It seems that the matter from which the stars, planets and human beings are formed makes up only a tiny part of the universe. Research into cosmic background radiation has shown that our cosmos consists of 74% dark energy, 22% dark matter and only 4% so called ‘normal’ matter. Dark matter holds galaxies together; without the gravity it provides, their rotation would cause them to fly apart. However, so far no one has been able to find out what dark matter consists of.
Dark energy is even more mysterious. It is thought to cause e the expansion of the universe to accelerate. It may be that dark energy is a kind of inner tension within space. Dark energy may one day cause the expansion of space to become so rapid that all matter will be torn apart. If true, such a catastrophe is only likely to occur more than 100 billion years from now- so we don’t need to start worrying about it just yet.