STRANGE BUT TRUE- Crocodile rocks: what makes it all go down easy

DRAWING BY DEBORAH DERR McCLINTOCK

Q. What do crocodiles, feeding often on whole fish, muskrats, turtles, etc., use for a digestive aid?–E. John

A. They swallow stones– up to 15 pounds of which have been found in the stomachs of some large specimens, says British zoologist Dr. Adam Britton. These help pulverize food and smash up bones, carapace and shells.

"X-ray evidence has shown stones rolling around as though they were in a blender once the croc swallows prey, flensing flesh from bone and cracking otherwise hard-to-digest materials." Not all crocs have 'em but many do, probably varying with how hard-shelled is their customary cuisine.

Q. Seeing may be believing, but when shouldn't it be?–W. Roentgen

A. History is riddled with photographic tamperings, as by Stalin, Hitler, Mussolini, Mao, Brezhnev– from creating more heroic-looking poses to erasing enemies or bottles of beer, says Hany Farid in Scientific American magazine.

Modern computers and commercial software have made manipulation of photos easier than ever and harder to detect, spawning the new field of "digital image forensics." In addition to business forgeries, fake images can sway public opinion, as when a 2004 faux newspaper clipping distributed on the Internet purportedly showed John Kerry on stage with Jane Fonda at a Vietnam War protest. A Los Angeles Times editor was fired in 2003 after a photo of his from Iraq was shown to be a composite of elements from two photos. In 1994, an altered mug shot of O.J. Simpson appeared as an infamous newsmagazine cover.

So, what to watch out for? Many fakes incorporate inconsistent lighting, such as improperly placed shadows or bright regions, or inconsistent specks of light ("specular highlights") reflected from subjects' eyeballs. Further, many images have "cloned" areas missed by the naked eye but detectable by computer scanners as subtle repetitions. "I expect that as the field progresses over the next 5-10 years, the application of image forensics will become as routine as the application of physical forensic analysis."

Q. What is it about a diamond that makes it such a gem among gems?–Z. Gabor

 A. Leading the list is that the supply is controlled by the diamond industry, driving up demand, say David Falk, et al, in Seeing the Light. A diamond is cut so that almost any ray of light hitting it from the front is internally reflected to another surface and eventually back out the front, giving it a brightness, even "brilliance." However, if you look from the back through a cut diamond at a light source, it will appear black since almost no light passes through. Unlike glass, diamond is highly "dispersive," so white light is spread out into a broader spectrum, hence the beautiful colors, or "fire."

View a cut diamond, and chances are the rays will be reflected from some source of light in the room, so as you move your eye slightly or rock the diamond, you see other rays following other paths– a sparkle or flash. "Diamonds are best shown off in rooms with lots of small lights or candles and mirrors, and must have been at their best when borne by the beauties in the ballroom of Versailles." 

Q. If you ever get an opportunity to walk in space, be sure to wear your spacesuit. Because if you don't... what?–N. Armstrong

A. In a famous scene from the movie 2001: A Space Odyssey, an astronaut goes for a brief unsuited walk and survives, says Jearl Walker in The Flying Circus of Physics. Some researchers speculate that this is possible, though there is more danger than a lack of oxygen. Temperature is an issue. One reason the temperature of a room feels comfortable is that the infrared radiation from the walls and the infrared radiation to the walls from you are approximately equal. So you gain energy at about the same rate as you lose it. If the radiation to you drops significantly, you feel cool or cold. In deep space, away from your spacecraft, there are no walls, so you would feel very cold very fast. In fact, you'd lose thermal energy at the rate of about 800 watts. Still, the lack of oxygen would be of much greater concern. Your exposure to the vacuum would also be an issue. "When water is exposed to a vacuum, it first boils (some of it vaporizes) and then it freezes. You have a lot of water in your body, and ... Well, maybe we should think of something more pleasant." 

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Send strange questions to brothers Bill and Rich at [email protected].

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