Meteoroids

Most of them are small, but...

A meteoroid is any of the small bodies that travels through space. They are often remnants of comets. A comet is a body that is moving about the Sun. A meteoroid hitting the Earth is called a meteorite. Meteoroids are hitting the Earth all the time, many times a day. Most of these are very small, maybe smaller than a grain of sand. If they are big enough, they will not be totally burned up in the Earth's atmosphere, and they will become a meteorite. Normally a meteoroid is not bigger than a few hundred meters in diameter.

When will the big one struck us?

The big danger is if a huge meteoroid should happen to crash with the Earth. Statistically a big meteoroid will hit the Earth once in a while. It has happened before, and will happen again. The question is when? The answer is hard to give. Maybe we can get a warning a few years before it is hitting the Earth, but that will give us way too little time to react if we are not already prepared.

Maybe the biggest menace for the humankind!

If the meteoroid hitting the Earth is big enough, it may be a threat towards the Earth and the humans living on it! Maybe this is the only accident that can destroy the humankind within the next 2-3 thousand million years. (After that the sun will boil us, read the section about the Sun expansion.)