Almost two thirds of our universe is made up of dark energy. It is invisibly interwoven with the empty space, and forces the universe to expand at an ever-increasing speed. This discovery, which two teams published simultaneously in 1998, was nothing short of a sensation. Nobody yet knows what is behind dark energy.
When a star is burned out and its time has come, it explodes in a supernova. Type 1a supernovae are particularly interesting for astronomers. They only arise in binary systems in which one star is a white dwarf and the other a red giant that is in a phase of expansion. The red giant’s mass flows to the white dwarf until this star reaches its maximum mass limit, which was already predicted by Chandrasekhar Subrahmanyan at the end of the 1930s; he was awarded the 1983 Nobel Prize for it. Consequently, the white dwarf explodes in a type 1a supernova. As the brightness of these explosions is physically always the same, observing the apparent brightness of supernovae allows astronomers to deduce their distance. A supernova occurs in every galaxy approximately once every 500 years. The gigantic universe has around ten type 1a supernovae every minute, however. One incredible feat achieved by the 2011 Laureates was detecting these supernovae at a distance of more than five billion light years, estimating their age, subtracting their signals from the vast quantity of digital data in order to record their luminosity. The other one was to not cast doubt on their own results: “Adam, did you do wrong?” Schmidt asked his colleague Adam Riess, when the latter showed him a diagram of his first measurements.
Most physicists consider the source of the dark energy to be the vacuum, because it is here that matter and energy continuously convert into each other at almost infinite speed - as the laws of quantum physics suggest. The energy which the vacuum can theoretically obtain through these fluctuations is less than the dark energy by the unimaginably large factor of 10 to the power of 122, however. Where are the gaps between theory and observation? Does the dark energy - albeit with opposite sign - correspond to the cosmological constant that Einstein had introduced into his equations, in order to not have to abandon his belief in a static universe? Or is it not constant at all, but originates from temporary force fields? If, as some theoreticians believe, the early universe experienced a sudden expansion resulting in an enormous, temporary increase in its energy density - could something similar be occurring now? And could this explain dark energy? These questions revolve around the greatest physics mystery facing us today. The fine line between speculation and science which they reveal is what makes them so fascinating for a dialogue between young scientists and Nobel Laureates.The radiating beginning of the world
Jan Keese | idw
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