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On 17 March 2014, the BICEP2 collaboration announced the first detection of so-called B-mode polarization, a possible signature of the exponential expansion of space in the early universe. This expansion, also called inflation, is believed to have lasted from $10^{-36}$ seconds after the Big Bang to sometime between $10^{−33}$ and $10^{−32}$ seconds. Inflation is thought to be resposible for the existence of large-scale structures and   to explain why the universe appears statistically homogeneous and isotropic\footnote{Meaning that at large scales the properties of the universe are the same for all observers}.  But was it really a swift-crawling baby universe what BICEP2 observed? Or something more mundane as the effect of dust? To collect the light of the CMB (cosmic microwave background, the elusive echo of the Big Bang), BICEP2 had to look through the window glass of our Galaxy with their South Pole telescopes. And it turned out that this window is not as clean as previously thought, the dirt being small dust particles. These dust particles modifiy a particular property of light called polarization, which incidentally is the same proxy used to detect the existence of an inflation period. So the B-mode polarization could either be imprinted by inflation right after the Big Bang, which occurred about 13.5 billion years ago, or been created by the presence of dust as the ancient light of the CMB finally passed through the Milky Way before reaching our telescopes.   In a paper submitted last night, the european satellite PLANCK reported that the amount of foreground dust present in the line of sight of BICEP2 instruments is exactly enough to explain the observed signal, previously attributed to cosmological inflation. While it could still be that part of the polarization signal is coming from inflation, it would require two very different, unrelated phenomena to contribute at a very similar level. Which statistically speaking is unlikely.   More work needs to be done before the dust is settled (literally), but interestingly it seems that the final word on this particular result will have to come from a joint effort between PLANCK and BICEP2. The two groups have complementary data: BICEP2 is looking at a very specific location of the sky and at a very specific frequency, but with high sensitivity to polarized radiation. PLANCK is looking to the whole sky and at 9 different frequencies. Overall only PLANCK can characterize the galactic dust foreground while BICEP2 is sensitive enough to detect the presence of a B-mode polarization from cosmological inflation. That's why the two competing teams decided to join forces and collaborate on a paper where they will jointly analyze the combined data.   While this intriguing story reminds us that trial and error will always be part of the scientific process, it also stresses that open science and collaboration are the future of scientific research.