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Peekaboo is a classic game for babies for a reason. Infants are fascinated by unexpected actions and images, yet when it comes to human characteristics they tend to focus on the familiar. By tracking babies’ gazes, pupil dilation and brain activity, researchers have uncovered several patterns in what piques their interest. The examples below highlight key factors that get an infant’s attention and the ways these curiosities contribute to our understanding of their cognitive development....

Scientists usually order laboratory mice online, but immunologist David Masopust went to more trouble. While doing research years ago at Emory University, he drove to a barn several hours away to trap the rodents himself. He suspected that commercially provided lab mice were missing some key immune cells because they had inexperienced immune systems—a result of being raised in extremely hygienic facilities. Masopust, now a professor at the University of Minnesota, went on to formally test his suspicion over the course of a decade and has found that it was correct: lab mice used by the scientific community and pharmaceutical world to test drugs and vaccines for human diseases are in some ways poor models of the human adult immune system....

Let’s hope that today’s close encounter of two old pieces of space junk is just a near miss as predicted, because a smashup would be pretty messy. Two long-dead satellites — the Infrared Astronomical Satellite (IRAS) and the Gravity Gradient Stabilization Experiment (GGSE-4) — will whiz past each other this evening (Jan. 29) about 560 miles (900 kilometers) above Pittsburgh, Pennsylvania. At closest approach, which occurs at 6:39 p.m. EST (2339 GMT), the two defunct craft will be just 43 feet to 285 feet (13 to 87 meters) apart, according to the latest calculations by California-based satellite-tracking company LeoLabs....

Interviews at hi-tech companies often include puzzles. Here is one that has made the rounds in spite of its violent content. You are an antique dealer and I am an unsavory character who has lent you money. Instead of the usual baseball bat, I have brought a revolver to emphasize the importance of repaying me. I put two bullets in adjacent chambers of the six-shot revolver and spin the chambers. I point it at a valuable vase and pull the trigger....

The closest supernovas to Earth may have blasted the planet with enough radiation to influence human evolution, researchers say. Supernovas are the most powerful star explosions. These outbursts from enormous dying stars are visible all the way to the edge of the cosmos, and are bright enough to briefly outshine all of the stars in their host galaxies. For more than 50 years, scientists have suggested that nearby stellar fireworks could have influenced life on Earth by disrupting global climate and even triggering mass extinctions....

Solutions: Bob bets 50 on heads and Carol bets 50 on tails. If Alice bets 49 or less, then she can’t possibly win because even if she guesses the correct coin orientation, her 100 will equal the 100 of one of Bob or Carol. If Alice bets 50 or more on heads, then she wins on heads and Carol wins on tails. So, Bob and Carol can guarantee themselves a 1/2 chance to win....

If someone plunks a random piano key, a tiny minority of people can identify the note based on its sound alone. These people boast perfect pitch, the ability to recognize individual sound frequencies without any external reference. But even these gifted few are not truly perfect. A new study shows that their errors, though subtle, provide a previously unseen glimpse into how biological and environmental factors together shape hearing. Absolute pitch, commonly known as perfect pitch, results from the confluence of early musical training and a rare genetic endowment....

Heart disease kills more people of all sexes than anything else. But for more women than men, a heart attack may start with nausea, shortness of breath or extreme fatigue rather than chest pain. These symptoms are still often thought of as “atypical,” which means many women don’t get the treatment they need in time. According to David Page, head of the Page Laboratory at the Massachusetts Institute of Technology’s Whitehead Institute, sex differences can actually be found all over the body....

Six geologists accused of misleading the public about the risk of an earthquake in Italy were cleared of manslaughter on November 10. An appeals court overturned their six-year prison sentences and reduced to two years the sentence for a government official who had been convicted with them. The magnitude-6.3 earthquake struck the historic town of L’Aquila in the early hours of April 6, 2009, killing more than 300 people. The judgement by the appeals court prompted many l’Aquila citizens who were waiting outside the courtroom to react with rage, shouting “shame” and saying that the Italian state had just acquitted itself, the Italian media reported....

Albatross—majestic, wide-winged seabirds—skim the ocean’s surface or dive into the water to catch fish, squid and crustaceans. They also seize opportunity, sometimes swooping down to grab the hooked bait trailed behind longline fishing vessels. But this apparently easy meal comes with a costly risk: the beaks and bodies of the birds often get snagged, and the lines pull them under until they drown. Each year 100,000 albatross die this way. In some populations, most of the victims are female....

Key concepts Stethoscope Health Exercise Amplification The heart Introduction Around Valentine’s Day heart-shaped images seem to be everywhere. But our actual hearts are at work all year—every hour, minute and second. The heart works hardest when we physically exert ourselves. How does its beating change? A doctor can figure this out by using a tool called a stethoscope, which is a long, thin plastic tube that has a small disc at one end and earpieces at the other....

The octopus is the ultimate softie. Lacking a skeleton, the animal can take any number of forms and can move its tentacles in any direction. But when performing point-to-point movements, such as those used during feeding, the octopus adopts a decidedly humanlike approach: it forms an elbow and other joints out of the tentacle grasping the food item and tips the treat back into its mouth. New research shows how the pliant animals create such a stiff limb....

By Eric HandPhysicists have measured the temperature inside the hottest fireball on Earth, a four-trillion-degree jumble of melted protons and neutrons.This soup of subatomic particles, created in collisions of gold nuclei at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in Upton, New York, is yielding other intriguing discoveries. Chief among them is evidence of tiny bubbles in the soup that could help explain a fundamental asymmetry: Why, if the Big Bang created matter and antimatter in equal parts, did matter win out moments later?...

Editor’s note (1/10/17): Ten years ago, on January 9, 2007, Steve Jobs introduced the world to the iPhone. In honor of the smart phone’s game-changing impact on personal electronics and communications, we are republishing the following story about Jobs’ battle with cancer, published shortly after his death in 2011. Steve Jobs was a rare case, right down to his death. Announced Wednesday, Jobs’s death from “complications of pancreatic cancer” only hints at the vast complexity of the disease to which he succumbed at the age of 56....

The U.S. Air Force’s X-37B space plane blasted into Earth orbit May 20, kicking off the robotic vehicle’s clandestine fourth mission—as well as the first flight of a tiny solar-sailing spacecraft. The robotic X-37B space plane launched atop a United Launch Alliance Atlas V rocket at 11:05 a.m. EDT (1505 GMT) from Florida’s Cape Canaveral Air Force Station. You can see a video of the X-37B space plane’s launch here. Most details about the space plane’s orbital activities are classified, so it’s unclear what exactly the X-37B will be doing as it zooms around Earth, or how long it will remain aloft....

Jan Scheuermann is not your average experimental subject. Diagnosed with spinocerebellar degeneration, she is only able to move her head and neck. The paralysis, which began creeping over her muscles in 1996, has been devastating in many ways. Yet two years ago she seized an opportunity to turn her personal liability into an extraordinary asset for neuroscience. In 2012 Scheuermann elected to undergo brain surgery to implant two arrays of electrodes on her motor cortex, a band of tissue on the surface of the brain....

By Janelle WEaverStaying young at heart has taken on a new meaning. Newborn mice can mend their own hearts, thanks to the replication of healthy cardiac cells. The findings, published today in Science, reveal striking similarities in the way that fish and neonate mammals rejuvenate their organs.Zebrafish (Danio rerio) can recover lost cardiac tissue throughout their life, even after a 20% amputation of the ventricle, in large part because of the proliferation of remaining heart muscle cells called cardiomyocytes....

The 24,000-year-old remains of a young boy from the Siberian village of Mal’ta have added a new root to the family tree of indigenous Americans. While some of the New World’s native ancestry clearly traces back to east Asia, the Mal’ta boy’s genome — the oldest known of any modern human — shows that up to one-third of that ancestry can be traced back to Europe. The results show that people related to western Eurasians had spread further east than anyone had suspected, and lived in Siberia during the coldest parts of the last Ice Age....

Gut bacteria from lean mice can invade the guts of obesity-prone cage-mates and help their new hosts to fight weight gain. Researchers led by Jeffrey Gordon, a biologist at Washington University in St. Louis, Missouri, set out to find direct evidence that gut bacteria have a role in obesity. The team took gut bacteria from four sets of human twins in which one of each pair was lean and one was obese, and introduced the microbes into mice bred to be germ-free....

From Quanta Magazine (find original story here). Two years ago, Nancy Moran moved from Yale University to the University of Texas, Austin, along with 120,000 bees. Bees are famous for living in large social groups, but Moran was interested in more than just the hive: She’s delving into the diverse ecosystem of bacteria that evolved along with the bees, a group that contributes to the health of hives and their resilience to infection....