The Cosmos on the Blackboard

Chalked across a long blackboard in an otherwise sparse office is a mass of numbers, symbols, lines, arrows and brackets. Smudged, overwritten and corrected, the rows of formulae bear witness to a brain hard at work. It’s easy to picture Marcelle Soares-Santos entering her office and lingering at the board to make a note or comment, adding further enhancements to the superformula designed to bring us closer to unraveling the secret of the cosmos.

Marcelle Soares-Santos is a professor of astrophysics specializing in dark energy. “It would be more accurate to call it invisible energy,” she says. Because that’s the whole problem with dark energy – its invisibility. “We can only detect it indirectly,” she explains. “Cosmic events, like the collision of two stars, or more specifically, the light and waves they emit, offer clues.” But what this mysterious force is, or the rules it follows, remains largely unknown.

The astrophysicist has been studying the mystery of dark energy for many years, the last of which has been spent at the University of Zurich. She settled in quickly, she says with a smile. As a nature-lover, the location of the Irchel Campus at the edge of a forest suits her perfectly. And, she chuckles, she’s even come to appreciate the climate here, despite hailing from Brazil, a country where the sun shines all year round. “You never need to check the weather forecast there,” she laughs.

But the four seasons have their attractions. When she first moved to the US, she found winter a challenge and snow an inconvenience. Last winter in Switzerland, however, she discovered skiing – and pleasure in snow!

A picture-perfect blue sky stretches above the campus, concealing the infinite universe beyond. To the suggestion that the cosmos remains a vast, unsolved riddle, Soares-Santos agrees with a nod. In fact, she explains, only about 5% of the universe consists of identifiable matter – stars, galaxies, planets – made up of elementary particles like electrons and nucleons familiar from standard physics.

Around a third of galaxy mass is unidentified dark matter, while a staggering 70% is dark energy. And this energy behaves in an utterly bewildering way: rather than holding space together as energy typically does, it drives it apart – and at an accelerating rate. Around 14 billion years ago, the Big Bang brought space and time into existence. Since then, the universe has been consistently expanding.

What is this force that propels space apart? Why does it do so, and under what conditions? These are the questions that Soares-Santos, along with many other astrophysicists worldwide, are battling to answer. There are a few hypotheses on the table, the professor says, including a return to the cosmological constant, a term Albert Einstein originally added to his equations for general relativity, only to later dismiss it. Some researchers point to the vacuum energy of space. Or perhaps dark energy operates according to entirely unknown physical laws? Ultimately, the mystery of the wondrous energy remains unsolved – as we simply don’t have the data.

This is what Soares-Santos is determined to change – starting with the formula written on the blackboard in her office, which she and her team are using to develop a sophisticated investigative method designed to help researchers gain greater insights into cosmic events. They’re in the process of building a kind of three-dimensional map that simulates the distances, luminosities, brightness levels and colors of different cosmological objects and phenomena.

The map is created by piecing together countless small bits of information – all the vibrations, signals, images and waves received from the universe that form part of the puzzle. Soares-Santos glances at the blackboard. “A process like this – in which data has to be calculated and revised, then tested, experimented on, optimized and verified – is incredibly complex and takes time,” she explains. “Only when it works on a small scale can we even consider scaling it up,” she says. Until they reach that point, the team must continue wracking their brains at the blackboard.

These trail-blazing calculations have taken Marcelle Soares-Santos on ventures that not only span galaxies but continents. She grew up in Vitória, the capital of Espírito Santo in southeastern Brazil, where she also attended university.

After earning her PhD at the University of São Paulo, she moved to the United States to work at Fermilab near Chicago. It was a great experience, she recalls, her eyes sparkling. People had come from all corners of the world, united by their passion for physics. It was there that she met her husband, a German astrophysicist with whom she has a four-year-old son, and who works just next door at the Department of Physics, researching dark matter.

While still at Fermilab, Soares-Santos had been quick to realize that to study galaxies, supernovae and star clusters billions of light-years away, effort needed to be invested in new measurement instruments. This led her to take part in the Dark Energy Survey (DES) collaboration, where she played a leading role in developing the Dark Energy Camera (DECam), a massive telescope that renders cosmic events and objects visible, helping scientists to explore the universe systematically. The enormous device – its camera alone weighs nearly 1.7 tons – is stationed in the Chilean Andes, recording occurrences across the universe.

Sunlight streams through the blinds, making Soares-Santos’ desk glow, almost like something from a distant galaxy. Having traveled with our thoughts into outer space, we return to Earth and pick up her story again: how did it all begin? The astrophysicist is reminded of a striking event from her childhood in Brazil that may have fueled her interest in physics.

In those days, her father worked for a mining company, and one day her school paid a visit to the mine. As part of a demonstration, the miners set off a controlled explosion – at a safe distance from the class, of course. “I saw the explosion but heard nothing at first; only after a delay did the sound reach me,” she says. For her as a little girl, it was astounding. “Wow! How is that possible?” Her teacher then explained that sound travels slower than light, a concept that she found truly fascinating – and perhaps never really left her. After all, she continues to study sound and light today, albeit in a very different context.

There’s a knock at the door. Her husband peeks in, asking if she’ll join him for lunch. Glancing at the blackboard, she shakes her head. She’s still got much to do.