Until the 16th Century,

geocentrism was a prevailing theory of what the universe looked like.

Geocentrism is the belief that the Earth,

our home planet,

is at the centre of the universe.

Everything else revolves around us.

This seemed obvious to ancient astronomers,

after all they observed the sun and the moon, the planets and the stars,

to move across the sky as we go forward through time,

just like we do today.

So this must mean that the Earth is in the centre of it all, right?

Wrong!

The earliest geocentric models of ancient Greek

philosophers/scientists/general all-rounders

such as Plato and Aristotle in the 4th Century BC

placed a stationary Earth at the centre

with the planets and the stars moving around us on circles or spheres.

The thing is, the simple geocentric model

couldn't quite explain all that we see when we watch the skies.

For a start, the planets change brightness,

which shouldn't happen

if they're always the same distance from the Earth.

Second, the paths of Mars and Jupiter through the sky

sometimes appear to go backwards for a time,

which shouldn't happen

if they're travelling round in these neat little circles.

Despite this, the theory had such a hold

and astronomers were so convinced by it

that they spent hundreds of years making all sorts of modifications

to try and make the general theory fit.

And as needlessly complicated as it now seems to modern astronomers,

this version of the universe proposed by Ptolemy in the 2nd Century,

was almost universally accepted for hundreds of years.

But not everyone was happy.

As far back as the 3rd Century BC,

Aristarchus of Samos

had suggested that the Sun was in the centre of the universe.

And in the years that followed Ptolemy's work

both European and Islamic scientists

started to question aspects of his geocentric model.

Finally in the 16th Century,

Polish astronomer Copernicus published his model of the universe,

which also put the Sun, not the Earth, at the centre of it all.

This is known as heliocentrism,

and for the first time, mainstream science took note.

Today we know that even heliocentrism doesn't tell the full story.

While the Sun may be at the centre of our solar system,

it is just one of over a hundred billion stars

in our Milky Way galaxy,

which is itself one of over a hundred billion galaxies

in the observable universe.

Not only do we have to contend

with being just one of probably countless planets out there,

modern cosmology tells us that the Earth and our solar system

doesn't even occupy a special place in the universe.

And in fact, it turns out that there is no centre to this universe at all.

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