Growing doubts about evidence for ancient gravitational waves don't undermine cosmic inflation, says the theory's co-founder Andrei Linde – and don't let feelings obscure science
Would the detection of gravitational waves from just after the big bang finally prove your theory of cosmic inflation?
If primordial gravitational waves were indeed detected by the BICEP2 telescope, they almost certainly would have been generated just after the big bang. But the media hyped this as the first evidence for inflation. That just isn't true: there has been a lot of independent support. I don't like the way gravitational waves are being treated as a smoking gun.
If we found no gravitational waves, it wouldn't mean inflation is wrong. In many versions of the theory, the amplitude of the gravitational waves is miserably small, so they would not be detectable.
The BICEP2 team used an unpublished map of cosmic dust in the Milky Way to correct for dust in their results. Was this good science?
Criticising this is silly. You have to use all available data. If they had not used this information, that would have been bad science. Maybe, despite the dust correction, they were a bit over-optimistic, and claiming the discovery of gravitational waves may have been premature. But to the best of their knowledge at the time, it was unlikely that 100 per cent of that signal was due to Milky Way dust.
Many cosmologists say the results won't stand the test of time. Do you agree?
I have no judgement about the likely outcome – nature can work either way. But it's a pity that the debate is becoming a bit too emotional. I find the way in which the BICEP2 team has been attacked a bit shameful. At the end of the day, if we put our emotions behind us, everyone will gain.
Will the European Space Agency's Planck satellite mission settle the debate?
In a few months, there will be a big data release from Planck. But there are rumours of an earlier publication of dust-related results – any time now. Planck and BICEP2 are very different experiments, so it will be hard to integrate the results, and even together they may not be 100 per cent conclusive. Most likely, other ground-based experiments are still necessary. But it's a very important first step.
If the finding is verified, what would that mean for the theory of cosmic inflation?
It would be tremendously important, and rule out many versions of inflation. Also, by showing that the gravitational field isn't smooth but quantised, like space itself, it would point toward a theory of quantum gravity, the long-sought reconciliation of general relativity with quantum mechanics.
These observations go back to when the universe was only 10-35 seconds old. Will we ever be able to explain the true beginning?
It's absolutely possible. It took the universe 13.8 billion years to bring us here, and only a century ago did we discover that there's more to it than our own Milky Way galaxy. Thirty years from now, we will have charted the most important features of the observable universe, like seafarers charted the Earth a couple of centuries ago. This is truly the age of the great cosmological discoveries.
This article appeared in print under the headline "Making cosmic waves"
Andrei Linde is a physicist at Stanford University in California. He is a founder of cosmic inflation theory. The apparent detection of primordial gravitational waves by the BICEP2 telescope at the South Pole in March supports the theory