Humanity at night

NASA scientists, at the American Geophysical Union’s annual meeting, revealed images from space of humanity—and our wonderful cultural behaviors.

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Sun dogs light up the sky

My friend Austin took this photograph last week, looking out his office window near the Metrodome in downtown Minneapolis. That flare in the distance isn't Photoshop. Nor is it the nuclear annihilation of St. Paul. Instead, it's a sun dog — an atmospheric phenomenon that happens when light from the Sun is refracted off of ice crystals in the air. The light gets bent as it passes through the crystals and we see the bright flash of a "false sun" to the side of the actual Sun. The same process can also form rings around the Sun. Whether you get a halo or a sun dog depends on which way the ice crystals are oriented in relation to you.

Double rainbows: Here's what they mean

The physics blog Skulls in the Stars has answers to your rainbow-related questions. Among the fascinating things we learn here — each color in a rainbow represents the light reflected by a separate group of raindrops; skydivers can see circular rainbows; and the famous double rainbow happens when light bounces off the inside of a raindrop not just once ... but twice.

How the face changes with shifting light sources

Nacho Guzman demonstrates how much a face appears to change with differing lighting positions, in a teaser for a forthcoming music video from OPALE.

The 2012 Nobel Prize in physics

Pretty much everyone — including, probably, you — thought that the 2012 Nobel Prize in physics would go to the people who discovered evidence of a particle that meets the description of the theoretical Higgs Boson.

But, it didn't.

Instead, the winners are Serge Haroche and David Wineland, two physicists whose work is all about the way that photons — the tiniest pieces of light, which simultaneously behave as both shifting waves and packaged particles — interact with everything else in the Universe.

I really dig this video put together by Brady Haran of Sixty Symbols, because it captures both the surprise associated with today's announcement (turns out, a lot of physicists thought the Higgs Boson would win, too) and does a good job of explaining what Haroche and Wineland do, and why it's important.

Quote of the day: "Have you tried to capture a single atom?"

The science of glow sticks

I stumbled across this randomly on YouTube today and had to share. The first 3/4 of the video are a chemistry experiment breakdown of what goes into a glow stick and what each of those ingredients is meant to do. But what makes me LOVE it is that, at the end, all of this coalesces into a fine explanation of the difference between light-absorbing dyes and fluorescent dyes. Come for the glow-stick "how to", stay for the better understanding of how light works and how it influences what you see!

Video Link

What we don't understand about the speed of light

Last June, researchers from the Hong Kong University of Science and Technology published the results of an experiment that proved that light does not move faster than light—specifically, that single photons can't move faster than the official speed of light under certain conditions.

Today, Skulls in the Stars—the nom de Internet of a UNC Charlotte physics professor—has a really great blog post up about this paper. It's very much worth a read. After all, this was basically a test to double check something we were already pretty sure was true. And what's the benefit to proving something you already knew?

A big part of why I'm recommending this post is because Skulls in the Stars does a good job of explaining some tangly optical physics in a way that is quite clear and should make good sense even if you don't have a deep background in this stuff. If you follow along, you'll come away with a good idea of why this particular study matters, and with a deeper understanding of the speed of light itself.

Let’s talk about how we measure the speed of an object first. If we’re looking at the motion of a rigid object, like a speeding car or a thrown baseball, the speed can be determined simply by measuring how much time it takes for an object to travel a distance. The speed is simply the distance divided by the time

There’s a small subtlety to this definition: cars and baseballs are extended objects! To accurately measure an object’s speed, we have to be consistent in how we define its position. For a car driving down the road, for instance, we should do all measurements of its position from a fixed position, such as the front bumper, to measure the speed.

But what do we do when the object doesn’t have a fixed position on it? For example, what is the best way to measure the speed of a hurled bucketful of water?

Image: Tap's eye view of water falling into bucket., a Creative Commons Attribution Share-Alike (2.0) image from kamathln's photostream