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A man buried in the inner chamber of Newgrange passage tomb was the product of a union between siblings, according to ancient DNA analysis. He was also more distantly related to people buried at passage tombs up to 150km away, suggesting that a network of related rulers controlled Ireland in the centuries after populations of Neolithic farmers first reached the island from mainland Europe. The find gives us new insight into the last phase of the Stone Age and the beginning of agriculture and settled village life in the area.

Some rumors never die

In the 11^th century CE, someone in County Meath, Ireland, finally wrote out a salacious folktale that had been passed down for about 4,000 years. According to the story, an ancient king, who hailed from a tribe of gods, had slept with his sister on the winter solstice as part of a magic ritual to restart the Sun’s daily cycle and save the world from endless night. The couple supposedly did the deed in one of the county’s huge burial mounds, which the locals named Fertae Chuile, or the Hill of Sin.

Newgrange Passage tomb stands about 12m (39 feet) high.

Today, we know that hill as the Dowth passage tomb, a construction in which buried sections are reached through an entry marked by large stones. Dowth is a close neighbor of the more famous Newgrange passage tomb. And every winter solstice, the sun shines through the stone passage at Newgrange and lights up the innermost burial chamber. And nearly a thousand years after the local legend was first written down, ancient DNA suggests that at least part of the story—the most troubling part, naturally—was actually true.

Enlarge / One interesting way to look at the world: the darker the red, the closer the correlation between local temperature and global mean. Blue areas tend to prefer contrarian temperatures. (credit: Brown and Caldeira/Earth and Space Science)

Meteorologists run weather-forecast models to provide good predictions of weather conditions over the next few days. Climate scientists, on the other hand, run global climate models to project the impacts of climate-changing greenhouse gas emissions over the next few decades. In between these two activities is an interesting task that has proven more difficult than either: predicting global temperature over a few years.

A new study by Patrick Brown and Ken Caldeira tries a new approach to this challenge using nothing more than statistical analysis of the previous two years’ temperatures.

The annual average surface temperature for the globe varies a bit from one year to the next even as a long-term warming trend is apparent. It’s those year-to-year wiggles that are hard to predict. They depend on variable regional weather patterns, most notably the El Niño Southern Oscillation. This seesaw pattern of warm surface water along the equatorial Pacific is significant enough to bump the planet’s average surface temperature up and down. It also affects weather patterns in many places around the world.

Enlarge / The moon is seen behind an antenna on the site of the radiotelescope of Nancay on October 03, 2019, near Vierzon, Central France. (credit: Guillaume Souvant | Getty Images)

In the search for extraterrestrial intelligence, there’s really only one big question: Where is everybody? This question has haunted alien hunters ever since the Nobel-winning physicist Enrico Fermi posed it to some colleagues over lunch 70 years ago. There are billions of sun-like stars in our galaxy, and we now know that most of them host planets. But after decades of searching, astronomers haven’t found any that appear to host life. This is the so-called Fermi paradox: Our galaxy seems like it should be teeming with alien civilizations, but we can’t find a single one.

Researchers working on the search for extraterrestrial intelligence, or SETI, have proposed a number of solutions to the Fermi paradox over the years. But the most persuasive answer is also the most obvious: Perhaps intelligent life is just far more rare than we thought.

How rare? Many scientists have attempted to answer this notoriously tricky question. Based on their conclusions, there are between zero and 100 million extraterrestrial civilizations in the Milky Way. That is not an especially helpful range of estimates, so a pair of physicists in the UK recently took another stab at it and arrived at a remarkably specific conclusion. As detailed in a new paper published this week in the Astrophysical Journal, the duo calculated there should be at least 36 communicating extraterrestrial civilizations in our galaxy.

Enlarge / One of the helpful study participants. (credit: Noah Whiteman (University of California, Berkeley))

The phrase “every color of the rainbow” isn’t quite as all-encompassing as it sounds. For one thing, the color chips in your hardware store’s paint aisle host some colors you’ll be hard-pressed to point to in a real rainbow. But even on a less hair-splitting level, purple is missing from that rainbow.

The “V” in “ROYGBIV” stands for violet, sure, but that’s not actually the same thing as purple. There is no purple wavelength of light—it requires a mixture of both red and blue wavelengths. That makes it a “nonspectral color”—in fact, it's the only non spectral color humans see. It requires our brains to interpret signals from both red-sensitive and blue-sensitive cones in our eyes and to see that as a separate color.

But while humans have three types of cones (making us “trichromatic”), many creatures have four, expanding their visible spectrum into ultraviolet (UV) wavelengths. In theory, this means they might be able to see additional nonspectral colors we humans struggle to imagine: UV mixed with either red, yellow, green, or purple. So… do they?