In his 1996 book The End of Science, John Horgan argued that scientists were close to answering nearly all the big questions about our Universe. Was he right?

The theoretical physicist Sabine Hossenfelder doesn’t think so. As she points out, the Standard Model of physics, which describes the behavior of particles and their interactions, is still incomplete as it does not include gravity. What’s more, the measurement problem in quantum mechanics remains unsolved, and understanding this could lead to significant breakthroughs.

Ultimately, Hossenfelder is optimistic that progress will be made in the next two decades, given the current advancements in quantum technologies and quantum computing.

SABINE HOSSENFELDER: Starting in the 1970s and 1980s, a lot of physicists became very optimistic that we're pretty close to finding a theory of everything that would explain all the interactions in nature in one coherent whole. And string theory was one of the biggest candidates for this. And partly in response to this overoptimism, John Horgan wrote "The End of Science" where he picked up several disciplines of science and tries to argue that actually, we're pretty close to the end. And I have to admit that it's a very good question to ask. You could have the perspective that there is a certain period in the history of mankind where we make those big fundamental discoveries in nature, and it's just behind us. It's not going to happen that we'll discover another continent. And it's a good question to ask. Like, is the same the case with science? Have we just discovered all the big things that there are to discover? And Horgan is not saying that we'll stop doing science or we'll stop doing research but he's saying that there'll be no new big discoveries. We'll just add some bits and pieces to the stuff we already have. 

And as someone who has worked in the foundations of physics, I have to totally disagree with him on his perspective on being close to a theory of everything. And I guess this also puts me in disagreement with a lot of my colleagues in the foundations of physicists. A theory of everything in the foundations of physics is a theory that combines all the fundamental forces of nature. We currently know four of those forces. That's the electromagnetic force, which pretty much everyone has heard of. Then there's the strong and the weak nuclear force. A strong nuclear force holds together the particles that make up atomic nuclei, and the weak nuclear force is responsible for nuclear decay. Those are all quantum theories. And then we have gravity. This is the fourth force. And it's not a quantum theory. And this is kind of the problem. It's kind of the weird outlier. And a theory of everything would combine all those four forces into one coherent whole. And I think we're nowhere close to such a theory. 

One of the reasons is that we still don't have a theory for quantum gravity that would combine the standard model with particle physics. And yes, string theory was a contender for this. But it's fallen out of favor. It's not even clear that'd actually solve the problem it was meant to solve in the first place. And pretty much the same thing could be said about other approaches to quantum gravity. So this thing is still unsolved. But maybe even more importantly, we have a much bigger problem in the foundations of physics, which is the measurement process in quantum mechanics. It's created some practical problems in how we analyze experiments. Physicists are just confused about what exactly it means, that we have to do this measurement update. Exactly what is the measurement? What does it take to do a measurement? We don't know. The theory can't answer this question. And I think that an answer is needed. And indeed, when we find this answer, it'll lead to a lot of progress. And it's not just progress in our theoretical understanding, it's also progress by way of new technology because if you look at all the technological devices that we use today, they're all based on quantum mechanics. So if we manage to improve this theory of quantum mechanics by eventually understanding how a measurement process works, I think this will also help us to improve our technological gadgets, and it'll have a huge impact on the entire world. 

So I don't think we're anywhere close to the end of science. Now, I'm actually quite optimistic that we'll be able to solve the measurement problem in quantum mechanics within the next one to two decades or so because it falls into an area, quantum technologies and quantum computing, quantum information, quantum optics where there is a lot of technological progress at the moment. So sooner or later, they'll just stumble over something new, something that they can't explain, and then they will call for the theorists to please explain this. And this is when a lot of progress is going to happen very suddenly.