Leonardo’s Rule of Trees

The Burning River

You might not think a river can burn. But in 1969, the Cuyahoga River that runs through Cleveland caught fire. The Cuyahoga was the most polluted river in the country, so fouled with industrial waste and sewage that it was completely devoid of life when a spark from a passing freight train ignited an oil slick that covered the water. The river had burned at least 10 times in the previous 100 years, but that short 1969 fire was when Cleveland said “enough.” A new mayor and young city architect launched an ambitious plan to rebuild the city sewage system, regulate industrial polluters and clean the river itself. It would be expensive, but the city put it to a vote, and it passed two to one. The Cuyahoga River fire hit the news cycle along with the Apollo 11 moon landing, and the nation took notice. Environmental movements sprung up on campuses, which led to the founding of Earth Day in 1970. Simultaneously, President Nixon was inspired to create the Environmental Protection Agency. Now more than 50 years later, the Cuyahoga has rebounded with life, enough that fish from the river are now deemed fit to eat. In 2019, it was named the nation’s River of the Year for its remarkable recovery. It’s a pity that it ever got that bad. But it just goes to show that, as we put our minds to it, we’re solving even serious environmental problems.

Rust Never Sleeps

If left unprotected, something made of iron will dissolve into dust. That’s because of rust. Some metals, like gold and platinum, are naturally stable and keep their shiny appearance. Other metals like aluminum, copper and silver develop patina or tarnish that protects the raw metal beneath. Iron is different. It’s the most abundant element on Earth, followed by oxygen—together they make up over 60% of all elements. And they like to get together: Almost all iron on the surface of Earth appears as an iron oxide—a mixture of iron and oxygen. We smelt iron oxides to get pure iron, which we use as a metal or blend into alloys like steel. But once it’s been separated from oxygen, it wants to bond again. When water gets involved, rust forms. It’s not well defined as a chemical process, but initially the iron oxidizes, then water turns that molecule into a new compound we call rust, which replaces the metal. And because the rust molecule is larger, it doesn’t fit in the same place and flakes off as rust. This exposes new metal, which will rust and flake off—until all the iron is gone. With so much of our buildings, bridges, pipelines and other infrastructure made of iron or steel, it’s important to keep them oiled, painted, coated or alloyed to be protected. Because as Neil Young said, rust never sleeps.

Do Fish Get Thirsty?

Drinking salt water is poisonous to humans. It’s four times saltier than our blood, so our kidneys pull water from our tissues to try to balance the seawater, which could lead to dehydration or death. Whales and dolphins, seals and walruses are all mammals, and they need fresh water too. But they live in salt water. So what do they drink? Nothing! Their digestive systems are superefficient at pulling all the fresh water they need from their food. What about fish? They need water too. You’d think this would be no problem for freshwater fish. But because their blood is more salty than the water they live in, they have to be careful not to drink it. When water goes in their mouth, they push it out through their gills, where the right amount of water is absorbed through osmosis. For saltwater fish it’s a different story. They get their fresh water by drinking salt water. They have special kidneys adapted to filter out and expel the salt. Scientists thought that highly venomous sea snakes also drank seawater and expelled salt. To test that, they captured a hundred of them before and after a rain. Those caught before the rain drank fresh water offered to them—they were thirsty. Those captured after the rain had no interest in water. The scientists realized they drank rainwater, which being less dense, floats on the surface of the salt water. All creatures require water to live. Even those living in water!

Much More Than Absolute Zero

One of our greatest scientists was given an aristocratic title by Parliament. But he began life simply, as a math teacher’s son. William Thomson was born in Belfast, Ireland. His father moved the family to Glasgow for a job at the university. He started William in classes at 10 years old. Immediately, his talent began to shine. In his teens, he published three papers on the relationship between heat and electricity, sparking a lifelong interest in these fields. He went to Cambridge at 17. But with his work already dazzling the scientific community, he was offered a department chair back in Glasgow at just 22. He stayed at the university for more than 50 years, the rest of his career, even as his work drew international acclaim. He collaborated with other leading scientists to shape the science of electromagnetism and define the physical behavior of gases. Also a practical inventor, he helped establish transatlantic telegraph communications. His inventions earned him 70 patents and a sizable fortune. At age 42, he was knighted by Queen Victoria. At 69, Parliament “ennobled” him with the title Lord Kelvin, chosen for the river that flowed by his Glasgow laboratory. He’s remembered today in the Kelvin scale, which redefined how temperature is measured, pegging it to absolute zero, where molecular motion ceases. This brilliant, versatile scientist would celebrate his 200th birthday this year.

Big Bend National Park is 80

Big Bend is one of the largest, most remote and least visited national parks in the U.S. It’s a land of great diversity. More than a mile of elevation change. More than 100 degrees Fahrenheit of temperature fluctuation annually. Diverse topography—deserts, mountains, canyons, rivers and springs—with different life in each ecozone. And because of that, more ecological diversity than any other national park: more species of birds, butterflies, bats, reptiles, ants and plants. And the largest age range of fossils, too, because of its complex geologic history. It also has a long and varied human history. Just after the last Ice Age, 11,000 years ago, nomadic hunters frequented the area. Tribes settled in Big Bend 7,500 years ago. Spanish explorers built forts in the area 500 years ago. Two-hundred years ago, the Apache then the Comanche displaced the indigenous Chisos tribe. The area became a stop on the Comanche Trail as they migrated from buffalo-hunting grounds in the Texas Panhandle to raid Spanish missions in Mexico. Big Bend became part of Texas when it became a republic, in 1836. Texas made it a state park a hundred years later, then donated it to the U.S. government. Since 1944, Big Bend has been part of the National Park Service—and this 80th anniversary would be a great time to visit!