveling through space. It is the glue that holds together entire galaxies. It keeps planets in orbit. It makes it possible to use human-made satellites and to go to and return from the Moon. It makes planets habitable by trapping gasses and liquids in an atmosphere.

There is less gravity in space because gravity decreases with distance.  That means that it is possible to be far away from a planet or star and feel less gravity. But that doesn’t account for the weightless feeling that astronauts experience in space. The reason that astronauts feel weightless actually has to do with their position compared to their spaceship. We feel weight on Earth because gravity is pulling us down, while the floor or ground stops us from falling. We are pressed against it. Any ship in orbit around the Earth is falling slowly to Earth. Since the ship and the astronauts are falling at the same speed, the astronauts don’t press against anything, so they feel weightless.

You can feel something very similar to what the astronauts feel for a moment in a fast-moving elevator going down or in a roller coaster, when you start going down a big hill. You are going down rapidly, but so is the roller coaster or the elevator so for a second you feel weightless.
           

Astronauts in training experience weightlessness by riding in an airplane called the KC-135. It is also called the Vomit Comet. It flies in a way that makes everything inside it float. The floating only lasts for about 25 seconds. For this bit of time, astronauts feel as if they are in space. Sometimes even experienced astronauts get sick in the KC-135. That is how it got the name Vomit Comet.

Thanks for your question,
Aubie and Dr. Overfelft