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What is it?

What is it?

Dark energy

daniel buenoIn 1929, American astronomer Edwin Hubble showed that the Universe is expanding. This process is supposed to have started 13.7 billion years ago by the Big Bang, the explosion from which the Universe, as it is known today, originated. Gravity is the only known force that functions at great distances and, as it is an attraction force, it used to be expected that it would act to slow down the expansion observed by Hubble. However, in 1998, two groups of researchers measured the brightness of supernova stars and concluded, quite independently of each other, that the expansion of the Universe was accelerating and not slowing down, as had been thought up to then. In other words, a type of antigravity seemed to exist.

However, what would cause a gravitational repulsion force? “As no one was able to find out what caused this force they named whatever was creating this ‘antigravity’ dark energy, which acted by opposing the usual gravity generated by the galaxies,” explains Daniel Vanzella, from the São Carlos Institute of Physics at the University of São Paulo. This energy could be what is contained in a vacuum; today it is known that a vacuum contains some type of energy. “When calculating the energy of a vacuum, we see that it has some of the necessary properties for generating gravitational repulsion.” The researchers who proved the accelerating expansion of the Universe, Americans Saul Perlmutter, Brian Schimidt and Adam Riess, won the Nobel Prize in Physics in 2011. By current calculations, 70% of the energy in the Universe is comprised of dark energy, 25% dark matter (a type of matter that does not emit or reflect light) and just 5% of the matter we know, comprising protons, neutrons and electrons.