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Making ripples: another Big Bang theory bites the dust

In March, the team of astronomers working on the Bicep2 telescope announced that they had seen ripples caused by the universe’s inflation. 

Tee time: at some point the universe blew up in size from subatomic to golf ball size. Photo: Getty
Tee time: at some point the universe blew up in size from subatomic to golf ball size. Photo: Getty

The internet can be treacherous to scientists. Anyone can visit the New York Times site, for instance, and remind themselves of the 18 March front-page story “Space ripples reveal Big Bang’s smoking gun”. Now it turns out that, much to the researchers’ embarrassment, the gun misfired.

After its presentation to the world, the team behind what was hailed in various places as “the discovery of the century” submitted their research to a journal, which commissioned independent reviews of the work. The result? A big downgrade. Maybe analysing results using data lifted from a keynote presentation slide posted on the web wasn’t such a great idea.

Before we get into the messy details, here’s a quick recap. Our best theory about the history of the universe doesn’t work unless we shoehorn in a period of “inflation”. During this fraction of a second, the universe blew up in size (for reasons no one knows) from subatomic to golf ball size. This violent expansion would have caused ripples in space and time – known as gravitational waves – leaving an imprint on the cosmic microwave background, the radiation that exists everywhere in the universe.

In March, the team of astronomers working on the Bicep2 telescope announced that they had seen those ripples. The story made the front page of most leading newspapers and physics chat turned to discussing exactly who would be collecting the Nobel Prize. Not any more: those ripples may have been due to nothing but cosmic dust.

The universe is filled with the remnants of exploded stars and other debris. Dust clouds distort the patterns in cosmic radiation in much the same way as inflation’s gravitational waves would. So, if you want to be sure that what you have seen is due to inflation, and not dust, you need to know how much dust is out there.

But we don’t, not really. The Bicep team didn’t, which is why it turned to data captured by a competing team. The European Space Agency’s Planck telescope data hadn’t been published when Bicep’s astronomers were doing their analysis, but it had been presented at a conference. Planck researchers posted their presentation online. Bicep found it and used it to make its initial estimate of how much the gravitational wave signal was due to dust and how much could be attributed to inflation. Unfortunately, that is also why the team has now been forced to backpedal.

Unsurprisingly, the data from the slide wasn’t good enough to make it into a peer-reviewed publication. It is possible that later this year, when more data comes in from Planck and other telescopes, we’ll be in a better position to say whether we really have evidence for inflation theory. For now, we don’t know.

That leaves plenty of time for finger-pointing. Andrei Linde, one of the architects of inflation theory, told New Scientist he hadn’t liked the way the media had hailed the results as a smoking gun. He said the Bicep scientists “maybe . . . were a bit overoptimistic, and claiming the discovery of gravitational waves may have been premature” – but he’s hardly in a position to criticise.

In March, Linde told a New York Times reporter he was “still hyperventilating” days after the announcement. Embedded in the story is a film clip of him toasting the news with champagne. It was posted online by a Bicep team member, and has been viewed a somewhat embarrassing 2.8 million times.