Since childhood, we have been told that space (or outer space beyond the earth’s atmosphere) is a vacuum. It contains nothing, just nothing. Well, to be accurate, the statement that “space is a vacuum” is technically wrong. It should be put like this- space as compared to earth is a vacuum. Before we delve into the depths of what exactly the space vacuum is, let us first get an idea what vacuum really is.
Basically, Vacuum is nothing. Rather it is a region which has nothing in it. A sealed box which is deprived of any kind of matter (including air) is the true example of a vacuum. Another definition of vacuum which is often used scientifically is that any place or region which has zero pressure is a vacuum. Now coming on to the Space vacuum. Why is the space a vacuum or how the space became a vacuum are some of the questions that have puzzled (and are puzzling) the greatest scientists and astronomers along with their physicist friends since we came to know about the space. But the point here is that space is not a complete vacuum. It has tiny atoms and molecules floating in it all the time. It’s just that the no. of these particles in one cubic meter or any other unit is so bleak as compared to billions and trillions on Earth that it is considered a vacuum. All the mass in the universe is nucleated in stars and galaxies which make up a big chunk of the universe and there is un imaginable amount of empty space between them. This empty space has one or two atoms floating in it, which have detached themselves from the parent star or galaxy, per cubic meter and this makes the outer space a vacuum. Moreover, an atom itself is an extremely tiny particle (of the order 10-20 meter out of which, 99% if again vacuum.
Gravity also has a big role to play in making the space what it is- nothing! Whenever there is a certain amount of matter, the gravitational pull attracts all the matter to each other and thus the region in which it was filled becomes void of anything. This is probably the reason for space to be a vacuum. Another fact is that the Universe is constantly expanding. It started off with an explosion and since then ( which is billions and billions of years in the past) it has been expanding. Thus the interstellar distances have been on the rise which further decreases the chances of it having any matter and the result is the space being a vacuum.
Let us say that one fine morning we found that we are thrown into the outer space, floating amongst the giant stars and their planets (as is the case in some science fiction comics and movies)we would not like that. This is because not only the space being devoid of air will suffocate us but also because of no atmospheric pressure, our bodies will explode due to internal pressure of fluids which cancels out the atmospheric pressure. Thus space vacuum is something but at the same time nothing!