Physicist Sabine Hossenfelder: ‘There are quite a few areas where physics blurs into religion’

To answer life’s biggest questions, says the German theoretical physicist and YouTuber, we need to abandon unscientific ideas such as the multiverse

Sabine Hossenfelder is a German theoretical physicist who writes books and runs a YouTube channel (with 618,000 subscribers at time of writing) called Science Without the Gobbledygook. Born in Frankfurt, she studied mathematics at the Goethe Universität and went on to focus on particle physics – her PhD explored the possibility that the Large Hadron Collider would produce microscopic black holes. She is now a research fellow 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 Questions, came out in August.

The first question you ask the physicists you interview in the book is: “Are you religious?” How about you?
I tried to be religious when I was a teenager. I was not Christianised because my parents were both atheists, but all of my friends were Christian, 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 get myself to believe that God exists.

You weren’t keen on physics at school. Why not?
It was to do with the way it was taught. We were given experiments that had been done in the past by other people, and were then supposed to do some sloppy reconstruction of it ourselves. I just thought it was terribly boring. I really only got interested in physics when I learned how differential equations work. Studying physics at university, I came to it from this weird angle where I was trying to figure out how much you can do with mathematics to understand nature. It’s why I don’t really fit into any particular area of physics, because I have this overview attitude. I just want to know what the mathematics is good for.

What prompted you to write the book?
The major message I wanted to get across was: we’re painting a very one-sided picture of physics in our education and in the popular science press – of a very technocratic, maths-heavy discipline with particle accelerators and all that kind of stuff. But physics also touches on big existential questions: How does the universe work? How did everything begin? What are we made of?

You write that a lot of research in physics, such as hypotheses for the early universe, is “religion masquerading as science under the guise of mathematics”. Could you elaborate on that?
There are quite a few areas where the foundations of physics blur into religion, but physicists don’t notice because they’re not paying attention. It’s 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 this is really just the simplest way you can extrapolate the equations into the past – and then you can add inflation, which is an exponential phase of expansion; or, like Roger Penrose, you can make it a cyclic universe. But maybe it was a big bounce, or it started with the collision of membranes. These ideas are all possible – they’re all compatible with the observations that we have. But I would call them ascientific – the kind of idea that evidence says nothing for nor against.

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

You don’t have much time for the multiverse either. Why not?
It’s another one of those ideas that I’d call ascientific. If you want to believe that there are infinite copies of you with small alterations – one of them maybe won the Nobel prize, another became a rock star – you can believe this if you want to, it’s not in conflict with anything we know. But from a scientific perspective, if you want to make progress in our understanding of natural law, I’d say it’s a waste of time exactly for that reason, because you can’t test it.

Can you understand why some giants of physics, such as Stephen Hawking, came to believe we are living in a multiverse?
I have guesses, but I can’t ask him. It’s not just Stephen Hawking, there’s quite a number of people in the foundations of physics, though if you read the popular science press, it overstates the number, because they’re very prominent. It’s very niche, actually, this whole multiverse thing. Those people are really confused about what science can actually do. How they come to this conclusion that the multiverse must exist is that they have some theory that predicts some things that agree with observations – that’s all well and fine. And then they jump to the conclusion that therefore all the mathematics that appears in this theory also has to exist in some sense. But this is not how it works. You’ve just assigned reality to some mathematical expressions. You can’t support it with a scientific argument.

You’re very exacting when assessing other scientists’ work, so I’m interested to know: which physicists working today do you hold in the highest regard?
Oh Jesus. Then you’ll print this and everyone else will hate me. Well, I very much 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 courageous, putting forward some ideas that are fairly out-there – like the stuff with the gravitationally induced collapse, or how consciousness plays a role in the human brain, or the cyclic universe. It’s all very original.

You wrote an opinion piece for the Guardian in September about physicists inventing new particles that provoked a lot of debate…
My argument was that it’s a really bad scientific strategy to just invent some mathematics, then proclaim we have to go and test it when there’s no reason it should work. There are infinitely many of those particles you can make up, and it’s not working. Just look at what’s come out of it in the past 40 years. It’s not a terrible lot. Maybe think about something better. Also, it worries me that we always talk about how science supposedly self-corrects, but it doesn’t seem to be happening. They’re just trying the same thing over and over again.

One reader wrote in saying that just because there was no low-hanging fruit, it doesn’t mean there is 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, it seems to agree with me. It’s not working. I’m not making very high demands. I’m just saying, please use your brain.

You’re a prolific tweeter. What would be lost if Twitter collapsed?
I’ve made friends on Twitter, I have my little interest group, so it would be shame if it died. But this is how it goes with internet startups. I have the impression that Elon Musk is taking a very experimental approach, he’s trying out 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 kind of person to do things slow and carefully.

You have a YouTube channel for your own music

Normally the way that I use it is to clear out my head when I’m stuck with something. It forces me to concentrate 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 Guardian and Observer order your copy at Delivery charges may apply


Killian Fox

The GuardianTramp

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