Nasa: What Is Microgravity?

Angry Birds Space has provided NASA an opportunity to share a core concept of space exploration: gravity. Not only does gravity play a vital role in the game but, in general, gravity is a force that governs motion throughout the universe. It holds us to the ground, and it keeps the moon in orbit around Earth and Earth around the sun. The nature of gravity … was first described by Sir Isaac Newton more than 300 years ago. Now three centuries later and more than 200 miles above our home planet on the International Space Station, astronaut Don Pettit shares the thrill of concepts like gravity and trajectories with some help from Red Bird.

Gravity is the attraction between any two masses, most apparent when one mass is very large (like Earth). The acceleration of an object toward the ground caused by gravity alone, near the surface of Earth, is called “normal gravity,” or 1g. This acceleration is equal to 32.2 ft/sec2 (9.8 m/sec2). If you drop an apple on Earth, it falls at 1g. If an astronaut on the space station drops an apple, it falls too. It just doesn’t look like it’s falling. That’s because they’re all falling together: the apple, the astronaut and the station. But they’re not falling towards Earth, they’re falling around it. Because they’re all falling at the same rate, objects inside of the station appear to float in a state we call “zero gravity” (0g), or more accurately microgravity (1×10-6 g.) On the International Space Station we use microgravity to conduct research. When you have the ability to turn gravity off in your experiment, it enables you to look at things from a new perspective. That makes the station unique, because you can do things on it that you can’t do anywhere else. NASA has studied things like gene expression, micro-organisms, fluids and other materials to see how their behavior is different on the station and how that applies to life back home. This unique environment has helped us learn more about life on Earth and ways to improve it for everyone. One of the most important things NASA is studying is how this lack of gravity affects human physiology over the long term. If we’re going to send humans to asteroids and Mars, they’re going to be in space for a long time, and there are a lot of health unknowns that only the microgravity of the station can help us study and overcome.  The condition of microgravity comes about whenever an object is in free fall. That is, it falls faster and faster, accelerating with exactly the acceleration due to gravity (1g). As soon as you drop something (like an apple) it is in a state of free fall. The same is true if you throw something; it immediately starts falling towards Earth. But how does something fall around Earth? Newton developed an experiment to demonstrate this concept: Imagine placing a cannon at the top of a very tall mountain. Once fired, a cannonball falls to Earth. The greater the speed, the farther it will travel before landing. If fired with the proper speed, the cannonball would achieve a state of continuous free-fall around Earth, which we call orbit. The same principle applies to the space station. While objects inside them appear to be floating and motionless, they are actually traveling at the same orbital speed as their spacecraft: 17,500 miles per hour (28,000 km per hour)!

Objects in a state of free fall or orbit are said to be weightless. The object’s mass is the same, but it would register “0” on a scale. Weight varies depending on whether you are on Earth, the moon or in orbit. But your mass stays the same.

Many amusement park rides create brief periods of free fall. Some rides that operate vertically without any applied forces are actually classified as free fall rides. Most roller coasters have a set of parabolic (rolling) hills that also create brief periods of weightlessness.

NASA participated with Rovio on Angry Birds Space under a Space Act Agreement to share the excitement of space with the Angry Birds community, educate users on NASA’s programs, and collaboratively create interactive educational experiences for the public.


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