An astronomical transit is the passage of a celestial body or satellite across the face of a relatively larger body. Transits are not the same thing as the familiar solar or lunar eclipse. In an eclipse, a large celestial body hides a major part of a smaller body. In an astronomical transit, a small body crosses in front of a larger one. An astronomical transit can involve two planets, but this has not been observed on Earth since 1818. When will the next planetary transit be visible from Earth?
Back in the day
In 1968, civil rights protests by Roman Catholics in Northern Ireland sparked violent conflicts with Protestants, resulting in the occupation of the province by British troops. The Bogside Massacre greatly worsened the situation. On "Bloody Sunday"—January 30, 1972—British troops shot 26 unarmed civil rights protesters. Thirteen victims—seven of whom were teenagers—died almost immediately, and a fourteenth later succumbed to his injuries. What did the first inquiry into the massacre find?
Born on a day like today
Born in South Africa, Theiler moved to the US in 1922 and became known for his research on yellow fever, encephalomyelitis, and other tropical viruses. At a time when yellow fever outbreaks were plague-like—one epidemic alone wiped out 20,000 people—his team proved that the disease is caused by a virus, not bacteria. Theiler's development of a safe and effective vaccine brought yellow fever under control, earning him the 1951 Nobel Prize in medicine. On what did he initially test his vaccine?