Weekend field trips on the Web

Here's wishing you a happy and safe Fourth of July weekend ... If you want to reflect on "the reason for the season," Daryl Cagle's collection of cartoons with Independence Day themes is a good place to start. You should also check out this meditation on Independence Days past and present, and this roundup of America's great Fourth of July celebrations. I'll be out of the office, celebrating the Fourth and the Fifth with my family. Regular postings will resume Tuesday the 6th. In the meantime, here are some Web links for the long holiday weekend.

• 'Nova' on PBS: 'Missing in MiG Alley'
• NPR: Thermonuclear fireworks in space
• Slate: What kind of invisible ink did spies use?
• The Economist: It's time for Internet arms control
• AFP via Cosmos: Prehistoric humans went to the movies
• Univ. of Washington: Microscopic bug-bot crawls into the ring