"We know how gas and stars react to these cosmic crashes and where they emerge from the wreckage. Comparing how dark matter behaves can help us to narrow down what it actually is," said lead author David Harvey of the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland.
ANALYSIS: The Higgs Boson May Disintegrate into Dark Matter
Dark matter's presence is known only by its interactions with normal matter through gravity. It does not, however, interact via the electromagnetic force, which is why we cannot directly see it - it does not emit, scatter or reflect light - it is more "invisible" than "dark."
In this new research, Harvey and his team realized just how invisible this stuff is, even to itself.
As two galactic clusters collide, the stars, gas and dark matter interact in different ways. The clouds of gas suffer drag, slow down and often stop, whereas the stars zip past one another, unless they collide - which is rare. On studying what happens to dark matter during these collisions, the researchers realized that, like stars, the colliding clouds of dark matter have little effect on one another.