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Leonardo da Vinci was a Renaissance genius. Not only did he paint masterpieces of art, but he was an obsessive scientist and inventor, dreaming up complex machines centuries ahead of his time, including parachutes, armored tanks, hang gliders, and robots. On the 500th anniversary of Leonardo’s death, with the help of biographer Walter Isaacson, NOVA investigates the secrets of Leonardo’s success. How did his scientific curiosity, from dissections of cadavers to studies of optics, shape his genius and help him create perhaps the most famous painting of all time, the "Mona Lisa"? (Premiered November 13, 2019)

Discover the science behind Leonardo da Vinci's masterpieces—and Mona Lisa's iconic smile.

Decoding da Vinci

In a new age of information, rapid innovation, and globalization, how can we prepare our children to compete? Once the envy of the world, American schools are now in trouble. Test scores show our kids lag far behind their peers from other industrialized countries, and as the divide between rich and poor grows wider, the goal of getting all kids ready for college and the workforce gets harder by the day. How can the latest research help us fix education in America? Can the science of learning—including new insights from neuroscientists, psychologists, and educators—reveal how kids’ brains work and tell us which techniques are most likely to engage and inspire growing minds? What role should technology play in the classroom? Teachers, students, parents, and scientists take center stage as NOVA explores a new vision for the “School of the Future.”

How can the science of learning help us rethink the future of education for all children?

School of the Future

Rockets are becoming cheaper and more powerful than ever before thanks to stunning new technologies. As companies like SpaceX and Virgin Galactic make space more accessible, and NASA returns to crewed spaceflight, a new era of space exploration seems to be on the horizon. But will this seeming rocket Renaissance become more than just hype? NOVA explores the latest rocket technologies and the growing role private citizens may have in space. (Premiered February 13, 2019)

With new technologies, NASA and private companies are promising a new renaissance in space travel.

Rise of the Rockets

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The Public Key Method to Encrypt Communications | Crypto Decoded

Learn about the development of a secure way to send messages over the Internet, and consider its value, with this video excerpt from NOVA: Crypto Decoded.

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What Is Bitcoin? | Crypto Decoded

Learn about Bitcoin and consider how much energy is required to mine it with these video excerpts from NOVA: Crypto Decoded.

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How Could Technology Help Predict and Prevent Crime? | Computer v. Crime

Learn how people are trying to use artificial intelligence in different ways to predict and prevent crime with these video excerpts from NOVA: Computers v. Crime.

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How Predictive Algorithms Can Contain Bias | Computers v. Crime

Learn how training computer algorithms on historical data can create bias with these video excerpts from NOVA: Computers v. Crime.

Why Induction Stoves Are Better for You and the Environment

Induction stovetops are an energy-efficient alternative to traditional gas stoves.
These stoves use electricity to create a magnetic field that causes the electrons inside pots and pans that contain iron to vibrate tens of thousands of times. This creates the friction and heat needed for cooking without the energy or fumes from gas stoves.
Why Induction Stoves Are Better for You and the Environment Published April 27, 2023MILES O’BRIEN: Traditional electric stoves create heat by simply resisting the electric current, but newer induction cooktops use electricity to create a magnetic field. The electrons inside pots and pans that contain iron try to align with the magnet, vibrating tens of thousands of times per second, creating friction and heat. The result is better energy efficiency, faster cooking and no combustion fumes. They have caught on in commercial kitchens in Europe and Asia, but in the U.S., chefs are skeptical.CHRIS GALARZA: The rest of the world is looking at us going, “What are you complaining about?” Because, effectively, we’re arguing about how to get a piece of metal hot, so we can cook.MILES O’BRIEN: The fossil fuel industry has done a good job at inducing resistance.“COOKING WITH GAS” (Educational video, 1998): Cooking with gas, cooking with gas…CHRIS GALARZA: We all remember the rap in the eighties.(Recorded Singing): …We all cook better when we’re cooking with gas…CHRIS GALARZA: It’s cringeworthy.(Recorded Singing): …Cooking with gas, cooking with gas. We all cook better when we’re cooking with gas…CHRIS GALARZA: There’s a lot to unpack there.(Recorded Singing): …I cook with gas because it cost is much less than electricity…CHRIS GALARZA: But you know what? That was effective. That was very effective because what was said in there still gets said today. Cooking gas is cheaper; it’s more precise, all these things which are just not true.(Recorded Singing) : …Cooking with Gas!MILES O’BRIEN: Today, Chris is an independent consultant who travels the country promoting induction in commercial kitchens. He gave me a quick demonstration. Okay. So, this has been in the freezer?CHRIS GALARZA: Correct. So this is just to show how quickly we can come up to temp. So, we’re going to dump this…MILES O’BRIEN: Oh, yeah. It is cold.CHRIS GALARZA: …getting the water off. So, things are hot. Oh, how hot?MILES O’BRIEN: All right. That was in the matter of, what?CHRIS GALARZA: Seconds, right? So, there is no more preheating. It’s just straight hot. And it doesn’t take long. Now, your shrimp got some good color on it, add our sauce, and there you go.MILES O’BRIEN: That was dinner in about two minutes.CHRIS GALARZA: In a fraction of the time. And here’s the beautiful thing: we just did all of that, not a sweat on you. Nothing gets hot, except for the pan itself. So, it’s time for us to evolve, to get together and say, “What’s better for our world?” And cooking with a flame is not.

Induction stovetops are an energy-efficient alternative to traditional gas stoves.

How Heat Pumps Can Help Cities Lower Carbon Emissions

Landlords are switching from gas furnaces to heat pumps to reduce their carbon footprint.
Heat pumps are a key solution to help reduce carbon emissions. Instead of creating heat, they move heat from one place to another and have a much lower carbon footprint. But can we make them accessible to all?
How Heat Pumps Can Help Cities Lower Carbon Emissions Published: April 27, 2023Miles O&#x27;Brien: On rooftops all over New York City. There is evidence that electricity is gaining currency in 2022. Americans bought more heat pumps than gas furnaces. Landlord Lincoln Eccles was thinking about his son Ace, when he made the decision.Lincoln Eccles: We&#x27;ve built an infrastructure based on oil and gas burning things. That&#x27;s what we&#x27;re used to. But it doesn&#x27;t have to be that way.Miles O&#x27;Brien: [It&#x27;s the third iteration for the early 20th century building he owns in Crown Heights, Brooklyn. When it was built, they burned coal in a boiler to stay warm. Now there&#x27;s a heat pump for each of the 14 units. Heat pumps work not by creating heat, but by moving it from one place to another. Inside, there&#x27;s a fluid called refrigerant that boils at 40 degrees below zero Fahrenheit. As long as it is warmer than -40. Outside, the refrigerant picks up heat from air. As it becomes a gas, it flows into an electric compressor where it is put under pressure. Adding more warmth to the gas, the warm gas flows into the room unit as it heats the space. The gas itself condenses back into a liquid. Now the liquid travels back out, flowing through a valve that lowers the pressure and thus the temperature and the cycle starts all over again. So in the winter, it can pump heat inside. And in the summer, the process is reversed to pump heat outside, cooling the room. In Lincoln&#x27;s building. Each unit has its own wireless thermostat.Miles O&#x27;Brien: Easy enough for his son to operate. Lincoln hopes Ace will be the landlord here someday. So you think when Ace is your age, everything around us here will be electric?Lincoln Eccles: Definitely. These two behind us are green. These developments over here. They&#x27;re green. If they could do my building, they could do every building on the block.Miles O&#x27;Brien: But heat pumps are not cheap. And for us to reach net zero, nearly every building will need to make the transition. So how can this technology become accessible to everyone? That is precisely the goal for Donnell Baird.Donnel Baird: If we can do one building, we can do a whole block of buildings. And if we do a block of buildings, we can do a whole city.Miles O&#x27;Brien: He is the CEO of a startup called BlocPower.Donnel Baird: BlocPower wants to turn buildings into Teslas. We want to make them smart, green, healthy, all electric.Miles O&#x27;Brien: Founded in 2014, BlocPower is making it more affordable for landlords to make the switch. Lincoln Eccles Whole building is one of about 2000 conversions the company says it has spearheaded so far.Donnel Baird: We have everything that we need to green all the buildings now. That&#x27;s why it&#x27;s so important that we focus on buildings because we don&#x27;t need any more innovation.Miles O&#x27;Brien: Donnel was able to mix the pressing needs of a landlord with a bad boiler and a planet boiling over into something attractive to Wall Street investors. It&#x27;s a company committed to executing the conversion at scale, bundling a lot of projects together to lower the cost and lower the risk.Donnel Baird: We show up and we say, look, we&#x27;ve got capital from Goldman Sachs and Microsoft to finance moving you to a functioning better system and it costs you nothing. As a matter of fact, you&#x27;re going to save money because the payment that you make to us over 15 years is going to be less than what you would pay to the oil company or to the gas company as an alternative.Miles O&#x27;Brien: The arithmetic relies on incentives from the government and assumptions that the cost of heat pump manufacturing and installation will decline. For BlocPower, the goal and the risks are big. Lincoln Eccles says it&#x27;s working for him.Lincoln Eccles: They just made it work. at the end of the day, it was a lot of back and forth. But it can be done. It&#x27;s not an impossible task.

Landlords are switching from gas furnaces to heat pumps to reduce their carbon footprint.

A woman in shorts walks across a concrete area surrounded by buildings, carrying an umbrella to block the blazing sun in the background

A pedestrian uses an umbrella to protect herself from the sun during a heatwave in London on July 18, 2022. Image Credit: Bloomberg, Getty Images

Why cities are so hot (and how we can fix it)

You don’t have to live in Phoenix, Arizona, to notice that cities are getting hotter, but it helps. Consistently the hottest major metropolitan area in the country, Phoenix spent more than a third of 2022 in triple-digit temperatures. It has also seen a dramatic uptick in heat-related deaths in recent years, with the Maricopa County public health department reporting more than 300 heat-associated deaths in 2021, an increase of 450% from 2014.
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“It's a really unfortunate, tragic data point that we find ourselves sharing a lot,” David Hondula, director of the city’s Office of Heat Response and Mitigation, said in an interview for the NOVA documentary “<a href="https://www.pbs.org/wgbh/nova/video/weathering-the-future/">Weathering the Future</a>.” People are often surprised to learn that heat is the leading cause of weather-related death, he said. It “lurks as a background hazard and doesn't always get the attention of hazards like thunderstorms, tornadoes, hurricanes, floods.”Phoenix did not hire Hondula because the planet in general is getting hotter but because cities are the hottest of all. That’s due to what’s known as the “urban heat island” effect, which refers to the ways that the design and infrastructure of cities tend to make that environment hotter—up to 20 degrees warmer than surrounding rural areas.We’ve known about the urban heat island effect for a long time; even the Romans noticed it. But it’s especially important now because of the health risks that come with heat, according Brian Stone, a professor of environmental planning at Georgia Institute of Technology. “Of all the stressors we associate with climate change, heat is the only one that has a physiological threshold that we know will lead to certain death,” he told NOVA. There’s a flip side, though. Since “we’ve basically engineered cities to be hot,” he said, “we can reverse engineer them to be cooler.”
<h3>What creates an urban heat island?</h3>Researchers have pinpointed four main factors that drive the urban heat island effect. First is vegetation, or lack thereof. Trees are often the first thing to go when cities expand. (Take Atlanta, which has lost nearly 80,000 trees to development since 2014.) Cutting down trees creates a double-whammy effect, since they not only offer shade but also soak up heat from their environment. When we cut down urban trees, “we reduce the capacity of the natural system to cool itself through evaporation, much like we cool ourselves through perspiration,” Stone said.Then, the materials we install in place of that lost greenery tend to aggravate the problem further. Mineral-based materials such as asphalt, concrete, shingles, and other roofing have a high “thermal capacity,” meaning they absorb a lot of heat during the day and then release it slowly back into the environment as they cool, even well into the night. That’s a problem in particular because the atmosphere doesn’t actually heat up very much from direct sunlight; instead, it warms more as heat is released from the ground.<h4>WATCH: HOW EXTREME HEAT OVERWHELMS THE HUMAN BODY</h4>
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Next, urban morphology, or the three-dimensional structure of a city, also contributes to increasing temperatures, since tall buildings are particularly good at trapping heat between them. And lastly, there’s waste heat, another double whammy. The process of consuming energy to do work, by anything from a car engine to a lightbulb to a computer, generates heat as a byproduct. Since cities are where most humans live together, they’re also where we consume the most energy: for transit, heating and cooling our homes, and the myriad electrified activities of daily life. And the waste heat that escapes into the environment from those activities measurably affects city temperatures.
<h3>Urban heat islands and human health</h3>As all of those factors accumulate, the consequences for human health add up, too. Human bodies can handle very hot temperatures briefly but are sensitive to heat over the long term. “It's the warm nighttime temperatures that cause the health problems,” Marshall Shepherd, director of the atmospheric sciences program at the University of Georgia, told NOVA. “And that's where the urban heat island comes in, because that's when it tends to peak”— with all those mineral surfaces re-releasing heat after dark.Our bodies respond to heat by elevating our heart rate, allowing us to better circulate moisture. That moisture becomes sweat, which we use to cool ourselves down. Most people can handle an elevated heart rate for a few hours a day. But “if you have to elevate your heart rate for 24 hours because it's 85 degrees at night in your home, then you are overly taxing your physiologic capacity to deal with heat,” Stone said. Then things start to get dangerous. Research shows that it’s generally the neighborhoods that can least afford it that get hit the hardest by urban heat. That’s in part because of discriminatory urban planning policies like redlining, which ensured that poorer neighborhoods had fewer trees and more industrial development. One recent study found a difference of 7 to 10 degrees between lower and higher income areas of the same cities. In another project, Shepherd and his colleagues compared redlining maps with satellite data tracking heat. The results showed “a clear heat island within the heat island for marginalized groups,” he said.
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<h3>What can we do about it?</h3>With Phoenix’s heat-related death rate doubling in just five years, the city went into crisis mode in 2021. Nighttime temperatures in Phoenix average about 10 degrees hotter than they were half a century ago, hovering around 85 degrees during the hottest part of the year. And there are some days when “we've measured pavement, for example, at 160 Fahrenheit, 170 Fahrenheit,” Hondula said, with similar numbers on, for example, metal playground slides—a temperature that can cause direct burns. As he’s stepped into his role managing the city’s heat crisis, Hondula has remained hopeful. Phoenix’s trends aside, “we've seen decreasing heat-associated deaths over the past several decades, as our planet has been warming,” he said. He attributes that to increased understanding of the urban heat island effect, which is beginning to lead to meaningful change in many cities.One place to start: more trees. Large cities such as Washington, D.C., Baltimore, Philadelphia, and New York currently average around 25%-40% tree canopy cover but could support up to 60% cover, the U.S. Forest Service has found. Even arid Phoenix has committed over $7 million to planting drought-tolerant trees over the next few years. Similar non-profit organizations all over the world have committed to planting trees in the coming decades: 170,000 in Paris, 1 million in Atlanta, 1 million in São Paulo, 4 million in Houston. 
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<img alt="Two adults talk while walking toward the camera through two rows of small trees in a grassy park" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Phoenix_cool_corridor.width-990.jpg"/>
<figcaption>Professor David Sailor (left) and Professor Na'Taki Osborne Jelks (right) walk through a "cool corridor," where trees have been planted to provide relief from the heat in Phoenix, Arizona. Image courtesy of GBH
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But it will take years, maybe decades, for those trees to mature and start making a difference. So Stone also sees great potential in changing the materials we use to build cities. For example, dark-colored slate roof shingles with high thermal capacity might make sense in London, or somewhere else cold and wet, but are much less logical in the southern United States. “We can engineer any color we'd like of roofing material, and so part of what we need is not just a technological change in the way we build, but a cultural shift to be more accepting of lighter, more reflective materials,” he said. Other more immediate solutions include initiatives like Phoenix’s cool pavement program, which encourages the use of alternative road materials, as well as the city’s work prioritizing shade structures at bus stops or in other places where trees might not be suitable.The powerful thing about recognizing the heat island effect is recognizing it as a phenomenon within local control. That means it’s possible to make progress without waiting for national or international policy change, Stone said. Research shows “we can substantially cool down cities in a relatively quick period of time without major expenditures.” Hondula takes this optimism even further. Even in the context of global warming, he said, efforts to increase tree and other shade cover and promote use of materials with lower thermal capacity mean “we could wind up with a city of the future that's cooler than the one we have today.”<h4>WATCH: WEATHERING THE FUTURE</h4>
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Even the Romans noticed that cities are engineered to be heat islands. But that means we can do something about it.

Topic: Tech & Engineering

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