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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.

They are the biggest questions that science can possibly ask: where did everything in our universe come from? How did it all begin? For nearly a hundred years, we thought we had the answer: a big bang some 14 billion years ago.But now some scientists believe that was not really the beginning. Our universe may have had a life before this violent moment of creation.Horizon takes the ultimate trip into the unknown, to explore a dizzying world of cosmic bounces, rips and multiple universes, and finds out what happened before the big bang.Neil Turok, Director of Perimeter Institute for Theoretical Physics in Canada, working with Paul Steinhardt at Princeton, has proposed a radical new answer to cosmology's deepest question: What banged?Answer: Instead of the universe inexplicably springing into existence from a mysterious initial singularity, the Big Bang was a collision between two universes like ours existing as parallel membranes floating in a higher-dimensional space that we're not aware of.One bang is followed by another, in a potentially endless series of cosmic cycles, each one spelling the end of a universe and the beginning of a new one. Not one bang, but many.Sir Roger Penrose has changed his mind about the Big Bang. He now imagines an eternal cycle of expanding universes where matter becomes energy and back again in the birth of new universes and so on and so on.