On Friday evening, shortly after sunset, the moon and Venus will appear to draw close together in the western sky — a conjunction visible across the United States with the naked eye. This geometry of orbits, which has stirred human wonder for millennia, asks nothing of us but a clear sky and a willingness to look up. For those in Miami, Denver, or Los Angeles, the conditions are favorable; for those in New York or Chicago, clouds may intervene, reminding us that even the most reliable celestial events depend on the humbler weather of our own atmosphere.