All About Space
Speaks with Brian Greene to discuss how our understanding of the universe around us is always evolving
It feels like we’re really coming into a golden age of black hole astronomy. We’ve got the Event Horizon Telescope (EHT), which gave us our first direct image of a black hole, and we’re seeing a lot of black hole mergers thanks to the Laser Interferometer Gravitational-Wave Observatory (LIGO). Do you feel we’re finally getting a better handle on these objects? If so, what could that tell us about the universe? There was a time, ten years ago, when you could still make an argument that black holes aren’t real – they’re just a figment of mathematics. But with LIGO, with the collision of two black holes giving that ripple in the fabric of space, and with the EHT, black holes have come into their own.
For someone like me who works on cutting-edge theoretical ideas, we’re struggling now to merge black holes and quantum mechanics to get a full understanding. Black holes are the prime theoretical laboratory for pushing our ideas to the limit. When we can fully understand black holes and quantum mechanics, our understanding of the universe is going to jump to a new level.
Are you optimistic that that’s going to happen relatively soon? Do you think there are breakthroughs on the horizon?
Yeah. There are many of us – those people who work on string theory and quantum gravity. Focusing upon black holes is really the predominant occupation at the moment. There’s so much exciting work that’s happening that I would suspect that even a year or two from now, our understanding today will look relatively primitive to the new ideas that will be developed.
People often throw up their hands after they read a study that says ‘we’ve made a big breakthrough’ and then they see another study that says, ‘actually, no’. A lot of people don’t know how science works, that it’s a process that builds upon things step by step and everything is always in flux. Is that something that you try to get across to people when you’re teaching them about science? of the discovery, where people put forward ideas, others react to the ideas, people test and observe and come back. It’s a wonderful, dynamic process of human discovery. And when you see science in that light, it brings it to life in a way that a textbook of facts could never.
I find talking to people – and to kids especially – they often don’t even view scientists as real people. They’re seen as caricatures, the wild-haired
guys in the movies. I think it’s really important to emphasise to kids that scientists are just people like them or like their mum or dad, and that’s something that most people don’t internalise.
It’s an important lesson. And there have been attempts – television shows, you know, The Big
Bang Theory perhaps being the most prominent of them. But again, in The Big Bang Theory the scientists were somewhat caricatures, right? It was good that it was mainstream, but still there’s a tendency to see scientists as this weird collection of people. In any large group, there are weird folks. But the vast majority of people are just like everybody else and just focus their attention on a certain class of questions.
Scientists are trying to come up with a theory of everything, to find one that stands the test of time. Do you still feel like that’s going to be string theory? Has what we’ve learned over the past five or ten years changed any of your thinking on the biggest questions?
Just to be clear, although I’m known for working on string theory and bringing string theory to general populations, I have never, ever said I believe in string theory. I have always said I have confidence that this is an interesting idea worthy of our attention that may ultimately be the final theory, but we just don’t know yet.
My assessment is pretty stable; it’s pretty much the same. In the last few years there have been great theoretical breakthroughs in string theory. There’s been less contact with experiments than I would have hoped. I’d hoped that the Large Hadron Collider would reveal some of the hints of string theory. That hasn’t happened. But that may well mean that the theory needs a bigger, better, more powerful machine to probe it, and that’s not unexpected.
I’d say that developments are happening at a fast and furious pace on the theoretical side in the hope that we’ll have some connection to experiments or observations in the not-too-distant future. But that’s difficult to predict.
Are there any experiments or projects in particular whose results you’re most looking forward to seeing in this regard? What could help us make progress?
Right now, it’s likely that if we do get any insight from observations into string theory, it could come from, say, verifying gravitational-wave observatories that might be able to probe the outskirts of a black hole with unprecedented
precision. It’s conceivable that in these kinds of experiments we might get a hint. But if you’re asking me in my heart of hearts, I think it’s probably going to be the case that in our lifetime we’re not going to get that observation or experimental insight. It may be the next generation or the generation beyond that.
That’s a little disappointing from an individual perspective because we all want to know; we all want to get the answers. But science is a process, and we’ve only been at this – trying to marry all the forces of nature and everything into one cohesive whole – for about a century, right?
Even less at some level. There was work a century ago, but I’d say [the last] 50 years is when the real work has happened. And we’re trying to push our understanding so far beyond the reach of today’s experiments that it’s not surprising that it may take a few generations to get there. We’re trying to answer some of the deepest questions that have ever been asked.
How did the universe begin? How do the fundamental forces integrate with one another? What are the fundamental ingredients? These are questions that, in one way or another, we’ve been asking for a thousand, or a couple thousand, years. If it takes another handful of decades before we get real insight, that’s just how it is.
Do you have confidence that our brains are actually capable of plumbing these depths? We’re basically apes that evolved to survive on the savanna on a timescale of around 7 million years. Are we capable of actually getting to the bottom of these mysteries, which may be much deeper than we can possibly comprehend?
I’m fundamentally an optimistic person, so I’ve always imagined that the answer to that question is yes. But you look around this planet and there are intelligent creatures like dogs and cats, who I suspect don’t understand Einstein’s general theory of relativity. Maybe I’m wrong; perhaps the dogs and cats are all laughing at us right now. Maybe they’ve got the final answer.
But putting that to the side, it could be that our brains are simply too limited to access the final answer, even though it’s staring us in the face right now. But you go forward, you push as hard as you can. We haven’t hit any insurmountable obstacles yet, and so we maintain our optimism and try to find the final answer.
I think it’s important to emphasise to kids that scientists are just people like them