Every morning at five o'clock, composer (作曲家) Walter Werzowa would sit down at his computer waiting for a particular daily e-mail. It came from a team that had been working all night to draft Beethoven's unfinished 10th Symphony. The e-mail contained hundreds of versions, and Werzowa listened to them all, looking for the perfect tune—a sound that was unmistakably Beethoven. But the phrases he was listening to weren't composed by Beethoven. They were created by artificial intelligence.

When Ludwig van Beethoven died in 1827, he left behind some musical drafts and notes. There was barely enough to make out a phrase, let alone a whole symphony. But that didn't stop people from trying.

Werzowa and a group of music experts and computer scientists teamed up to use machine learning to create the symphony. Ahmed Elgammal led the AI side of the team. The team's first task was to teach the AI to think like Beethoven. To do that, they gave it Beethoven's complete works, his drafts and notes. They taught it Beethoven's process—like how he went from four notes to his entire Fifth Symphony. Then they taught it to compose a bridge between two sections. With all that knowledge, the AI came as close to thinking like Beethoven as possible. But it still wasn't enough. The AI doesn't really produce something that can continue for a long time and be consistent. So the team had to put the selected pieces together to build a symphony.

Matthew Guzdial researches creativity (创造力) and machine learning at the University of Alberta. He didn't work on the Beethoven project, but he says, "Modern AI, modern machine learning, is all about just copying small local patterns. And it's up to a human to then take what the AI outputs and find the genius (天资). The genius wasn't in the AI. The genius was in the human who was doing the selection."

Jennifer Brophy, a professor of Stanford, is working on methods that she hopes will be used to improve commercial plant species so that they can survive harsh conditions. Initially, she studied green architecture in her undergraduate years. Once she started taking architecture classes, she realized it wasn't her passion—but when she encountered an article about a company that creates biofuels (生物燃料) from bacteria, something clicked. "I thought that was just the coolest thing. It got me really interested in pursuing bioengineering," she says.

Today, Brophy is developing new genetic engineering techniques that can help plants grow in various conditions. By changing the genome (基因组) of both commercial crops and soil bacteria, she thinks it's possible to help plants survive droughts.

Brophy is building what she calls "genetic circuits". Besides changing the genes within plant cells, this method also changes how and when those genes are triggered. If the plant senses a specific sugar, it can express one protein; if it senses another signal, it'll express a different protein. If both signals are there, the plant may be able to express something else entirely. "Using circuits to all these different inputs," she says.

"A plant doesn't necessarily know what's coming. It just knows whether it's hot or temperate (温和的) right now," says Brophy. This can lead to problems when weather becomes erratic. A plant that usually flowers in spring may flower in winter if there're a few unseasonably warm days. When temperatures fall again, the flowers die, which ruins a year of crops. "It'd be great to be able to communicate with plants to tell them, 'Hey, you should wait on that flowering, " she adds.

Brophy is still testing the concept in the lab using a small weedy plant called Arabidopsis. She notes engineering crops in the future may also involve genetically modifying soil bacteria. As the bacteria's surroundings change, they could potentially send out chemical signals that tell nearby plants to shift their growth accordingly. Brophy thinks engineering crops could benefit farmers and society at large.

I'm 52, and as surprising as it may seem. I'm a gymnast. In a sport for young girls, I have found an unlikely path to joy. When I enter the gym, no matter how much stress I might be feeling, my mind clears and I forget my life. I think of nothing but what I am doing.

When I was 9, I went every Saturday to a gymnastic academy. The coach had gray hair and wore ballet shoes and had boundless enthusiasm. He would say, "You are going to be a gymnast." And I believed him. I vividly remember the first time I did a round off back handspring by myself, the weightlessness of it. I lived for Saturday mornings. I only ever did gymnastics recreationally — I didn't even know real gyms existed — but I always loved it.

That longdormant love came roaring back in my forties. It happened in an instant, at parents' day for my daughter's beginning gymnastics class. The bars were just sitting there, and I had this overwhelming urge to grab hold and swing. But I couldn't make it through the warm-up at the first adult class I went. I felt bad during conditioning. I was the oldest person there. But that spark of memory glowed with possibility. I went back to class again, and again. It was hard and it was humbling. But soon I was doing back handsprings like I used to.

There is nothing like the thrill of getting a new skill, that combination of speed, mechanics, timing, muscles, and bravery. There is an indescribable (不可言喻的) element, too, something like faith. By the time we reach middle age, most of us have had to deal with our fair share of unwelcome surprises, like illness, family crisis or the death of a beloved parent. But gymnastics has brought the most delightful surprises — I keep getting better, overcoming what I thought were limits, amazing myself by what I can do. At a time in life when many things feel like they are sliding down the slope (斜坡) towards old, gymnastics is a gift of fluency and competence in motion. I'm in the best shape of my life. I'm a better gymnast now than I was at 16.