Smithsonian.com

The photo above shows the Hope Diamond, a 45.52-carat “blue diamond” on permanent display at the Smithsonian in Washington, D.C. When you see this King Of All Bling in regular white light, it looks blue. But if you see it under ultraviolet light, the Hope glows red. (In fact, the Hope will continue to glow—or “phosphoresce”—red even several minutes after the UV light is turned off!) Now scientists have found that this red phosphorescence may be the key to distinguishing all real blue diamonds from the fakes.

Diamonds are made of mostly carbon, and their exact color is determined by traces of other elements mixed in. Yellow diamonds, for instance, contain relatively large nitrogen impurities. Blue diamonds contain low levels of nitrogen and higher levels of boron.

Under UV light, the vast majority of blue diamonds look not red, but blue. So in the past, gemologists thought that the few blue diamonds that glowed red under UV light must have been children of the Hope (which, when originally mined from India in the 1600s, was 112 carats). But it turns out that all authentic blue diamonds contain a red phosphorescent component; it’s just that for most of them, the red light is overpowered by blue-green. The researchers think that it’s the precise mix of nitrogen and boron impurities that causes the lasting red glow.

The discovery was made by researchers from the Smithsonian Institution and the Naval Research Laboratory. They used a portable spectrometer to analyze several dozen blue diamonds, including the Hope, and found a red component in all but five. They also tested three phony blue diamonds—of which none had the telltale red signature. They published their findings in the January issue of the journal Geology.

Most interesting to me is that the researchers never moved the Hope from its display location. “If you want to study the Hope diamond using spectroscopy, you need to bring the machine to the Hope diamond,” Penn State geoscientist Peter J. Heaney said in a press release. “You cannot bring the Hope to the machine.” Heaney’s team could only take measurements in the early mornings and evenings, when the museum was closed to the public.

(Flickr, via absolutwade)

The Plaza de las Tres Culturas, in Mexico City, is so named because it showcases the new, the old, and the very old. As shown above, modern offices of the Mexican foreign ministry (upper right) not only neighbor the 17th-century Templo de Santiago church (center), but ruins of Aztec temples built hundreds of years before that (foreground left).

Last month, Mexican archaeologists unearthed the ruins (36 feet tall!) of an 800-year-old pyramid that suggests the ancient Aztec city of Tlatelolco is at least a century older than previously believed. “The (Aztec) timeline is going to need to be revised,” archaeologist Patricia Ledesma said at the site on Thursday, Reuters reported.

Fifteen years ago, a different pyramid finding dated Tlatelolco to 1325. But the newly found pyramid is 100 to 200 years older. The scientists also found a sculpture of a god (representing either Tlaloc, a rain god, or Tezcatlipoca, god of the sky) and five skulls.

Check out Reuters 48-second video clip of the ruins.

(Flickr, via schizoform)

The bold brush strokes and striking colors of the impressionist painters make for some of the most acclaimed and recognizable pieces in the world’s finest art collections. Claude Monet’s “Twilight, Venice,” above, is a good example. But what if its lack of detail and blurring of color were not so much deliberate choices by the artist, but rather, unintentional consequences of his failing eyesight?

Monet was diagnosed with cataracts in 1912, though even seven years before that he had complained that “colors no longer had the same intensity…reds had begun to look muddy.” Mary Cassatt had cataracts, too, and Edgar Degas suffered from macular degeneration.

Recently, Stanford ophthalmologist Michael Marmor made computer simulations that showed how degenerative eye diseases change color perception in the visual field. Based on his research, published in the Archives of Ophthamology, Marmor told the New York Times that “[Monet] couldn’t judge what he was seeing or see what he was painting…It is a mystery how he worked.â€?

We’ll never know, of course, whether Monet intended his beautiful landscapes to blur. We do know that he underwent cataract surgery three years before he died, in 1923. After the surgery, he destroyed many of his previous pieces. He also painted works like “Roses,” (1925-26) below, with supposedly more refined lines and subtle colors. Kinda looks the same to me.

(Hat tip: Neurophilosopher; “Twilight, Venice,” Claude Monet, 1908, via Wikimedia Commons; “Roses,” Claude Monet, 1925, via Pierre-Olivier Douphis.)

Abraham Lincoln was assassinated in 1865, when he was just 56. But one California doctor now theorizes that Honest Abe—who before his death had lost a lot of weight and complained of intense headaches and cold extremities—might not have lived much longer, anyway.

Stanford Cardiologist John Sotos said yesterday at a Johns Hopkins talk that Lincoln probably had a rare genetic syndrome, called MEN 2B. MEN 2B causes small, benign tumors to grow on victims’ lips and inside their intestines.

Sotos analyzed 130 photographs and plaster face masks of the stoic 16th president stored in the National Portrait Gallery. He claimed that these tell-tale bumps were clearly visible on his lips, and surmised that tumors in Lincoln’s gut could have caused his notorious problems with constipation.

Even more evidence of a genetic disease: Two of Lincoln’s sons had the same lip tumors, and died at young ages, Sotos said.

The only glitch in the theory is that people with MEN 2B usually develop cancer in their 20s and die in their 30s, a full two decades sooner than Lincoln.

A DNA analysis of Lincoln’s blood or brain tissue is the only surefire way to test Sotos’ hypothesis. (Anybody know who currently holds these samples? Yuck.) No such tests have been planned yet.

(Hat tip: Greg Laden; Image by telethon on Flickr)

On Friday, Hugh wrote about scientists who used DNA analyses to trace sawfly evolution. New research from relics of an ancient Greek shipwreck shows that traces of DNA might also help us learn more about ancient trading economies.

In 2005, researchers from the Woods Hole Oceanographic Institute and the Hellenic Centre for Marine Research drudged up a 2,400-year-old shipwreck near the Greek island of Chios. They gleaned from the wreckage, among other booty, two amphoras (above). As published October 10 in the online version of the Journal of Archaeological Science, scrapings from the inside of these ceramic jugs held genetic traces of olive oil, oregano and mastic, a shrub used in ancient times to preserve wine. (Apparently Mediterranean culture hasn’t changed much over two millennia…)

As the first study to show that ancient DNA can be extracted from underwater artifacts, the research team writes that the discovery “opens a new field of molecular archaeology.”

(Courtesy of the WHOI/Hellenic Ministry of Culture, Ephorate of Underwater Antiquities)