dvandom

Way back in high school, in 1987 or 1988, I was introduced to the equation for angular magnification (as by a magnifying glass), that being m_θ = 25cm/f (where 25cm is the standard "near point" and f is the focal length of the lens). The explanation was kinda handwaved, and I didn't really get it, but I didn't need to get it in order to use the equation.

Yesterday, I finally ran into a homework question that required understanding the derivation, and I had to figure it out during class (the textbook being almost no help at all) so I could explain it to my students, oops. Turns out there's two very important assumptions that tend to get hidden or glossed over: you don't leave the object in the same place (i.e. you look at it as close as you can without the lens, then put the lens in place and MOVE THE OBJECT until you get a clear image), and the lens has to be right up in your eye so that the angular size of the object and the image are the same. Even our multiple-teaching-award-winning distinguished professor who's helping teach this class got tripped up on the second assumption.

300 Million year old sea scorpions may have used the shells of the dead as crude breathing aids while venturing onto land. Clearly, only the Permian-Triassic extinction saved the world from domination by Scorpio Sapiens. (Link via bbaugh's twitter feed to his facebook.)

( SCIENCE behind cut )
Because I can. And because I plan to bring my extra 3D glasses along next time we cover polarization in class.

A lot of SF in the 1970s involved the idea of global cooling, that we might be going into a new ice age (or just continuing with the previous one, which never really ended). It was prevalent enough that kiddie-SF picked up on the trope.

Turns out scientists didn't take it seriously for more than an eyeblink, if ever.