The mysterious dark matter has been mapped in the finest detail yet

It is described as the most detailed map ever of the influence of dark matter throughout cosmic history.

A telescope in Chile has tracked the distribution of these fuzzy objects over a quarter of the sky and across nearly 14 billion years.

The result was once again a brilliant confirmation of Einstein’s ideas.

Although dark matter makes up about 85% of the total mass in the universe, it is extremely difficult to detect and defies ready description.

But dark matter affects the large-scale structure of everything we see — where all the galaxies are, and where the voids in space are. They are the scaffolding upon which the visible structure of the universe hangs.

It does not emit or absorb light. The only way you can clearly infer its existence is through its interaction with gravity.

Large, rotating galaxies of stars would be drifting apart were it not for an invisible mass pulling them together and keeping them intact.

But dark matter will bend, or lens, background light, and that’s how its whereabouts have been determined by the Atacama Cosmology Telescope (ACT).

The Chile facility has observed the cosmic microwave background, or CMB — a diffuse but faint glow of long-wavelength radiation that comes to us from the edge of the visible universe.

ACT identified subtle distortions in this ancient light introduced as it passed through all the intervening materials.

You can liken it to the way light bends as it passes through the bulges and bumps in an old stained glass window.

If you know what you’re looking at on the outside, you can use distortions to say something about the glass.

In the same way, the CMB can be decoded to reveal all the structures involved in their journey to us.

There have been similar “gravitational lensing” detections in the past, most notably by the European Space Agency’s Planck observatory a decade ago. But ACT surpasses all in terms of accuracy and sensitivity.

Successive experiments indicate that the cosmic contents include:

The universe is 13.8 billion years old

In the image at the top of this page, the colored regions are the parts of the sky that the telescope studied.

Orange areas show where a larger mass or material is located along the line of sight; purple where there is less. Typical features span hundreds of millions of light-years.

The gray/white regions show where polluted light from dust in our Milky Way galaxy has obscured a deeper view.

The distribution of the substance is in good agreement with scientific expectations.

ACT notes that the universe’s “lump” and expansion rate after 14 billion years of evolution are just what you’d expect from the Standard Model of cosmology, which includes Einstein’s theory of gravity (general relativity) at its foundation.

Recent measurements that used alternate background light, one emitted by stars in galaxies rather than the CMB, indicated that the universe lacked sufficient clusters.

It’s one of those ‘cosmic tensions’ we’re all talking about,” said Professor Jo Dunkley of Princeton University in the US. “But with this new finding, we’re finding just the right amount of clumping – no tension!” she told BBC News. So if there is tension, it is something that shows up in the galaxy data — not in our data.”

Another tension has to do with the expansion rate of the universe – a number called the Hubble constant.

When Planck looked at the temperature fluctuations across the CMB, he put the rate at about 67 kilometers per second per megaparsec (A megaparsec is 3.26 million light-years).

Or to put it another way – the expansion increases at a rate of 67 kilometers per second for every 3.26 million light-years we look out into space.

It is a difference that cannot be easily explained.

ACT, which uses its lens technology to determine the rate of expansion, produces a number similar to Planck’s. “It’s very close – about 68 kilometers per second per megaparsec,” said Dr. Matthew Madhavashiril of the University of Pennsylvania.

ACT team member Professor Blake Sherwin from the University of Cambridge, UK, added: “We, Planck and many other probes come in on the down side. Obviously you can have a scenario where the measurements are right and there’s some new physics that explains the discrepancy. But we’re using independent techniques, And I think we’re now starting to bridge the gap where we can all ride this new physics and one of the measurements has to be wrong.”

Papers describing the new findings have been submitted to The Astrophysical Journal and are published on ACT website.

The telescope, which operated from 2007 to 2022 before being dismantled, was funded by the US National Science Foundation. The scientific collaboration hasn’t finished analyzing all of its data yet.