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"Big Bang Signal" Could All Be Dust
An anonymous reader writes Scientists have shown that the swirl pattern touted as evidence of primordial gravitational waves — ripples in space and time dating to the universe's explosive birth — could instead all come from magnetically aligned dust. A new analysis of data from the Planck space telescope has concluded that the tiny silicate and carbonate particles spewed into interstellar space by dying stars could account for as much as 100 percent of the signal detected by the BICEP2 telescope and announced to great fanfare this spring. The Planck analysis is "relatively definitive in that we can't exclude that the entirety of our signal is from dust," said Brian Keating, an astrophysicist at the University of California, San Diego, and a member of the BICEP2 collaboration.
Which sounds hard, because what can you measure changes in besides the light, which would be affected by magnetic dust?
The spectral shape of the dust signal and the CMB signal are different, so multi-frequency analysis can be used to tease out the various effects. There are various technical reasons the BICEP2 team chose a single frequency (150 MHz) but additional measurements at different frequencies (353 MHz is mentioned in TFA) would allow untangling of the two, albeit with some loss in sensitivity. This sounds like the approach that will be taken in future by various teams investigating this.
The BICEP2 team got bitten by designing their experiment around a flawed theoretical understanding of the dust distribution in our galaxy, which is too bad, but this is the way science works: we publicly test our ideas, and let others see if what we've done can stand up to scrutiny. I've worked on experiments in the design phase where the design team has missed important backgrounds: it's easier than you'd think. And I once worked on an experiment that had been taking data for two years before it was found that there was a background process that precisely aped the signal (it had been missed originally because of a dropped sign in a calculation that caused two terms to nearly cancel when they should have added up.)
In the best case we find these sorts of things before we publish. In the worst case--such as this one--after.
Blasphemy is a human right. Blasphemophobia kills.
I'm an "old earth" creationist. The Earth is obviously old. But I do beleive in a Creator. Science shows us several things in this regard.
- The universe did not come from nothing. Thermodynamics prevents this.
- The universe did not create itself. Thermodynamics prevents this.
- The universe was created by an intelligent Creator is the sole, logical conclusion.
God for me is faith. Science still can prove, one way or another, the origins of the universe with science. Science is a useful tool given to us by God via our increased knowledge as we grow as a species. God and science go hand in hand. One cannot exist without the other.
The Planck dust measurement in pretty damning, but it is not the final word.
(1) Planck measured the dust contamination with greatest sensitivity at 353 GHz. It was not sensitive enough to measure the dust signal at 150 GHz, where BICEP was observing. They had to extrapolate the dust contribution from the higher frequency to the lower. This is actually a pretty big extrapolation, since the dust emission at 150 GHz is less than 1% of the dust emission at 353 GHz.
(2) The uncertainty in the dust emission amplitude is still pretty high, so the Planck measurement is consistent with an "all dust" model, or with a "mostly dust" model, or with a "mostly primordial, with some dust" model. It does pretty conclusively rule out a "no dust" model.
(3) They have not released the results of a joint analysis of Planck and BICEP2, which is what is necessary to actually shed some light on exactly how much of the BICEP2 signal is likely to be dust.
But it's clear that the BICEP team was being over-optimistic in their assumptions about galactic dust, which is a bummer.
There seems to be a lot of confusion about this article.
The dust only accounts for the swirl patterns in the cosmic microwave background (CMB), not the CMB itself. In other words, the 'imprint' of gravitational waves in the CMB might be an erroneous discovery, and this is not unexpected at all, since gravitational waves have yet to be demonstrated.
But the CMB is still there, and it's still pretty strong proof of the big bang, as it always was. Nothing about this news disproves the big bang.
A fool and his hard drive are soon parted.