The South Pole is the most inhospitable place on Earth—yet, each year, around 50 brave scientists and staff endure the winter there. Outside temperatures approach minus 120 degrees Fahrenheit in constant darkness.

And they better hope nothing goes wrong. Because no one can come to help them.

The South Pole is 800 miles from the nearest human contact. That’s farther than the International Space Station, which orbits less than 400 miles above Earth.

From research bases on the Antarctic coast, it takes planes 5 to 8 hours to fly to the South Pole. But it’s so cold in winter that jet fuel turns to slush, meaning no flights can come or go.

An over-land caravan of snow tractors in the summer takes 40 days.

The sun is up in summer for more than 4,000 hours, one six-month-long day. At that time, the South Pole research station has its highest population, 200 scientists and staff. They study solar spots and atmospheric ozone, cosmic rays and neutrinos.

Low temperatures still average negative 20 degrees Fahrenheit.

In the fall, the sun nears the horizon for six weeks of dusk. Then it sets and is gone for three months for that seemingly endless night that is Antarctic winter.

It takes a special person to endure the isolation, darkness, danger and lethal cold.

Landslides happen when a slope becomes unstable—because of denuding, from a fire or deforestation; over-steepening, from erosion or mining; overloading, from a reservoir or heavy snowpack; or oversaturation, with rain or melt water.

So many things can cause a landslide that they happen in every U.S. state and nearly every country.

When the slope gives way, soil can speed downhill at 50 to 100 miles an hour, carrying trees, boulders, cars, even houses.

Earthquakes trigger just five percent of landslides. Twenty percent are caused by human activities, while three-quarters come from precipitation.

Though some landslides happen suddenly, most give warning signs: cracks in pavement or soil, earth bulging at the base of a slope, water springs in new places.

Your chances of getting caught in a slide are remote. But if you live in a landslide-prone area, keep these things in mind:

Risk comes from uphill. You may want to move bedrooms or living areas to the downhill side of the house.

If you suspect a slide is coming, open downhill windows and doors to allow debris that could pass through the house to exit.

To escape a landslide, go up! Upstairs, and up on top of furniture, to have the best chance to stay on top of the debris.

In the very unlikely event you’re trapped, never give up. Make noise so rescue teams can find you.

Herbivores eat plants, and carnivores eat animals that eat plants, to get their energy.

Plants and many bacteria create their own energy through photosynthesis, which depends on chlorophyll…which requires nitrogen.

As we’ve described in other episodes, most nitrogen on Earth is in the form of N2, the inert nitrogen gas that won’t bond with other compounds, making it useless to plants.

So, most plants rely on bacteria that cling to their roots and split the nitrogen in the soil for them. But when they can’t get enough, humans help them out, with nitrogen-rich fertilizers.

Early fertilizers relied on naturally concentrated nitrogen. For instance, bat colonies eat insects, which contain nitrogen, then excrete nitrogen-rich droppings. For centuries, humans harvested tons of bat guano to fertilize our crops.

But demand outstripped supply, so we had to invent a new source. At the start of the twentieth century, two German chemists devised a way to combine the nitrogen in air with hydrogen produced from natural gas to form ammonia, NH3. And their work won a Nobel prize…

Because liquid ammonia could then be used to mass produce nitrogen-rich fertilizers. This drove the massive expansion of industrial agriculture—which has both created and allowed us to feed a growing global population.