I call our world Flatland, not because we call it so, but to make its nature clearer to you, my happy readers, who are privileged to live in Space. ~A. Square In the past few years, you’ve probably heard something about graphene—whether as a replacement for silicon, as the next generation of organic solar cell, as the material in fast-charging batteries, or as one of the strongest materials ever discovered. There’s been so much hype that people have begun calling the flood of research and investment the graphene gold rush. In this post, I’ll give you a brief primer
jonah
Jonah is the author of The Physics Mill.
Mathematics / probability / Science And Math
Throwing Darts for Pi
The ancient Greeks defined the number as the ratio of the circumference of a circle to its diameter. Since then we’ve discovered that is incredibly important. It appears everywhere in physics, mathematics, and engineering. But how does one calculate it? is an irrational number, so it’s impossible to calculate perfectly precisely. Nevertheless, it’s important to have an accurate approximation. The Greeks originally calculated by taking a piece of rope or twine of known length, bending it into the shape of a circle and comparing the diameter of the circle to the length of the twine. Since then, many many
optics / Physics / Quantum Mechanics / etc.
Mode-Locked Lasers: The Beating Pulse of Metrology
Your hand opens and closes, opens and closes. If it were always a fist or always stretched open, you would be paralysed. Your deepest presence is in every small contracting and expanding, the two as beautifully balanced and coordinated as birds’ wings. ~Rumi Although we don’t usually notice them, ultrafast pulsed lasers are all around us. They are keep time in the atomic clocks on GPS satellites. Metrologists and chemists use them to measure the properties of atoms and molecules. Astronomers use them to measure the color of light from distant stars. Particle physicists use them in supercollidors. Materials
Physics / Quantum Mechanics / Science And Math
Quantum Field Theory in A Cavity
So I’m still mired in final exams–this time a final project for my quantum field theory course. The downside is that it will be yet another week before my next “real” post. The upside is that I still have a little something for you all this week. The above image shows part of what I’m working on for my project. Imagine that you make a square box of mirrors, and with some magic quantum tweezers, you put exactly fifty-one photons into your box. Light is a special oscillation in an electromagnetic field, which we usually describe classically. But if
Uncategorized
Post Delayed
This week I’m in Savannah Georgia for the April APS meeting. So far, it’s been a blast! I met fellow blogger +Hamilton Carter, who writes at Copasetic Flow. If you’re interested in relativity or the history of physics, you should definitely check it out. He had a very nice talk on the history of special relativity, and he blogged about it here. And next week, I’ll be taking an exam. So for the next two weeks there may be no posts. To tide you over, I’ll put up a guest post by my good friend Michael Schmidt soon.
optics / Physics / Quantum Mechanics / etc.
Scattering Part Two: A Quantum of Scattering
We come spinning out of nothing, scattering stars like dust! ~Jalāl ad-Dīn Muhammad Rūmī Last week, I explained Rayleigh and Raman scattering from a classical point of view. In the process, I explained why the sky is blue and introduced Raman spectroscopy, a powerful tool for studying the structure of molecules. This week, I fill in the gaps and explain scattering from a quantum-mechanical point of view. Before we can talk about scattering, though, we need to review some important ideas from quantum mechanics: energy levels and the Heisenberg uncertainty principle. Energy Levels The story of energy levels starts
optics / Physics / Quantum Mechanics / etc.
Why The Sky is Blue: Lord Rayleigh, Sir Raman, and Scattering
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!