Why satellites do not fall from the sky?

Why satellites do not fall from the sky?

The summer vacations have finally begun and many of us are taking off for our vacations by car. We travel hundreds of kilometers to enjoy the sun on the beach, for example. But the far away vacation destination is sometimes not so easy to find. That's why some people use a navigation system that knows the way to their vacation. Such a smart companion can be really useful.

However, the navigation system only knows the correct route with help from space. Because up there, far above us, satellites are flying, telling the navigation system the right route to take.

Launching with a rocket
"The word satellite comes from latin, the language of the ancient romans, and means 'companion'.", explains doctoral student tobias beuchert. Satellites fly around the earth in their orbit. So the satellites accompany the earth.

In order to reach this orbit, the satellite must be shot away from the earth with a rocket at a very rough speed. If the rocket starts too slowly, it will fall back to the ground. "This is due to the so-called gravitational pull of the earth", female tobias beuchert.

You have surely noticed this many times. For example, if you knock an object off a table, it falls to the floor. Even if you throw a ball high and as hard as you can towards the sky, it will fall back to the earth in a high arc.

But now imagine a spaceship that has managed to overcome the earth's gravitational pull and has gone on a journey. Now it flies out of space straight towards the earth again and brakes shortly before it comes to a standstill. Earth's gravitational pull would ensure that the spaceship would simply fall to the earth. "For that not to happen, you need an opposing force", clarifies tobias beuchert.

Attraction and centrifugal force are equal roughly
Overcoming earth's gravitational pull alone is not enough. The opposite force could be, for example, rockets, which are constantly fighting against the earth's gravitational pull. But that would be far too expensive.
It is much easier to use the so called centrifugal force.

You can imagine it like this: if you tie a stone to a string and throw it around, the string will rub at some point. Responsible for this is the centrifugal force acting outwards. If these two forces, gravitational attraction or gravitational force, are the same, they are the same and centrifugal force are equal, then the satellite can always move on the same orbit. As soon as a force becomes stronger, it sinks closer to the earth or moves further away from it.

"A satellite flies at a speed of about seven kilometers per second in a typical orbit at a height of a few hundred kilometers to maintain an equilibrium of forces.". For comparison: a human walks an average of five kilometers per hour. Of course, it often happens that the earth's gravitational pull is stronger and the satellite comes close to the earth.

Satellites are slowed down
One reason is that some satellites fly through a very high part of our atmosphere. This will slow them down. Because the air that surrounds us and also satellites in higher layers is anything but empty. Let's take our stone on a string again as an example. If the stone is slowed down by auben, then it will not pull so hard on the string anymore.

For this the scientists have given some satellites rockets on board, which they can ignite in order to become faster again.

But when a satellite is no longer needed or has no more rockets to accelerate, it falls to earth. Don't worry – the satellites won't fall on our heads anyway. The earth's atmosphere, the gaseous envelope around the earth, is so dense that the satellites are exposed to strong friction and simply burn up. We don't really notice any of this here on earth.

If a satellite does not burn up completely we still do not need to worry. The scientists can drop the remains of the satellite into the sea in a controlled manner, for example.

For television and weather
By the way, satellites are not only needed for a navigation system. They also transmit signals for television, photograph and study other celestial bodies, or determine the weather.

Astrophysicists, i.E. Scientists like tobias beuchert who study space, use satellites to explore the universe far beyond our solar system and the milky way, our home galaxy.

For example, they point telescopes at distant galaxies. With them they explore above all the rontgen light, which is much more energetic than the light visible to us.

Satellites for a view of the universe
This "strong" light cannot penetrate our atmosphere, and that is a good thing. "That's why satellites are so important, so that we can get a clearer view of the universe, explains beuchert.

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