What is Microgravity?
The presence of Earth creates a gravitational field that acts to attract objects with a force inversely proportional to the square of the distance between the center of the object and the center of Earth. When measured on the surface of Earth, the acceleration of an object acted upon only by Earth’s gravity is commonly referred to as one g or one Earth gravity. This acceleration is approximately 9.8 meters/second squared (m/s 2 ). The term microgravity (mg) can be interpreted in a number of ways depending upon context. The prefix micro – (m) is derived from the original Greek mikros, meaning “small.” By this definition, a microgravity environment is one that will impart to an object a net acceleration small compared with that produced by Earth at its surface. In practice, such accelerations will range from about one percent of Earth’s gravitational acceleration (aboard aircraft in parabolic flight) to better than one part in a million (for example, aboard Earth-orbiting free flyers). A
It is not necessary to go far out into space to create a microgravity environment. Such an environment can be created through the act of freefall. Imagine riding in an elevator to the top floor of a tall building (see Figure 1). At the top the cables break, causing the car and you to fall to the ground. Since you and the elevator car are falling together, acted on only by gravity, you will float inside the car. In other words, you and the car are accelerating downward at the same rate. If a scale were present, your weight would not register because the scale would be falling too. This is shown in the right-hand column of Figure 1, and in cartoon version in the videotape.
