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Why Do Speed Skaters Use Such Weird Ice Skates?

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If you watch the speed skaters during this year’s Winter Olympics, you’ll certainly notice something strange about the footwear they’re sporting. With a hinged blade that moves independently from the boot, modern speed skates look nothing like hockey or figure skates—they're clap skates. What’s the purpose of such freaky footgear?

Clap skates were invented almost a hundred years ago, but it took until the last few decades for them to gain traction in the competitive sport. “The modern day clap-skate was developed by a Dutch group in the mid 1980s,” says Scott Van Horne, a former Canadian national speed skater who has studied the biomechanics of skaters using clap skates.

“At first the elite skaters wouldn’t touch them,” Van Horne says, but in 1996, some of the Dutch women’s team took a chance, and switched over. The results were astonishing—everybody in the sport noticed. “Suddenly skaters you might otherwise deem ‘hacks’ were now using clap skates and contending for the podiums,” Van Horne says.

By 1997, clap skaters were breaking world records, and “by the next year everybody had switched,” Van Horne says. At the 1998 Winter Olympics in Nagano, Japan, speed skating was dominated by the footwear—and has been ever since.

Although these new skates were shaving precious seconds off the Olympians’ times, for a while, nobody really knew why.

“Originally people thought the skate helped reduce friction,” Van Horne says. “With the traditional skates, it used to be that at the end of your stride, you’d push up on to the front of the skate’s blade. You could even see the ice fly into the air.” Conversely, on a clap skate, the blade keeps flat contact with the ice throughout the entire stride.

But as much sense as that makes, reduced friction isn’t really why clap skates are so effective. “Basically what clap skates do is give a more advantageous position for generating power at the knee,” Van Horne says. With the old skates, pushing up on to the front of the skate’s blade meant that the skater’s knee was absorbing a tiny bit more of his/her energy—about 5 percent, according to Van Horne. Pretty small, he admits, but just enough to make a big difference out on the rink.

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Big Questions
Where Is the Hottest Place on Earth?
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The summer of 2017 will go down as an endurance test of sorts for the people of Phoenix, Arizona. The National Weather Service issued an extreme heat warning, and planes were grounded as a result of temperatures exceeding 120 degrees. (Heat affects air density, which in turn affects a plane’s lift.)

Despite those dire measures, Phoenix is not the hottest place on Earth. And it’s not even close.

That dubious honor was bestowed on the Lut Desert in Iran in 2005, when land temperatures were recorded at a staggering 159.3 degrees Fahrenheit. The remote area was off the grid—literally—for many years until satellites began to measure temperatures in areas that were either not well trafficked on foot or not measured with the proper instruments. Lut also measured record temperatures in 2004, 2006, 2007, and 2009.

Before satellites registered Lut as a contender, one of the hottest areas on Earth was thought to be El Azizia, Libya, where a 1922 measurement of 136 degrees stood as a record for decades. (Winds blowing from the nearby Sahara Desert contributed to the oppressive heat.)

While the World Meteorological Organization (WMO) acknowledged this reading as the hottest on record for years, they later declared that instrumentation problems and other concerns led to new doubts about the accuracy.

Naturally, declaring the hottest place on Earth might be about more than just a single isolated reading. If it’s consistency we’re after, then the appropriately-named Death Valley in California, where temperatures are consistently 90 degrees or above for roughly half the year and at least 100 degrees for 140 days annually, has to be a contender. A blistering temperature of 134 degrees was recorded there in 1913.

Both Death Valley and Libya were measured using air temperature readings, while Lut was taken from a land reading, making all three pretty valid contenders. These are not urban areas, and paving the hottest place on Earth with sidewalks would be a very, very bad idea. Temperatures as low as 95 degrees can cause blacktop and pavement to reach skin-scorching temperatures of 141 degrees.

There are always additional factors to consider beyond a temperature number, however. In 2015, Bandar Mahshahr in Iran recorded temperatures of 115 degrees but a heat index—what it feels like outside when accounting for significant humidity—of an astounding 163 degrees. That thought might be one of the few things able to cool Phoenix residents off.

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Big Questions
How Does Autopilot Work on an Airplane?
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How does autopilot work on an airplane?

Joe Shelton:

David Micklewhyte’s answer is a good one. There are essentially a few types of features that different autopilots have. Some autopilots only have some of these features, while the more powerful autopilots do it all.

  • Heading Hold: There’s a small indicator that the pilot can set on the desired heading and the airplane will fly that heading. This feature doesn’t take the need for wind correction to desired routing into account; that’s left to the pilot.
  • Heading and Navigation: In addition to holding a heading, this version will take an electronic navigation input (e.g. GPS or VOR) and will follow (fly) that navigation reference. It’s sort of like an automated car in that it follows the navigator’s input and the pilot monitors.
  • Altitude Hold: Again, in addition to the above, a desired altitude can be set and the aircraft will fly at that altitude. Some autopilots have the capability for the pilot to select a desired altitude and a climb or descent rate and the aircraft will automatically climb or descend to that altitude and then hold the altitude.
  • Instrument Approaches: Autopilots with this capability will fly preprogrammed instrument approaches to the point where the pilot either takes control and lands or has the autopilot execute a missed approach.

The autopilot is a powerful computer that takes input from either the pilot or a navigation device and essentially does what it is told to do. GPS navigators, for example, can have a full flight plan entered from departure to destination, and the autopilot will follow the navigator’s guidance.

These are the majority of the controls on the autopilot installed in my airplane:

HDG Knob = Heading knob (Used to set the desired heading)

AP = Autopilot (Pressing this turns the autopilot on)

FD = Flight Director (A form of navigational display that the pilot uses)

HDG = Heading (Tells the autopilot to fly the heading set by the Heading Knob)

NAV = Tells the autopilot to follow the input from the selected navigator

APR = Tells the autopilot to fly the chosen approach

ALT = Tells the autopilot to manage the altitude, controlled by the following:

VS = Vertical Speed (Tells the autopilot to climb or descend at the chosen rate)

Nose UP / Nose DN = Sets the climb/descent rate in feet per minute

FLC = Flight Level Change (An easy manual way to set the autopilot)

ALT Knob = Used to enter the desired altitude

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

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