Dark matter may not be entirely "dark" Astronomers believe they have spotted what may be the first potential signs of dark matter interacting with a force other than gravity. An international team of scientists led by scientists at Durham University in the UK made the discovery using the Hubble Space Telescope and the European Southern Observatory's Very Large Telescope to view the simultaneous collision of four distant galaxies at the center of a galaxy cluster 1.3 billion light-years from Earth. In a paper published in the journal Monthly Notices of the Royal Astronomical Society, scientists reported that the dark matter cluster appeared to lag behind the galaxy that surrounds it. According to scientists, the cluster is displaced from the galaxy by 5,000 light years - the distance the Voyager spacecraft would have traveled in 90 million years. This shift is explained by collisions that occur when dark matter interacts, even if very weakly, with forces other than gravity. Computer simulations showed that the extra friction from the collisions caused the dark matter to slow down, which would eventually lead to lag. Scientists believe that all galaxies exist within clumps of dark matter - which is called "dark" because it is believed to interact only with gravity and is therefore invisible. No one knows what dark matter is, but it is believed to make up up to 85% of the mass of the Universe. Without the holding effect of its extra gravity, galaxies like our Milky Way would fly apart as they spin. In the latest study, scientists were able to "see" a clump of dark matter by the distorting effect its mass has on the light of background galaxies - an effect called gravitational lensing. The scientists also add that their findings potentially rule out the standard theory of cold dark matter, in which dark matter interacts only with gravity. Lead author Dr Richard Massey, a Royal Society Fellow at the Institute for Computational Cosmology at Durham University, said: “We tend to think that dark matter is around and doesn't care. But if it slows down as it collides, it would be the first dynamical evidence that dark matter notices the world around it. After all, dark matter may not be entirely 'dark'." The scientists note that while they appear to have observed dark matter shifting, more detailed studies are needed to identify other potential effects that could cause dark matter to lag behind the surrounding galaxy. Scientists believe that dark matter may well interact with forces other than gravity. “The parallel universe around us is becoming more interesting,” says Lilia Williams of the University of Minnesota. “This dark sector may contain physics and exhibit complex behavior.” Last month, Dr Massey and colleagues published observations showing that dark matter interacted very weakly in 72 collisions between galaxy clusters (each containing 1,000 galaxies). The latest research is being conducted using individual galaxies as examples. Scientists say collisions between these galaxies take longer than galaxy cluster collisions - allowing even small frictional forces to build up over time. If you've read the article this far please like and subscribe - it really helps the channel. Open the link to find thousands of interesting articles: https://wwwwww.youtube.com/...ityt3yt3.ggpht.com/...-v1