That’s a question scientists have yet to find an answer to, but a new theory suggests spacetime itself might be a ‘liquid superfluid’.
And, if proven true, it could force us to take another look at the Standard Model of physics.
Is spacetime a liquid? New research says that, if zero, it would have a viscosity of zero
The idea of spacetime being a fluid, known as ‘superfluid vacuum theory’ (SVT), isn’t entirely new – it was suggested as long as half a century ago.
But researchers Stefano Liberati, a professor at the International School for Advanced Studies (SISSA) and Luca Maccione, a research scientist at the Ludwig-Maximilian University in Munich, are the first to tackle the question of the viscosity of such a liquid.
That is, they worked out how ‘thick’ the liquid would be – and they found it to be almost zero.
In their paper Astrophysical Constraints on Planck Scale Dissipative Phenomena, they tackle the question of spacetime being a fluid.
They did this by creating models attempting to fuse gravity and quantum mechanics into ‘quantum gravity’.
One of the biggest problems in understanding the universe has been trying to figure out how things move through space.
Consider how waves move through water, for example – the wave propagates through the water, using it as a ‘medium’ through which to move.
As far as we know, a transfer of energy of this sort requires a medium, like how sound passes through air or heat through metal.
How, then do electromagnetic waves, photons and so on move through space, where there is believed to be nothing?
The supposed existence of a medium in space is more commonly known as an ether, but proving or disproving its existence has been a struggle.
In Liberati and Maccione’s research, they suggest that this ether is in fact a superfluid.
They say to us, the spacetime just appears as one ‘classical’ object, something that is whole.
But instead we should consider it as being merely the ‘visible’ aspect of a fluid.
WHAT IS SPACETIME?In Einstein’s 1905 Theory of Special Relativity, he was the first to propose that space and time might be linked.
The term ‘spacetime’ was coined three years later by mathematician Hermann Minkowski.
Einstein postulated that the speed of light (about 300,000,000 metres per second) is the same for all observers.
He also said that anyone moving at constant speed would observe the same physical laws.
However, when someone moves through space, they would experience time at a slower rate.
This is because space and time can be thought of as one.
Consider a moon in orbit around a planet – the moon stays in orbit because the planet ‘warps’ space, keeping the moon snared in its gravity.
In the same way, if you were to synchronise two clocks and then fly one away at great speeds into space, they would lose their synchronisation.
This is because a great mass, or speed, can warp time just as it warps space.
Thus, Einstein concluded that space and time must be inherently linked as spacetime.
It is believed that some neutron stars left behind by supernovas, like the one at the centre of the Crab Nebula (pictured), may have superfluid cores
,+may+have+superfluid+cores.jpg)
Consider, in the same way, how we perceive water – to us it appears to be a flowing liquid, but in actuality it is a mass of H2O molecules.
Spacetime, the researchers say, is made of its own H20 molecules – although what these would be is unknown.
A key point of evidence for their theory revolves around the four fundamental forces of the universe – electromagnetism, weak interaction, strong interaction and gravity.
Quantum mechanics is able to explain all of these except for gravity.
The researchers say that a plausible model for quantum gravity would be the superfluidity of the cosmos.
But to model it as a fluid requires us to understand its viscosity, how thick it is, which they estimate to be close to zero.
‘If spacetime is a kind of fluid, then we must also take into account its viscosity and other dissipative effects, which had never been considered in detail,’ explains Liberati.
The reason for a viscosity of almost is that this would allow photons and other particles to travel with ease.
WHAT IS A SUPERFLUID?A superfluid is a fluid that can flow endlessly without losing energy.
It is a phase of matter that is achieved by liquids or gases when they are cooled sufficiently.
At certain temperatures near absolute zero, their atoms begin to occupy the same ‘quantum state’.
This means that the atoms lose their individual identities, and instead behave like a single super-atom.
Helium, for example, exhibits superfluid properties at 2 Kelvin (-271.15ºC, -456.07ºF).
Superfluids have several unique properties.
They can, for example, climb the walls of unsealed containers.
They also transfer heat exceedingly well – a superfluid will evaporate before it has a chance to boil.
In our current models quantum mechanics can explain all the forces of the universe - except gravity
‘We can see photons travelling from astrophysical objects located millions of light years away,’ continues Liberati.
‘If spacetime is a fluid, then according to our calculations it must necessarily be a superfluid.
‘This means that its viscosity value is extremely low, close to zero.
‘We also predicted other weaker dissipative effects, which we might be able to see with future astrophysical observations.
‘Should this happen, we would have a strong clue to support the emergent models of spacetime.
‘With modern astrophysics technology the time has come to bring quantum gravity from a merely speculative view point to a more phenomenological one.
‘One cannot imagine a more exciting time to be working on gravity.’
Source: Dailymail
Post a Comment Blogger Facebook