Professor Salman Hameed on the outer universe; poet Kevin McCaffrey on the inner universe.
Federal authorities are stepping up security and asking Americans to be vigilant ahead of the holiday weekend.
The average purchase price rose by 4.9 percent, according to the latest figures.
Even the most patriotic among us can learn something from these little-known facts about Independence Day.
More than 40 million Americans are expected to hit the road for the long holiday weekend.