Letters from the September 4, 2004, issue of Science News

Funny pages

Horvath and Toffel’s comparison of the environmental impacts of the paper versus the electronic editions of the New York Times is a bit misleading (“Newspaper’s Footprint: Environmental toll of all the news that’s fit to print,” SN: 6/12/04, p. 374: Newspaper’s Footprint: Environmental toll of all the news that’s fit to print). A personal digital assistant isn’t good for advertising or newspaper browsing. In other words, the PDA users aren’t getting a comparable product. Still, the day is probably not too far off when digital displays will be sufficiently large, bright, light, flexible, and portable to handle newspaper-size pages with the ease and convenience of paper. Then, there will be powerful environmental and economic reasons for the shift to electronic news delivery.

Paul Danish
Boulder, Colo.

It would have been interesting to see figures on using a laptop computer rather than a PDA, since a laptop is a lot closer to satisfactory for the purpose.

James Thomas
Sandy Spring, Md.

I note that no mention is made of the trees cut down to make the paper, or of the amount of carbon dioxide those trees would remove from the atmosphere if left standing. Yet I agree with Brad Allenby’s statement that not many people will curl up with their PDAs on Sunday mornings.

Bill White
Homestead, Fla.

Squashed

Does it really take a team of scientists running computer simulations to come up with the common sense that the greater the common surface area of two objects that touch, the more efficient the stacking (“Squashed spheres set a record for filling space,” SN: 6/19/04, p. 397: Squashed spheres set a record for filling space)? The closer objects are to being flat, the more efficiently they will stack. Hence ellipses will, of course, stack more efficiently than spheres.

Howard Zimmerman
New York, N.Y.

“Stacking sheets of paper, cubes, or books [which fill all of a space] is a completely different problem” than stacking curved objects, says Salvatore Torquato of Princeton University. The closest-packed ellipsoids share no surface area, but each touches its neighbors at 14 points, he adds.—P. Weiss

The article states that “piles of cubes can occupy every last niche of a space.” True only for rectilinear spaces. Consider the nightly challenge faced by air-cargo carriers such as FedEx and UPS.

Ira Dember
Houston, Texas