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The Science of the Solstice

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Today at 4:48 UTC (Coordinated Universal Time) we marked the winter solstice. (Those of you in Eastern Standard Time experienced it at 11:48 p.m. on December 21.) It's the longest night and shortest day of the year in the Northern Hemisphere. So what is a solstice, and why is it affecting your day?

The Earth doesn't spin vertically like a top as it orbits the Sun. Instead, imagine a line drawn directly through the Earth at its poles. Tilt the Earth along that line at 23.5 degrees. That is the Earth's axial tilt. The direction of the Earth's axial tilt doesn't change as it orbits the Sun (for our timescale, at least), which means the Sun is directly overhead different parts of the Earth at different times of the year. For half the year, the Southern Hemisphere is "closer" to the Sun and its radiation; for the other half, the Northern Hemisphere is closer. You might recognize this phenomenon as the reason we have seasons.

The axial tilt also affects the length of days. Consider a map of the Earth, with horizontal lines dividing it latitudinally, and vertical lines longitudinally. Among the best-known latitudes are the equator, at 0 degrees; the Northern Hemisphere's Tropic of Cancer, at 23.5 degrees; and the Southern Hemisphere's Tropic of Capricorn, at -23.5 degrees. Recognize that number? Now we're getting somewhere.

The winter solstice in the Northern Hemisphere occurs when the Tropic of Capricorn experiences an overhead Sun, which makes that latitude's day 13 hours, 27 minutes long. Because less of the Northern Hemisphere is in direct sunlight, the higher up the Earth you get from the Tropic of Capricorn, the shorter the day. The day is 12 hours long at the equator; just over 10.5 hours at the Tropic of Cancer; and 0 hours at the Arctic Circle, which is in total darkness.

If the lack of sunlight on the shortest day of the year has you weeping into your whiskey, take heart: Beginning tomorrow, the days slowly start to lengthen again. It may be the first day of winter, but spring is on the way. On March 20, 2016, the Sun will be directly "over" the equator. This is the vernal equinox. The Sun is again over the equator in September—the autumnal equinox. And exactly halfway between them is the day that sun worshippers probably consider the best one of the year: the summer solstice, when the Sun is directly over the Tropic of Cancer. 

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Pop Culture
Neil deGrasse Tyson Recruits George R.R. Martin to Work on His New Video Game
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Kevin Winter / Getty Images

George R.R. Martin has been keeping busy with the latest installment of his Song of Ice and Fire series, but that doesn’t mean he has no time for side projects. As The Daily Beast reports, the fantasy author is taking a departure from novel-writing to work on a video game helmed by Neil deGrasse Tyson.

DeGrasse Tyson’s game, titled Space Odyssey, is currently seeking funding on Kickstarter. He envisions an interactive, desktop experience that will allow players to create and explore their own planets while learning about physics at the same time. To do this correctly, he and his team are working with some of the brightest minds in science like Bill Nye, former NASA astronaut Mike Massimino, and astrophysicist Charles Liu. The list of collaborators also includes a few unexpected names—like Martin, the man who gave us Game of Thrones.

Though Martin has more experience writing about dragons in Westeros than robots in outer space, deGrasse Tyson believes his world-building skills will be essential to the project. “For me [with] Game of Thrones ... I like that they’re creating a world that needs to be self-consistent,” deGrasse Tyson told The Daily Beast. “Create any world you want, just make it self-consistent, and base it on something accessible. I’m a big fan of Mark Twain’s quote: ‘First get your facts straight. Then distort them at your leisure.’”

Other giants from the worlds of science fiction and fantasy, including Neil Gaiman and Len Wein (co-creator of Marvel's Wolverine character), have signed on to help with that same part of the process. The campaign for Space Odyssey has until Saturday, July 29 to reach its $314,159 funding goal—of which it has already raised more than $278,000. If the video game gets completed, you can expect it to be the nerdiest Neil deGrasse Tyson project since his audiobook with LeVar Burton.

[h/t The Daily Beast]

Flying Telescopes Will Watch the Total Solar Eclipse from the Air

If you've ever stood on the tips of your toes to reach something on a high shelf, you get it: Sometimes a little extra height makes all the difference. Although in this case, we're talking miles, not inches, as scientists are sending telescopes up on airplanes to monitor conditions on the Sun and Mercury during the upcoming total eclipse.

Weather permitting, the Great American Eclipse (as some are calling it) will be at least partially visible from anywhere in the continental U.S. on August 21. It will be the first time an eclipse has been so widely visible in the U.S. since 1918 and represents an incredible opportunity not only for amateur sky-watchers but also for scientists from coast to coast.

But why settle for gawking from the ground when there's an even better view up in the sky?

Scientists at the Southwest Research Institute (SwRI) have announced plans to mount monitoring equipment on NASA research planes. The telescopes, which contain super-sensitive, high-speed, and infrared cameras, will rise 50,000 feet (about 9.5 miles) above the Earth's surface to sneak a very special peek at the goings-on in our Sun and its nearest planetary buddy.

Gaining altitude will not only bring the instruments closer to their targets but should also help them avoid the meteorological chaos down below.

"Being above the weather guarantees perfect observing conditions, while being above more than 90 percent of Earth's atmosphere gives us much better image quality than on the ground," SwRI co-investigator Constantine Tsang said in a statement. "This mobile platform also allows us to chase the eclipse shadow, giving us over seven minutes of totality between the two planes, compared to just two minutes and 40 seconds for a stationary observer on the ground."

The darkness of that shadow will blot out much of the Sun's overpowering daily brightness, giving researchers a glimpse at rarely seen solar emissions.

"By looking for high-speed motion in the solar corona, we hope to understand what makes it so hot," senior investigator Amir Caspi said. "It's millions of degrees Celsius—hundreds of times hotter than the visible surface below. In addition, the corona is one of the major sources of electromagnetic storms here at Earth. These phenomena damage satellites, cause power grid blackouts, and disrupt communication and GPS signals, so it's important to better understand them."

The temporary blackout will also create fine conditions for peeping at Mercury's night side. Tsang says, "How the temperature changes across the surface gives us information about the thermophysical properties of Mercury's soil, down to depths of about a few centimeters—something that has never been measured before."


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