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Report: Universe began by colliding with another

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Artist rendering of what the theoretical Big Bang collision may have looked like  

(CNN) -- The physical universe began not with a primordial Big Bang but with a monumental collision with another universe, a bold new theory suggests.

And unlike the older Big Bang cosmological model, the Big Collision surmises that time and space existed long before our universe exploded into physical reality.

According to the scientists, the universe began as a three-dimensional void in a higher-dimensional space. Attracted to another such universe, the two lined up and bumped into each other along their surfaces.

"The universe was quiet, vacuous. Very slowly, a weak attraction brought them together, creating a collision that made particles and energy," said Paul Steinhardt, one of the researchers.

The Princeton University physicist and colleagues said the theory, while tentative, explains many observations of the universe better than the Big Bang.

Recent observations of background radiation from the "edges" of the cosmos, relics of early moments of the universe, reveal a startling homogeneity in all directions.

"The opposite sides of the universe have not had enough time to communicate with each other. Yet throughout the sky we find the universe to be extraordinarily homogeneous," Steinhardt said.

It is as if two chefs on opposite sides of the Earth inadvertently cooked up the exact same dish.

"You would think that they cheated to come up with exactly the same thing," he said.

The Big Collision, however, would have created almost instantaneously the energy and matter in all regions of the newly blossoming universe.

"At the moment of collision, the energy of the moving universe gets transferred into matter and radiation," said another researcher, Justin Khoury, also of Princeton.

While explaining the consistency or smoothness the universe, the new model allows for the slight ripples in the cosmic fabric that created the seeds for the formation of galaxies and large-scale structure in the universe, the researchers said.

Moreover, the new theory also accounts for the absence of super-massive particles known as monopoles, which the intense heat of the early Big Bang should have produced in great amounts.

"With this universe, the temperature at which you heat up the universe is finite. It never reaches infinite densities like the Big Bang model," Khoury said.

The new model takes generous helpings from string theory, an increasingly popular explanation for the subatomic composition of all known particles.

But it competes with the so-called inflation theory, which proposes a period of exponential expansion of the universe shortly after the Big Bang.

Steinhardt concedes that the theory explains the known universe as well as the Big Collision. He should know, having helped come up with the inflation model in the 1980's:

"Since I worked on both theories, I think that they are both interesting and both have the possibility of being correct."

Planned observations in the coming decades of theoretical gravitational waves in the universe could help determine which is right, he said.

Besides Steinhardt and Khoury, Neil Turok of Cambridge University and Burt Ovrut of the University of Pennsylvania developed the so-called Ekpyrotic Universe model. Ekpyrosis is Greek for "conflagration" or "cataclysmic fire."

The four submitted a paper on the matter to the journal Physical Review D.



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