In 1998, astronomers discovered something strange about the universe.
It is speeding up, not slowing down as expected under the pull of gravity.
Something is pushing the universe apart faster and faster and astronomers are clueless as to what is causing it.
This mysterious force has been given the equally mysterious name of dark energy.
Astronomers can see its effects by its tug on galaxies.
It is the biggest mystery of them all and it makes up 74 per cent of the universe.
When astronomers try to create a detailed inventory of all the matter and energy in the universe they run into a curious problem — the vast majority of it is missing.
In reality, only four per cent of the matter and energy in the universe has been found.
The other 96 per cent, made up mainly of dark energy and dark matter, remains elusive.
Strange as it may sound, most of the universe made up of stuff we cannot see.
Dark energy is really weird stuff, best thought of as an elastic, repulsive gravity, which cannot be broken down into particles.
Astronomers know what it does, but they do not know what it is.
So far, the greatest achievement with dark energy is giving it a name.
We are really at the very beginning of this puzzle.
Cosmologists estimate the acceleration of the universe started roughly seven billion years ago.
If the acceleration continues indefinitely, the ultimate result will be that all the galaxies we can see will disappear, lost forever beyond our cosmic horizon.
So, what lies beyond space?
Good question. Do you have another? Because this is a toughie.
When we look around us, we take the space for granted.
We know space is the distance between two objects but, what lies beyond is unknown at this stage.
Probably more space?
Astronomers know at the time of Big Bang everything exploded out of a point called singularity.
What most of us do not realise is that at that time there was no space.
There was only this single point in the cosmos and nothing else.
It is difficult to imagine and understand, isn’t it?
David Reneke is a feature writer for Australasian Science magazine and a science correspondent for ABC and commercial radio. Get David’s free astronomy newsletter at www.davidreneke.com