How dark is dark matter? Which elementary particles are we missing that would explain the phenomenon – and, by extension, the rest of particle physics? On 24 March, it will be exactly 30 years since Belgian astrophysicist Dirk Frimout took off on a nine-day voyage on the space shuttle Atlantis. During those nine days, he flew around the earth 143 times, carrying out numerous experiments. Shortly after returning to Earth, he and meteorologist Frank Deboosere met a boy who would go on to become a professor of experimental particle physics at VUB. If the two men knew how much of an impression they made on the teenage Steven Lowette that Wednesday afternoon, and what ground-breaking research would result from their encounter, they would no doubt be proud.
Lowette, then a teenager with a healthy interest in astronomy, was invited by the fledgling weatherman Deboosere to the Radio 1 studio to meet Frimout during the youth programme Van Kattekwaad tot Erger, presented by Kathy Lindekens. “I had given a talk about the planets in the fifth grade,” Lowette recalls. “I was so fascinated by the universe that my parents decided to enrol me in a course at the MIRA Observatory in Grimbergen. But I was too young. Deboosere – who was working there as a volunteer at the time – took me under his wing and gradually taught me basic astronomy. From then on, my interest in the universe and space travel only increased. I even kept a scrapbook about it and collected everything to do with space travel, including the popular Artis Historia books, in which you had to paste pictures to complete your book.”
Passionate physics teacher
So Lowette was very impressed when, on that Wednesday, he stood with Frimout in the lift of Belgium’s national broadcaster and was allowed to spend an afternoon firing questions at the astronaut, whose space mission had been completed. While Lowette’s parents had occasional contact with Frimout subsequently, the teenager chose his own path. “In the last years of secondary school, I had lessons from an inspiring, enthusiastic and passionate physics teacher,” he says. “With him you really had to earn your grades, but everyone loved going to his lessons. I dreamed more and more of a career in the sciences and when I finished secondary school, I took the entrance exam to study civil engineering at VUB. I passed, but in the end I chose statistical physics. As far as I was concerned, it could be as theoretical as possible. Then I did a more experimental doctorate in the field of particle physics, which I became increasingly passionate about. Upon completion of my PhD I started working at the University of Santa Barbara in the US, a very strong university in the field of physics. After six months, the whole group moved to CERN, after which I went to live in Geneva for six years to do research. I’d got to know CERN well when I was preparing my PhD.”
Since then, Lowette’s scientific record has only grown more impressive. At CERN, where he has been working for 20 years, he specialised in research into what happens on the smallest scale known to nature: elementary particles. He was involved in the first observations of the Higgs-Boson (Englert) particle, the existence of which had been theoretically predicted 50 years earlier by his ULB colleague, the Nobel Prize winner François Englert, among others.
It’s there, but we can’t see it
“We know that existing theories generally work well, but they are less conclusive when it comes to particles with very high kinetic energy,” says Lowette. “Since 2009, CERN has had the Large Hadron Collider, a particle accelerator with which we can generate many collisions of particles at very high energy. This accelerator enabled us to demonstrate the Higgs-Boson in 2012.”
While scientists at CERN try to simulate the theoretical models on which particle physics is based and figure out how nature and the universe are built, Lowette now goes much further in his research, as the gaps in the general theory of particle physics continue to intrigue him. Researchers from all over the world are trying to fill those gaps in a satisfactory way.
“We’ve known for about a century that there is something we can’t see but that has a big impact on our universe,” says Lowette. “We see that influence mainly in gravitation. Many scientists are looking for the hidden particle that causes this gravitation: we cannot see it, but it is there and it has a mass, because it attracts other mass. In calculating the total mass and energy in our universe, we are left with an enormous amount that we cannot see. Only 15% is normal mass, about 2% is in the stars, but at least 85% is hidden somewhere in some form or other. In our jargon, we speak of dark matter. Dark matter is something other than black holes. We actually understand black holes reasonably well and they can be explained from the existing theory, as mass with such a density and gravitation that not even light escapes from them. Dark matter is something else, something that we are almost certain cannot consist of the same particles as observable matter.”
Too old to be an astronaut
The search for dark matter is popular among particle physicists. Lowette: “Every day, new theories or possible explanations are published about it. What interests us is the first second after the Big Bang. Not the moment when the first stars were formed, because then it is already too late: stars were formed long after the Big Bang. In fact, it is the dark matter that made matter start to clump together, and was eventually able to ignite the first stars.”
Professor Lowette now teaches at VUB’s Department of Physics, and is a member of the Research Group Elementary Particle Physics. “There may have been a time when I dreamed of going to space myself,” he says. “But I am definitely too old for that now. Space travel continues to fascinate me, however. I continue to be fascinated by experiments on the International Space Station within my field, such as the search for antimatter, or the design of a gravitational telescope that will go into space in the near future. And the recently launched James Webb space telescope will soon start making beautiful observations.”
Lowette has not seen either Dirk Frimout or Frank Deboosere since his youth. Thirty years after that fateful Wednesday, and with so much experience and knowledge acquired in the meantime, perhaps it is time for a reunion.
On the occasion of the 30th anniversary of Dirk Frimout's space journey (March 1992) and the 20th anniversary of Frank De Winne's space journey (October 2002), VUB and ULB welcome an international space delegation in October 2022. In collaboration with Belgian Space Week, we invite students from the third grade of secondary school to an inspiring programme about space.