23. KUIPER and OORT BELT

Space explorations leads us to the conclusion that space in our solarsystem is awesome empty. Distances to the sun vary from 50 million to 6 billion km, that means that in a ball volume with radius of 6 billion km the planets are completely negligible with respect to their part of the content, neither have asteroids any significance, their mutual distances are millions of kilometers.
Thus empty, nasty empty!
But still there are the KUIPERBELT and the OORTCLOUD, comprising numerous comets. Are they filling up space perhaps a bit more? Let's have a look.
Kuiper has calculated that between about 50 AU and 500 AU ( "Astronomical Unit" with 1 AU = 150 million km) there is a belt with a very large quantity of ice bodies. That belt is considered as to be the birthplace of "short-periodic comets". It is estimated that there are 35.000 of such comets larger than 100 km, the rest, a 100 to 200 million comets, are all smaller or very small. Neptune has a strong influence on all those smaller ones if coming in its neighbourhood, which then are swung into far space or are found back in orbits between the other planets, even inside the inner part of our solarsystem. A rough calculation tells us that all those comets still have on average mutual distances of billions of kilometers.
The OORTCLOUD is also result of very accurate calculations, based on the orbits of 19 comets, by another famous Dutch astronomer: van Oort. It concerns a spherical cloud around the whole planetsystem on a distance of a bit less than a trillion km (= 10^12 km) up to more than about one lightyear ( = 10^13 km). He estimated the content of that cloud on a trillion comets, but that means that the distance between the comets are billions of kilometers on average if you confine the comets into a shell of 10^11 to10^13 kilometers thick.
Conclusion: we cannot deny that space in our planet system is empty, it remains an unbelievable "nothing"!
The difference with the Kuiperbelt is the orbit of an object: these orbits lay in completely ad random planes not making small angles with the plane of the planets, as do orbits in the Kuiperbelt.
The OORT cloud is considered to be the source of long-periodic comets. It is unknown how these clouds have been created, but it is for sure that they are remnants of the original nebula from which the solar system evolved.