Does the Amazon Rainforest Really Produce 20 Percent of the World's Oxygen?

SL_Photography/iStock via Getty Images
SL_Photography/iStock via Getty Images

Richard Muller:

No. In fact, under normal conditions (prior to human-caused fires) the Amazon [rain]forest is in a steady state. Oxygen is produced by photosynthesis and consumed by decay. If these were out of balance, then the mass of wood in the Amazon must change.

That means if the Amazon were to disappear today, instantly (e.g. we harvested all the wood and used it to build houses) then the oxygen and carbon dioxide in the atmosphere would continue on at the same level. Until, that is, the wood rots. Then the carbon dioxide levels would increase.

Except for the biomass decrease from human-caused fires, the biomass of the Amazon has not been changing. That means that no net carbon dioxide is being removed from the atmosphere, so no net oxygen is being released from carbon dioxide.

Recently the Amazon biomass has been changing due to fires. When that happens, the wood and other carbohydrates in the trees combine with oxygen and produce CO2 and H2O. Thus the burning of the rainforests contributes to global warming.

But under normal situations, when the biomass of the Amazon is not changing, there is no net production of oxygen or carbon dioxide.

Incidentally, many writers who don’t understand this—and mistakenly think that the Amazon produces net oxygen—double their error by using a backward metaphor. They refer to the Amazon basin the "lungs of the world," but lungs are the organ that remove oxygen from the air and replace it with carbon dioxide, not the other way around.

Where did the 20 percent figure come from? The best guess is that ecologists have calculated that 20 percent of the photosynthesis of the world takes place in the Amazon basin. But so does 20 percent of the consumption.

This post originally appeared on Quora. Click here to view.

What's the Difference Between a College and a University?

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Chinnapong/iStock via Getty Images

Going off to college is a milestone in any young adult’s life. The phrase itself conjures up images of newfound independence, exposure to new perspectives, knowledge, and possibly even one or more sips of alcohol.

In America, however, few people use the phrase “going off to university,” or “headed to university,” even if they are indeed about to set off for, say, Harvard University. Why did college become the predominant term for postsecondary education? And is there any difference between the two institutions?

While university appears to be the older of the two terms, dating as far back as the 13th century, schools and students in North America have embraced college to describe most places of higher learning. There is no rigid definition of the words, but there are some general attributes for each. A college is typically a four-year school that offers undergraduate degrees like an associate or a bachelor’s. (Community colleges are often two-year schools.) They don’t typically offer master’s or doctorates, and the size of their student body is typically the smaller of the two.

Universities, on the other hand, tend to offer both undergraduate and graduate programs leading to advanced degrees for a larger group of students. They can also be comprised of several schools—referred to as colleges—under their umbrella. A university could offer both a school of arts and sciences and a school of business. The University of Michigan has a College of Engineering, for example.

While many of these traits are common, they’re not guaranteed. Some colleges can be bigger than universities, some might offer master’s degrees, and so on. To complicate matters further, an institution that fits the criteria of a university might choose to call itself a college. Both Dartmouth College and Boston College qualify as universities but use the college label owing to tradition. Schools may begin as colleges, grow into universities, but retain the original name.

People tend to think of a university as being more prestigious or harder to get into, but there are too many variables to make that determination at a glance. Some colleges might ask more of applicants than universities. Some universities might be smaller than certain colleges. Either one can be public or private.

Things get a little more convoluted abroad. In the UK, students go off to university (or uni) instead of college. The British version of college is typically a two-year program where students either focus on learning one particular skill set (much like a vocational school) or use the time to prepare for exams so that they can advance to university. Language matters, too; in Spanish, colegio usually refers to high school.

While the terms aren’t strictly interchangeable, there is enough of a difference between the two to try and make the distinction. Keep in mind that some states, like New Jersey, have rules about how institutions label themselves. There, a university has to have at least three fields of graduate study leading to advanced degrees.

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Why Do We Eat Candy on Halloween?

Jupiterimages/iStock via Getty Images
Jupiterimages/iStock via Getty Images

On October 31, hordes of children armed with Jack-o'-lantern-shaped buckets and pillow cases will take to the streets in search of sugar. Trick-or-treating for candy is synonymous with Halloween, but the tradition had to go through a centuries-long evolution to arrive at the place it is today. So how did the holiday become an opportunity for kids to get free sweets? You can blame pagans, Catholics, and candy companies.

Historians agree that a Celtic autumn festival called Samhain was the precursor to modern Halloween. Samhain was a time to celebrate the last harvest of the year and the approach of the winter season. It was also a festival for honoring the dead. One way Celtics may have appeased the spirits they believed still walked the Earth was by leaving treats on their doorsteps.

When Catholics infiltrated Ireland in the 1st century CE, they rebranded many pagan holidays to fit their religion. November 1 became the “feasts of All Saints and All Souls," and the day before it was dubbed "All-Hallows'-Eve." The new holidays looked a lot different from the original Celtic festival, but many traditions stuck around, including the practice of honoring the dead with food. The food of choice for Christians became "soul cakes," small pastries usually baked with expensive ingredients and spices like currants and saffron.

Instead of leaving them outside for passing ghosts, soul cakes were distributed to beggars who went door-to-door promising to pray for souls of the deceased in exchange for something to eat. Sometimes they wore costumes to honor the saints—something pagans originally did to avoid being harassed by evil spirits. The ritual, known as souling, is believed to have planted the seeds for modern-day trick-or-treating.

Souling didn't survive the holiday's migration from Europe to the United States. In America, the first Halloween celebrations were a way to mark the end-of-year harvest season, and the food that was served mainly consisted of homemade seasonal treats like caramel apples and mixed nuts. There were no soul cakes—or candies, for that matter—to be found.

It wasn't until the 1950s that trick-or-treating gained popularity in the U.S. Following the Great Depression and World War II, the suburbs were booming, and people were looking for excuses to have fun and get to know their neighbors. The old practice of souling was resurrected and made into an excuse for kids to dress up in costumes and roam their neighborhoods. Common trick-or-treat offerings included nuts, coins, and homemade baked goods ("treats" that most kids would turn their noses up at today).

That changed when the candy companies got their hands on the holiday. They had already convinced consumers that they needed candy on Christmas and Easter, and they were looking for an equally lucrative opportunity to market candy in the fall. The new practice of trick-or-treating was almost too good to be true. Manufacturers downsized candies into smaller, bite-sized packages and began marketing them as treats for Halloween. Adults were grateful to have a convenient alternative to baking, kids loved the sweet treats, and the candy companies made billions.

Today, it's hard to imagine Halloween without Skittles, chocolate bars, and the perennial candy corn debates. But when you're digging through a bag or bowl of Halloween candy this October, remember that you could have been having eating soul cakes instead.

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