Picture of universe getting clearer—but much remains unknown

Even though we can explore the universe with great precision, there is still a lot we don’t know, according to Ulf Danielsson, professor of theoretical physics at Uppsala University. Besides doing research, he is keen to explain science more broadly—most recently in the book “Människan är ett mirakel” (“Human Life is a Miracle”), a collaboration with author Björn Ranelid.

Thanks to science, the universe has been mapped with a precision that was unthinkable just a few decades ago. New instruments and measurements have enabled scientists to see almost all the way back to the Big Bang.

“Even though our overall picture of the universe has evolved in an amazing way, absolutely fundamental questions remain. What is the universe really made of?” asks Danielsson.

Mysterious dark energy

Only a fraction, a few percent, of the universe is made up of the matter we know—the matter that makes up stars, planets and people. The rest is something else entirely.

“We know that about 70% is dark energy and 25% is dark matter. But we don’t know what that is. There have been ideas about dark matter being some kind of unknown type of particles, but it hasn’t really been possible to confirm any of these suggestions,” he says.

And dark energy is even more mysterious.

“It’s bound up with really fundamental paradoxes in our basic description of the universe. We simply don’t know what it is.”

Transparent but invisible

The term “dark matter” is actually misleading, in Danielsson’s view.

“It’s not that it’s hiding in the darkness between the stars. It doesn’t shine, but it doesn’t reflect or absorb light either. It’s more or less transparent.”

It was a Swedish astronomer, Knut Lundmark, who first started talking about dark matter in 1930. Then the term was picked up by the Swiss astronomer Fritz Zwicky, and it has been around ever since.

Despite almost a century of research, the nature of dark matter is still unknown.

“We actually know less about what it is now than we thought we knew perhaps 20 years ago,” says Danielsson.

The quest for a single theory

Another great challenge in physics is that the two major theories—quantum mechanics and gravity as described in Einstein’s general theory of relativity—do not fit together. String theory is an attempt to reconcile them.

“String theory states that the smallest constituents of nature are tiny elongated strings—little snippets of thread. They are so small that we cannot yet see them, but if the world is made up of such strings, many of the most difficult paradoxes between quantum mechanics and gravity seem to be resolved.”

As yet, there is no experimental evidence. There were hopes of making lots of new discoveries at the LHC particle accelerator, such as finding supersymmetric particles. But so far nothing has been found beyond the Higgs particle and the paradoxes remain. This leaves researchers groping in the dark, says Danielsson.

“Nature doesn’t have to deliver the riddles in measured doses, so that we can make a giant discovery once a generation. Maybe it will happen in a few years, or maybe it will take a thousand years.”

Life on other planets—more likely than we think

The question of whether we are alone in the universe is one that interests many people. For Ulf Danielsson, the answer is beyond doubt.

“I’m absolutely convinced we are not alone. To me, it seems completely unreasonable for there not to be life on other planets. I see the life that came into being on our Earth as a natural process, though obviously the conditions have to be right.”

Since the 1990s, scientists have discovered thousands of planets around other stars, and they now estimate that there could be hundreds of millions of Earth-like planets in the Milky Way alone. There may even be life on other planets in our own solar system.

“Perhaps there is, or has been, microscopic life on Mars. And down in the dark beneath the ice-covered seas of Jupiter’s and Saturn’s moons, there might be something living there.”

Popular science as a research method

For Danielsson, explaining difficult ideas is not just a service to the public—it is a way of thinking.

“Trying to explain things to others makes you understand them better yourself. When working with something complex, you need to simplify and create helpful images—not just to teach others, but to be able to see the connections yourself.”

He describes popularization as a reciprocal process, in which storytelling and research enrich each other.

“For my own research and creativity, this popularization is enormously rewarding. It broadens perspectives and also has a deeper existential meaning for me. I like to connect what I talk about with culture and human experience.”

Conversation as a way forward

Precisely this approach characterizes his new book “Människan är ett mirakel” (“Human Life is a Miracle”), written with Björn Ranelid. The collaboration began unexpectedly, after they ended up on different sides of a discussion on SVT’s program “30 minuter.”

“Instead of arguing, we decided to talk and write a book together,” Danielsson explains.

The result was a kind of exchange of letters in chapter form.

“It’s not polemical—we write about the same topics, but from different perspectives. At its core, it’s about our shared sense of wonder at existence.”

Knowledge as humility

For Danielsson, science is about the fundamental questions around the existence of the universe and human life.

“We’re quite fragile biological beings living in a very vulnerable situation on a planet that we are totally dependent on, and that should make us more humble.”

He argues that perhaps the most important task of science is to remind us of precisely this—our place in the whole.

“We are not outside nature, we’re part of it. And this knowledge hasn’t really got through, which is one of the reasons why we are stuck with these huge problems and an Earth that is ravaged and partly wrecked by climate change.”

Waiting for the next stroke of genius

While waiting for the next stroke of genius, Danielsson and his fellow researchers continue to explore the structure of the universe and look for comprehensive theories—which it may be possible to find through string theory or in some completely different way.

“Actually, we know both very, very much and very, very little. But if we look historically at how knowledge of the universe has developed over the last century and in recent decades, a tremendous amount has happened,” Danielsson concludes.