Dark matter makes up 85% of the total mass, of the universe.
Scientist still have no idea what it is.
Scientist have a new hypothesis of what it could be.
They propose that dark matter could be changing all the time,
from ghostly particles in the Universe's biggest structures,
to a strange superfluid state, at smaller scales.
Dark matter is hypothetical substance proposed, to account for the clear imbalance,
between the amount of matter in the universe,
and the amount of gravity that holds our galaxies together.
We cannot directly detect dark matter, but we can see its effects on everything around us.
The way galaxies rotate, and the way light bends as it travels through the Universe,
suggest the existence of dark matter.
The traditional view of dark matter is that its made up of weakly interacting particles,
such as axions, which are influenced by the force of gravity,
in ways that we can observe at large scales.
This 'cold' form of dark matter can be used to predict how massive clusters of galaxies would behave.
Scientists suggest that all galaxies are connected within a vast intergalactic web,
made up of invisible filaments of dark matter.
When we scaled down to individual galaxies, and the way their stars rotate,
in relation to galactic centre, something just does not add up.
Most of the mass, which is dark matter is segregated from where most of the ordinary matter lies.
On a cosmic web scale this does well in fitting with the observations.
On a galaxy cluster scale this does pretty well.
However of the scale of galaxies, it does not fit.
Scientist propose that the reason we cannot reconcile dark matter behaviour on both large and small scales,
in the universe, is because it shifts forms.
We get the 'cold' dark matter particle for massive galaxy clusters,
but on a singular galactic scale, they suggest that dark matter takes on a super fluid state.
Superfluids are a form of cold densely packed matter, that has zero fiction and viscosity.
They can sometimes become a Bose- Einstein condensate.
This is referred to as the fifth state of matter.
Researchers recently announced that they were able to create light that acts like a form of superfluid,
at room temperature.
Superfluids may exists inside neutron stars.
Some researchers speculate that space time itself, might be superfluid.
The idea is that 'halo of dark matter that exists around individual galaxies,
create the conditions to form a superfluid.
The gravitational pull of the galaxy, ensures that it is densely packed.
The coldness of space keeps the temperature suitably low.
Zoom out to a larger scale, and the gravitational pull becomes too weak to form a superfluid.
The key here is that the existence of superfluid dark matter could explain the strange behaviours,
of individual galaxies, that gravity alone cannot explain.
It could be creating a second, as-yet-undefined force, that acts like gravity,
within the dark matter halos surrounding them.
When we disturb an electric field, we get radio waves.
When we disturb a gravitational field, we get gravitational waves.
When we disturb a superfluid, we get phonons, or sound waves, and this extra force,
could work in addition to gravity.
It is the property of the dark matter medium that gives rise to this force.
As of now this theory is only a hypothesis, and scientist are working to test and prove it.