CLOSE
ThinkStock
ThinkStock

Has a U.S. River Run Backwards Before?

ThinkStock
ThinkStock

The ongoing drought conditions wreaking havoc across large swaths of the country have driven the water in Lake Michigan an inch below its previous record low, and aren’t stopping. Last month, the U.S. Army Corps of Engineers announced that, if this continues and the lake water drops below the level of the Chicago River, the river could reverse course and begin flowing back towards its source. (Thankfully, there’s a series of locks separating the two, which will help prevent the less-than-clean river from flowing into the lake and the city’s source of drinking water.) Has an American river ever done an about-face like this before?

Right Back Where it Started From

Oh yeah. In fact, the Chicago has done it before. If the river does reverse course, it won’t be running backwards so much as running forwards again. 

When Europeans first settled in the Chicago area, the river drained into Lake Michigan, which was fine—except that settlers used the river to dump waste, and used the lake for drinking water. As the city grew, there were numerous outbreaks of typhoid and cholera because of contaminated drinking water, and something had to be done. 

In the late 1800s, the city decided to solve their problem with an ambitious engineering feat: They would reverse the flow of the river and send it away from the lake and towards the Mississippi River. The so-called “Chicago Diversion” worked: It not only diverted contaminated water away from the city’s drinking water, but also connected the Great Lakes and Mississippi River water systems and opened up the possibility of commercial travel and trade between them. 

It hasn't been just barges and haulers that could cross from one system to the other, though. Invasive Asian carp, introduced decades ago to southern fish farms as pond cleaners, have gradually made their way north, threatening native species and altering food webs as they go. With the fish nearing the Great Lakes, the idea of un-reversing (re-reversing?) the Chicago River has been kicked around, but now it looks like the river could take care of the problem itself. 

All Shook Up

The most famous of American Rivers, the mighty Mississippi, also might have gone backwards more than once. In 1811 and 1812, three earthquakes—the most powerful to ever hit the eastern U.S.—struck what was then a sparsely populated area of the Louisiana Territory. 

Eyewitness accounts from the quake read like Michael Bay scripts: The ground rippled and quivered; chasms opened up and swallowed livestock and wagons; sand and dirt exploded from the ground like volcanic eruptions and blotted out the sun; the Mississippi shook with such violence that the water ran backwards and boats were dragged upstream. 

One boatman, wanting to get away from the trees falling over on the river banks, put his boat out into the middle of the river and soon found, he claimed, that “the current changed, and the boat hurried up, for about the space of a minute, with the velocity of the swiftest horse,” fast enough that he had to hold on to his hat to keep it on his head. 

Gradually, the man said, the river returned to its normal course. Exactly how long that took is unclear, and various firsthand accounts have the river going backwards for anywhere from a few hours to a few days. Whether the river even reversed itself at all is questionable, and the United States Geological Survey says that ground uplifts and waves moving upstream may have just created the illusion that the water was moving backwards. 

What’s more certain is that the Mississippi reversed course for about 24 hours when Hurricane Isaac struck last year, and when Hurricane Katrina hit in 2005.

nextArticle.image_alt|e
iStock
arrow
Big Questions
How Do Hummingbirds Sleep?
iStock
iStock

How do hummingbirds sleep?

Anusha Shankar:

Ooh this is an exciting question—I’ve spent the past five years thinking about just this!

Look at these infrared images from a crowdfunded project we did in the summer of 2017: The bird on the left is generating heat, keeping itself warm, while the one on the right is in torpor. It has allowed its body temperature to become the same as the air temperature and has stopped "thermoregulating," or maintaining a high body temperature.

Hummingbirds find a nice and sheltered place at night, and they latch onto a branch with their tiny feet, and then they go to sleep. Some of them ... use a strategy called torpor, where they can lower the amount of energy they use by about 85 percent. They do this by basically shutting down a bunch of their bodily functions—they allow their body to get cold as the night gets colder. You and I spend a lot of energy keeping our bodies warm so everything functions normally. Hummingbirds in torpor give up this "normal" function, and become more like lizards, in that they can get ‘cold-blooded’ in torpor.

Torpor is a tricky state to be in, because they can’t respond to outside stimuli for 20 to 30 minutes, until they warm their bodies back up. They take that risk just to have enough energy in their tiny bodies to make it to the next morning.

I recently wrote a blog post for National Geographic to talk a bit more about hummingbird sleep (includes videos!).

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

nextArticle.image_alt|e
iStock
arrow
Big Questions
Are There Number 1 Pencils?
iStock
iStock

Almost every syllabus, teacher, and standardized test points to the ubiquitous No. 2 pencil, but are there other choices out there?

Of course! Pencil makers manufacture No. 1, 2, 2.5, 3, and 4 pencils—and sometimes other intermediate numbers. The higher the number, the harder the core and lighter the markings. (No. 1 pencils produce darker markings, which are sometimes preferred by people working in publishing.)

The current style of production is profiled after pencils developed in 1794 by Nicolas-Jacques Conté. Before Conté, pencil hardness varied from location to location and maker to maker. The earliest pencils were made by filling a wood shaft with raw graphite, leading to the need for a trade-wide recognized method of production.

Conté’s method involved mixing powdered graphite with finely ground clay; that mixture was shaped into a long cylinder and then baked in an oven. The proportion of clay versus graphite added to a mixture determines the hardness of the lead. Although the method may be agreed upon, the way various companies categorize and label pencils isn't.

Today, many U.S.  companies use a numbering system for general-purpose, writing pencils that specifies how hard the lead is. For graphic and artist pencils and for companies outside the U.S., systems get a little complicated, using a combination of numbers and letters known as the HB Graphite Scale.

"H" indicates hardness and "B" indicates blackness. Lowest on the scale is 9H, indicating a pencil with extremely hard lead that produces a light mark. On the opposite end of the scale, 9B represents a pencil with extremely soft lead that produces a dark mark. ("F" also indicates a pencil that sharpens to a fine point.) The middle of the scale shows the letters and numbers that correspond to everyday writing utensils: B = No. 1 pencils, HB = No. 2, F = No. 2½, H = No. 3, and 2H = No. 4 (although exact conversions depend on the brand).

So why are testing centers such sticklers about using only No. 2 pencils? They cooperate better with technology because early machines used the electrical conductivity of the lead to read the pencil marks. Early scanning-and-scoring machines couldn't detect marks made by harder pencils, so No. 3 and No. 4 pencils usually resulted in erroneous results. Softer pencils like No. 1s smudge, so they're just impractical to use. So No. 2 pencils became the industry standard.

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios