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How Effective is the Eye Black that Athletes Wear?

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Sometimes it’s literally a glob of grease, other times it’s a synthetic sticker. We’ve all seen baseball and football players with the black rectangles under their eyes on sunny days, which is thought to help reduce the sun’s glare and allow athletes to better pick up the ball. But does it actually work?  

The underlying concept behind eye black is that it reduces the amount of glare that reaches your eyes thanks to the fact that the color black absorbs most light frequencies. In theory, excessive light from sources in our peripheral vision will be absorbed by the black color, increasing the contrast of the objects we're are looking at and focusing on directly.  

There have been a handful of studies done in the past decade, including one by the University of New Hampshire and one by Yale University. Although these two and others began with skepticism and have all yielded slightly different results—while accounting for the effect of variables such as eye color and gender—they have agreed that traditional eye grease made of beeswax, paraffin, and carbon does in fact reduce glare and improve contrast sensitivity. They also all concluded that anti-glare stickers and petroleum jelly have no impact.

“I thought we would find it to be like war paint and a psychological advantage more than anything else,” Dr. Brian M. DeBroff, the lead author of the Yale study, told The New York Times. “We were surprised to find a benefit from the grease.”

Even though the effect was found to be somewhat minimal, DeBroff has adopted somewhat of an “it can’t hurt” stance regarding its application to high-intensity sport situations.

“Certainly in football and baseball, where tracking a ball at high speed is an important aspect, any competitive advantage could be beneficial,” DeBroff said.

Despite this, researchers are still unsure how much impact the glare reduction and contrast improvement translates into an “on-the-field” advantage for athletes. Dr. Kenneth Fuld, chairman of the University of New Hampshire’s psychology department and the sponsor of the aforementioned study conducted by the university, points out that tennis players regularly perform at a high level despite the fact that they do not wear eye black.

“I would be highly doubtful that it would have much of an effect, if any,” Fuld said.

Although it is extremely reasonable to conclude that it is a coincidence, it is interesting to note that last year’s two top NFL receivers in terms of receiving yards, Calvin Johnson of the Detroit Lions and Andre Johnson of the Houston Texans, both regularly wear eye black during games.

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Big Questions
Why Is Soda Measured in Liters?
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Never a nation to fall in line, America is one of the few countries to resist the metric system. We stubbornly measure distance in miles and weight in pounds. So what’s with those two-liter bottles of soda?

First, a clarification: Soda is far from the only substance we measure in metric units. Heck, it’s not even the only beverage. Wine, liquor, and bottled water are sold by the milliliter. The healthcare field is all about metric units, too, from cholesterol levels to prescription, over-the-counter, and supplement dosages. We run 5-kilometer races, ride on 215-millimeter tires, and use 8-millimeter cameras, or at least we used to.

In most other things, we determinedly cling to our imperial measurements. Attempts to convince Americans to join the rest of the metric-measuring world have been met with great resistance.

Ken Butcher of the National Institute of Science and Technology has been working with the government’s tiny Metric Program for years. Speaking to Mental Floss back in 2013, Butcher explained that we’re so entrenched in our way of doing things that switching measurement systems now would be both chaotic and expensive.

"If we were going to start a new country all with the metric system, it would be easy," he said. "But when you have to go in and change almost everything that touches people’s everyday life and their physical and mental experience, their education, and then you take that away from them—it can be scary."

Here and there, though, when it’s convenient, we have been willing to budge. The soda bottle is a good example. Until 1970, all soft drinks in the U.S. were sold in fluid ounces and gallons, mostly in glass bottles. Then the plastic polyethylene terephthalate (PET) bottle came along, and soft drink makers decided it was time for a product redesign.

The redesign process coincided with two key factors: a short-lived wave of government interest in going metric, and the burgeoning environmental movement.

The folks at PepsiCo decided to meld all three into its exciting new vessel: a lightweight, cheap, recyclable, metric bottle, with built-in fins so it could stand up on supermarket shelves. Two liters: the soda size of the future.

The two-liter bottle took off. The rest of the soft drink world had no choice but to get on board. And voila: liters of cola for all.

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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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.

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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