Stephen Hawking’s ‘ghosts’ found
ALL the evidence shows our universe emerged from a single event: an eruption commonly known as the Big Bang.
What preceded that point is a mystery.
But it has significant implications.
It's about the fate of our universe.
We know space is expanding. We can see that in the way all the galaxies around us are moving outward. But how far can it extend? What happens next?
Will the universe merely boil away into the void as its component parts get further and further apart?
Or will it reach some kind of tipping point, where space turns around and begins to contract on itself?
The late Stephen Hawking had his own ideas. Now astronomers may have discovered one of the critical telltales that could prove his notions to be true.
The leading theory of the birth of our universe has a problem: the evidence doesn't back it up.
At its heart is the idea that a single quantum speck of infinite gravity and density - similar to the singularity at the core of a black hole - suddenly became energised. It then erupts, inflating into an infant universe in a split second.
It seems to fit. It's also a neat solution for most astronomical observations.
But such an event should have left behind visible signs.
The way the universe fizzed into existence could reveal something about where it came from.
There should be regular, predictable gravitational waves rippling through the cosmos.
We've not yet found them.
Then there is the question of entropy (a technical term for the way things tend towards messy disorder over time).
Why isn't the universe a bubbling cauldron of disorganised subatomic particles strewn about in a uniform layer? How did subatomic particles bind themselves into atoms, molecules, gas, dust - and stars?
Physics tells us that, for this to have happened, the early universe must have had even lower entropy than we do now. But how?
You can't unbreak an egg. Yet that's precisely what cosmic inflation proposes.
Black holes are so immense and so infinitely strange that traces of them may survive the end of the universe.
At least, that's the proposal of a research team from Oxford University, the University of Warsaw and the New York Maritime College.
But such an extraordinary idea requires gargantuan evidence.
Something on a cosmological scale.
Enter supermassive black holes.
And an idea put forward by Hawking and Oxford mathematical physicist Sir Roger Penrose.
Their theory - conformal cyclic cosmology - argues our universe isn't the first. Nor is it the last.
"In cyclic cosmology," 87-year-old physics legend Penrose says, "there is no beginning, and nothing is lost."
Big Bangs still happen.
They're followed by the creation of the cosmos as we know it.
Then, things eventually cool down. Galaxies fly apart. The stars die.
The universe becomes almost empty - dominated by energy and radiation, not matter.
Only black holes survive.
"If the universe goes on and on and the black holes gobble up everything, at a certain point, we're only going to have black holes," New York Maritime College mathematician Daniel An says. "Then what's going to happen is that these black holes will gradually, gradually shrink."
The black holes themselves evaporate.
That is Stephen Hawking's most significant discovery: that black holes actually bleed off mass and energy by emitting gravitons and photons. It's called Hawking radiation.
What's left behind is - nothing. And everything
"The thing about this period of time is that massless gravitons and photons don't really experience time or space," An says.
"And so it starts all over again."
LOOK TO THE SKIES
One clue left over from the quantum-soup that formed the opening moments of our universe is the radiation left over from the Big Bang - the cosmic microwave background.
It still contains the patterns imprinted on it at the moment time began.
And that may include influences from a preceding time - the universe before our own.
Bright imprints could be produced by the concentrated Hawking radiation of the last dying black holes.
They're called Hawking Points.
The cosmic radiation background (CMB) has been mapped. But it's a mess.
Studying it is like looking for patterns in the clouds.
It's a point Hawking himself wryly highlighted, pointing out what looked to be his initials imprinted in the universe itself!
So, just as seemingly random clouds form larger weather patterns, Penrose and his colleagues set about creating a model of the universe that would reveal the larger patterns within it.
Our images of the cosmic radiation background are faint. They're also often overexposed by nearby stars and galaxies.
But one-third of the night sky is relatively clear.
So, the researchers calculated what they would expect to find if Hawking Points were there - and attempt to match them with what we know. This was then compared with 8000 different simulated universes in an attempt to ensure they weren't simple illusions.
They found about 20 distinct 'bright' patches.
They're not the ancient black holes themselves.
Instead, they corresponded with the notion that vast clouds of Hawking radiation from dying black holes would carry over from one universe into the next.
The apparent bubbles in the cosmic radiation background are enticing. But they're not yet definitively defined.
So they're not yet evidence.
Some physicists argue that they have not adequately eliminated the prospect they are merely the product of random scattering.
Others say that if cyclic cosmology was true, then there should be tens of thousands of Hawking Points evident in our skies.
And such 'flares' in the structure of our cosmos could actually indicate something else.
It could be the point at which some separate, concurrent, universe has 'bumped' into our own.
There's also one sizeable unexplained leap in the theory's logic: how does a cold, empty universe suddenly flare into a new, high-energy universe?
But Penrose - who admits his idea is radical - remains confident.
He even believes he knows will come next.
"The next universe will be just like ours - but only in overall appearance, not in detail, of course," Penrose says.