A 32-page primer from the National Academies.

What You Need to Know About Energy

Networks -- used throughout the sciences in the study of biological, technological, and social complexity -- can often be too complex to visualize or understand.

In a May 1 Nature paper, “Hierarchical structure and the prediction of missing links in networks,” Santa Fe Institute (SFI) researchers Aaron Clauset, Cristopher Moore, and Mark Newman show that many real-world networks can be understood as a hierarchy of modules, where nodes cluster together to form modules, which themselves cluster into larger modules -- arrangements similar to the organization of sports players into teams, teams into conferences, and conferences into leagues, for example.

This hierarchical organization, the researchers show, can simultaneously explain a number of patterns previously discovered in networks, such as the surprising heterogeneity in the number of connections some nodes have, or the prevalence of triangles in a network diagram. Their discovery suggests that hierarchy may, in fact, be a fundamental organizational principle for complex networks.

Unlike much previous work in this area, Clauset, Moore, and Newman propose a direct but flexible model of hierarchical structure, which they apply to networks using the tools of statistical physics and machine learning.

Nature paper describes technique for extracting hierarchical structure of networks

Unlike adults, children don't integrate different types of sensory information.

One sense at a time

Far from protecting the environment, most rail transit lines use more energy per passenger mile, and many generate more greenhouse gases, than the average passenger automobile. Rail transit provides no guarantee that a city will save energy or meet greenhouse gas targets.

While most rail transit uses less energy than buses, rail transit does not operate in a vacuum: transit agencies supplement it with extensive feeder bus operations. Those feeder buses tend to have low ridership, so they have high energy costs and greenhouse gas emissions per passenger mile. The result is that, when new rail transit lines open, the transit systems as a whole can end up consuming more energy, per passenger mile, than they did before.

Even where rail transit operations save a little energy, the construction of rail transit lines consumes huge amounts of energy and emits large volumes of greenhouse gases. In most cases, many decades of energy savings would be needed to repay the energy cost of construction.

Rail transit attempts to improve the environment by changing people’s behavior so that they drive less. Such behavioral efforts have been far less successful than technical solutions to toxic air pollution and other environmental problems associated with automobiles.

Does Rail Transit Save Energy or Reduce Greenhouse Gas Emissions?

NPR:

Engineers build bridges, buildings, roads, structures that shelter us and help us move around. But now there's a new class of engineer. These folks build living things.

Minty E. Coli and Other Bioengineering Feats

At the world's leading baby brain research lab at Harvard University, Elizabeth Spelke's team is conducting experiments that reveal not only that humans are born with a range of innate skills, but that our prejudices are formed within the first few months of life.

Harvard's baby brain research lab

The Star Trek physicist enters the Seed Salon to discuss participation, the politics of knowledge production, and seduction with the artist/engineer.

Lawrence Krauss and Natalie Jeremijenko | Seed Video

Hubble is all grown up now!

Arp 148 is the staggering aftermath of an encounter between two galaxies, resulting in a ring-shaped galaxy and a long-tailed companion. The collision between the two parent galaxies produced a shockwave effect that first drew matter into the centre and then caused it to propagate outwards in a ring. The elongated companion perpendicular to the ring suggests that Arp 148 is a unique snapshot of an ongoing collision. Infrared observations reveal a strong obscuration region that appears as a dark dust lane across the nucleus in optical light.

Arp 148 is nicknamed “Mayall’s object” and is located in the constellation of Ursa Major, the Great Bear, approximately 500 million light-years away. This interacting pair of galaxies is included in Arp’s catalogue of peculiar galaxies as number 148.

Click through to celebrate Hubble's 18th anniversary.

Imagery from Hubble

“He determined that if they cross-pollinate, they produce more seed and more vigorous seedlings,” said Margaret Falk, a horticulturalist and associate vice president at the New York Botanical Garden. The variation is evolution’s way of increasing cross-pollination, she said.

Now the Botanical Garden is replicating this work, and more of Darwin’s Down House experiments, in a stunning, multipart exhibition called “Darwin’s Garden: An Evolutionary Adventure.”

What Darwin Saw Out Back

If almost every species on Earth was killed some 250 million years ago, how did our ancient ancestors survive and evolve into us?

Seed: Suspending Life