“There are some areas where physics mixes with religion”

Sabine Hossenfelder is a German theoretical physicist who writes books and runs a YouTube channel (with 618,000 subscribers at the time of writing) called Science Without the Gobbledygook. Born in Frankfurt, she studied mathematics at Goethe Universität and continued to focus on particle physics: her PhD explored the possibility that the Large Hadron Collider produces microscopic black holes. She is now a researcher at the Frankfurt Institute for Advanced Studies, where she leads a group studying quantum gravity. Her second book Existential Physics: A Scientist’s Guide to Life’s Biggest Questionsreleased in August.

The first question you ask the physicists you interview in the book is, “Are you religious?” And you?
I tried to be religious when I was a teenager. I haven’t been Christianized because my parents were both atheists, but all my friends were Christians, so I went to church with them. And I kind of liked it: the singing, the social events. I considered joining, but I just couldn’t bring myself to believe that God exists.

You weren’t into physics at school. Why not?
It had to do with how it was taught. We were given experiments that had been done by other people in the past, and then we had to reconstruct them ourselves. I just thought it was terribly boring. I only really got interested in physics when I learned how differential equations work. Studying physics in college, I came at it from this weird angle where I was trying to figure out how much math can be done to understand nature. That’s why I don’t fit into any particular area of ​​physics, because I have this big-picture attitude. I just want to know what math is for.

It’s very niche, this whole multiverse thing. Those people are really confused as to what science can actually do

What prompted you to write the book?
The main message I wanted to convey was: We are painting a very one-sided picture of physics in our education and in the popular science press – of a very technocratic, math-heavy discipline with particle accelerators and all that sort of thing. But physics also touches on big existential questions: how does the universe work? How did it all start? What are we made of?

You write that much research in physics, such as hypotheses for the early universe, is “religion masquerading as science under the guise of mathematics.” Could you elaborate?
There are some areas where the basics of physics get mixed up with religion, but physicists don’t notice because they don’t pay attention. It is a lack of education in the philosophy of science in general. For example, the most commonly accepted story about the beginning of the universe is the big bang, and to some extent that’s really just the easiest way to extrapolate the equations into the past – and then you can add inflation, which is a exponential phase of expansion; or, like Roger Penrose, you can make it a cyclical universe. But maybe it was a big bounce, or it started with the membranes colliding. These ideas are all possible, they are all compatible with the observations we have. But I would call them unscientific, the kind of idea that the evidence says nothing for or against.

Is it equally reasonable to say that God or some other higher power created the universe?
This is a tough question. There is a difference between them in that the theories that physicists work with are mathematical in nature, whereas the God hypothesis is not a mathematical thing.

You don’t have much time for the multiverse or. Why not?
It’s another one of those ideas that I would call unscientific. If you want to believe that there are countless copies of you with minor alterations – one maybe won a Nobel Prize, another became a rock star – you can believe it if you want, it doesn’t conflict with anything we know. But from a scientific point of view, if you want to make progress in our understanding of natural law, I would say it’s a waste of time for that very reason, because you can’t test it.

Can you understand why some physics giants, like Stephen Hawking, have come to believe that we live in a multiverse?
I have guesses, but I can’t ask him. It’s not just Stephen Hawking, there are quite a few people in the fundamentals of physics, although if you read the popular science press, overstate the number, because they are very important. It’s very niche, actually, this whole multiverse thing. Those people are really confused as to what science can actually do. How they come to this conclusion that the multiverse must exist is that they have a theory that predicts some things that agree with observations – it’s all good. And then they jump to the conclusion that therefore all the mathematics that appear in this theory must also exist in some sense. But that’s not how it works. You just assigned reality to some mathematical expressions. You can’t back it up with a scientific argument.

You are very picky about evaluating the work of other scientists, so I’m interested to know: Which physicists working today do you hold in the highest regard?
Oh Jesus. Then you print this and everyone else will hate me. Well, I really admire Roger Penrose, who has a really sharp mind and has done so many amazing things. He has also been outspoken in his criticism of some of the trends in the foundations of physics, including string theory. And he’s brave, proposing some ideas that are quite out there—like stuff with gravity-induced collapse, or how consciousness plays a role in the human brain, or the cyclical universe. It’s all very original.

Elon Musk is trying new things, and that’s okay. I just wish it would be a little less destructive

You wrote an opinion piece for the Keeper in September about the physicists who invented new particles that caused a lot of debate…
My argument was that it’s a bad scientific strategy to simply invent some math, and then proclaim that we have to go test it when there’s no reason why it should work. There are infinitely many of those particles you can come up with, and it doesn’t work. Just look at what has come of it over the past 40 years. It’s not a terrible lot. Maybe think of something better. Also, I’m concerned that there’s always talk about how science supposedly corrects itself, but it doesn’t seem to be happening. They’re just trying the same thing over and over again.

One reader wrote in that just because there were no low-lying fruit, doesn’t mean there was no fruit to be found.
This is entirely correct. It’s possible that one of those experiments will find something. I’m just saying it’s incredibly unlikely, and if you look at the evidence, he seems to agree with me. Its not working. I’m not making very high demands. I’m just saying please use your brain.

You are a prolific tweeter. What would be lost if Twitter collapsed?
I’ve made friends on Twitter, have my own little interest group, so it would be a shame if he died. But that’s the way it is with internet startups. I have the impression that Elon Musk is taking a very experimental approach, he’s trying new things, and that’s good. I just wish he would do it a little less destructively, a little slower, a little more carefully. But then he doesn’t seem to be the type of person to do things slowly and carefully.

You have a YouTube channel for your music
Normally the way I use it is to clear my head when I’m stuck with something. It forces me to focus on something else. But I guess everyone needs a hobby.

• Existential Physics: A scientist’s guide to life’s biggest questions is published by Atlantic (£16.99). To support the Keeper And Observer order your copy at guardianbookshop.com. Shipping costs may apply

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