Cities have long been likened to organisms, ant colonies, and river networks. Yet clever analogies fail to capture the essence of how cities really function.  

A paper in Science attempts to derive a series of mathematical formulas that describe how cities' properties vary in relation to their population size, and then posits a unified, quantitative framework for understanding how cities function and grow. The resulting theoretical framework predicts dozens of statistical relationships observed in thousands of real cities around the world for which reliable data are available.

Arp 142 looks like the profile of a celestial bird but its imagery shouldn't overlook the fact that close encounters between galaxies are a messy business.

The interacting galaxy duo Arp 142 contains the disturbed, star-forming spiral galaxy NGC 2936, along with its elliptical companion, NGC 2937.

Once part of a flat, spiral disk, the orbits of the galaxy's stars have become scrambled due to gravitational tidal interactions with the other galaxy. This warps the galaxy's orderly spiral, and interstellar gas is strewn out into giant tails like stretched taffy.

The Red Queen hypothesis, a popular idea in evolution named after Lewis Carroll's character who in "Through the Looking Glass" described her country as a place where "it takes all the running you can do, to keep in the same place", recently got studied by a group of researchers who were thinking beyond the death of individual species -  they examined how the lack of new emerging species also contributes to extinction. 

Environmental brochures highlight fears about groups of animals, such as frogs or the "big cats," going extinct. But in science that is only part of the story.

A student who shows up on time, listens respectfully and appears fully engaged to teachers might still lack emotional and cognitive involvement with the course material, according to survey results

More importantly for educators, the paper in Learning and Instruction suggests that student engagement—essential for success in school—is malleable, and can be improved by promoting a positive school environment. The result may lead to diagnostic tools for recognizing disengagement, as well as strategies for creating a school environment more conducive to student engagement. 

Mealybugs only eat plant sap but sap doesn't contain all the essential amino acids the insects need to survive - so mealybugs have developed a symbiotic relationship with two species of bacteria, one living inside the other in a situation unique to known biology, to manufacture the nutrients sap doesn't provide.

The net result: The bacteria get a comfy mealybug home, and the bugs get the nutrition they need to live.

University of Montana microbiologist John McCutcheon describes such mutually beneficial relationships used to solve life's little problems as "almost hilariously complicated. But animal-bacterial relationships are extremely common in nature, and it's my goal in life to help people understand that it's normal."

Terrorism-induced smoking is a new explanatory factor that will keep public health academics from accepting that free choice happens - some people will do things that are bad for them.

 A Weill Cornell Medical College public health study is stuck in pre-9/11 determinism too; the author concludes that the September 11th, 2001 terrorist attacks caused 1,000,000 former smokers to take up the noxious weed again - and maintain it.

The analysis in Contemporary Economic Policy is distinct in that it is the first to examine terrorism-induced smoking in the United States and come up with net societal costs they feel are directly linked to terrorism.  All determined by phone surveys.

If you support less efficient agriculture, organic food or conventional food without science optimization, crop yields will not be enough to feed the population of 2050. It's the population bomb scare of the 1950s and '60s reborn a century later.

While American agriculture has dematerialized in the last few decades - we produce far more food on far less land - Europe and other countries have not kept pace. Due to that, crop yields worldwide won't increase quickly enough to support estimated global needs in 2050, according to the claims of a paper in PLoS ONE.