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Gravity in Orbit

So, is there Gravity in Orbit?

Space is nearly a perfect vacuum; beyond Earth’s atmosphere there is no air to produce lift or drag. Gravity is the main force to be dealt with in space, and thrust is the force that allows a spacecraft to get into space and maneuver.

A spacecraft in orbit is not beyond the reach of Earth’s gravity. In fact, gravity is what holds it in orbit—without gravity, the spacecraft would fly off in a straight path. As the spacecraft orbits, it is actually falling, though it never reaches the ground.

Why Doesn’t an Orbiting Spacecraft Fall to Earth?

The faster an object travels, the more horizontal distance it covers as it falls, and the gentler the curve of its path. An orbiting spacecraft travels so fast that the curve of its path matches the curve of the Earth. So, the distance between the spacecraft and the Earth stays constant.

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Picture Yourself in Orbit: Are You Really Weightless?

An object in orbit is constantly falling, and falling is what causes “weightlessness.” Gravity acts on you even while you are in orbit, and therefore you still have weight. But what is missing is the familiar sensation of weight. Without air resistance, all objects fall at the same rate. Because you and your spacecraft are falling at the same rate, there is no force between you and it to provide a sensation of weight. You feel “weightless.”

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Q:

What is a geostationary orbit?

A:

Many weather and communications satellites need to remain above a particular point on the Earth. To do so, a satellite’s speed must exactly match the Earth’s rotation—it must orbit once every 24 hours. Such an orbit is called a geostationary or geosynchronous orbit. ... more

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Did You Know?

You can lose weight by just moving from the first floor of a building to the second floor. By increasing your distance from the center of the Earth, you will lose weight. Granted, the difference will be very slight—about the weight of a fly. If you want to lose even more weight, try going to the top floor of a really tall building! Of course, you will gain it all back when you return to the first floor. Instead of trying to lose weight, you should try to lose mass. That, of course, takes more effort.

Pop Quiz

There is no gravity in space.

A) True
B) False

False: Gravity exists everywhere in space.  Don't be fooled by the somewhat misleading term "zero-gravity."  Gravity from the Sun reaches throughout the solar system and beyond, keeping the planets in their orbits.  Gravity from Earth keeps the Moon and human-made satellites in orbit.  It is possible to far away from a planet or star and feel less gravity, because gravity decreases with distance.  But that doesn't account for the weightless feeling that astronauts experience in space.