This week a hectic chapter closes in search of answers about the history of the universe. Which began in March 2013 with the announcement of the discovery of gravitational waves from the early universe, following the observations of the microwave background radiation made by the telescope Bicep2. It’s the same chapter that in recent months became fashionable terms like cosmic inflation and primordial gravitational waves; which led to the cover image of a lone telescope observing the sky from the South Pole and returned the Big Bang to the daily news.
The discovery of gravitational waves supports the theory of cosmic inflation, one of the best ideas we have about how our universe reached its size and what was the origin of its structure. However, the set of data Bicep2 and Planck satellite, the European Space Agency (ESA) analysis indicates that there is no conclusive evidence of the presence of such waves.
This was announced by the ESA Last Friday, after the test results were leaked and disseminated through Twitter, without giving time to the explanations that were to accompany its publication in issue of the journal Physical Review Letters, scheduled for Tuesday.
But you must then file our knowledge about the Big Bang? No. The Big Bang remains our best explanation of the origin of the universe and is based on very firm observations. For example, the existence of the background radiation microwave in heaven or accelerated expansion that we measured with the light of supernovae.
We do not know very well what happened in the moments that followed the Big Bang. Detect gravitational waves from that time would allow us to tie many loose ends. So astrophysicists are seeking their presence through the observations of space telescopes (as Planck), telescopes balloon (like Spider) and telescopes on the surface of the Earth (as Bicep2 Keck and SPT, at the South Pole, or ACT and PolarBear in the Atacama Desert in Chile).
But what was the case with measurements? The microwave background radiation, which is just as microwave light coming from all parts of the sky, was discovered in 1965 and has since become an essential tool to study the origin of the universe. In the last 50 years we have learned to measure the light with great precision and now we sensitive instruments that, in principle, we allow see the imprint of gravitational waves.
The Big Bang is not the only source microwave light in the sky. The dust in our galaxy also shines on those frequencies. In the same way you can not tell if the dress Ingrid Bergman in Casablanca is actually blue or violet-because the film is in black and white-, experiments need to measure more than one color to see the difference between radiation microwave background and interstellar dust.
In technical terms, the Keck telescope Bicep2 and his successor, measure microwave radiation at frequencies of light through the atmosphere of Earth and is coincidentally in those frequencies where the background radiation is brighter. The frequencies of light where the interstellar dust is brighter not penetrate the atmosphere and therefore it is difficult to determine if the light comes only measure microwave radiation background or is contaminated by the glow of interstellar dust. So to know if the dress Ingrid Bergman in Casablanca is blue or violet (combination of blue and red), necessary to measure the blue and red light, which is exactly what makes a film camera or color the human eye.
When Bicep2 made the announcement in March 2013, they ruled out the presence of the brightness of interstellar dust in the portion of sky observed, based on the available models. They had seen a little picture of the dress with greater sensitivity than any other experiment, but saw it in black and white and used information from other sources to assert that it was not purple. Planck located between Earth and Mars, observes the sky in nine different frequencies, including some dominated by the glow of interstellar dust. Planck see the full dress, with less sensitivity to Bicep2 or Keck, but with a camera Technicolor.
The result presented this week is the product of joint analysis of the two teams worked for more than six months. And the conclusion is that measuring Bicep2 is contaminated by the glow of interstellar dust.
But in reality are far from the final chapter in our quest for answers about the universe. With Spider waiting to be rescued in Antarctica, Keck at the South Pole, the imminent announcement of the analysis of Planck and the numerous proposals for new experiments, the search for gravitational waves just beginning.
* PhD in Astronomy and Astrophysics. Member of Planck consortium and collaboration Spider.
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