Exactly one year ago today came stunning news out of Cambridge, Mass., at a news conference at Harvard: Astronomers had discovered gravitational waves emanated in an inflationary spasm at the dawn of time. It’s hard to overstate the stunning nature of this announcement. This was a direct detection of quantum gravity at work in the initial fraction of a second after the birth of the universe. It supported the theory of cosmic inflation, which explains why the universe looks the way it does.
The cosmological signal was, the scientists said, right there in the sky, in the microwave background radiation. They had measured the polarization of the CMB caused by the gravitational waves generated in that initial inflationary upheaval. The astronomers had detected this by going to the end of the Earth, literally — the South Pole. They used a telescope as part of an experiment called BICEP2. The announcement led to front-page stories around the world, including my story in The Post.
But then the great discovery started to fall apart. As I reported last May, other scientists felt that the BICEP2 team had overstated its case. The problem was that the BICEP2 team had to account for the presence of dust in our own galaxy, which also produces polarized light. The BICEP2 scientists used the best data available to estimate the amount of dust and concluded that, even if some of what they were seeing was caused by dust, they still had a robust cosmological signal. But then new data from the European Planck satellite showed that there’s a lot more dust in that part of the sky than the BICEP2 team had realized. After peer review, the BICEP2 team had to revise the initial scientific paper to acknowledge that the entire “signal” might be caused by dust.
There was no discovery in any scientific sense — just a lot of tantalizing but ambiguous data. Did BICEP2 see gravitational waves from cosmic inflation? Maybe. But this is not a business in which maybe is good enough.
Last month I visited one of the BICEP2 leaders, John Kovac, at his office at the Harvard-Smithsonian Center for Astrophysics, and, despite going through a very rough year, he remains upbeat and optimistic that he and his colleagues can resolve the mystery. They’ve got a new instrument at the South Pole, the BICEP3 telescope, and are continuing to sort through data from a number of experiments.
“We’re very far along in the next analysis of the next data set. It’s going to be much more powerful,” Kovac told me.
This is a man who has devoted his professional life to South Pole astronomy, making 24 trips there, each as arduous as you can imagine (fly to New Zealand, then to the McMurdo station on the Antarctica coast, then to the South Pole). In his early 20s, he overwintered at the South Pole, spending 14 months straight at the bottom of the world. In the early 1990s, South Pole astronomer was a much more rugged affair with primitive equipment and a lot of exposure to the elements. He showed me a photograph in which, dressed almost like an astronaut, he’s climbing onto a telescope with a giant tank of liquid helium on his back. This kind of astronomy requires very cold instruments, which is why he has spent two decades lugging liquid helium to the South Pole. As he puts it, the South Pole just isn’t cold enough by itself.
It’s safe to say that if Kovac and his colleagues can’t detect the signal of cosmic inflation, it won’t be for lack of trying.
I asked if the new observations will tell us whether there really are cosmological signals in the CMB, or just polarization generated by dust.
“That’s going to depend on what the universe has to say,” he said. “The power of our data is going to keep getting better.”
He understands that it’s a big deal if the signal is cosmological, but he won’t let that color his interpretation of the data: “I’m not invested in any particular answer here. I think as an experimentalist that’s the right attitude to take…You’ve got to be really strict and say, whatever the universe says, I’m going to be equally happy. It’s probably going to be a more spectacular answer than whatever your notions were going in.”
He doesn’t worry that we’re going to run out of big cosmological discoveries.
“The universe is never going to stop being generous and offering us new frontiers,” he said, but added. “It’s possible that our curiosity will run out, and that will be tragic.”