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Dark energy is not over.

According to some media recent research have refuted the accelerated expansion of the universe discovery, which in 2011 was awarded the Nobel Prize for physics. But things are not so. In recent weeks, some media have fired titles like “The universe is expanding at an accelerated rate, or not?” And, “The universe is expanding, but not at the accelerated rate. New research debunks the theory was awarded the Nobel Prize.” After reading the study, however, you can safely say that there is no need to review our current conception of the universe. Any item that does slightly reduce our certainty about what we know, and what’s more just discarding the majority of cosmological data on which we base our understanding of the universe. It also ignores important details in the data considered. But even leaving aside these problems, the titles are still wrong. The study concluded that now we are sure that only 99.7 percent of the universe is accelerating, which is certainly not the same thing “is not accelerating.”

The initial discovery that the universe is expanding at an accelerating rate was done by two teams of astronomers in 1998 using supernovae as cosmic LA type measuring instruments. Supernovae – exploding stars – cause some of the most powerful explosions in the cosmos, more or less equivalent to a billion billion billion atomic bombs that explode at once. Those of LA type are special because, unlike other supernovae, exploding always all with the same brightness or almost, probably because of a critical mass limit. this similarity it means that the differences in their observed brightness are almost entirely related to how far apart they are. And this makes them ideal for measuring cosmic distances. Also, they are relatively common objects, and are so bright that we can see them billions of light years away. This shows us how the universe appeared billions of years ago, and so we can compare it to how it looks today.

For their consistency these supernovae are often called “standards”, but it would be more correct to call “candles standardized” candles because in practice their precision and accuracy can be further improved taking into account small differences in their explosions, observing the time required to ‘ explosion by unfolding and what turns into the red color of the supernova by dust between us and them. The search of the way to make these corrections solid was what led to the discovery of the acceleration of the universe. The recent article that gave rise to those titles he used an LA kind of supernovae catalog put together by the scientific community, which has already been analyzed numerous times. But the authors used a different calibration method, and we believe this compromises the accuracy of the results. The authors assume that the average properties of supernovae of each of the samples used to measure the expansion history are the same, although it has been shown that they are different, and the analyzes carried out in the past have given account of these differences. However, even ignoring these differences, the authors still find that there is a chance of 99.7 per cent that the universe is speeding up: something very different from what the titles suggest. In addition, the extraordinary confidence of astronomers in the fact that the universe is expanding faster than they happen billions of years ago is based on much more than measurements of supernovae, including the small fluctuations in the heat pattern residue after the big bang (ie, the cosmic background radiation) and the footprint of the fluctuations in the current distribution of galaxies that surround us (the so-called baryon acoustic oscillations).

The study also ignores the presence of a significant amount of matter in the universe – confirmed numerous times and with different methods since the seventies – further reducing the confidence in that analysis. These data further show – independently from supernovae – that the universe is accelerating. If we combine these observations with other data on supernovae, switching from a security of 99.99 percent to a 99.99999 percent. This is quite safe! Currently we know that dark energy – what we believe to be the cause of the accelerated expansion of the universe – accounts for 70 percent of the universe, while the matter is the rest. The nature of dark energy is still one of the greatest mysteries of all astrophysics. But since this picture has consolidated a decade ago, there has been no really in-depth discussion on the fact that there is dark energy, or that the universe is accelerating. Now many new investigations are underway, both on land and in space, whose priority over the next two decades is to understand exactly what could be this dark energy. For now, we must continue to improve our measurements and question our assumptions. Although this recent article does not disprove any theory, it is always good to lead all of us to stop for a moment and remember how tough the questions we ask, the way we have reached the current findings and how seriously we have to test each element of our knowledge.



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