Monday Science Links

This week's science! (Sorry about last week - my trip to the UK was screwed up by US Airways and the whole thing became much more stressful than it should have been - plus twice as long.)

• Dave at Cognitive Daily blogs on learning to judge size: If we can be so easily fooled, it might make you wonder: What, exactly, are we learning about the sizes of distant objects as we grow older? The prevailing notion for decades has been that we gradually learn cues to the size of objects and how far away they are. By the time they are ten, most kids are about as good at judging the size of distant objects as adults -- they are said to have achieved "size constancy." But recently Carl Granrud has begun to challenge that notion. Even in normal perceptual circumstances (in an open field, say, rather than an Ames room), adults make systematic errors, overestimating the size of distant objects. Granrud believes that the perceptual system simply doesn't give us enough information to accurately judge the size of distant objects, and so we develop a system of compensation. While young kids undercompensate, adults often overcompensate.


• Dr Brazen Hussy at What the hell is wrong with you? is catching birds - for science, and then releasing them! She's posting a picture a day - so go check out the angry birds.


• Ed Yong at Not Exactly Rocket Science posts on spiders posing as ants: The animal world is full of harmless liars, who mimic species more dangerous than themselves in order to avoid the attention of predators. But none do it quite like the dark-footed ant-spider Myrmarachne melanotarsa. As its name suggests, this small species of jumping spider, discovered just nine years ago, impersonates ants. In itself, that's nothing special - ants are so aggressive that many predators give them a wide berth and lots of species do well by imitating them. The list includes over 100 spiders but among them, M.melanotarsa's impression is unusually strong. It doesn't just mimic the bodies of ants, but their large groups too. Unlike all of its relatives, the spider lives in silken apartment complexes, consisting of many individual nests connected by silk. These blocks can house hundreds of individuals and while moving about them, the spiders usually travel in groups. Now, Ximena Nelson and Robert Jackson from the University of Canterbury have found evidence that this social streak is all part of the spiders' deception.


• Erik at Eruptions warns us that Redoubt might not be done: In other words, the dome continues to extrude and part of it roll down the volcano. The lava dome is still growing (lots of impressive images on the AVO website), mostly extending slowly down the steep north slope of the volcano (see image below). There is still the strong possibly that the dome will catastrophically collapse causing a pyroclastic flow and potentially a plinian eruption to follow as the pressure is released, but so far, nothing of the sort has occurred. However, the dome is unstable (says Allison Payne of AVO), so a collapse might happen at any moment. Until then, most Alaskans just hope that Redoubt behaves itself during the lucrative tourist season in the state after the lost revenue from the Cook Inlet oil production.


• Anne Jefferson guest blogs at Highly Allochthonous on where rocks, water, and history intertwine: "Ten thousand rocks and grassy islets meet the traveler's eye, ten thousand murmuring streams meander through them. During low water the cattle delight to graze upon the islets...at such times they furnish a curious spectacle in the midst of a mighty river." So wrote architect Robert Mills in 1826, describing an outcrop of ~550 million year old diorite in the Catawba River south of Rock Hill, South Carolina. The Catawba River is one of the principal rivers of the Carolinas, with an annual average flow of 4018 cubic feet per second (114 m3/s) just upstream of our diorite outcrop. The outcrop is about 2.6 km long, and changes the single-thread river into a substantially wider, multi-thread anabranching river (Figures 1 and 2). This cattle-friendly piece of rock then represents a major obstacle to flow of the river, and that has ensured it a place in the region's history.

Enjoy!