The cosmological constant theory is centred around the energy density of space – known as vacuum energy – that arises in Einstein’s general relativity, providing a unified description of gravity as a geometric property of space and time. Einstein originally introduced the concept in 1917 to counterbalance the effects of gravity and achieve a static universe, a notion which was the accepted view at the time, but the German physicist abandoned the theory in 1931 after Edwin Hubble’s discovery of the expanding universe. But he may have been right all along after a scientist discovered in 1998 that the universe is not only expanding but accelerating at a rapid rate, implying the possibility of a positive nonzero value for the cosmological constant, as hypothesised by Einstein.
Professor Brian Cox revealed in his two-part film, “Life of a Universe” how the saga unfolded, leading to what scientists now refer to as “dark matter”.
He said in 2017: “Science has a habit of opening up new possibilities, often when you least expect them.
“We’ve known our universe is expanding since the Twenties when we thought the expansion rate was slowing down.
“Then, in the late Nineties, it was discovered that the expansion rate of our universe is actually speeding up.
“Nobel Prize winner Brian Schmidt was as surprised as anyone by his discovery.”
Dr Schmidt explained how he thought he had made a mistake by possibly proving Einstein was right all along.
He added: “In 1998 we went through and measured everything and found out the universe wasn’t slowing down at all, it was speeding up.
“It looked to me like a big mistake and I had somehow wasted three-and-a-half years of my life getting some nonsensical answer.
“We knew that Einstein had invented something called dark energy, or the cosmological constant, that makes gravity push, rather than pull, but that seemed pretty crazy.
“But it’s not the only theory about how our universe could end.”
But, Professor Cox also had an alternative theory.
He continued: “The heat death, this idea that the universe just grinds to a halt and carries on expanding forever is a bit miserable, but the physics of the far future is not very understood, so there are other possibilities.
“Cosmologists have come up with an even more devastating idea, called phantom dark energy, which eventually leads to the universe ripping itself apart.
“The Big Rip idea can be combined with a theory we have describing the beginning of our universe, known as inflation.
“This describes a time before the Big Bang when our universe was expanding extremely rapidly.”