Cosmic microwave background seen by Planck.
Cosmic microwave background seen by Planck.
Ah, I remember it like it was just last spring. The flurry of rumors, the initial shock, the charge of surprise, the sheer delight before a major scientific discovery. Yes, I remember it like it was last spring because — it was.
And now it's all dust.
On March 17, researchers from the BICEP2 collaboration announced they had discovered extraordinary evidence for gravity waves from the barest instants after the Big Bang. It was big, big news — and I remember scrambling that morning to put together a post that captured the excitement the entire physics community was feeling. Before my 6:30 a.m. coffee had cooled, I was at my desk writing:
"It's not every day that a new window on the birth of the universe is thrown open. It's not every day that human beings get the chance to leap into the void and have their conceptions of space and time stretched to the limits. It's not every day that we see the wildest dreams of scientists realized, written into the fabric of space and time and light."
Then, with hopes of poetic flourish I added: "Today appears to be one of those days."
Only, it wasn't.
A week ago, scientists from the Planck satellite team announced results of a study similar to that of BICEP2. Both the Planck satellite and the South Polar BICEP2 telescope are designed to study what's called the cosmic microwave background (CMB). These are fossil light waves (in the microwave band of the electromagnetic spectrum) emitted just 300,000 years after the Big Bang. Since its serendipitous discovery in 1964, the CMB has been the go-to data set for the study of cosmology. It's the gift that keeps on giving, as scientists of every generation since its discovery have learned to tease out more secrets about the young universe from patterns in the CMB light.
What both BICEP2 and Planck were looking for was evidence of ripples in the fabric of space-time from a period much earlier than 300,000 years after the Big Bang. And when I say much earlier, I'm not kidding. The gravity waves, if they exist, would be relics from a period that is an almost unimaginable fraction of a second after the universe began. Most importantly, the gravity waves might tell us about the epic violence of the universe during the period of so-called "inflation" when our little sliver of space-time underwent a brief and insane period of expansion.
Inflation is a critical part of cosmology these days for lots of good reasons and, while there is some evidence that it actually happened, a gravity wave detection would have been considered proof positive. It also would have been much more, allowing physicists to finally begin differentiating between the many different theoretical versions of inflation that have been proposed.
And then there's the multiverse. That's the theory that our cosmos is just one of many universes out there. It might seem like a crazy science-fiction idea, but for many scientists, inflationary cosmology implies exactly that — an almost infinite number of parallel cosmos existing right now as you read these words. For some physicists, like Max Tegmark of MIT, the BICEP2 results pointed strongly to the multiverse's reality. In the Huffington Post that March day, Tegmark said:
"I'm writing this from the Harvard press conference announcing what I consider to be one of the most important scientific discoveries of all time. Within the hour, it will be all over the web, and before long, it will lead to at least one Nobel Prize. ... Today is a great day for most scientists except multiverse skeptics — at least in this particular universe."
Which brings us back to a few weeks ago. After carefully analyzing their own observations for the cosmic microwave background, the Planck team concluded that the supposed signal for gravity waves was, more likely, just emission from dust.
No gravity waves from the first instants of creation heralding (a kind of) proof for the multiverse. Instead, the evidence was pointing to good old, run-of-the-mill dust of the sort that's been floating around the galaxy for the last 10 billion years or so.
So what happened?
Well, on the one hand, this is just a story about how beautifully science works. The BICEP2 team worked their butts off doing the very best job possible obtaining super-high precision data, then completing a super-sophisticated statistical analysis and then, finally, interpreting their results in light of known theoretical models. But Planck, for a number of reasons, had a better view of the CMB than BICEP2. And when the Planck team released their study, the strongest conclusions in the BICEP2 results went away.
And, of course, that is just the way the science cookie crumbles. As Marcelo Gleiser wrote this summer:
"Confusion is an essential part of the creative process. Science is about figuring things out; that usually doesn't include finding the answer wrapped up and ready to go. It's rarely that easy. Amazing claims require amazing evidence. And patience, lots of it."
So there — nature spoke for itself. No evidence for gravity waves yet. Maybe evidence will be found in the future, but for now, sorry, folks.
But there is another side to this story that I'm particularly sensitive about as someone straddling the worlds of doing science and writing about science. The BICEP2 results were announced in a press conference before they had gone through the referee process. That meant the hard-core examination of the data and their analysis had not yet been subject to a peer review by someone (or a bunch of someones) who was not part of the team. It would have been the referee's job to be merciless in his or her criticism, catch potential problems and, hopefully, make the paper better. Peer review is an awesome process and it's one critical reason behind science's powerful capacity for finding the true voice of the world.
Scientists often complain about how the media blow science stories out of proportion or get the details of those stories wrong. But in this case, by press-releasing their results before this full scientific process was completed, the international media machine was engaged by the scientists themselves. Thus stories of Nobel Prizes and cosmos-shattering discoveries flowed in a torrent before the final piece of foundation had been laid for those very, very public claims. And while, of course, everyone was careful to include "if these results are confirmed," the point is — within weeks — people were already noticing problems with dust and the BICEP2 results related to dust.
We live in a crazy time when it comes to science and the public, as the ongoing "debate" about climate change shows us again and again. In light of that unfortunate reality, we scientists should be very attentive to showing people exactly how the scientific process works — and why it works so well (as in the end it did here). There was nothing wrong or malicious with the press-releasing of the BICEP2 results. But in this case there was no reason not to let the referee process do its work, for it would have spared the public a cycle of frenzy that was not yet warranted.
As a scientist who spends a lot of time explaining science to the public, I just wish the BICEP2 press-released team had waited. I wish they'd have let the usual scientific process run its course before they made such a grand announcement. If they had, odds are, it would have been clear that no such announcement was warranted — at least not yet — and we'd all be better off.