In the next quarter century, 66 percent of the world’s population will live in urban spaces — and the world’s major cities are scrambling to keep up.

Irish physicist Laurie Winkless thinks science needs to step up and start pitching in to design better cities that are sustainable, inclusive, and efficient. Winkless’s new book, Science and the City, tries to figure out ways urban planners can infuse science into cities — and what we still need to figure out, from getting rid of poop to figuring out traffic.

Inverse spoke with Winkless to learn more about what she’s uncovered during her research into her new book.

What’s the central thesis of your new book?

It’s a book for the uninitiated: Everything that’s around you in the city has been designed for a specific purpose. For example, what happens when you push a traffic button at a pedestrian stop, how does all that work? In New York and a lot of places, it actually doesn’t do anything, but in other cities, there’s a function.

I was trying to balance a sense of joy and fascination I have with science and engineering, with the skepticism that comes from having been in a research lab for several years. I tried to do some future-gazing. As a physicist, that’s not something you’re supposed to do — every time you try to predict the future, you’re wrong. But I really wanted to talk to some of the people who are at the forefront of these emerging technologies that might not initially seem they’re relevant to urban living. I wanted to present things in a very “science-fact” manner, as opposed to science fiction.

Were you able to see the extremes on the spectrum of science and technology manifest in the transformation of urban environments?

There were two big things on one end of the spectrum. One is traffic. Whether we realize it or not, there’s a huge amount of fundamental mathematics behind how we move people on the road through our cities. One of the things I talk about in the book is that having a huge network of traffic lights like we do in cities is incredibly complex mathematically. It’s what’s called a ‘computationally intractable problem.’

In theory, there is a perfect solution to free-flowing traffic and hitting only green lights if you’re moving in one direction. But in reality, calculating what that is would take way too long — it would be completely impractical. So there is no practical way that we could do that because of [human nature] and the way we drive, and the number of cars on the road.

I was really surprised at the number of mathematicians looking at the flow of traffic like they are particles moving through a medium. But they’re changing the way traffic lights are being programmed, and even how pedestrians are flowing through cities.

The other big thing is money. I talk about money and time in the same chapter — and that’s not a coincidence. One of the things we do now is move money electronically. A lot of what we rely on is timing, to make sure all of our purchases are timestamped. If we look at high-frequency trading on the stock market, they have to be timestamped to an unbelievably high degree — so much so that a ton of high financial centers are buying atomic clocks, so they can have the most accurate measurement of time possible. Again, that is absolutely, fundamentally physics.

The other thing which is on the other end of the spectrum is human waste: It’s a huge challenge for cities. A lot of cities are in different stages of development when it comes to waste. We still have a lot of developing nations with open sewers, or have fallen into disrepair because of lack of funding. Keeping us away from our waste is one of the ways we live longer, and it’s one of the biggest successes of more modern cities. Flushing a toilet and not having to think about where it goes puts us in a very privileged position; other cities don’t have that 100 percent coverage of sanitation. The answer to that kind of stuff isn’t fundamental physics — it’s engineering. That kind of infrastructure is so critically tied to human health. A city without sewers will very quickly collapse.

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There isn’t one perfect city that’s managing to do all of these things well. I thought I would find one that would be the leading city which we could all look to — which would be the most prepared for the busy future ahead of us. I didn’t find one. I found lots of cities with different priorities, instead. It means we all have things to learn from each other.

Were there any patterns you noticed among what kind of priorities certain cities were pushing forward with the most?

Pretty much every city I’ve looked at is looking towards mass transit solutions. Tram, bus, underground train — whatever. They’re all pursuing transit networks that move people in and out. Or they’re investing in newer ones, or cleaner ones — such replacing diesel buses with hybrid ones. The amount of people moving into cities means that mass transport has to be a top priority.

In terms of renewable energy, I didn’t come across a city that wasn’t trying to move away from fossil fuels, but every city has a different approach. Close to the equator, there’s a huge amount of investment in solar power, but not just in the traditional silicon stuff we see now. There’s also a bit of investment in what I think is the next big sexy thing, which is peroxide materials, which can be used in solar devices so thin you make them into a glass pane. We see a lot of people with ambitions to use this to make skyscraper glass that wouldn’t have any obvious solar panels on them. This isn’t some crazy idea — this is based off some really solid physics in materials science. There are other trends to develop more wind turbines on the coast.

Other cities are trying to make better use of landfill waste. In cities in India, they mine landfills for waste plastics, which they shred and mix into gravel for roads, which become stronger and last longer. Plastic is a particular problem in India, so this is a really clever way of using it.

In Bogota, there’s an architect there who’s using thicker waste plastic from containers and tires and everything in between to produce bricks. And they’re building houses from those bricks, since in Bogota there is a huge issue with housing. So that’s a solution that kills two birds with one stone.

What are some of the stranger projects that some cities are pursuing?

There’s a lot of research looking into if mealworms could actually eat plastic waste and make it biodegradable, in a looser sense. Another one I really loved was a bioreceptive concrete. You know sometimes when you’re in a city and you see a mossy surface? Normally that’s a problem, since it means the surface is damp and therefore is unsafe. I met with an academic that made a surface that taps into that moisture. It’s like of a four-layer that has a reverse waterproofing layer that attracts water into the second layer, which helps to grow microbes onto the first layer. It sounds like a weird thing to do, but if you use this concrete for a building, you have something that’s very unique to its surroundings. Because it’s only the microbes that are present that will colonize it. And they’ll grow in a moss-like way. The microbial environment of a city constantly changes throughout the year, so it will also change through the seasons.

What about moving forward? What have you learned about the future of cities and how do you think the world will adjust to increased urbanization?

I’m more optimistic about the future of cities than I was when I first started researching for this book. I kind of felt a little bit like maybe we should all be closer to the countryside. I’ve definitely changed my opinion on that. Because so many of us are in cities, were starting to see incredibly innovative solutions. There are problem-solvers and innovators in every single city in the world. And we’re starting to see them talk to each other and collaborate.

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I also didn’t realize I was a huge tunnel nerd — so that’s been a huge awakening. Turns out I really love trains and tunnels!

Photos via Flickr/ Sam Howitz