Wednesday, April 9, 2014

The Reason for the Earth’s Seasons as Explained From Space

The reason for the Earth’s seasons is succinctly explained using space imagery in this 2011 video from NASA Earth Observatory. As the year goes on, and the Sun’s rays hit the Earth differently based on the planet’s relative position to it, the seasons change. Winter in a hemisphere is essentially a lack of sunlight.
The four images below, starting with the upper left and going clockwise, show the way sunlight hit the Earth on December 21st, 2010, followed by March 20th, 2011, then June 21st, 2011, and finally September 20th, 2011. Each was taken at 6:12AM using the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on EUMETSAT‘s Meteosat-9 meteorological satellite in geosynchronous orbit.

Seasons of Space

Image via NASA/Robert Simmon

Monday, April 7, 2014

Life Cycle of Bees

The Crow Bee dusted in Sunflower pollen. Source: Sam Droege, UCGS.
During the spring, summer, and fall most forager bees work themselves to death.

Foragers are typically weakened by three weeks of "backbreaking" labor. A weak bee will be eaten by predators — wasps love weak bees! — or find themselves unable to continue on a long flight, dying away from the hive. Bees rely on glycogen stores in their fat bodies to provide energy for their flight muscles. This is laid down during their larval and young adult life stages, but not continually added to at a sufficient rate when foraging. As a result, they 'run out of fuel' while foraging and become unable to fly. Death then occurs usually through a secondary medium (predation, hypothermia, starvation, etc.).

Bees which do not fly, such as the queen or overwintering bees, can have lifespans of months or years — and foraging bees, which have become flightless, can be made to fly again for extended periods when artificially provided with glycogen.

Source: Pollinator 
Plenty of bees die inside and around the hive, and caretaker bees will carry them out. However, depending on how hygienic the particular colony is, they may not carry them away from the hive. Plenty of hives have tons of dead bees on the ground around them and are perfectly healthy.

In beekeeping, the term 'Hygienic bees' is used to refer top particular traits of a colony, colonies or lineage, where the bees perform more hygienic actions. This predominantly refers to self-cleaning, in relation to varroa. This often refers to certain stock that has originated in Russia, where bees had earliest exposure to varroa mites, and thus have had the longest to adapt to this parasite and begin to show 'hygienic' behaviors. However, in the most part it is something that has been selected for by bee breeders.

Bee hives on stands are more likely to leave dead bees lying around the outside of the hive but highly hygienic bees will carry the dead further away from the hive. (The primary source of disease transmission has little to do with how far the bees carry away the dead.)

If you want to explore just how truly beautiful bees can be, check out the high resolution images on the National Geographic. There's also a cool article on why honeycombs are hexagons.

Saturday, April 5, 2014

Physiological Underpinnings of Political Ideology

"We know that liberals and conservatives are really deeply different on a variety of things," Hibbing explains on the latest episode of the Inquiring Minds podcast (stream above). "It runs from their tastes, to their cognitive patterns—how they think about things, what they pay attention to—to their physical reactions. We can measure their sympathetic nervous systems, which is the fight-or-flight system. And liberals and conservatives tend to respond very differently."

This episode of Inquiring Minds, a podcast hosted by neuroscientist and musician Indre Viskontas and best-selling author Chris Mooney, also features a discussion of whether we are finally on the verge of curing AIDS, and new research (covered by Grist here) suggesting that great landscape painters, like JMW Turner, were actually able to capture the trace of volcanic eruptions, and other forms of air pollution, in the color of their sunsets.

To catch future shows right when they are released, subscribe to Inquiring Minds via iTunes or RSS

Friday, April 4, 2014

A Sea in Space: Scientists Announce Saturn's Moon has a Watery Ocean

Scientists have confirmed today that Enceladus, one of Saturn's moons, has a watery ocean. The Guardian has an excellent article discussing how "water is not the only factor that makes Enceladus such a promising habitat. The water is in contact with the moon's rocky core, so elements useful for life, such as phosphorus, sulfur and potassium, will leach into the ocean."

Previously, Europa — another of Saturn's moons — was considered the place that was most likely for mankind to find life on. Europa also has a liquid ocean but it also has an oxygen atmosphere. On the other hand on Enceladus we now have contact from the rocky core. So what's the ocean on Europa in contact with, if not a rocky core?

 Europa and Enceladus

Europa has a drastically different structure than Enceladus. If you compare the densities:
  • Europa: 3.01 g/cm³ 
  • Enceladus: 1.61 g/cm³ 
In general, the further from Sun you go, the sparser the material gets. Mercury is the closest to the Sun and has a large metallic core, Mars is already much less dense than Earth, and the trend continues in the outer Solar system. (Jupiter has a similar trend inside its moon system, where Io and Europa are denser than Ganymede and Callisto). This is because more volatile material was pushed to the outside regions of Solar system during formation, leaving denser materials closer to the Sun.

Jupiter probably had a similar effect on its moons, as it probably generated a lot of heat through gravitational contraction and accretion during the early stages of formation. This means that while Europa has a similar structure to Earth's Moon and Mars, with a rocky crust and mantle and a small metallic core (compared to Earth). Enceladus was formed from material with much less heavier materials and much more ices (water, ammonia, methane - which are in general more abundant in space than rocks or metals). This means that it has, in theory, an icy, not rocky crust and mantle, and a rocky core, with only traces of metals.

What this study shows is that at least a part of its icy mantle is molten, similar to how Earth's asthenosphere (upper mantle) is ductile - partially molten.

Thursday, April 3, 2014

Meteorite Almost Hits Norwegian Skydiver

When a meteoroid enters the Earth’s atmosphere, it slows down and ionizes molecules around it; it is this blazing track across the sky that is called a meteor. When the light disappears, the meteorite enters the stage called "dark flight"; it then no longer travels at an angle, but falls straight down.

“It has never happened before that a meteorite has been filmed during dark flight; this is the first time in world history,” said Amundsen. That fact means that the meteorite, which Amundsen says would normally be worth a few hundred thousand kroner, is actually far more valuable than its weight would suggest.