The Light Side: We Let Facebook Friends Influence App Choices

July 11, 2014

Even Geckos Eventually Lose Their Grip

Infographic: Near-Outer Space Is Getting Cluttered

Insanely Weird -- and Useful -- Smartphone Cases

Scientists have proven why Angry Birds and Candy Crush have become such hugely popular smartphone games. You decided to play them because your friends do, along with a gazillion others.

Word of mouth and jumping on the bandwagon were powerful forces even before viral media existed, but they are omnipotent influencers on Facebook when it comes to which smartphone apps and games go on to become hits. Through a recent study, researchers have concluded that people are more likely to download apps that they saw their friends download on their Facebook news feeds versus seeing what's on the popular app list.

Using data from an empirical study on 100 million app installations originating from Facebook over the course of two months in 2010, researchers from the University of Limerick, University of Oxford, and the Harvard School of Public Health were able to match up the patterns they saw in app downloads that year with a mathematical model. This model was finalized after 15,000 hours of grueling supercomputer processing at the Irish Centre for High-End Computing, where the researchers ran literally thousands of simulations using various versions of their basic mathematical formula.

In the end, the mathematical model they reached weighs much more heavily toward "recent installations" than "cumulative popularity," i.e., a Facebook user's decision to download an app is predominantly determined by the download by a friend a few days earlier rather than by "bestseller" influence. The instinct to copy the behavior of others was far more dominant, which the 2010 study was unable to determine conclusively, although it did conclude four years ago that once an app reached a popularity threshold (as measured by the installation rate), it tended to rise to stellar proportions.

In studying popularity dynamics, the researchers called this the copycat tendency in human behavior and noted that within a short period of time usually, the things we do are influenced by the activities of others; the layman's term could be "peer pressure." The researchers have authored a paper in the journal Proceedings of the National Academy of Sciences to describe their findings.

"We hope that our paper can help serve as a guide for modeling complex systems and how data can be incorporated directly into such modeling efforts," said co-author Mason Porter, associate professor at the Mathematical Institute at the University of Oxford. "The importance of mathematical modeling often seems to be lost amidst the overabundance of empirical studies, and I cannot stress enough that mathematics is also crucial to help illustrate how things work."

Associate Professor Felix Reed-Tsochas of the Saïd Business School, who is also director of complexity economics at the Institute for New Economic Thinking at the University of Oxford, noted that mathematical models remain important in conclusively determining the drivers behind human behaviors seen through pure observation. "[We found that the 'copycat' tendency plays a very important role in online behavior," he noted. "This might be because users need to make quick decisions in information-rich environments, but other research has identified similar imitative behavior in the off-line world."

Even Geckos Eventually Lose Their Grip

Not even geckos and spiders can sit upside down forever. Nanophysics makes sure of that.

Geckos and spiders that seem to be able to sit still forever and walk around upside down have fascinated researchers worldwide for many years. We will soon be able to buy smart new fasteners that hold the same way as the gecko's foot. But the fact is, sooner or later the grip is lost, no matter how little force is acting on it. Stefan Lindström and Lars Johansson, researchers at the Division of Mechanics of Linköping University, together with Nils Karlsson, a recent engineering graduate, have demonstrated this in an article just published in Physical Review E.

Still, it's a phenomenon that can have considerable benefits -- for instance, in the production of graphene. Graphene consists only of one layer of atom and which must be easily detached from the substrate.

In his graduation project, Karlsson studied both the mechanics of a gecko's leg as well as the adhesion of its foot to the substrate. The gecko's foot has five toes, all with transverse lamellae. A scanning electron microscope shows that these lamellae consist of a number of small, hair-like setae, each with a little film at the end that resembles a small spatula. These spatulae, roughly 10 nm thick, are what adheres to the substrate.

The movement of the molecules is negligible in our macroscopic world, but it's not in the nano-world. Karlsson's project suggested that heat, and consequently the movement of the molecules, has an effect on the spatulae's adhesion. "We wanted to do further analyses and calculate what actually happens," Lindström explained.

They applied their mathematical model to a thin film in contact with an uneven surface. The film only contacts the uppermost parts of the uneven surface. The researchers also chose to limit the calculations to the type of weak forces that exist between all atoms and molecules -- van der Waals forces.

"It's true, they are small, but they are always there, and we know that they are extremely reliant on distance," Johansson said.

This means that the force is much stronger where the film is very close to a single high point than when it is quite close to a number of high points. Then, when the film detaches, it does this point by point. This is because both contact surfaces are moving, i.e., vibrating. These are tiny movements, but at some stage the movements are in sync, so the surfaces lose contact. Then the van der Waals force is so small that the film releases.

"So in reality, we can detach a thin film from the substrate simply by waiting for the right moment," Lindström said. "This doesn't require a great deal of force. The part of the film that remains on the substrate vibrates constantly, and the harder I pull on this part, the faster the film will detach. But how long it takes for the film to detach also depends on the structure of the substrate and the film's stiffness."

In practice, this means that even a small force over a long period will cause the film, or for that matter the gecko's foot, to lose its grip. Which is fine for the gecko, who can scoot off, but maybe not so good for a fastening system. Still, in the right application, this knowledge can be of great industrial benefit.

This article was originally published on

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Infographic: Near-Outer Space Is Getting Cluttered

The website World Science Festival

blithely states, "Where humans go, garbage tends to follow." That includes space, ever since mankind figured out how to travel or launch things into orbit. WSF has put out a simultaneously humorous and disturbing infographic on space junk, the 500,000 pieces of known man-made debris that are orbiting Earth at nearly 18,000 miles per hour.

NASA and the Defense Department actively track 21,000 of those objects and categorize them among three threat levels. The debris can do major damage to spacecraft and satellites and are mortal threats to astronauts aboard any space vehicle that reaches perilously close to their paths. Even tiny paint flecks can damage a spacecraft when traveling at the velocities they do in orbit. And the scary part: There are many millions of unknown pieces of debris that are so small they can't be tracked.

As the infographic shows, some of the space junk are larger than a softball. What zooms several hundred miles above our planet ranges from accidentally discarded astronaut items, to frozen urine (dumped by said astronauts), to the ashes of Star Trek creator Gene Roddenberry. Other debris were produced by satellite mishaps, such as collisions and explosions. While most of that space junk stay in space, some do fall back toward Earth every year -- like what happened on Thursday


However, the good news is that your chances of being struck by space garbage are lower -- much lower -- than being hit by lightning or winning the lottery. Just don't tell the Australians that.

Click to enlarge. Credit: World Science Festival

Click to enlarge. Credit: World Science Festival[/caption

Insanely Weird -- and Useful -- Smartphone Cases

Let's face it: If it weren't for your identifiable cellphone case, you probably would have had wrongly picked up someone else's iPhone or Samsung Galaxy more than a few times by now. That's why as audacious as some of the phone cases assembled in the photo gallery below are -- such as the one adorned by a miniature, three-dimensional woman's bottom half, complete with skirt and high heels -- can you really blame their owners for being able to say, "Yeah, that's my phone," with full conviction?

If that's not enough, a lot of other phone cases have been designed to turn cellphones into multipurpose devices. We're not talking about apps -- more like a combination phone/cigarette lighter... or a phone/personal defense system courtesy of a 650,000-volt stun gun or good old-fashioned pepper spray... or a phone/hand tool that would give a Swiss Army Knife a run for its money.

Click on the gallery compiled at the CNN website to see what we mean. Bunny-ear phone cases are so yesterday.

Top photo credit: arztsamui at


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