When was the Apollo 12 KREEP Ejected?
When was the last time a professional astronomer actually looked into an eyepiece at an observatory such as Palomar?
When was the last time the two stars of Alpha Centauri were closest?
When Were Glaciers Present in Tharsis? Constraining Age Estimates for the Tharsis Montes Fan-shaped Deposits
When will (or did) the galactic equator intersect the ecliptic at the solstice points?
When will a pulsar in supernova 1987a be seen?
When will enough be enough?
When Will RS Ophiuchi Next Blow Its Stack?
When will the Antarctic ozone hole recover?
When will the last ever total solar eclipse occur?
When will the tidal force stabilize with one side of the Earth always facing the Moon?
When will Voyager 1 and 2 cross the termination shock?
When will we know a muon collider is feasible? Status and directions of muon accelerator R&D
When Worlds Collide
When Worlds Collide: Jetted Vapor Plumes and the Moon's Origin
When Worlds Collide: Quantum Probability From Observer Selection?
When Worlds Don't Collide - Earth Escapes Asteroids
When You Wish...
When Zeus Made Night from Midday
Whence Come Comets?