Each week we uncover the most interesting and informative articles from around the world, here are 10 of the coolest stories in science this week.

The top images here show a normal brain. The bottom images show the brain of former University of Texas football player Greg Ploetz, who died at age 66.
Credit: Dr. Ann McKee, Copyright: BU Photography

A study of the brains of more than 200 deceased football players — including 111 who played in the National Football League (NFL) — reveals that nearly 90 percent of the players had a brain disease called chronic traumatic encephalopathy (CTE).

In the study, published today (July 25) in the journal JAMA, researchers found evidence of CTE in 177 out of 202 brains, or 87 percent of the individuals. Among the brains of NFL players, 110 out of 111, or 99 percent, had CTE. (The other men who had donated their brains for the study played football either semiprofessionally, or in college or high school.) [Read more about CTE.]

Prince Rupert's drops are weird little glass confections that can resist a hammer strike to the head, but shatter with the slightest pressure to the tail. New research has revealed the physics behind the strange phenomenon.
Credit: Trevor Mahlmann/Purdue University

The mystery of tiny teardrop-shaped glass confections that can survive a hammer blow, yet shatter to smithereens with the slightest touch to the stem, has finally been solved.

Over the centuries, scientists puzzled over the riddle of Prince Rupert's drops. In 1994, Chandrasekar and a colleague used a high-speed camera to capture 1 million frames per second of the drops as they shattered. The footage revealed that tiny cracks that form in the tail rapidly spread into the head. [Read more about the solved mystery.]

A preserved toe is famously served as a key ingredient in a by-request cocktail at a Canadian hotel saloon.
A preserved toe is famously served as a key ingredient in a by-request cocktail at a Canadian hotel saloon.
Credit: PR Services

The notorious "Sourtoe Cocktail" — a shot of alcohol containing a dehydrated human toe — is a bizarre tradition at the Downtown Hotel's Sourdough Saloon, in Dawson City, Yukon Territory. The cocktail craze kicked off in 1973, after riverboat Capt. Dick Stevenson found a preserved toe in an abandoned Yukon cabin; the toe was thought to belong to a 1920s-era bootlegger named Louie Linken, the Sourtoe Cocktail Club website says.

To date, 71,468 people have downed the drink and tasted the toe, toe captain Terry Lee recently told NPR. [Read more about the drink.]

A group of scientists in Oregon has successfully modified the genes of embryos using CRISPR, a cut-and-paste gene-editing tool.

In general, editing the germ line — meaning sperm, eggs or embryos — has been controversial, because it means permanently changing the DNA that is passed on from one generation to the next. Some scientists have called for a ban on germ-line editing, saying the approach is incredibly risky and ethically dubious. [Read more about the procedure.]

A burial jar containing the remains of an ancient inhabitant of the Canaanite city of Sidon. This individual was one of five whose DNA was sequenced to reveal the ancestry of the Canaanites.
A burial jar containing the remains of an ancient inhabitant of the Canaanite city of Sidon. This individual was one of five whose DNA was sequenced to reveal the ancestry of the Canaanites.
Credit: Dr. Claude Doumet-Serhal/The Sidon Excavation

The people of modern-day Lebanon can trace their genetic ancestry back to the Canaanites, new research finds.

Haber, Tyler-Smith and their colleagues extracted ancient DNA from the bones of five Canaanites who died in the ancient city of Sidon (an area now in Lebanon). The skeletons dated from between 3,750 and 3,650 years ago. The researchers then compared the genetic sequences of these ancient Canaanites with those of 99 modern Lebanese people, as well as with ancient DNA sequences of more than 300 other people from an ancient DNA database. [Read more about the dig.]

Sperm counts among men in Western countries have dropped considerably in the last several decades, according to a new study.

The researchers said that they cannot determine from their data what might have caused the decline, but it could be related to environmental or lifestyle factors. The findings are concerning, not only because men's sperm counts are linked with their chances of conceiving a child, but also because poor sperm counts have been linked with a number of other poor health outcomes, including an increased risk of early death. [Read more about the mystery.]

The May 29 total solar eclipse in 1919.
Credit: Public Domain

For some skywatchers, the upcoming total solar eclipse on Aug. 21 is more than just a chance to catch a rare sight of the phenomenon in the United States. It's also an opportunity to duplicate one of the most famous experiments of the 20th century, which astrophysicist Arthur Eddington performed in an attempt to prove that light could be bent by gravity, a central tenet of Albert Einstein's theory of general relativity.

But later analyses of Eddington's data seemed to suggest that the astrophysicist's confirmation might not have been the slam dunk he thought it was. Bruns said the debate over Eddington's data is why he wants to do the experiment again. [Read more about testing Einstein's theory.]

What's in your drinking water? Whether you're wondering if your water is safe or just what that weird smell is, a new tool is now available that could help.

In total, the tests found nearly 270 contaminants in drinking water across the country. Eight of the contaminants, including arsenic and lead, were reported in all 50 states. [Read more about the database.]

Scientists have found that a "ghost" lineage of archaic human may have interbred with the ancestors of modern humans in what is now sub-Saharan Africa around 200,000 years ago.
Credit: Bob Wilder/University at Buffalo

A protein that helps make human spit slimy reveals signs that the ancestors of modern humans interbred with an extinct human lineage that was an even more distant relation than Neanderthals, a new study finds.

Now, researchers suggest that a "ghost" lineage of ancient humans may have contributed the DNA for a protein called mucin-7 found in the saliva of modern humans living in sub-Saharan Africa today. [Read more about our unknown ancestors.]

"Star Wars" microscopic midi-chlorians were born on the fictional Wellspring of Life.
Credit: Lucasfilm

Mitochondria: totally real cell organelles that convert sugars, fats and oxygen into usable energy for cells. Midi-chlorians: completely made-up and widely derided microscopic life-forms that give Jedi warriors their ability to use the Force in the "Star Wars" movies.

The paper was a hoax written by the so-called Neuroskeptic, who blogs pseudonymously for Discover magazine. The point? To expose "predatory journals," which claim to offer peer-reviewed, open-access publication but in fact publish almost anything for a fee, according to the Neuroskeptic. [Read more about the hoax.]

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