The Future of Cosmology

“All truths are easy to understand once they are discovered; the point is to discover them.” 
- Galileo Galilei

Starting in late 1609, Galileo Galilei drew back the curtain on the night sky from Padua, Italy, using his new and improved telescope, through which he could see the Moon’s mountains, valleys, and enormous craters. He discovered new moons orbiting Jupiter, the phases of Venus, and countless new stars.

Galileo’s findings triggered one of the greatest revolutions in human thought, changing the way we understood ourselves and our place in the cosmos. 

No longer could we believe that we were at the centre of a perfect and unchanging heavenly sphere. The universe was rich, deep, complex, and much more dynamic than anyone could comprehend.

Now, 417 years later, we have telescopes in space and on the ground observing the universe in visible light, but also in radio waves, X-rays, gamma rays, neutrinos and gravitational waves. 

We can see galaxies that were forming just a couple hundred million years after the Big Bang; we have images of black hole horizons; we have detected numerous collisions of black holes and neutron stars; we use gravitational microlensing to detect exoplanets that are tens of thousands of light-years away. We also have baby pictures of the universe in the images of the cosmic microwave background (CMB), the microwave radiation afterglow from when the cosmos was just 380,000 years old.

All of this data and the incredible technology that powers it gives us a vista of the universe that Galileo could never have dreamed about. 

Perimeter has built a vibrant research hub, Centre for the Universe, that aims to establish Canada as a world leader in cosmology.

The collaborative work across the fields of cosmology, strong gravity, and particle physics will help to answer questions about how spacetime evolves; how black holes interact with surrounding matter; how to understand the nature of dark matter and dark energy, and how to fit the theory of gravity together with quantum theory.

The new technologies and ways of analyzing data make this an exciting time for scientists-in-the-making such as Sofia Chiarenza, who is doing her PhD at Perimeter Institute and the University of Waterloo.

Chiarenza, who is originally from Italy, works in the realm of multiprobe astronomy, helping to cross-correlate data between instruments. This can involve, for example, correlating data from the Planck Cosmic Microwave Background lensing maps with data from the Dark Energy Spectroscopic Instrument (DESI), to understand dark energy fluctuations in the universe.

She has also been involved in creating the software algorithms to correlate those data sets. The idea is to not only be able analyze the huge data sets coming from the new surveys such as those from DESI, Euclid and the Legacy Survey of Space and Time (LSST), but “the idea is to also combine these data sets and do a joint analysis,” Chiarenza explains.

Chiarenza won one of the 2025 Waterloo Centre for Astrophysics (WCA) student paper prizes for her work on Blast, a software package that reduces the errors and the cost of running the computational models for these cross-correlations. “It is an algorithm that performs some calculations for multiprobe analysis more efficiently than what was previously possible,” she says. “It’s approximately ten times faster than what was previously achieved, and it is as accurate, or even more accurate than the other algorithms.” 

Already, it is being deployed within Euclid, a space telescope project that is creating maps of billions of galaxies in order to better understand dark energy, the mysterious force that appears to be causing the universe to expand at an accelerating rate. 

Although optimizing the software to make the analysis more efficient may appear to some people to be boring work in a field that is all about the amazing and incredible wonders of the night sky, “it is very much needed for the amount of data that is coming,” Chiarenza says.

Chiarenza’s PhD supervisor, Will Percival, an associate faculty member at Perimeter and director of the University of Waterloo Centre for Astrophysics, is a key player in both the Euclid and DESI missions.

He and his colleagues are measuring the cosmological expansion rate and growth of large cosmological structures — the vast interconnected web of galaxies, gas and dark matter spanning billions of light-years across the universe.

With these instruments “we can work out how fast galaxies are moving away from us and get an estimate of their distance,” Percival said. A central aspect of his work involves analyzing baryon acoustic oscillations, patterns imprinted in the distribution of galaxies by sound waves in the early Universe, that give us a ‘ruler’ for the universe’s expansion.

Hints of variable dark energy

One of the big unsolved puzzles in cosmology has to do with the cosmological constant that Einstein called lambda. Lambda describes the energy density of space, or what we call the dark energy. We know it acts as a repulsive force that is accelerating the expansion of the universe, but we really don’t know what it is, or how it operates.

An intriguing recent finding from the DESI collaboration is that dark energy could actually be variable over time, possibly getting weaker. In the standard model of cosmology, where lambda is the dark energy, the value of dark energy should be constant. So if the latest results are confirmed, that could rewrite our understanding of how the cosmos evolved, and its ultimate fate. 

The discoveries will continue. There are future releases coming from Euclid and DESI into the next decade. 

Meanwhile, researchers are also excited about the upcoming Nancy Grace Roman Space Telescope mission, which will be able to observe the distant universe in unprecedented detail, using multiple techniques to understand dark energy.

At the same time, the new Vera C. Rubin Observatory which is running the LSST project will be mapping billions of galaxies to better understand dark energy and will create a 10-year time-lapse movie of the southern sky.

Taken together, and by correlating the data and analyzing it, a new era of discovery awaits young people going into astrophysics today. 

“The next 10 years will be a great time to be doing cosmology,” Percival says.

Perimeter faculty member Neal Dalal is one of those researchers excited about what is to come. The Vera C. Rubin Observatory data, for example, will help scientists to see tiny galaxies that were previously too far away and too faint. 

That could help answer questions about dark matter, yet another mystery in the cosmos, Dalal says. 

We know that some sort of unseen mass is affecting the movement of stars around galaxies and the clustering of galaxies, but we don’t know what that is made of. That is why it is called “dark matter.” Gravitationally, it dominates the universe, and yet it does not emit, absorb, or reflect electromagnetic radiation. 

At Perimeter, a number of other faculty members are interested in solving the mystery of dark matter, including Asimina Arvanitaki, the Stavros Niarchos Foundation Aristarchus Chair in Theoretical Physics, and Junwu Huang, both particle physicists whose work intersect with cosmology.

They are not only relying on the data from these big instruments probing the universe but also designing smaller-scale and ultra-precise “tabletop” experiments that might detect the candidate particles for dark matter.

Faster photodetectors and digital processing boost optical telescopes

Dalal, meanwhile, is helping revive an old technique known as intensity interferometry using today’s ultra-fast photon counters.

Interferometry, which puts together information from different telescopes to give us a bigger window into the universe, is a technique that has long been used with radio telescopes. The Event Horizon Telescope that gave humanity its first images of black holes uses a world-wide array of radio antennas, allowing it to produce an image as if it were a single telescope the size of the Earth. But doing the same thing with optical telescopes using visible light has, until now, been much more challenging. 

Robert Hanbury Brown and Richard Q. Twiss developed intensity interferometry for optical telescopes in the 1950s, using it to measure diameter of Sirius A. But the technique was largely abandoned in the 1970s because the detectors and timing instruments for intensity interferometry were simply too slow. It took hours of work to capture and cross-correlate the information about optical light.

But now, with the advent of better and faster photodetectors that are now available at commercial scale, coupled with super-fast digital processing made possible by today’s computer chips, there are new possibilities for intensity interferometry. Perimeter Institute hosted a conference on the future prospects for intensity interferometry in 2024.

“The main thing we can do with it is to get much higher resolution pictures of the sky,” Dalal says. “If you could get visible observations from telescopes separated across the earth, you could get angular resolution that is maybe thousands of times better than even the Event Horizon Telescope,” he says.

In the long term, it might also be possible to use intensity interferometry to get an even better measure of the expansion rate of the universe, he adds.

Canada’s contributions to cosmology research

Canada’s cosmologists and data scientists have been very much on the forefront of using new technology to collect data and explore the universe.

Perimeter faculty member, Daniel Family James Peebles Chair in Theoretical Physics and Director of the Centre for the Universe Kendrick Smith, for example, is a “data-oriented cosmologist” who led the development of new mathematical algorithms and software for the Canadian Hydrogen Intensity Mapping Experiment (CHIME).

That award-winning CHIME collaboration has been mapping the expansion rate of the universe by observing hydrogen gas in distant galaxies and it has also been a huge success in detecting Fast Radio Bursts (FRBs) which are brief (few millisecond) bursts of radio waves coming from far beyond our Milky Way galaxy.

But now, Canada has the even more sensitive Canadian Hydrogen Observatory and Radio-transient Detector (CHORD) under construction.

Scientists such as Perimeter associate faculty member and University of Waterloo professor Avery Broderick have also taken the lead in the discoveries coming from the Event Horizon Telescope that has gave humanity its first images the horizons of black holes

‘Ripples in spacetime’ can now be analyzed

Another new research program, only made possible in the last decade, comes from the advent of gravitational wave detectors, such as LIGO, Virgo and KAGRA, which allow physicists to better understand gravity in extreme environments such as the mergers of black holes and neutron stars.

Ripples in spacetime caused by the collisions of massive objects were predicted by Albert Einstein in 1916. About 100 years later, on February 11, 2016, the scientists at LIGO announced the first-ever detection of gravitational waves caused by the distant merger of two black holes.

Perimeter faculty member Luis Lehner, Carlo Fidani Rainer Weiss Chair in Theoretical Physics,  was one of the early pioneers in the field of gravitational wave research. When he was doing his PhD in the mid-1990s, gravitational wave detectors were just being constructed. He and his colleagues developed new methods for detecting and studying observable signals from these powerful cosmic events. 

And now, 10 years after that first detection, “we have transitioned from getting signals one at a time, to getting many, many signals, and we are able to analyze them much more deeply,” Lehner says.

Most recently, Sizheng Ma, a postdoctoral researcher at Perimeter, was part of a group that detected a characteristic “frame-dragging” signal from the horizon of the merger of two black holes, an event known as GW250114, which was captured by LIGO on January 14, 2025.

It was the first time that researchers were able to detect this particular signal from the horizon of merging black holes. 

The GW250114 event from 2025 was not too much different from LIGO’s first detection of gravitational waves in 2016. But this signal was dramatically louder and clearer, thanks to ten years of technological advances that have reduced signal noise.

That enabled Ma and his colleagues to test their theoretical predictions describing the distinctive wave signature at the horizon of merging black holes against an actual merger event. 

Lehner says the computational technology and power have made a big difference in the field. “The technology has started matching our dreams so that what we can simulate using powerful computers can be contrasted with our observations.”

“In about 10 years, we hope to have at least one detector in space,” Lehner adds. The Laser Interferometer Space Antenna (LISA) is a planned European space mission that is designed to detect and measure gravitational waves. 

Gravitational wave data also allows researchers to put Einstein’s theory of gravity, known as general relativity, to the test. So far, the gravitational wave data seems to confirm Einstein’s predictions with high precision, but scientists are always looking for deviations that might lead to new physics. Faculty member William East is also part of the LIGO Scientific, VIRGO and KAGRA collaborations putting general relativity to the test. 

Physicists throughout Perimeter Institute are on a quest to combine Einstein’s gravity theory with quantum theory. The extreme events like collisions of neutron stars and black holes are environments where they might get deeper insights into the nature of gravity.

New Artificial Intelligence tools help analyze cosmology data

Many physicists also believe that new tools — like artificial intelligence (AI) — will help accelerate the analysis of the multitude of data that is coming to us from all these instruments.

As Lehner points out, the data that comes from detectors can be noisy and it can take humans a heroic amount of time to sort it out. AI can help clean it up and speed up the analysis.

“There are obvious places where researchers can use AI, and of course, they are also using it to try and tame the equations and get more predictions. Whether we like it or not, AI is becoming ubiquitous and is finding its way into research.”

The speed of the advances in knowledge now is simply remarkable, and that is what makes physics today such an exciting field to be in, Lehner says.

“As humans, we have been looking at the night sky since we first gained consciousness, but only in the last few decades of the human timeline have we been able to scan the sky in all these frequency ranges. It is amazing how fast this field is progressing,” Lehner says.

He says more of that is bound to come in the future.

“This research will enjoy growth and there will be plenty of data and plenty of interesting questions to work with for the next several decades,” he adds.

This is part three of an ongoing series about the Future of Physics. Read part one here, Part two here, and stay tuned for more!