The Sky is the Daily Bread of the Eyes ~Ralph Waldo Emerson At some point in his or her life, almost every child on Earth asks, “Why is the sky blue?” The question is so prevalent that, to me, it has come to represent the wonder that the world holds for a a child. Adults don’t ask such questions… at least, not unless they’re scientists. Part 1: John Tyndall In 1859, physicist John Tyndall thought he’d found the answer to the sky’s color. His studies of infrared radiation required him to use containers of completely pure air. He
Condensed Matter / cosmology / Physics / etc.
BICEP2, Primordial Gravity Waves, and Cosmic Inflation
“Like the microscopic strands of DNA that predetermine the identity of a macroscopic species and the unique properties of its members, the modern look and feel of the cosmos was writ in the fabric of its earliest moments, and carried relentlessly through time and space. We feel it when we look up. We feel it when we look down. We feel it when we look within.” ~Niel Degrasse Tyson There was some very big news today! If you haven’t already heard, the BICEP2 research group at Harvard has found evidence of ancient gravitational waves in the sky. A lot
abstract algebra / History / Mathematics / etc.
International Women’s Day Spotlight: Emmy Noether
The connection between symmetries and conservation laws is one of the great discoveries of twentieth century physics . But I think very few non-experts will have heard either of it or its maker[:] Emily Noether, a great German mathematician. But it is as essential to twentieth century physics as famous ideas like the impossibility of exceeding the speed of light. It is not difficult to teach Noether’s theorem, as it is called; there is a beautiful and intuitive idea behind it. I’ve explained it every time I’ve taught introductory physics. But no textbook at this level mentions it. And
Uncategorized
Hiatus
Unfortunately I will be taking a hiatus on blog posts until mid December. The reason is that graduate school is pretty hectic at the moment and I’m feeling a bit too overwhelmed. See you all in about three weeks!
optics / Physics / Quantum Mechanics / etc.
How Things Work: Lasers
You know, I have one simple request. And that is to have sharks with frikkin laser beams attached to their heads! ~Dr. Evil Always look on the bright side …unless you’re holding a laser pointing device. ~Unknown The laser is, without a doubt, one of the most ubiquitous, archetypal technologies of modern times. And it is one of the most direct applications of quantum mechanics. But how do lasers work? It All Starts In The Atom The story starts deep within the atom. I’ve previously discuss the fact that particles are waves and that this forces electrons to have
Astrophysics / Physics / Science And Math
Why Black Holes Glow: Accretion Disks
The patient accretion of knowledge, the focusing of all one’s energies on some problem in history or science, the dogged pursuit of excellence of whatever kind these are right and proper ideals for life. ~Michael Dirda Nothing can escape from a black hole, not even light. This is why we call them “black.” One would imagine, then, that black holes are black invisible menaces, lurking out in the depths of space. Surprisingly, though, black holes glow. The cover image shows a radio photograph of the center of the Milky Way. The center glow, Sagittarius A, is partly due to
Physics / Quantum Mechanics / Science And Math
Between the Two Shores: Covalent Bonding
But let there be spaces in your togetherness and let the winds of the heavens dance between you. Love one another but make not a bond of love: let it rather be a moving sea between the shores of your souls. ~Kahlil Gibran Two weeks ago now, I flew to Conway, Arkansas to attend the wedding of my very good friends Vincent and Mary. This and an academic conference got in the way of blogging for a little while but I’m back. As such I decided to a post in their honor about bonding. Not human bonding, mind you,
cosmology / Discrete Math / Geometry / etc.
Quantum Geometry: Causal Dynamical Triangulations
A “quantum gravity expert” is presumably someone well acquainted with the details of our immense ignorance of the subject. I suppose I count. ~John Baez I long ago promised that I would discuss some of my own research. Here’s the first post that makes good on that promise. Today I’ll discuss a theory of quantum gravity. Why Quantum Gravity? Without a doubt, the two greatest advances in physics in the last 120 years were the advent of general relativity and quantum mechanics. These two amazing theories have totally changed the way we see the world. Quantum mechanics describes the
Analysis / Mathematics / Physics / etc.
Between Being and Non-Being: Imaginary Numbers
Imaginary numbers are a fine and wonderful refuge of the divine spirit almost an amphibian between being and non-being ~Gottfried Wilhelm Liebnitz One of the first things we learn how to do is multiply numbers. . That sort of thing. But what if we multiply a number by itself? This is the familiar operation, which we call squaring a number. and . That sort of thing. You can take a number to a power by multiplying it by itself some number of times equal to the power. So if you square a number, you’ve taken it to the second power.
Physics / Quantum Mechanics / Science And Math
Reality Is—The Feynman Path Integral
Will you understand what I’m going to tell you? …No, you’re not going to be able to understand it. … I don’t understand it. Nobody does. ~Richard Feynman on the Path Integral The “paradox” is only a conflict between reality and your feeling of what reality “ought to be.” ~Richard Feynman, in his lectures on physics Quantum mechanics is a very strange beast. Things tunnel and ooze. You can’t know both position and momentum at the same time. These strange properties come from the amazing realization that particles are waves. Not only that, but the amplitude of the wave