Cutting-Edge Science or Pure Fantasy? Sometimes It’s Hard to Tell
(Bloomberg Opinion) -- If physicists are not badly mistaken, a new kind of observatory is endowing humanity with the ability to “hear” ripples in space. We're told that these ripples, called gravitational waves, are emanating from a dramatic series of collisions between black holes, and one between two burned out stars made of material so dense that a teaspoon made from it would weigh a billion tons.
Scientists this week announced four new collisions, making a total of 11 since 2015. When black holes collide, they can give off, for an instant, more energy than all the stars in the known universe combined. With our universe such an active demolition zone, it’s probably a good thing that “hearing” is strictly an analogy.
But what if the physicists are wrong? Some critics have floated the possibility that the researchers are misinterpreting the signals from their detectors — twin instruments in Louisiana and Washington state, collectively known as LIGO, joined more recently by a third, called Virgo, in Italy. One group, led by physicist Andrew Jackson of the Niels Bohr Institute in Copenhagen, has used LIGO data to try to replicate some of LIGO’s early results. The group found they couldn’t.
That failed replication led to a cover story in the magazine New Scientist under the headline “Exclusive: Grave doubts over LIGO’s discovery of gravitational waves.” The story was not necessarily so grave, however. One of the strengths of physics is that this kind of cross checking is normal. In social science and some areas of biology, it’s been traditional for papers to enter the scientific literature without independent verification. That’s led to the unhappy discovery of a “replication crisis,” with follow-up studies in those fields calling into question as much as half the published literature.
Physics has had its share of blunders, many of them back in the early and mid-20th century, but since then, physicists have gotten in the habit of verification. Bad results often get exposed within weeks of initial publication. And so the science can build upon itself. We don’t have to assume, for example, that black holes exist even though we can’t see, hear or smell them.
Back in the early 1990s, I wrote a story for Science called “How to Find a Black Hole,” which explained how, if black holes indeed existed, they would exert gravitational force and could move objects around them in such a way that scientists could infer their locations and masses. Now there’s a whole catalogue of them.
It’s one thing to observe the way invisible objects move visible ones, but now we’re talking about invisible collisions between invisible objects sending out invisible waves. Is this getting too far from reality? To find out, I called LIGO physicist Neil Cornish, of Montana State University. He’d been quoted in the New Scientist story talking about the failed replication.
He said he and his colleagues have taken those criticisms seriously. They’ve looked at the Danish group’s calculation and figured out why it differed from their own. It doesn’t call into question any of the 11 published detections, he said.
Another criticism in the New Scientist story was that some of the LIGO group’s detections rely on a sort of template — a theoretical picture of what a black hole collision would look like, against which they compare their data. When they subtract what they think is a signal, they should be left with noise. That, so the critics charged, would limit them to finding only what they expect to see — and perhaps put them at risk for confirmation bias.
But they also analyze their data with methods that rely on different theories, or don’t rely on pre-conceived models in the first place, Cornish said. “We’re a large collaboration and there are multiple semi-independent groups within the collaboration that used really quite different methods.”
And so they are moving on from detecting gravitational waves to using them to observe the cosmos. “We’d like to see a neutron star get torn apart by a black hole,” he said. Then there’s the possibility of detecting weird effects from spinning black holes, including what he called a space-time tornado. And then there’s the hope they will find something completely unexpected.
Could this all be illusory? As time goes on the odds get lower. MIT physicist Scott Hughes, who is not part of the LIGO collaboration, said that the data have always been available and that now the collaborators are planning to offer tutorials in how they did their analysis. There’s always a risk of being wrong in science, but less so when there’s ample opportunity for outside criticism and double checking.
As more of the obvious, easy things in the universe are discovered and studied, scientists are forced to resort to ever more indirect, difficult kinds of observations. Beyond the risk that LIGO wouldn’t work, there was also a risk that the kinds of phenomena powerful enough to set off its detectors didn’t exist. But if these results are not a grand illusion, we can conclude that there’s a lot more to the universe than meets the eye.
This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.
Faye Flam is a Bloomberg Opinion columnist. She has written for the Economist, the New York Times, the Washington Post, Psychology Today, Science and other publications. She has a degree in geophysics from the California Institute of Technology.
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