How Do Eyes Get Their Color?

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Paul Newman wasn't too fond of his blue eyes. The actor, who earned admiration from audiences and critics in everything from Cool Hand Luke to The Verdict, had a piercing set of blue irises that were as recognizable as Sylvester Stallone’s deltoids. He found the attention they received slightly grating. “If blue eyes are what it’s all about … I may as well turn in my union card right now and go into gardening,” the actor/philanthropist told The Saturday Evening Post in 1968.

If Newman knew the science behind his distinctive peepers, maybe he wouldn’t have been so hard on them. Although your genes are responsible for the color of your eyes, it’s a very complicated hereditary trait. Where you fall on the spectrum from light Newman blue to dark brown is the result of how much melanin pigmentation you have.

The iris—the colored part of the eye surrounding the pupil—is made of layers. The iris pigment epithelium is in the back and has some black or brown pigmentation to it. The layer over it is the stroma, which sometimes has brown melanin pigment, as well as colorless collagen. The black dots or “strings” you see in the eye are typically coming from the epithelium and are visible through the stroma.

Color is determined by the amount of melanin in the stroma. If you have brown eyes, you have brown melanin in the stroma that will absorb available light and make the iris appear darker in color. If you have green eyes, there’s not much melanin or collagen, and the light will be scattered. If your eyes are blue, you have no melanin at all—all of the light hitting the eye is scattered and reflected back. That’s why people with blue or green eyes can seem to shift eye color, depending on the amount of light in a room.

So how are genes involved? While they don’t directly program your body for a certain eye color, they do affect the quality and quantity of melanin in the stroma, which dictates your hue. While Newman’s brand of blue is a little more unusual than brown—the most common color—he probably would’ve been equally perturbed by grey. That shade, possibly caused by excess collagen, is considered the rarest eye color of all.

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Will the Sun Ever Stop Shining?

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Viktor T. Toth:

The Sun will not stop shining for a very, very long time.

The Sun, along with the solar system, is approximately 4.5 billion years old. That is about one-third the age of the entire universe. For the next several billion years, the Sun is going to get brighter. Perhaps paradoxically, this will eventually result in a loss of carbon dioxide in the Earth’s atmosphere, which is not good news; It will eventually lead to the death of plant life.

Within 2.5 to 3 billion years from now, the surface temperature of the Earth will exceed the boiling point of water everywhere. Within about about 4 to 5 billion years, the Earth will be in worse shape than Venus today, with most of the water gone, and the planet’s surface partially molten.

Eventually, the Sun will evolve into a red giant star, large enough to engulf the Earth. Its luminosity will be several thousand times its luminosity at present. Finally, with all its usable nuclear fuel exhausted and its outer layers ejected into space, the Sun’s core will settle down into the final stage of its evolution as a white dwarf. Such a star no longer produces energy through nuclear fusion, but it contains tremendous amounts of stored heat, in a very small volume (most of the mass of the Sun will be confined to a volume not much larger than the Earth). As such, it will cool very, very slowly.

It will take many more billions of years for the Sun to cool from an initial temperature of hundreds of thousands of degrees to its present-day temperature and below. But in the end, the remnant of the Sun will slowly fade from sight, becoming a brown dwarf: a cooling, dead remnant of a star.

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

Why Do So Many Airports Have Chapels?

Inside Our Lady of the Airways Chapel at Boston Logan International Airport
Inside Our Lady of the Airways Chapel at Boston Logan International Airport

There are only so many ways to kill time during a long layover. You might browse the magazines at a Hudson News or take the time to test out a travel pillow or two. If it's a particularly trying travel day, you may want to while away a few hours at an airport bar. But if you’ve killed enough time in enough U.S. airports, you've probably noticed that most of them have chapels tucked into a corner of the terminal. Some of them are simple, some of them are ornate. Some cater specifically to members of one religion while others are interfaith. So where did they come from, and why are they there?

The biggest surprise in answering the latter part of that question might be that airport chapels weren't originally built for airport passengers at all. According to Smithsonian.com, the first U.S. airport chapel opened in 1951 at Boston's Logan International Airport and was specifically created for the airport’s Catholic staff, largely to offer mass services for workers on longer shifts.

Dubbed “Our Lady of the Airways,” Boston's airport chapel concept was quickly embraced by Catholic leaders around the country. In 1955, Our Lady of the Skies Chapel opened at New York City's Idlewild Airport (which was renamed John F. Kennedy International Airport in 1963). Other Catholic chapels followed.

In the 1960s, JFK added both a Protestant chapel and a Jewish synagogue to its terminals. By the 1980s, Protestant chapels had opened in the Atlanta and Dallas airports as well.

Single-faith chapels dissipated for the most part during the 1990s and into the new millennium. In 2008, The Christian Index ran a story about the changing face of on-the-go religious spaces and declared "Single-faith chapels a dying breed at U.S. airports." As interfaith chapels became the new normal, this inclusiveness extended to the chapels' patrons as well. Instead of remaining gathering places for airport employees, the chapels opened their doors to the millions of passengers traveling in and out of their cities each year.

Today, more than half of America's busiest airports feature chapels, the majority of which are interfaith. Most existing chapels are welcoming to people of all faiths and often include multiple religious symbols in the same room. They have become important spaces for meditation and reflection. Many of them still offer worship services for each of their represented practices, including places like the interfaith chapel at Washington Dulles International Airport, which hosts a Catholic mass on Saturday evenings as well as daily Jewish prayer services. Though each airport chapel is unique in design and services, they all endeavor to offer a much-needed spiritual refuge from the hassle of air travel.

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