EarthDate

Supersonic Jets

You may remember the Concorde, the passenger jet that rocketed from New York to London in just three hours. And you may wonder, why do we now settle for much slower airplanes? Speed is actually the reason. Achieving it required a great deal of maintenance and fuel, making the Concorde very expensive to operate. But a bigger reason was noise. The Concorde flew at twice the speed of sound, so it created a sonic boom. It was so loud, the FAA prohibited it from flying across land, relegating it to transoceanic flights. Few routes and high ticket prices meant the jet was unprofitable and thus taken out of service. A sonic boom happens when an object exceeds the speed of sound, about 700 miles an hour depending on air temperature. It pushes sound pressure waves in front of it so fast that they collide with each other, eventually fusing into a single shock wave that we hear as loud noise. Bullets and bullwhips move fast enough to make small sonic booms. Lightning heats the air so fast that it expands faster than the speed of sound, which we hear as thunder. New supersonic jets now in development are shaped so that the boom doesn’t reach the ground, creating a smaller effect that its designers call a “sonic thump.” More research in these areas could see a “boom” in supersonic air travel in the future.

Rain Shadow

Mountains can shape not only a region’s weather, but its climate. When wind blows warm moist air against a mountain range, the air is pushed upward by the mountain. As it rises, it cools. The moisture within it condenses into rain, which falls on the front side of the range, creating a lush landscape. But behind the range, the air—now empty of moisture—can leave the landscape extremely dry. The mountains have essentially blocked the passage of weather systems. This is called a rain shadow. These very dry areas occur frequently when oceans, or even very large lakes, meet coastal mountain ranges. The air charges with moisture over the body of water, dumps it on the coast and leaves the interior dry. We see rain shadows in California, where the Sierra Nevada catches the moisture from the Pacific and produces Death Valley to the east. And in China, on the Tibetan Plateau, where the Gobi Desert stretches out behind the Himalayas. And in South America, where the Atacama Desert has formed behind the Andes—it’s one of Earth’s driest environments. Even the Great Plains of the U.S., once called the Great American Desert, are kept sometimes dangerously dry by the Rocky Mountains, which form a barrier across the country. Rain shadows are a permanent climatic feature on the landscape—or at least, as permanent as the mountains and winds that create them.

We Are Stardust

Nearly everything in the universe was made by stars. Stars are fueled by nuclear fusion. They fuse atoms of the lightest element, with only one proton—hydrogen—into the next lightest element, with two protons—helium. In every fusion reaction, they’re creating an atom of a new element. When they’ve used up their hydrogen, they begin to fuse the remaining helium into a heavier element, carbon. Then they’ll fuse that into oxygen and progressively heavier elements. Each of these fusion reactions is less energetic, so by the time the star is fusing iron, it’s nearing the end of its life. The star may soon explode in a supernova, dispersing the elements it created into other solar systems where they may be used to form planets. After a supernova, the star may continue to exist as a black hole or an extremely dense neutron star. In this environment, elements like iron can capture free neutrons to form still heavier elements like silver, gold or plutonium. The atoms that came together to form Earth 4.5 billion years ago were once part of stars that lived and died long before. Almost every atom in your body is billions of years old, from the calcium in your bones to the carbon in your DNA, recycled countless times. That song was right: we are stardust. Stars made the elements that make us.

Fast Moving India

What do India and Antarctica have in common? They were once part of the same landmass. Long ago, like all land on Earth, India was contained within the supercontinent of Pangaea. But around 200 million years ago, Pangaea began to break apart. The southern portion separated into Gondwana, which included India. India then began to set its own course. It rifted away from Africa, then tore off from Antarctica. As it traveled north, it shed Australia, then Madagascar. This is partly because India was on the fastest-moving tectonic plate on Earth, racing along at a few inches a year and leaving the others behind. For 20 million years, India was its own continent, but it continued to move. In the end, it traveled 1,200 miles in 150 million years—a record—until it collided with Asia and became the Indian subcontinent we know today. Because the crusts of the two plates were similar in density, neither subducted beneath the other, but crushed together. The buckle zone between them raised the highest mountain range on Earth, the Himalayas. As a result, you can find fossils of trilobites and other ancient sea creatures at the summit of Mount Everest! The Indian plate is still pushing its way north, but now much more slowly, producing earthquakes while continuing to lift the Himalayas higher.  In more ways than one, India is on the rise.

Extreme Nematodes

Nematodes aren’t toads at all, but worms. Roundworms, specifically, with cylindrical bodies. Different species are so nondescript we have a hard time telling them apart. That may make them sound uninteresting, but I assure you, they’re anything but. Nematodes are some of the oldest animal lifeforms on Earth, having appeared perhaps a billion years ago. And they’ve been a huge success. To start, their population is enormous. For every human on the planet, there are 60 billion nematodes. You might wonder where they are, then. Many live in the dirt. There are millions beneath your feet, digesting organic matter to enrich the soil so plants can grow. Some live below the dirt. They’ve been found 12,000 feet deep, in mines. Others have evolved to be parasitic, living within all kinds of organisms. Many species are tiny, just 1 millimeter long. But the kind that lives in whale intestines can reach 40 feet! Scientists recently found 46,000-year-old, previously unknown nematodes frozen in Siberian permafrost. When thawed, they wriggled back to life. Samples of nematodes even survived the deadly space shuttle crash. Which begs the question: Could extraterrestrial organisms have survived a meteor ride to Earth millions of years ago to diversify and populate the planet? If so, maybe it was the not-so-lowly nematode.