Friday, September 30, 2005

Books (Science): Shadows

Before I started Endless Forms Most Beautiful, I had read most of the way through Shadows: Unlocking Their Secrets, From Plato to Our Time by Roberto Casati. Unfortunately, one morning before work I couldn't find my copy and, unwilling to go into the office without a book, I started on Endless Forms instead.

Shadows is a recent book in the recently popular sub-genre of books that focus exclusively on the history of one (or a handful) of pieces of science or technology. The first one I encountered was Dana Sobel's Longitude, which was fun, and there've been several since then. (Jon Stewart poked fun at a book of this sort about rubber vulcanization while joking about how boring C-SPAN is.)

I finally found my copy of Shadows yesterday, and finished it off during my lunch hour. It's another fun book that covers how we percieve and understand shadows, both developmentally (how we, as individuals, figure shadows out as we're growing up as children) and historically.

Naturally, he starts with Plato and the cave, and in fact he uses dialogues bewteen Plato and his shadow to introduce the various sections. These dialogues help tie the book together, which is useful because it is a little fragmented. The first section deals with shadows and human psychology -- how children learn to understand what shadows are and the rules concerning their behaviour, etc. The next two sections are about geometry and astronomy (including Erastothenes's measurement of the circumference of the Earth, Galileo's discovery of mountains on the Moon, using the Galilean satelites to measure the speed of light, and so on). After that comes a section of the relationship bewteen shadow projections and perspective projections (and, of course, their relation with Renaissance art).

While there are a lot of good stories and history in the book, it does miss out on a couple of opportunities to bring the shadow stories right up to modern times (only a couple of sections in the book deal with anything much later than the Enlightenment). The field of computer graphics, for example, has made an extensive study of the properties of shadows, far more detailed (I suspect) than anything that has gone before, but Casati doesn't mention it at all.

Shadows has got me thinking about shadows more when doing photography. Not that I've managed to do anything interesting with photographing shadows yet, but I'm keeping my eyes open.

2 comments:

Anonymous said...

Thanks for the review! One of the reasons I did not mention computer vision studies in The Shadow Club is that they are very well covered by another book (and a very good one at that, Shadows and Enlightenment by M. Baxandall). The other reason is that computer vision studies are now considered as somewhat remote from the actual workings of cognition. they provide elegant mathematical accounts of shadow information, but the visual system seems to work differently (for instance, it tolerates inconsistent shadows).
All best
Roberto Casati

James said...

This appears to be Author's Week at 77 Track 7 -- first Jessica Sachs, now you. Neat.

One other interesting use of shadows that I've seen recently is Ramesh Raskar's Depth Edge Detection and Highlighting Using a Multi-Flash Technique. By using four flashes firing from around the lens, Raskar can use the shadows created to find the edges of the shapes photographed. His paper and a video on the subject are available on the site.