An international team of researchers has created a large map of mysterious, unseen matter throughout the universe, to be published in the Monthly Notices of the Royal Astronomical Society.
The map developed by the team of researchers - members of the international team "Dark Energy Survey" - is a diagram of the distribution of dark matter throughout the universe, and aims to reveal the spread and places of concentration of dark matter.
The map is expected to help astronomers understand the components of the universe and how it evolved, and may reveal an error in Einstein's theory of relativity, after they discovered the existence of voids in the universe that violate the laws of physics contained in the theory of relativity.
Dark matter
in astronomy and cosmology; Dark matter is a substance that has been hypothesized to explain a large portion of the universe's total mass. It is described as the most elusive matter in the universe, and is not directly visible, hence the term darkness.
We cannot see dark matter or interact with it directly using telescopes, as it does not emit or absorb light or any other electromagnetic radiation at any level, but its existence and properties are inferred from the effects of gravity exerted on visible matter, radiation and the great structure of the universe.
Dark matter makes up about 27% of the universe, and its gravitational force is enough to mesh entire galaxies together in a structure known as the cosmic web. Now, scientists have created the largest ever map of this mysterious substance – and it could imply that there’s something wrong with Einstein’s theory of relativity.
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| The DES dark matter map (in purple) superimposed on an image of the Milky Way galaxy. |
Creating a dark matter map
Astronomers are able to map the existence of dark matter by looking at light travelling to Earth from distant galaxies; if the light has been distorted, this means there is matter in the foreground, bending the light as it comes towards us.
Using artificial intelligence methods to analyse images of 100m galaxies, members of the international Dark Energy Survey (DES) team – a collaborative effort to reveal the nature of the mysterious dark energy that is driving the expansion of our universe – have created a map that covers a quarter of the sky of the southern hemisphere (an eighth of the total night sky visible from Earth).
The map - created by scientists - showed new parts of the universe that had not been seen before, revealing the existence of vast voids in the sky to which the laws of physics may not apply, and therefore it can challenge the famous scientist Albert Einstein's theory of relativity, which describes gravity as the force that created lumps. .
Dr Niall Jeffrey, of University College London and École Normale Supérieure, Paris, who co-led the project, said: “It shows us new parts of the universe that we’ve never seen before. We can really see this cosmic web structure, including these enormous structures called cosmic voids, which are very low-density regions of the universe where there are very few galaxies and less matter.”
Scientists are interested in these structures because they suspect that gravity may behave very differently inside them. By identifying their shapes and locations, the map could therefore provide a starting point for further study.
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| A zoomed-in view of the Dark Energy Survey's dark matter map. Dark Energy Survey Collaboration |
Maybe Einstein was wrong
This unexpected discovery of cosmic voids raises questions about Albert Einstein's general relativity, a cornerstone of 20th century physics and our best model of gravity to date. Although the results do not rule out Einstein's models entirely; They are not completely identical.
According to the standard model of cosmology, the universe started with the big bang, and then it expanded and matter evolved according to Einstein’s theory of general relativity, which describes gravity. These gravitational forces are what created the clumps and voids of matter, which constitute the cosmic web.
Although calculations by the DES team suggest that the distribution of this matter is broadly consistent with predictions in the standard model, it is not a perfect fit. “If you look out into the universe, the matter isn’t as clumpy as expected – there are hints that it is smoother,” said Jeffrey.
“It may seem a relatively small thing, but if these hints are true then it may mean there’s something wrong with Einstein’s theory of general relativity, one of the great pillars of physics.”
One possibility is that some of the measurements used to calculate how the universe should look are not quite right, said co-author Prof Ofer Lahav, also at UCL and chair of the DES UK consortium said. Alternatively, it may be a problem with the underlying model. “Some people would even push it to say maybe Einstein was wrong,” he said.
Sources:
- https://iopscience.iop.org/article/10.3847/1538-4357/abf040
- https://www.theguardian.com/science/2021/may/27/astronomers-create-largest-map-universe-dark-matter-einstein
- https://www.darkenergysurvey.org/
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