"The idea that everything began with the big bang is no longer entirely convincing," says Jean-Luc Lehners, a researcher at the Max Planck Institute for Gravitational Physics in Potsdam, just outside Berlin. "There are many indications that there was a before."
Looking for El Dorado
A possible alternative to the standard big-bang theory is the model of a "cyclical universe," whereby the cosmos is constantly being reborn and then vanishing again, in a potentially endless cycle of birth, death and rebirth.
Each time the universe came to an end, after many trillions of years, when the last stars had been extinguished and matter had dissolved, there would be another dramatic event, a new beginning. According to this theory, the universe, which had been continually expanding until then, would suddenly contract. The contraction would lead to the accumulation of an enormous amount of energy, creating tension that would subsequently be released in an original explosion, expanding space once again.
As in the inflation model, the new universe therefore begins with a massive release of energy, from which the stars later condense. "But what happens in a fraction of a second, according to inflation theory," says cosmologist Lehners, "takes a billion years in the cyclical universe."
The contraction and renewed expansion of a cyclical universe would also generate telltale background radiation, albeit with a different pattern than with an inflationary universe. "This is why the details are so important now," says Lehners. "We will have to take a close look at the Planck measurements."
In addition to these two theories, there are other ideas on how the universe may have been born. According to an especially bizarre scenario, two parallel universes once collided with one another, triggering the big bang and the birth of a new universe.
As absurd as it may sound, this too would have led to the creation of background radiation, and actual observations reinforce the theory.
"In studying the big bang, we are in a situation similar to that which occurred when America was discovered," concludes astrophysicist Ensslin. "We know the route to the new continent, and with Planck we can travel along the coastline, but we probably won't be finding the exact location of El Dorado just yet."
Translated from the German by Christopher Sultan