According to the Solar Energy Industry Association, the number of solar panels installed(安装)has grown rapidly in the past decade, and it has to grow even faster to meet climate goals. But all of that growth will take up a lot of space, and though more and more people accept the concept of solar energy, few like large solar panels to be installed near them.

Solar developers want to put up panels as quickly and cheaply as possible, so they haven't given much thought to what they put under them. Often, they'll end up filling the area with small stones and using chemicals to control weeds. The result is that many communities, especially in farming regions, see solar farms as destroyers of the soil.

"Solar projects need to be good neighbors," says Jordan Macknick, the head of the Innovative Site Preparation and Impact Reductions on the Environment(InSPIRE)project. "They need to be protectors of the land and contribute to the agricultural economy." InSPIRE is investigating practical approaches to "low-impact" solar development, which focuses on establishing and operating solar farms in a way that is kinder to the land. One of the easiest low-impact solar strategies is providing habitat for pollinators(传粉昆虫).

Habitat loss, pesticide use, and climate change have caused dramatic declines in pollinator populations over the past couple of decades, which has damaged the U.S. agricultural economy. Over 28 states have passed laws related to pollinator habitat protection and pesticide use. Conservation organizations put out pollinator-friendliness guidelines for home gardens, businesses, schools, cities—and now there are guidelines for solar farms.

Over the past few years, many solar farm developers have transformed the space under their solar panels into a shelter for various kinds of pollinators, resulting in soil improvement and carbon reduction. "These pollinator-friendly solar farms can have a valuable impact on everything that's going on in the landscape," says Macknick.

"What would the world be if there were no hunger?" It's a question that Professor Crystal would ask her students. They found it hard to answer, she wrote later, because imagining something that isn't part of real life—and learning how to make it real—is a rare skill. It is taught to artists and engineers, but much less often to scientists. Crystal set out to change that, and helped to create a global movement. The result一an approach known as systems thinking—is now seen as essential in meeting global challenges.

Systems thinking is crucial to achieving targets such as zero hunger and better nutrition because it requires considering the way in which food is produced, processed, delivered and consumed, and looking at how those things intersect (交叉) with human health, the environment, economics and society. According to systems thinking, changing the food system—or any other network- requires three things to happen. First, researchers need to identify all the players in that system, second, they must work out how they relate to each other, and third, they need to understand and quantify the impact of those relationships on each other and on those outside the system.

Take nutrition. In the latest UN report on global food security, the number of undernourished (营养不良) people in the world has been rising, despite great advances in nutrition science. Tracking of 150 biochemicals in food has been important in revealing the relationships between calories, sugar, fat and the occurrence of common diseases. But using machine learning and artificial intelligence, some scientists propose that human diets consist of at least 26,000 biochemicals—and that the vast majority are not known. This shows that we have some way to travel before achieving the first objective of systems t hinking - which,in this example, is to identify more constituent parts of the nutrition system.

A systems approach to creating change is also built on the assumption that everyone in the system has equal power. But as some researchers find, the food system is not an equal one. A good way to redress (修正) such power imbalance is for more universities to do what Crystal did and teach students how to think using a systems approach.

More researchers, policymakers and representatives from the food industry must learn to look beyond their direct lines of responsibility and adopt a systems approach. Crystal knew that visions alone don't produce results, but concluded that "we'll never produce results that we can't envision".

Quantum (量子) computers have been on my mind a lot lately. A friend has been sending me articles on how quantum computers might help solve some of the biggest challenges we face as humans. I've also had exchanges with two quantum-computing experts. One is computer scientist Chris Johnson who I see as someone who helps keep the field honest. The other is physicist Philip Taylor.

For decades, quantum computing has been little more than a laboratory curiosity. Now, big tech companies have invested in quantum computing, as have many smaller ones. According to Business Weekly, quantum machines could help us "cure cancer, and even take steps to turn climate change in the opposite direction." This is the sort of hype (炒作) that annoys Johnson. He worries that researchers are making promises they can't keep. "What's new," Johnson wrote, "is that millions of dollars are now potentially available to quantum computing researchers.

As quantum computing attracts more attention and funding, researchers may mislead investors, journalists, the public and, worst of all, themselves about their work's potential. If researchers can't keep their promises, excitement might give way to doubt, disappointment and anger, Johnson warns. Lots of other technologies have gone through stages of excitement. But something about quantum computing makes it especially prone to hype, Johnson suggests, perhaps because ""quantum' stands for something cool you shouldn't be able to understand." And that brings me back to Taylor, who suggested that I read his book Q for Quantum.

After I read the book, Taylor patiently answered my questions about it. He also answered my questions about PyQuantum, the firm he co-founded in 2016. Taylor shares Johnson's concerns about hype, but he says those concerns do not apply to PyQuantum.

The company, he says, is closer than any other firm "by a very large margin (幅度)" to building a "useful quantum computer, one that "solves an impactful problem that we would not have been able to solve otherwise." He adds, "People will naturally discount my opinions, but I have spent a lot of time quantitatively comparing what we are doing with others"

Could PyQuantum really be leading all the competition "by a wide margin", as Taylor claims? I don't know. I'm certainly not going to advise my friend or anyone else to invest in quantum computers. But I trust Taylor, just as I trust Johnson.