For a while it looked like the biggest science story of 2014. But those elusive waves from the Big Bang have bitten the dust – literally.
Scientists working with the European Space Agency’s Planck satellite have overturned a widely publicized claim made by another group of researchers last March about the origin of the universe.
That earlier result, based on data from an experiment called BICEP2, involved the apparent observation of ripples in the fabric of spacetime that were created when the universe was less than a fraction of a second old. The ripples, known as gravitational waves, were touted as direct evidence that the universe underwent a period of rapid inflation during its initial moments – a finding that offered a spectacularly important clue to the origin and nature of the cosmos and an obvious candidate for a Nobel Prize.
Only it isn’t.
“There’s no way of putting it other than the original claim was wrong,” said Neil Turok, a theoretical cosmologist and director of the Perimeter Institute in Waterloo, Ont., who is not a member of either team.
The latest analysis shows that last year’s breakthrough finding can be accounted for entirely by microscopic dust grains adrift in our own Milky Way galaxy. The grains are caught up in the galaxy’s magnetic field, which causes them to line up in an organized fashion. When so aligned, the dust can mimic the signature of gravitational waves from the early universe.
The result does not rule out the existence of gravitational waves – telltale evidence of the inflation scenario – but it means they can only be at a level that would keep them hidden from BICEP2.
“There could still be a signal that is half of what they claimed lurking in the data,” said Douglas Scott, a cosmologist with the University of British Columbia and a member of the Planck team.
Both teams were involved in the effort, which combined Planck’s global view of the heavens with data from BICEP2 and a third experiment called the Keck Array. The re-analysis has been submitted to the journal Physical Review Letters.
Where all of this leaves the field is a matter of opinion.
Broadly speaking, the finding is not a blow to the Big Bang theory, the well-supported idea that the universe began in a state of high temperature and density 13.8-billion years ago and has been cooling and expanding ever since. But it leaves open the question as to which particular version of the theory best corresponds to observation.
The majority of cosmologists support the inflation scenario because it accounts for many of the features of the universe as we know it. But others, including Dr. Turok, favour alternative explanations that would be ruled out by the detection of gravitational waves from the early universe.
In the short term, the result means Dr. Turok will not have to pay the $200 claimed by celebrated Cambridge University physicist Stephen Hawking after the two bet on whether gravitational waves from the early universe would be found at a level that can be detected by Planck. Dr. Turok bet against the the waves.
More seriously, the new result means that only those versions of inflation theory in which gravitational waves are too muted to appear in the existing data are viable. The next few years will be especially telling, as a host of new detectors, including SPIDER, a balloon-borne experiment partly built at the University of Toronto, weigh in on the question.
Meanwhile, Dr. Turok said, this week’s news offers a cautionary tale for other experimental teams: “Don’t be too hasty in your claims about the universe – there’s nothing bigger at stake in science.”Report Typo/Error