* They fly around earth in circular or elliptical orbits.
* These satellites are at 900 km height. That is 100 times higher than the highest mountain on earth.
* Up there is still a tiny bit of air which makes slower and slower. But at that height it takes 1000 years until they fall back down to earth. That is more than 10 times the life span of a human.
* We have many satellites and leftover parts of rockets up there in space. But space is also big, so there is rarely the danger of a collision. Most big parts move on paths where they don't hit each other.
* When these two satellites hit each other they will break apart into thousands of small pieces. The satellites fly very fast and the small pieces will be faster than a bullet.
* Some of the small pieces fall back to earth where they will burn in the atmosphere. Other pieces fly away in all directions. Some pieces as tiny as a bullet will hit other satellites and destroy them. Some bigger pieces will rip apart other satellites creating more bullets.
* There is the danger that many satellites are destroyed and millions of small pieces fly around in space.
* When you launch a rocket you must pass through this area with a high danger of being hit by one of the bullets which would destroy the rocket and create more bullets.
* We might have to wait until most of the dangerous debris has fallen back to earth until we can launch rockets again. This could take hundreds of years.
* If we don't clean up space and put more and more waste in orbit we will never be able to leave earth and explore deep space.
* Good night and sleep tight.