Stonehenge is carefully aligned on a sight-line that points to the winter solstice sunset, but, this year as in most recent years, the revelry began before sunrise.
Eric Verlinde's new theory of gravity - an alternative to Einstein's theory - eliminates the need for dark matter. To test it, astronomers measured gravity around 33,000 galaxies.
Mars' atmospheric pressure is less than 1% that of Earth, so spacecraft come down hard. Europe has been trying for a Mars' soft landing since 2003. How they plan to succeed.