Does weightlessness mean you can’t get weighed in space?  That’s exactly what it means. On earth you can step on a scale, in zero gravity if you step on a scale nothing would happen. There wouldn’t be any force of gravity to pull you down.

Weightlessness

Unlike a sky diver, astronauts who step out into space won’t fall to earth. They will just continue to orbit around earth or stay in one place if they were outside the earth’s orbit. This state is called weightlessness, micro gravity, or zero gravity. Zero gravity does not mean that gravity doesn’t effect the shuttle. It just means that the effects are mostly canceled out by centrifugal force. An example of centrifugal force is if something is orbiting a center, centrifugal force will cause it to move away from that center. Have you ever ridden on a roller coaster with a 360-degree loop? As you speed around the loop, gravity is pulling you towards the ground. But at the same time, speed on a curved path creates a centrifugal effect that pushes you outward, away from the center of the loop. This is another example of centrifugal force.

Zero Gravity can get messy. Whenever an astronaut opens a locker or a pocket, loose objects float out and drift around the cabin. When they eat, all of the dish and beverage containers have Velcro on the bottom so they can stick to the Velcro strips on the counter tops. To keep from floating around while they’re eating, astronauts slip their feet into loops on the cabin floor. In zero gravity, long hair should be held in place by a cap, clip, or a ribbon. Otherwise it will go all over the place!

Discovering Gravity

One day in the 17th century a young student saw an apple fall from a tree to the ground. His name was Isaac Newton. Before his 24th birthday he figured out that the apple fell to earth because of gravity.  All objects have a gravitational pull on one anther, Newton stated. The amount of pull depends on how far apart the objects are and how much mass each one has. The greater the mass, the greater the pull.

Newton was the fist person to say that gravity doesn’t act only near the earth. There is gravity from other planets, the stars, and everywhere in the universe. Scientists measure weight in Newtons named after Isaac Newton. (Weight is the downward force of gravity pulling on an object.)

All objects fall towards the earth at the same speed no matter how big or heavy they are. Galileo Galilei discovered that before Newton noticed the falling apple. According to one story, Galileo dropped steel cannonballs with different weights from the Leaning Tower of Pisa, in Italy. Galileo measured the time each cannon took to reach the ground, and he discovered that they had reached the ground at the same time!

Gravity on the Moon

On the moon in 1969 American astronaut Neil Armstrong dropped a hammer and a feather at the same time. Even though the feather had a larger surface area, they both landed at the same time. The moon has less mass so its gravity is much weaker. If you weigh 600N (Newtons) on earth you’ll only weigh 100N (Newtons) on the moon because astronauts only have only one-sixth of their normal weight when they are on the moon.  When you jump on the bed, why don’t you float up to the ceiling and stay there? What makes you sink back down to the mattress? It’s the force called gravity! If you jump on the moon there is a weaker force of gravity to pull you down, so you float a little and come down more slowly. On Earth there’s a stronger force of gravity to pull you down, so when we jump, we come right back down. It depends on the planet if you were to jump on it. The bigger the planet is the more gravity it has so it would be even harder to jump on than on earth.  

How Much You Would Weigh On Each Planet, The Moon, and The Sun?

On some planets you weigh more then you normally weigh ( on Earth) because the gravitational pull is stronger. On other planets you weigh more or less because the gravitational pull is different. Here is a chart of how much you would weigh on each planet in our solar system, the sun, and the moon if you weighed 100 pounds on Earth.

With each shuttle mission astronauts learn more about living in zero gravity. Will weightlessness ever seem normal to humans? Probably not. Never for a single moment (in space) are you fooled into thinking you’re on Earth because there isn’t any gravity to pull you down, and it feels very different.