As 2012 comes to a close, top social sites are remembering the year that was. On Twitter, President Barack Obama's "Four more years" tweet became the most popular post of the year—and of the 6-year-old site's history—with more than 760,000 retweets
Click here to read Bob's blog.
Courtesy of NOAA/Institute for Exploration/University of Rhode Island
The last passenger pigeon dies, World War II begins, the Soviet Union…
No email address was supplied by
To complete your registration on this site, please supply an address.
Please confirm or modify the email address to which you will have subscription offers sent.
For a more personalized experience, please supply the following optional information.