Counting aliens: “Perhaps intelligent life is just far more rare than we thought. How rare? Many scientists have attempted to answer this notoriously tricky question. Based on their conclusions, there are between zero and 100 million extraterrestrial civilizations in the Milky Way. That is not an especially helpful range of estimates, so a pair of physicists in the UK recently took another stab at it and arrived at a remarkably specific conclusion. As detailed in a new paper published this week in the Astrophysical Journal, the duo calculated there should be at least 36 communicating extraterrestrial civilizations in our galaxy.”