# Astronauts feel gravity

## Weightlessness: Anyone can fly

How does that feel? To be weightless like an astronaut. Do you want us to tell you something? It's easier than you think! Even you have been weightless, believe it or not. All you have to do is jump in the air. Even if you jump off the three-meter board in the outdoor pool, you are weightless for a short time. How it works? We'll explain it to you.

### No up and down

But first let's take a look at what weightlessness actually is. When you read or hear the term, you immediately think of space. Objects fly around there, there is no up and down any more. Everything that you don't hold on to or that isn't secured flies away. Astronauts don't feel anything pulling them down. You are weightless there. This means that they no longer feel any gravity. But what is interesting: the force of gravity is still there! Does that sound contradictory? But it is not. Weightlessness is not only the opposite of gravity, but both phenomena are directly related. Without one, the other would not exist.

### Law of gravitation

As the physicist Isaac Newton stated in his law of gravitation in the seventeenth century, every body has a force of attraction. The heavier the body, the greater this force. The earth is much larger than the moon and has a much greater gravitational pull. You can imagine why we are then drawn to the earth. But why isn't it the same with the moon? This is exactly the reason why astronauts are weightless in their space capsules in space.

The moon orbits the earth. Because of its fast speed, the same thing happens here as when you drive around a corner in a fast car: it pulls you outwards. The invisible force that you then feel is called centrifugal force. The centrifugal force that the moon develops on its orbit is so strong that it can counteract and balance gravity. This is exactly what happens when astronauts orbit the earth with a fast satellite. So the conclusion is as follows: The gravitational pull of the earth is still there in space. However, it is counteracted by other strong forces so that you can no longer feel it. We speak of weightlessness when we are exposed to gravity but can no longer feel it due to the strong centrifugal forces.

### Freefall

Weightlessness can also be observed on Earth for a few seconds - in free fall. A skydiver falls freely for a short period of time before opening his parachute. During this short period of time, as they say in physics, it is weightless. This means that it would be no heavier in the air than any other object that would fall with it. You can try this out by picking up a book and jumping upstairs with it. As long as you fall back to the ground, the book in your hand no longer weighs anything. The moon, which orbits the earth, is practically continuously in free fall because it is attracted by the force of the earth. Due to the strong centrifugal force, however, it does not fall on the earth, but around the earth.

### Parabolic flights

You are probably wondering why you haven't noticed being weightless yet. This is because these moments on earth are usually so short that you cannot feel them so quickly. Researchers use weightlessness to prepare budding astronauts for space and for investigations. That's why they built trap towers to observe weightlessness for a few seconds. Often, however, parabolic flights are also carried out. Airplanes fly steeply upwards at high speed and then fall freely for a few kilometers. The researchers on board then experience the state of weightlessness for 25 to 30 seconds. For a lot of money you can even book such flights as a private person.

### Research makes it possible

It is very important to us that science has these possibilities to conduct research in space. Many solutions and innovations from today have their origins in space research. For example, the aerodynamic design of Daimler's trucks is based on NASA technology. It causes the trucks to have less drag when driving.

But there is another very important thing that would not exist without our satellites, which orbit the earth weightlessly in space: navigation systems. In the meantime, we can use the GPS signals from space to calculate data with an accuracy of one centimeter. This precise data enables the car manufacturer to further develop autonomous driving. This is because GPS technology helps cars drive safely on the roads without a driver.

Image: Daimler AG

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