One of the hottest problems in science involves the mystery of “dark matter”—what it’s made of and why it accounts for so much of our universe. Solving the riddle is quite likely to net a Nobel Prize but, more importantly, will usher in a new era of understanding about how nature works at a fundamental level—from the tiny world of particle physics through to incredibly vast expanses of galaxies and clusters on cosmological scales.
Canadian research activities are part of a global drive to understand dark matter. Various approaches to the mystery involve theorists at Perimeter Institute for Theoretical Physics (PI) in Waterloo, Ontario; experimentalists at SNOLAB, in Sudbury, Ontario; researchers at a variety of universities and institutes across the country; as well as Canadian scientists who are actively collaborating at CERN in Geneva, Switzerland, home of the Large Hadron Collider. Not only are they propelling scientific understanding throughout the physics community, many of these top scientists are sharing their passion for research with others through an innovative enrichment program you can enjoy online.
Shedding Light on Dark Matter
For thousands of years, astronomy has been about light. Astronomers have studied light from distant stars, galaxies, planets, and other objects in space. However, over the last few decades, physicists have come to realize that celestial objects that emit any type of light make up only a tiny fraction of the universe.
The rest of the universe is made of unseen material that does not emit, reflect, or absorb any type of electromagnetic radiation. This “dark matter” dominates galaxies, making up about 90% of the mass of every galaxy in the universe. Without it, galaxies (including our own) would be inherently unstable and would rapidly fall apart.
One of the earliest theories of dark matter was that it consists entirely of compact celestial objects such as planets, dwarf stars, and blackholes. Careful observations have ruled out this theory. Today, most physicists think that dark matter is made of a type of subatomic particle that, to date, has never been detected in the laboratory.
Dr. Chris Jillings, SNOLAB
“…what makes it compelling”, says Dr. Cliff Burgess, a theorist at Perimeter Institute and McMaster University who spends time collaborating at CERN, “is that there are many lines of independent evidence that point in the same place. In that sense, it is like the evidence for atoms one-hundred years ago. What convinced people that atoms existed was not any one line of evidence, but that you had many lines of evidence that all converged on the same conclusion. Dark matter is like that.”
Dr. Chris Jillings, an experimentalist at SNOLAB agrees, “So all the evidence for dark matter is circumstantial if you like, but there are four pieces of circumstantial evidence all pointing the same way, so this has got to be looked at.”
With the mystery of dark matter now in the hands of the observers, Dr. Justin Khoury, a cosmologist at Perimeter Institute says, “It is a real opportunity for physics. It’s not just explaining one missing thing in the universe. Once we understand what dark matter actually is, we’ll have understood a completely new direction in physics. There is no question.”
Visualizing With the Experts
See how these and other Canadian-based scientists share their understanding in Perimeter Explorations' first video module entitled The Mystery of Dark Matter. The video was produced by the outreach team at Perimeter Institute in conjunction with teachers and researchers across the country. The enrichment program is viewable online and is also available, to educators, in a kit form that includes a teacher guide and student worksheets for in-class purposes.
