Our sun may be special to us, but among all the stars in the galaxy, it's not unique. According to a study published this month in the journal Science, our beloved star can be classified as an ordinary "solar-type" star, meaning that the internal processes that control its activity are similar to those seen in many other nearby stars.
The sun goes through an 11-year cycle where its magnetic poles flip — imagine the north and south poles on Earth changing place — and during this time the sun's activity changes between subdued and tumultuous. When activity is low, it is known as solar minimum, and when activity is high, it is known as solar maximum.
Ultraviolet images taken by NASA's Solar Dynamics Obserervatory reveal the difference. (See photo, left.) The left half shows the sun toward the end of the latest solar minimum. The right half was taken during the current solar maximum period, in December 2014.
As the sun nears solar maximum and its activity cycle ramps up, its surface gets covered in sunspots, which are ephemeral dark marks created by strong magnetic activity.
The sun's emissions can interact with satellites and even influence power grids on Earth. So to better predict the sun's activity, scientists need to better understand the 11-year cycle and how it generates magnetic fields.
Nicholas St. Fleur, New York Times
A robot security guard rolled into a fountain
Robots can do all kinds of things that humans just can't. They can sit in the same place for years and weld car parts together with a level of precision that no human can faithfully reproduce. Some smart machines can speak dozens of languages. Others can fly hundreds of feet in the air, surveilling life down below.
But sometimes the biggest challenges for robots are things that we humans take for granted. Like, say, not falling into decorative fountains.
Last week a robot security guard from the startup Knightscope fell in a fountain outside of a Washington, D.C., office building. The wheeled robot was making its rounds when it encountered a common feature of manmade environments it's not built to handle: a fountain with stairs.
Knightscope says that this is an isolated incident and that it's replacing the robot at no charge. Presumably, the robot is equipped with computer vision software that should be able to detect obstacles, like bodies of water or cars. But clearly, its smart eyes didn't quite work in this instance, demonstrating how difficult it is for robots to navigate a world built for humans.
Knightscope's robot is supposed to deter criminals and act as a roving security camera that can call for backup if it senses something has gone awry. But because it's on wheels, it can't pursue a human for very long, especially say, if the suspect walks up a flight of stairs. It also seems clear now that a savvy intruder would head to a water trap to evade his mechanical pursuer.
April Glaser, Slate
Living another day, thanks to grandparents who couldn't sleep
You may not look forward to sleeping less as you get older. But maybe it wouldn't seem as bad if you knew it once played an important role in human survival.
A study, published this month in Proceedings of the Royal Society B, suggests that the way sleep patterns change with age may be an evolutionary adaptation that helped our ancestors survive the night by ensuring one person in a community was awake at all times. The researchers called this phenomenon the "poorly sleeping grandparent hypothesis," suggesting that an older member of a community who woke before dawn might have been crucial to spotting the threat of a hungry predator while younger people were still asleep. It may explain why people slept in mixed-age groups through much of human history.
Researchers analyzed the sleep patterns of a society of hunter-gatherers in Tanzania called the Hadza. Thirty-three members of the Hadza community wore small watchlike tracking devices on their wrists for 20 days. The Hadza sleeping environment may have similarities to that of earlier humans, researchers said. They sleep outdoors or in grass huts in groups of 20 to 30 people without artificially regulating temperature or light. These conditions provide a suitable window to study the evolutionary aspects of sleep.
Out of more than 220 total hours of sleep observation, researchers found only 18 minutes when all adults were sound asleep simultaneously. Typically, older participants in their 50s and 60s went to bed earlier and woke up earlier than those in their 20s and 30s. On average, more than a third of the group was alert, or lightly dozing, at any given time.
Aneri Pattani, New York Times
The very hungry caterpillars that turned to cannibalism
If you're a very hungry caterpillar and you've got a choice between eating a plant or another caterpillar, which do you choose? You pick your fellow caterpillar, scientists have found — if the plant is noxious enough.
In a study published this month in Nature Ecology and Evolution, scientists sprayed tomato plants with a substance that induces a defensive response — a suite of nasty chemicals — and found that caterpillars became cannibals instead of eating the plant.
The team's findings support a growing body of research suggesting that plant defenses are far more sophisticated than we have thought. Plants cannot run or hide, but they possess powerful strategies capable of altering the minds of herbivores that try to eat them.
The fight begins when an insect bites a plant, which triggers an immune-like defense response. The plant produces chemicals that hungry herbivores find toxic, unappealing or difficult to digest. For example, caffeine and nicotine, both toxic in high doses, are byproducts of the defense responses of tobacco and coffee plants.
Joanna Klein, New York Times