From PHD Comics, and explanation of what gravitational waves are and why their discovery is so important to the future of science. (via df)
Update: Brian Greene's explanation of gravitational waves to Stephen Colbert is the best one yet:
Greene is great at explaining physics in terms almost anyone can understand. Even though it's more than 15 years old now, his book, The Elegant Universe, still contains the best explanation of modern physics (quantum mechanics + relativity) I've ever read.
As a young graduate student, Brian Greene caught the very beginning of the superstring revolution in physics. 30 years later, Greene provides an accessible overview of string theory's current status.
While spectacularly successful at predicting the behavior of atoms and subatomic particles, the quantum laws looked askance at Einstein's formulation of gravity. This set the stage for more than a half-century of despair as physicists valiantly struggled, but repeatedly failed, to meld general relativity and quantum mechanics, the laws of the large and small, into a single all-encompassing description.
Such was the case until December 1984, when John Schwarz, of the California Institute of Technology, and Michael Green, then at Queen Mary College, published a once-in-a-generation paper showing that string theory could overcome the mathematical antagonism between general relativity and quantum mechanics, clearing a path that seemed destined to reach the unified theory.
The idea underlying string unification is as simple as it is seductive. Since the early 20th century, nature's fundamental constituents have been modeled as indivisible particles-the most familiar being electrons, quarks and neutrinos-that can be pictured as infinitesimal dots devoid of internal machinery. String theory challenges this by proposing that at the heart of every particle is a tiny, vibrating string-like filament. And, according to the theory, the differences between one particle and another -- their masses, electric charges and, more esoterically, their spin and nuclear properties -- all arise from differences in how their internal strings vibrate.
From Phil Plait at Bad Astronomy, a list of ten things you might not know about black holes. Some of this I knew, but this one is incredible:
If you were to rope off the solar system out past Neptune, enclose it in a giant sphere, and fill it with air, it would be a black hole!
See also this recent tweet from physicist Brian Greene:
Remove all the space within the atoms making up the human body, and every person that's ever lived would fit inside a baseball.
(via @daveg & @rosecrans)