How the universe cast its oldest light on its oldest secret; Scientists offer clues to how the Big Bang made something out of nothing

March 17, 2014 6:37 pm

How the universe cast its oldest light on its oldest secret

By Anjana Ahuja

Scientists offer clues to how the Big Bang made something out of nothing, writes Anjana Ahuja

Fourteen billion years ago, within a monstrously energetic, infinitesimally small fraction of a second, nothingness exploded into everything. For decades, scientists have been scouring deep space for gravitational echoes of the Big Bang, in an attempt to prove key features of the only credible explanation for the origin of the universe.

At a press conference on Monday in Massachusetts that followed a weekend of intense speculation, scientists announced that they had indeed “heard” the echoes – or, rather, seen its effect on light arriving from the edge of the universe. If confirmed, it is a spectacular finding that is as important to fundamental physics as the unearthing of the Higgs boson.

The afterglow of the Big Bang is still detectable in the form of low-level radiation that permeates every corner of the cosmos. This so-called cosmic microwave background was released 380,000 years after the event itself, when the universe cooled enough for light particles to travel uninterrupted across the cosmos. It has been described as the oldest light in the universe.

And this is where scientists have been searching for evidence: namely, a twisting of that oldest light by primordial gravitational waves, created during the early part of the Big Bang called the inflationary phase. As the fabric of space-time billowed out in the first trillionth of a trillionth of a trillionth of a second, the theory of inflation goes, these primordial gravitational waves were generated. The waves had a subtle but indelible effect on the ancient light, polarising it, or twisting it like a spiral. Finding this spiral signature buried in the light arriving at ultra-sensitive telescopes would be like spotting a cosmic birthmark from the earliest growth spurt of the universe.

It is these tell-tale spirals that have been discerned by the BICEP 2 Telescope at the South Pole, suggesting that a crucial pillar of the Big Bang theory – inflation – is now generously supported by experimental evidence. BICEP 2 is one of several telescopes located in Antarctica’s gloriously named Dark Sector Laboratory. This region of the white continent is bone-dry due to the cold and altitude; water in the atmosphere would otherwise absorb the primordial light and all the gravitational secrets buried within.

That made Monday’s announcement at the Harvard Smithsonian Center for Astrophysics all the more convincing – although other teams will want to check its veracity. Professor John Kovac, the head of the BICEP 2 team (the acronym stands for Background Imaging of Cosmic Extragalactic Polarization), said they had delayed publishing their results for a year, to make sure that the curl-shaped signals were genuine gravitational messages from the birth of the cosmos, and not lookalike spirals created by distant light becoming twisted by galactic dust en route to Earth.

The title of the press release, “First Direct Evidence of Cosmic Inflation”, drily conveyed the news that this was the inflationary breakthrough that cosmologists have been awaiting for decades, as well as clear proof that gravitational waves exist. “There’s a chance it could be wrong, but I think it’s highly probable that the results stand up,” said Alan Guth of Massachusetts Institute of Technology, who first predicted inflation in 1980. Many are predicting that he will be in line for a Nobel Prize, possibly along with Andrei Linde, the Stanford University professor, the other surviving big name in inflation theory. Stanford University posted a video of Prof Linde on Monday drinking champagne with Chao-Lin Kuo, a Stanford academic on BICEP 2, who broke the news. Prof Linde, after an initial stunned silence, jokes that he hopes it is not a trick.

Uncovering evidence for inflation – a hyper-expansion at the start of the Big Bang – is a big deal for physics. An initial, rapid, chaotic ballooning, followed by the more leisurely expansion we see today, explains why the universe looks smooth in all directions, studded with a scattering of galaxies. This can only happen with a faster-than-light expansion at the start of the Big Bang, with small irregularities appearing later. These irregularities blossomed into galaxies, including our own, which has found much illumination from the oldest light in the universe.

The writer was named best science commentator at the 2013 Comment Awards