The Centre of Attention

Fact: The Earth is at the centre of the universe.

Remember when the church argued that the Earth was the centre of the universe? Turns out, if you look at the physics in a certain way its hard to argue with them.

The universe is constantly expanding, so galaxies are constantly getting further and further apart. If we look out into space in any direction, everything is moving away from us, which means that here on Earth we are – in one sense – at “the centre of the universe”. Of course there is nothing special about Earth – since the entire universe is expanding, you could stand at any point in space and everything would be moving away from you in all directions. Therefore it’s not just Earth but everywhere that could legitimately be called the centre of the universe.

Of course, we aren’t actually the centre of the universe in the traditional sense. The centre of a circle is defined as being midway between the outer limits of that circle – without those limits, we cannot define a point as the ‘centre’. The universe is infinite (without limits) and therefore it cannot have an overall centre.

Everything rushing away from us in all directions is an effect of being at the centre of our ‘local universe’. Think about it in terms of an inflating balloon. If you are on the surface of that balloon, as it stretches it appears that everything around you is moving away – and therefore you are at the centre of your local universe. The 3D balloon has a centre point inside the balloon, but the 2D surface of a balloon doesn’t itself have an overall centre point.

The universe is simply a 4-dimensional version of that balloon. The 2D surface of the balloon corresponds to 3D space in our universe. The inflation of the balloon, which drives everything to move away from everything else, corresponds to the passage of time – our fourth dimension. Therefore, the ‘centre point’ inside a 3D balloon is the equivalent of the ‘centre of time’ in our universe – otherwise known as the Big Bang, when time began. However, because our 3D universe is curved like the surface of that balloon, it has no centre point in space.

So depending on your perspective, either the universe has no centre or everywhere is the centre of the universe. A real life paradox.

‘Another one of Mr Shaunak’s Little Bites of Science’
Image under Creative Commons License, taken by J. Emerson:
https://commons.wikimedia.org/wiki/File:Screenshot_from_IMAX®_3D_movie_Hidden_Universe_showing_the_Helix_Nebula_in_infrared.jpg

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