Models of the Universe

We may never know how the universe came into existence or even what the universe is, however we can make pretty good, evidence-based guesses.

What are our models?

Since about the beginning of the 20th century, there have been two main models of our universe. The first, the Steady State theory, suggests that the universe is infinite and constantly expanding with matter being created continuously. The other, the Big Bang theory, suggests that the universe is finite with a finite amount of matter, all originating from a singularity (incredibly dense point).


Image of galaxies, moving away as shown by the general red colour

What evidence do we have for the Big Bang theory?

The observations we have taken over the last century point towards the Big Bang theory being the correct model. The main pieces of supporting evidence are:

  • Most galaxies appear redder than they should and so are moving away so the space between must be expanding.
  • The universe is mainly made up of hydrogen and helium, whereas in the Steady State model, where the universe has always been here, the hydrogen and helium would already have been made into other elements.

James Gooding, 2017

All image credits go to NASA (and respective centers/universities)