The ever-expanding debate on universe expansion theories

Astronomers have recently found that the universe is expanding at a rate about 10 per cent faster than previously thought but the debate on accurate information continues to rage.

A Nasa Hubble Space Telescope view of the spiral galaxy NGC 4603, the most distant galaxy in which a special class of pulsating stars has been found. Jeffrey Newman, University of California at Berkeley and NasaShow less

From the global economy and the climate to the cost of living, nothing is doing what it should. Now the entire universe seems to have joined the club.

Like the pace of life on earth, it seems to be speeding up. And no one knows why.

Astronomers have long known that the universe is expanding, propelled by its explosive birth in the Big Bang about 14 billion years ago.

The discovery of the cosmic expansion was a revelation that wrong-footed even Albert Einstein, who in common with everyone else thought the universe was infinite and unchanging.

Then in the late 1990s, a second shock arrived, in the form of evidence that the universe was not merely expanding, but doing so at an ever-increasing rate. This blew apart the view that the fate of our universe was dictated simply by the force of gravity. Another, anti-gravitational, force was needed to explain the accelerating pace of the expansion.

That force has been dubbed Dark Energy, a name as enigmatic as its source. It seems to emerge from the very interstices of space and time, creating a force that has proved even more potent than gravity on cosmic scales for billions of years.

That was a discovery so radical that it prompted the award of Nobel prizes to the astronomers responsible, among them Adam Riess, of Johns Hopkins University, Baltimore.

Now Professor Riess may have uncovered another twist in this mind-boggling tale.

He and a team of a dozen colleagues have now published evidence that there may yet be another influence on the cosmic expansion – one that is causing it to accelerate even faster than Dark Energy can manage.

In findings just submitted to the Astrophysical Journal, the team uses studies of relatively nearby galaxies to deduce that the cosmos is now expanding about 10 per cent faster than expected.

That might not sound a big difference but the observations are precise enough to make mere fluke an unlikely explanation.

Certainly Prof Riess thinks the effect is real. “I think that there is something in the standard cosmological model that we don’t understand,” he told leading research journal Nature. Professor Kevork Abazajian, a cosmologist at the University of California, Irvine, agreed, describing the finding as potentially “transformational”.

Yet astronomers know only too well how the universe has played nasty tricks on those with the temerity to uncover its mysteries.

And none of them is deeper than the nature of forces that drive it.

Isaac Newton glimpsed this when applying his own theory of gravity to the universe. In correspondence with fellow scholar Richard Bentley in 1692, Newton realised that if gravity were the sole force, the universe would be unstable. Just the slightest bit of lumpiness would lead the universe to collapse on itself.

Over two centuries later, Einstein ran into strikingly similar problems. His own theory of gravity, General Relativity, also refused to give a stable, static universe. His response was to fiddle with its equations to extract the “right” answer from them.

When astronomers later discovered the universe wasn’t static, Einstein realised he’d missed out on making his greatest-ever scientific prediction, which he allegedly later viewed as the greatest blunder of his life.

Ironically, the discovery of Dark Energy showed that Einstein’s equations did need a “fiddle-factor” after all, to boost the effect of gravity. But it’s not just theorists who have come unstuck pondering the cosmos.

When astronomers first measured the rate of cosmic expansion, the results implied that the Big Bang occurred 1.8 billion years ago. By the 1950s, it was clear this could not be correct, as radioactive dating methods showed that the Earth was far older still – an obvious absurdity.

For decades afterwards, astronomers tried but failed to get a definitive result for the rate at which the universe is expanding – and thus its age.

The breakthrough finally came in the 1990s, with satellite studies of the heat left over from the Big Bang.

Analysis of its strength and spread allowed astronomers to work out the expansion rate and age of the universe with unprecedented precision.

The current best estimate is that the Big Bang occurred 13.8 billion years, give or take just 20 million years.

Ironically, that astonishing precision is now at the core of the latest cosmic conundrum. That’s because the satellite data is very hard to square with the results found by Riess and his colleagues.

They have measured the expansion rate of the universe in more recent times, using exploding stars in galaxies relatively close to us.

In theory, it’s possible to work out the distances to these so-called Type 1a supernovas by recording how their light fades. Combined with measurements of the speed of their galaxies, the result is an estimate of the cosmic expansion rate.

Riess and his colleagues wanted to boost confidence in this method by cross-checking it with a similar technique using pulsing stars known as Cepheid variables. Like the supernovas, their distance can also be estimated from studies of changes in their brightness.

The good news is that the team succeeded in doubling the number of galaxies whose distances are now known using both methods.

The trouble is, the resulting figure for the cosmic expansion rate is higher than that found by the ultra-precise satellite data – so high, in fact, it’s hard to dismiss as a mere fluke.

As ever, theorists have proved able to supply all kinds of weird and wonderful explanations.

Some suggest Dark Energy – whatever it is - might simply be getting more powerful over time. Others think something called Dark Radiation may be needed to explain the mis-match.

Are we about to see a revolution in our understanding of the universe? Cynics would point out we’ve been here before.

The debacle over the ludicrously short age of the universe was traced back to faulty understanding of Cepheid variables – the very same type of stars now used by Riess and colleagues. While far more is known about them now, there are still concerns about their reliability as a measure of distance.

Riess and his team plan to get to the bottom of the mystery using new data from orbiting observatories.

The smart money is probably on the discrepancy fading away but only a fool would bank on there being no more Nobel prizes in the quest to understanding the cosmos.

Robert Matthews is Visiting Professor of Science at Aston University, Birmingham. His new book “Chancing It: The Laws of Chance and what they mean for you” is out now.