Expansion process.
Just what do the theoretical expansion stages of the universe look like?
you should love watching a kettle boil, or a star form, or a universe expand.
The space between the stars out in the great Cosmos is almost empty. By the standards of reference that we have on Earth, it would be called perfect vacuum. While the normal air contains slightly below one quadrillion of particles per cubic centimetre, the best vacuum that can be achieved in laboratories is about a billion of particles per cubic centimetre. The vacuum in outer space contains from 0,00001 up to less than 1 particle per cubic centimetre, which is far, far better than the best vacuum achieved on Earth.
Note: one quadrillion = 1024 = 1 000 000 000 000 000 000 000 000.
The materia in the inter-stellar space has a name: the Inter-stellar Medium, consisting mainly of hydrogen and helium.
When the condensation of particles exceeds 1 particle per cubic centimetre, we start talking about an inter-stellar cloud. And think now: if the inter-stellar cloud is that empty, then there is no mass inside it then. Both yes, and no..
A cubic centimetre or even a cubic kilometre of inter-stellar cloud contains a very limited number of particles and weighs extremely little. But the inter-stellar space is immense, so immense that the volume is no longer calculated in cubic centimetres or kilometres, but in years of light. And… a cloud of a few hundred cubic years of light will contain an extremely vast number of particles and will have a very substantial mass.
All particles in the cloud attract each other by gravitational force. According to calculations of scientists, a cloud having the mass comparable to the mass of our Sun can be self-sustained in the meaning that the gravitational force will keep it together. The cloud itself is very cold, somewhere around a hundred degrees Kelvin, that is far below -150ºC.
Better yet, check out this Slideshare…..
