Lots of objects in the night sky are green, but they are green for a variety of different reasons.
The level of precision in astronomical data is amazing.
The laws of physics conspire to keep you trapped within a black hole. You could no more escape a black hole than you could walk backwards in time.
Cosmic rays are powerful. Too powerful, in fact.
Stars get warmer as they age, which means there was a time when our Sun was too cool to liquify water on Earth. But the evidence is clear water existed on Earth for much longer. What gives?
Nothing can be colder than absolute zero, or can it? Arthur Eddington wrestles with the paradox of stellar thermodynamics.
In an infinite and ageless cosmos, how is it possible that the Universe is cold, dark and dominated by gravity?
What happens when one set of evidence contradicts another set of evidence?
A grism lets astronomers study the colors of starlight.