How Do Water Towers Work?

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As infrastructure goes, water towers are pretty picturesque. Some people turn them into houses once the city no longer needs them. The designers at Pop Chart Lab have created a visual ode to New York City’s water tower taxonomy. But why exactly do we need to store our water hundreds of feet above the city?

Most water towers are pretty simple machines. Clean, treated water is pumped up into the tower, where it’s stored in a large tank that might hold a million or so gallons—enough water to run that particular city for a day. When the region needs water, water pumps utilize the pull of gravity to provide high water pressure. Because they work with gravity, they have to be taller than the buildings they’re providing water to in order to reach the highest floors. Each additional foot of height in a water tower increases water pressure by .43 pounds per square inch.

Here's a basic diagram of what a water tower system looks like:

Image Credit: Jonathan Cretton via Wikimedia Commons // Public Domain

Keeping water high off the ground plays another important role for a city infrastructure. It allows regions to use smaller water pumps. In general, water demand for a city fluctuates throughout the day. Lots of folks are taking showers before work and school, but fewer people are running a lot of water at 3 a.m. Without a water tower, the municipality would have to buy a water pump big and powerful enough to keep up with peak demand in the mornings, which would then largely go to waste during less busy parts of the day for water usage (plus incur extra costs). Instead, municipalities can buy a pump just large enough to satisfy the region’s average water demand for the day, and let the power of the water tower take over during the times with demand that exceeds the pump’s capabilities. When water demand goes down at night, the pump can replace the water in the tower. Also, if the power goes out and the city’s water pumps fail, the water tower can keep water running smoothly for at least 24 hours.

Go inside a water tower in Edmond, Oklahoma:

And in Bloomington, Minnesota:

Look at that tank!

Screenshot via YouTube

And here's a 1-million-gallon water tank getting cleaned:

While water towers generally seem like the product of a bygone era, they’re still very much relevant today. The Louisville Water Tower in Kentucky, built in 1860, is the oldest surviving water tower in the country, and it's still in use. In New York City, millions of people still get water from water towers, though it's one of the last large cities to rely on the system. Stored on top of tall buildings, these water towers provide the pressure for water to flow even if the electricity goes off (especially during a fire).

And, of course, one cannot discount the cultural importance of the water tower:

Image Credit: Jonathunder via Wikimedia Commons // CC BY-SA 3.0

Every city deserves a skyscraper-sized civic monument to its favorite crop. Or beverage decanter.

What Would Happen If a Plane Flew Too High?

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Tom Farrier:

People have done this, and they have died doing it. For example, in October 2004, the crew of Pinnacle Airlines 3701 [PDF]  was taking their aircraft from one airport to another without passengers—a so-called "repositioning" flight.

They were supposed to fly at 33,000 feet, but instead requested and climbed to 41,000 feet, which was the maximum altitude at which the aircraft was supposed to be able to be flown. Both engines failed, the crew couldn't get them restarted, and the aircraft crashed and was destroyed.

The National Transportation Safety Board determined that the probable causes of this accident were: (1) the pilots’ unprofessional behavior, deviation from standard operating procedures, and poor airmanship, which resulted in an in-flight emergency from which they were unable to recover, in part because of the pilots’ inadequate training; (2) the pilots’ failure to prepare for an emergency landing in a timely manner, including communicating with air traffic controllers immediately after the emergency about the loss of both engines and the availability of landing sites; and (3) the pilots’ improper management of the double engine failure checklist, which allowed the engine cores to stop rotating and resulted in the core lock engine condition.

Contributing to this accident were: (1) the core lock engine condition, which prevented at least one engine from being restarted, and (2) the airplane flight manuals that did not communicate to pilots the importance of maintaining a minimum airspeed to keep the engine cores rotating.

Accidents also happen when the "density altitude"—a combination of the temperature and atmospheric pressure at a given location—is too high. At high altitude on a hot day, some types of aircraft simply can't climb. They might get off the ground after attempting a takeoff, but then they can't gain altitude and they crash because they run out of room in front of them or because they try to turn back to the airport and stall the aircraft in doing so. An example of this scenario is described in WPR12LA283.

There's a helicopter version of this problem as well. Helicopter crews calculate the "power available" at a given pressure altitude and temperature, and then compare that to the "power required" under those same conditions. The latter are different for hovering "in ground effect" (IGE, with the benefit of a level surface against which their rotor system can push) and "out of ground effect" (OGE, where the rotor system supports the full weight of the aircraft).

It's kind of unnerving to take off from, say, a helipad on top of a building and go from hovering in ground effect and moving forward to suddenly find yourself in an OGE situation, not having enough power to keep hovering as you slide out over the edge of the roof. This is why helicopter pilots always will establish a positive rate of climb from such environments as quickly as possible—when you get moving forward at around 15 to 20 knots, the movement of air through the rotor system provides some extra ("translational") lift.

It also feels ugly to drop below that translational lift airspeed too high above the surface and abruptly be in a power deficit situation—maybe you have IGE power, but you don't have OGE power. In such cases, you may not have enough power to cushion your landing as you don't so much fly as plummet. (Any Monty Python fans?)

Finally, for some insight into the pure aerodynamics at play when airplanes fly too high, I'd recommend reading the responses to "What happens to aircraft that depart controlled flight at the coffin corner?"

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

Why Are Some Men's Beards a Different Color Than Their Hair?

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Throughout civilization, beards have acted as a silent communicator. For some, it's a symbol of virility and power. For others, being hirsute is mandated by religion, marital status, or both. (Amish single men are clean-shaven; husbands are not.) Seeing an unkempt, scraggly beard could be an indication of a person's economic status or their lack of vanity. One man, Hans Langseth, sprouted a 17-foot-long chin warmer for the unique identity it afforded him. (He kept it neatly rolled over a corn cob when he wasn't busy showing it off.)

Langseth's whiskers, which wound up in the Smithsonian, present a curious timeline of his life. The furthest end of the beard was a vibrant brown, grown out when he was younger. The ends closer to his face—and to the end of his life in 1927—were yellowed.

While age can certainly influence hair and beard color, it doesn't explain why a younger man can sport a decidedly different beard tone than what's on the rest of his head. Other follicular forces are at work.

By default, scalp hair is white. It gets its color from melanin, turning it everything from jet black to dirty blonde. Pheomelanin infuses hair with red and yellow pigmentation; eumelanin influences brown and black. Like shades of paint, the two can mix within the same hair shaft. (Melanin production decreases as we age, which is why hairs start to appear gray.) But not all follicles get the same dose in the same combination. While you might sport a light brown top, your beard could be predominantly dark brown, or sport patches of lighter hairs in spots. Eyebrow hair will probably appear darker because those follicles tend to produce more eumelanin.

If you're wondering why these two-toned heads often have a red beard but not red hair, there's an answer for that, too. While all hair color is genetic, one gene in particular, MC1R, is responsible for a red hue. If you inherit a mutated version of the gene from both parents, you're likely to have red hair from head to toe. (Hopefully not too much toe hair.) But if you inherit MC1R from just one parent, it might only affect a portion of your follicles. If that swatch of color annoys you for whatever reason? There’s always beard dye.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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