The first concussion came playing football in high school, the second playing the game at Annapolis, and a third playing rugby. It meant the end of contact sports for U.S. Navy Captain and doctor James L. Hancock, but not the end of his risk for traumatic brain injury.

Over the last year, websites operated by the governments of Iran, Egypt and Tunisia, as well as corporations including PayPal, Sony, Mastercard and Visa, have all been taken down by hackers. A concerted cyber attack against targets in the United States could have serious consequences, experts agreed at a AAAS discussion.