pulsar
"The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lies their strength. They are radical. Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality." -Hermann Minkowski
When it comes to gravity, you probably think you understand it pretty well.
Image credit: Heavens Above, via http://heavens-above.com/.
Everything with mass (or energy) attracts everything else with mass-or-energy, explaining everything from falling…
"This nebula had such a resemblance to a comet in its form and brightness that I endeavored to find others, so that astronomers would not confuse these same nebulae with comets just beginning to shine." -Charles Messier
Let's take a journey back in time to when our known Universe was a lot smaller. The only planets discovered were Mercury through Saturn: the naked eye planets. The well-known objects were our Moon, the (naked-eye) planets and their moons, and the stars and the Sun. After those, the only new objects that were routinely hunted in the night sky were those two-tailed recurring…