If a candle is lit and a glass put on top of it, the light will extinguish.  Why?  The fire extinguishes because it runs out of oxygen and fire needs oxygen to burn.   It is a demonstration of how a vacuum might work.  A vacuum is supposed to be devoid of oxygen and all matter.  How, then, one may ask,  does a spaceship burn fuel in outer space which is called a vacuum?  How can this paradox be explained?  It can only be explained if space is not a vaccum.  Does space contain similar gases to those found on earth but in much lower concentration?  When you climb to the top of a mountain, they always say the air is thinner at the zenith.  How much more so would that hold true outside Earth’s ozone layer?  The ozone layer acts as a bubble to maintain Life and the atmosphere which makes it possible.  Once, you leave Earth’s atmosphere,  the natural gases found on Eath will be at much lower concentration in outer space.  Yet, there is enough atmosphere in outer space to propel a spaceship.  That way, intergalactic travel is possible. 

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