Friday, July 8, 2016

Big Bang or Big Bounce?

An illustration of the big bounce concept, with the big bang singularity in the centre.

Cosmology has a problem. The problem begins, as the universe does, with the big bang. The standard cosmology imagines the universe’s first instant as a singularity: that is, a single point, taking up no space at all, but with all the stuff of the universe inside it. As if all of reality had been divided by zero, the singularity is undefined. It has neither interior nor exterior; it cannot be described. In the face of it, the laws of physics break down entirely.

“This is a problem,” says Neil Turok, cosmologist and director of Perimeter Institute. “The standard cosmology begins with an impossibility.”

Working with Steffen Gielen, a former Perimeter postdoc who is now a fellow at Imperial College London, Turok has cast a fresh eye on the universe’s seemingly impossible beginning. The new research is featured as an Editor's Suggestion in Physical Review Letters

Gielen and Turok’s research imagines the big bang as a big bounce – not just the beginning of this universe, but the end of a previous universe. The predecessor universe would have contracted toward a dense state that marked its big crunch end, and our universe’s big bang beginning. 

But while that idea is intuitively satisfying – it at least explains where that single point of matter and energy came from – it does not by itself resolve the problems with the singularity. It is still just as impossible, just as indescribable. For all physics can predict, there be dragons. 

So how did Turok and Gielen avoid the dragon(s)?

They began by looking at the behavior of all the stuff present in the early universe. For its first 50,000 years, the universe was dominated by radiation. What matter there was, was at very high energy, and also behaved like radiation. These materials have a special property that turns out to be crucial to this research: they are conformal. 

“Conformal” has a precise technical meaning in physics and mathematics, but a shorthand translation might be “does not depend on scale.” Light, for example, is conformal. Light can take the form of radio waves that are kilometers wide, or X-rays that are the width of an atomic nucleus. Maxwell’s equations govern radio waves and X-rays, and make no distinction between them. This is not unique to light: particle physics strongly hints that at very high energy, all matter is likewise blind to scale.

“Our work starts from this observation,” says Turok. “We make the assumption that the early universe is filled with things that have no scale. And then we try to describe a quantum universe that is filled with such material: how does it behave?” 

It behaved more simply than the researchers had ever dreamed. They were surprised to discover they could use standard quantum mechanics, with no bells, whistles, or fudge factors added, to describe and predict how the universe grew. Or, winding the film the other way, how it shrinks toward the big bang singularity.

As Turok puts it: “It turns out, to our surprise, that in this very special case, where everything present in the universe is conformal, and all we are studying is the size of the universe, we could quantize the theory exactly, and work out exactly how a universe of one size transitions into a universe of another size, quantum mechanically.” 

Describing the growing or shrinking universe is a major accomplishment, but doesn’t slay the dragon. But there, too, the researchers had an idea.

“Quantum mechanics saves us when things break down,” says Gielen. “It saves electrons from falling in and destroying atoms, so maybe it could also save the early universe from such violent beginnings and endings as the big bang and big crunch.”

It turns out that it could. 

In the model Gielen and Turok created, the universe approaches the singularity point – and then skips over it. Like a clock that avoids striking midnight by swinging its hands up and out from the clock face, it does this by accessing another dimension. 

The “extra” dimension in question is imaginary: it is described by numbers containing the square root of negative one. The quantum universe in this model is described by complex numbers – numbers with both an imaginary and real component. At the point of the singularity, where the clock strikes midnight, it might have no real size, but could still have an imaginary size – and thus still be described by the laws of physics. So the problem of the singularity is resolved, the dragon avoided.

It seems perhaps like a cheat, but imaginary and complex numbers are everywhere in quantum physics. In this work, Turok and Gielen are using the well-established mathematics that describe quantum tunneling: a quantum mechanical phenomenon in which a particle tunnels through a barrier that is too high for it to clear.

More than a mathematical sleight of hand, quantum tunneling explains how fusion works in the sun, and is behind established technologies such as tunneling electron microscopes.

Bottom line: big bounce cosmology – where one universe contracts into a big crunch until another explodes outward as a big bang – is not a new idea. Turok in particular has been a leading proponent of such a cyclical cosmology for more than a decade. But the sticking point has always been the moment of the bounce itself: the singularity. 

This new work shows how merely assuming that everything in the early universe was conformal allows one to describe a quantum cosmology that runs the universe backward toward the singularity, smoothly over it, and out the other side. No dragons involved. 

No wonder the researchers described their work as “A Perfect Bounce.”

1 comment:

  1. In modern science lacks understanding of the absolute basics, and this is a space that does not disappear and does not appear, it has always been , is and will be, because it is nothing, absolute emptiness, and all that fills it was created from nothing, out of emptiness of spatial opposites - energy which formed all of the material body, without exception. Hence, there are scientific errors in the logical view, and matter and energy = content changing in time.
    Only absolute emptiness of space has no limit in the volume or in the volume of micro or in macro scale. That is the absolute absence of any device from the environment characterizes infinity full spatial volume, where there is always enough free space, and for the number and size of quality of all content. https://new.vk.com/tviss
    Matter is not the basis, that is, all existing matter is the derivative energy in the limit speed = time which creates a lot - which again you can obtain and extract the energy, but the energy initially creates matter, and the vast emptiness of space. And the vacuum important to understand, not what appear energy pulses, and WHERE? - they appear... and that's the FACT - the absolute basics, still does not understand neither science nor the vast majority of people!!!

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