MIT Expertise Assessment Explains: Let our writers untangle the complicated, messy world of expertise that will help you perceive what’s coming subsequent. You may learn extra from the sequence right here.
We will put a very good determine on how a lot we all know in regards to the universe: 5%. That’s how a lot of what’s floating about within the cosmos is atypical matter—planets and stars and galaxies and the mud and gasoline between them. The opposite 95% is darkish matter and darkish power, two mysterious entities aptly named for our lack of ability to make clear their true nature.
Cosmologists have solid darkish matter because the hidden glue binding galaxies collectively. Darkish power performs an reverse position, ripping the material of house aside. Neither emits, absorbs, or displays gentle, rendering them successfully invisible. So fairly than instantly observing both of them, astronomers should fastidiously hint the imprint they depart behind.
Earlier work has begun pulling aside these dueling forces, however darkish matter and darkish power stay shrouded in a blanket of questions—critically, what precisely are they?
Enter the Vera C. Rubin Observatory, one in every of our 10 breakthrough applied sciences for 2025. Boasting the most important digital digicam ever created, Rubin is predicted to check the cosmos within the highest decision but as soon as it begins observations later this 12 months. And with a greater window on the cosmic battle between darkish matter and darkish power, Rubin would possibly slim down current theories on what they’re made from. Right here’s a take a look at how.
Untangling darkish matter’s net
Within the Nineteen Thirties, the Swiss astronomer Fritz Zwicky proposed the existence of an unseen power named dunkle Materie—in English, darkish matter—after learning a bunch of galaxies referred to as the Coma Cluster. Zwicky discovered that the galaxies have been touring too shortly to be contained by their joint gravity and determined there should be a lacking, unobservable mass holding the cluster collectively.
Zwicky’s concept was initially met with a lot skepticism. However within the Nineteen Seventies an American astronomer, Vera Rubin, obtained proof that considerably strengthened the thought. Rubin studied the rotation charges of 60 particular person galaxies and located that if a galaxy had solely the mass we’re in a position to observe, that wouldn’t be sufficient to comprise its construction; its spinning movement would ship it ripping aside and crusing into house.
Rubin’s outcomes helped promote the thought of darkish matter to the scientific neighborhood, since an unseen power appeared to be the one rationalization for these spiraling galaxies’ breakneck spin speeds. “It wasn’t essentially a smoking-gun discovery,” says Marc Kamionkowski, a theoretical physicist at Johns Hopkins College. “However she noticed a necessity for darkish matter. And different folks started seeing it too.”
Proof for darkish matter solely grew stronger within the ensuing many years. However finding out what may be behind its results proved tough. Numerous subatomic particles have been proposed. Some scientists posited that the phenomena supposedly generated by darkish matter is also defined by modifications to our concept of gravity. However to this point the hunt, which has employed telescopes, particle colliders, and underground detectors, has didn’t determine the offender.
The Rubin observatory’s principal software for investigating darkish matter will probably be gravitational lensing, an observational approach that’s been used because the late ’70s. As gentle from distant galaxies travels to Earth, intervening darkish matter distorts its picture—like a cosmic magnifying glass. By measuring how the sunshine is bent, astronomers can reverse-engineer a map of darkish matter’s distribution.
Different observatories, just like the Hubble Area Telescope and the James Webb Area Telescope, have already begun stitching collectively this map from their pictures of galaxies. However Rubin plans to take action with distinctive precision and scale, analyzing the shapes of billions of galaxies fairly than the tons of of thousands and thousands that present telescopes observe, based on Andrés Alejandro Plazas Malagón, Rubin operations scientist at SLAC Nationwide Laboratory. “We’re going to have the widest galaxy survey to this point,” Plazas Malagón says.
Capturing the cosmos in such excessive definition requires Rubin’s 3.2-billion-pixel Giant Synoptic Survey Telescope (LSST). The LSST boasts the most important focal aircraft ever constructed for astronomy, granting it entry to giant patches of the sky.
The telescope can be designed to reorient its gaze each 34 seconds, which means astronomers will have the ability to scan your entire sky each three nights. The LSST will revisit every galaxy about 800 instances all through its tenure, says Steven Ritz, a Rubin mission scientist on the College of California, Santa Cruz. The repeat exposures will let Rubin group members extra exactly measure how the galaxies are distorted, refining their map of darkish matter’s net. “We’re going to see these galaxies deeply and often,” Ritz says. “That’s the facility of Rubin: the sheer grasp of having the ability to see the universe intimately and on repeat.”
The last word objective is to overlay this map on totally different fashions of darkish matter and look at the outcomes. The main concept, the chilly darkish matter mannequin, means that darkish matter strikes slowly in comparison with the velocity of sunshine and interacts with atypical matter solely by way of gravity. Different fashions recommend totally different conduct. Every comes with its personal image of how darkish matter ought to clump in halos surrounding galaxies. By plotting its chart of darkish matter towards what these fashions predict, Rubin would possibly exclude some theories and favor others.
A cosmic tug of battle
If darkish matter lies on one aspect of a magnet, pulling matter collectively, then you definitely’ll flip it over to search out darkish power, pushing it aside. “You may consider it as a cosmic tug of battle,” Plazas Malagón says.
Darkish power was found within the late Nineteen Nineties, when astronomers discovered that the universe was not solely increasing, however doing so at an accelerating charge, with galaxies transferring away from each other at larger and better speeds.
“The expectation was that the relative velocity between any two galaxies ought to have been reducing,” Kamionkowski says. “This cosmological enlargement requires one thing that acts like antigravity.” Astronomers shortly determined there should be one other unseen issue inflating the material of house and pegged it as darkish matter’s cosmic foil.
Thus far, darkish power has been noticed primarily by way of Kind Ia supernovas, a particular breed of explosion that happens when a white dwarf star accumulates an excessive amount of mass. As a result of these supernovas all are inclined to have the identical peak in luminosity, astronomers can gauge how distant they’re by measuring how vivid they seem from Earth. Paired with a measure of how briskly they’re transferring, this knowledge clues astronomers in on the universe’s enlargement charge.
Rubin will proceed learning darkish power with high-resolution glimpses of Kind Ia supernovas. However it additionally plans to retell darkish power’s cosmic historical past by way of gravitational lensing. As a result of gentle doesn’t journey instantaneously, once we peer into distant galaxies, we’re actually relics from thousands and thousands to billions of years in the past—nevertheless lengthy it takes for his or her gentle to make the prolonged trek to Earth. Astronomers can successfully use Rubin as a makeshift time machine to see how darkish power has carved out the form of the universe.
“These are the kinds of questions that we wish to ask: Is darkish power a continuing? If not, is it evolving with time? How is it altering the distribution of darkish matter within the universe?” Plazas Malagón says.
If darkish power was weaker prior to now, astronomers count on to see galaxies grouped much more densely into galaxy clusters. “It’s like city sprawl—these big conglomerates of matter,” Ritz says. In the meantime, if darkish power was stronger, it could have pushed galaxies away from each other, making a extra “rural” panorama.
Researchers will have the ability to use Rubin’s maps of darkish matter and the 3D distribution of galaxies to plot out how the construction of the universe modified over time, unveiling the position of darkish power and, they hope, serving to scientists consider the totally different theories to account for its conduct.
After all, Rubin has a lengthier record of objectives to verify off. Some prime objects entail tracing the construction of the Milky Manner, cataloguing cosmic explosions, and observing asteroids and comets. However because the observatory was first conceptualized within the early ’90s, its core objective has been to discover this hidden department of the universe. In spite of everything, earlier than a 2019 act of Congress devoted the observatory to Vera Rubin, it was merely referred to as the Darkish Matter Telescope.
Rubin isn’t alone within the hunt, although. In 2023, the European Area Company launched the Euclid telescope into house to check how darkish matter and darkish power have formed the construction of the cosmos. And NASA’s Nancy Grace Roman Area Telescope, which is scheduled to launch in 2027, has related plans to measure the universe’s enlargement charge and chart large-scale distributions of darkish matter. Each additionally goal to sort out that looming query: What makes up this invisible empire?
Rubin will check its methods all through most of 2025 and plans to start the LSST survey late this 12 months or in early 2026. Twelve to 14 months later, the group expects to disclose its first knowledge set. Then we’d lastly start to know precisely how Rubin will gentle up the darkish universe.