Scientists know the universe is expanding and that it has been doing so since the Big Bang 13.8 billion years ago. But there are several knowns and unknowns regarding the universe’s expansion. Perhaps the key unknown is what exactly the universe is expanding into – the observable universe is the part of the cosmos which experts are able to see, an area with a diameter of approximately 93 billion light-years.
Beyond that, scientists have no idea. Another seemingly intractable question is that depending on your perspective on the universe, everything else seems to be moving away from you.
Here on Earth, it looks as if all the other galaxies are moving away from us as if we are the centre of the universe.
However, if you were on a planet in the Andromeda galaxy – the Milky Way’s much larger next door neighbour –it would seem that everything is moving away from you, and that would be the centre of the universe, to you at least.
This expansion is linked to something known – or indeed not known – as dark energy.
What exactly dark energy is has kept scientists stumped since it was theorised in 1980 as a sort of anti-gravity, pushing galaxies farther and farther away from each other.
Why this is, no one knows, and why scientists cannot agree on the pace of the expansion also remains a mystery.
However, one physicist has suggested that an undiscovered particle which is “lurking” in the background could be the cause of the ever changing pace of the universe’s expansion, and it has been there since the dawn of time.
Theoretical physicist Massimo Cerdonio at the University of Padova believes these particles are axions – particles which are about 500 million times lighter than electrons.
The particles seem to exist in a quantum field which is somehow responsible for the changes in dark energy.
Mr Cerdonio argues that the particle is already out there, and while it has never been detected, it is a boson particle – an entity which interacts with the forces out there.
READ MORE: Big Bang: Scientists ‘won lottery’ using Hawking’s ‘key clue’
As previously stated, the cosmos has been constantly expanding since the dawn of time and once there is absolutely nothing left and as dark energy overtakes the effects of gravity, the universe to expand at a quicker and quicker rate, until its pace reaches the speed of light.
Entropy, which essentially dictates the order of molecules making up the universe, stops as there is nothing left to play with.
However if it is the case that the end is nearer, it still will not happen for trillions of years.