We cannot see it, barely understand it, but we know that it exists because of the strong influence it exerts on space.
Dark matter makes up about 27% of the universe, and its gravitational force is enough to interconnect entire galaxies in a structure known as the cosmic web. Now scientists have created the largest map of this mysterious substance – and this could mean that something is wrong with Einstein’s theory of relativity.
They also mapped the location of huge cosmic cavities where the conventional laws of physics may not apply.
Astronomers can map the existence of dark matter by looking at light traveling to Earth from distant galaxies. If the light has been distorted, it means that there is matter in the foreground that bends the light when it comes towards us. Members of the international DES (Dark Energy Survey) team used artificial intelligence to analyze images of 100-meter galaxies – a collaborative effort to uncover the nature of the mysterious dark energy that drives the expansion of our universe – and created a map that this map covers a quarter of the sky in the southern hemisphere (one eighth of the total night sky visible from earth).
The brightest areas of the map are shown as pink, purple and black speckled spots in a pale ring (an overlaid image of the Milky Way), showing the densest areas of dark matter corresponding to superclusters of galaxies, while the black patches are cosmic cavities (see Fig Main picture).
Dr. Niall Jeffrey from University College London and the École Normale Supérieure in Paris, who jointly led the project, said: “It shows us new parts of the universe that we have never seen before. We can really see this cosmic web structure, including these enormous structures called cosmic voids. These are very sparse regions of the universe with very few galaxies and less matter. “
Scientists are interested in these structures because they suspect that gravity behaves very differently in them. By identifying their shapes and positions, the map could therefore provide a starting point for further investigation.
The map published in the Royal Astronomical Society’s monthly notices, It also brings us closer to understanding what the universe is made of and how it evolved.
According to the Standard Model of Cosmology, the universe began with the Big Bang, then expanded, and matter evolved according to Einstein’s general theory of relativity, which describes gravity. These gravitational forces created the clumps and voids of matter that make up the cosmic web.
Although calculations by the DES team suggest that the distribution of this matter is broadly in line with the predictions in the Standard Model, it is not a perfect fit. “When you look at the universe, it isn’t as lumpy as you might expect – there is evidence that it is smoother,” said Jeffrey.
“It may seem relatively small, but if these pointers are correct, it may mean that something is wrong with Einstein’s general theory of relativity, one of the great pillars of physics.”
One possibility is that some of the measurements used to calculate the appearance of the universe are not entirely accurate, said co-author Prof. Ofer Lahav, also at UCL and chair of the DES UK consortium. Alternatively, it could be a problem with the underlying model. “Some people would even press to say that maybe Einstein was wrong,” he said.
Lahav isn’t ready to go this far himself: “What I’m saying is, ‘Look, don’t be too relaxed. There is something that could indicate an inequality. Work hard, try to understand it by conventional means, but keep your eyes open that it could lead to a revolution in physics. ‘ ”