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(PhysOrg.com) -- Through precise cosmological measurements, scientists know that about 4.6% of the energy of the Universe is made of baryonic matter (normal atoms), about 23% is made of dark matter, and the remaining 72% or so is dark energy. Scientists also know that almost all the baryonic matter in the observable Universe is matter (with a positive baryon charge) rather than antimatter (with a negative baryon charge). But exactly why this matter and energy came to be this way is still an open question. In a recent study, physicists have proposed a new mechanism that can generate both the baryon asymmetry and the dark matter density of the Universe simultaneously.

Albert Einstein's towering reputation is only enhanced by his self-styled biggest blunder. It might not have been a blunder after all. At stake is the fate of the universe. In 1915, Einstein derived the equations of general relativity that describe the workings of a gravity-dominated cosmos. He added a fudge factor called the cosmological constant to ensure that, in keeping with contemporary tastes, the universe described neither expanded nor contracted. Soon after, though, Edwin Hubble showed that distant galaxies were receding from us, blowing the static universe apart. Einstein reputedly disowned his idea. He might now want to disown the disowning. The discovery in 1998 that very distant supernovae appear to be not just receding but accelerating away from us suggests the presence of a mysterious "dark energy" that counteracts gravity's pull (The Astronomical Journal, vol 116, p 1009). And it turns out that a good way to reproduce this effect is to add the fudge back into Einstein's cosmological recipe. That is not to everyone's taste, largely because no one knows what dark energy might be. Some cosmologists favour other solutions. If Earth were at the heart of a giant cosmic void, for instance, that too would create the illusion that the distant cosmos is flying away from us. But that would involve abandoning an idea we have held dear for centuries: the "Copernican principle" which says that Earth's place in the universe is not at all special (New Scientist, 15 November 2008, p 32). Working out the true story may take some time. But if the evidence collected on these pages is anything to go by, science rarely shies away from slaughtering its sacred cows.