Did force field lead to the Big Bang?

For once, it was a news story that could claim to be cosmically important: the first compelling evidence for the cause of the Big Bang.

Scientists who have spent their careers wrestling with the mysteries of the universe are still hailing the discovery as the biggest advance in cosmology for decades. Yet the reason for their excitement over “B-mode polarisation effects” in the “cosmic background radiation” isn’t immediately obvious. So what’s in it for us?

Simply put, if you’re the parent of small children, you can now give them a better answer to the question: “Where did everything come from?”

It is truly mind-boggling how the answer to that question has changed over the generations.

When our grandparents were children, the best scientific answer was “Search me”. As far as astronomers could tell, the universe just was: infinite in extent, infinite in age, static, unchanging.

That view changed with the First Cosmic News Story: the announcement in 1929 by the American astronomer Edwin Hubble that the universe is expanding.

Even Einstein struggled to get his head around that. His own theory of gravity, General Relativity, had hinted at the possibility of an expanding universe, but he was so wedded to the standard view of a static universe he’d fiddled his equations to get the “right” answer.

That, in turn, led to the First Cosmic Why Question: why is the universe expanding?

One didn’t need to be Einstein to guess at an answer: that sometime in the very distant past, the universe must have been much smaller, and somehow exploded in what one cosmologist jokingly labelled a “Big Bang”.

Obvious answers to cosmic questions tend to be treated with suspicion by scientists, however, and some remained sceptical of the Big Bang theory until the Second Cosmic News Story, which broke in 1965.

Two scientists working for Bell Telephone Labs in New Jersey had discovered that the whole sky is “hissing” at microwave frequencies – and the hiss had exactly the properties expected of the faint radiation left over from the Big Bang.

So it seemed the simple answer to why the universe is expanding was right after all. Around 14 billion years ago, there really had been a cosmic detonation that started the whole process off.

But for a small child, that just leads to another Cosmic Why Question: why did the universe explode?

It is this question that last week’s announcement was all about.

Around 30 years ago, theorists started to sketch out ideas for what could have triggered the Big Bang. They discovered that the laws of physics allow the existence of strange force fields with astonishing powers.

Firstly, they could be anti-gravitational in effect, and capable of expanding the very fabric of space and time.

Second, they could also be extremely powerful, triggering an explosive expansion that allowed the universe to grow from smaller than a subatomic particle to the size of a grapefruit in a trillion-trillion-trillionth of a second.

Known as “inflation”, this expansion could take place faster even than the speed of light, Einstein’s famous ban on such speeds circumvented by the fact it applies only to objects travelling through space, not space itself.

Inflation was such a neat idea that it also triggered an explosion in theoretical work. Yet what it lacked was support from observations of the real universe.

That is what now seems to have emerged, in the form of patterns left in the cosmic microwave radiation by so-called gravitational waves.

Predicted by Einstein almost a century ago, these waves should be generated whenever huge masses undergo violent accelerations – but they’ve never been directly observed.

Given that masses don’t get bigger than the whole universe, nor accelerations more violent than inflation, gravitational waves should have been generated aplenty if there is any truth to the theory.

And now it seems they have been seen – by an international team of astronomers using microwave detectors at the Antarctica.

Known as BICEP (Background Imaging of Cosmic Extragalactic Polarisation), these detectors have been trained on patches of the sky over the South Pole, with the aim of picking up the twist – “polarisation” – in the microwave signals left over from the Big Bang.

The pattern of twisting reveals the distorting effect on the radiation created by the gravitational waves produced by the Big Bang.

While the waves themselves have long since decayed, their imprint should still be detectable – just like the ripples in the sand on a beach long after the tide has gone out.

The scientists started to detect just such a pattern several years ago. Yet despite its huge significance – and the risk of being scooped by rival teams – they have spent the intervening time trying to find boring explanations for what they’ve found.

Last week they felt confident enough to make an announcement, and let other scientists try to tear their work apart.

Early reaction has been very positive, with many experts saying the results are consistent with both the existence of gravitational waves, and the basic idea of inflation.

So can parents now tell their youngsters the answer to the question “Why did the universe explode?”

Well, it might be worth putting them off a little longer.

First, the size of the effect found by the BICEP scientists is stronger than many expected – themselves included. They only became convinced when results from a new set of detectors at the South Pole seemed to confirm the signal size.

Secondly, everyone will feel happier if the results are supported by the findings of a similar study by an orbiting observatory called Planck, built by the European Space Agency.

Expected later this year, these should provide the confirmation needed to convince even the die-hards.

But even then, parents shouldn’t bank on finally being able to put an end to the “why” questions of their offspring at bedtime.

Certainly, if the BICEP results hold up, a good answer to the question “why was there a Big Bang?” will be “because when it was created, the universe was filled with a sort of anti-gravitational force that made it inflate like a balloon”.

Yet for the time being at least, the best response to “So why was there a force-field in the first place?” remains “That’s enough questions – time for bed”.

Robert Matthews is visiting reader in science at Aston University, Birmingham