"We are bits of stellar matter that got cold by accident"

Last night, we took a midnight drive into the desert for a chance to catch the Leonids at their peak intensity. It wasn't altogether without its hiccups -- the air smelled kind of weird, I got sand in my clothes and hair, I had too much catch-up work to ever justify staying up so late, and try as we did, we almost but never totally escaped all light pollution around the horizon.

Not that any of it mattered -- it hardly seems to, whenever something like the night sky makes you feel really infinitesimally small in the universe. It's a crazy thing to think about: these meteor showers are just space dust and debris, little remnants of a comet trail dating back to 1400s. For over five centuries, this whole stream of rocks has been whirling around the sun, left behind at a time when the printing press on Earth was the technological bombshell of its day. Back then, Copernicus wasn't even born yet, much less Kepler, Galileo, Newton, and everyone else who made it possible to even predict these showers from year to year, and here I am teaching to premeds, in mere weeks, what took them entire lifetimes to accomplish. Every shooting star in the sky was a piece of cosmic litter that had been sitting in our solar system for generations upon generations, through every terrible and amazing thing we've done in a species in all that time, only to burn up this very year in the fragile atmosphere of our tiny planet.

It boggles the mind. Anyway, hopefully someone else also looked up for a night and wished for something nice.

But officer, the light was doppler-shifted to green

Most of the major intersections we pass through in Doha are roundabouts, in which otherwise normal drivers are transformed into complete maniacs. For better or worse, though, they (the roundabouts, not the drivers) are very good at making traffic flow more efficiently than signaled intersections. However, there are still a lot of traffic light intersections, as well as "controlled" roundabouts in which traffic lights direct the flow of cars through the roundabout (the latter combines the worst of both worlds, and I don't understand why they even need to exist). Some of these lights stay red for an unusually long time, which makes it just a little frustrating to wait at those intersections.

There's a way around this that was mentioned the other day: if you're driving fast enough, the red light will look green to you. Most people are familiar with the Doppler effect for sound waves, whether or not they know it by name: a siren traveling toward you will sound higher in pitch than one standing still with you, and in turn, a siren traveling away from you will sound lower in pitch. The same is true for light waves, but you need to use special relativity to describe it since light travels at the same speed no matter how fast you're going (sound travels at the speed of sound, but only relative to the air itself). If you're driving toward a light, you'll see it as a shorter wavelength ("blue-shifted," but not necessarily blue) than if you were just standing still with the light.

So the question is how fast you have to go for a red light to look like a green one. This is a problem you'd typically get in a special relativity class, but I'd forgotten the answer for some time so here is the calculation. If the traffic light is normally shining red, and you're speeding toward it at a velocity $$v$$, then the wavelength of light you see changes according to the equation (derivation, if interested)

\[\lambda_{obs} = \lambda_{red} \sqrt{ \frac{1 - v/c}{1 + v/c} } .\]
where $\lambda_{obs}$ is the wavelength of light that you observe from your speeding car, $\lambda_{red}$ is the wavelength of the red light, and $c$ is the speed of light (300 million meters per second). Rewriting the equation gives you

\[v = c \left( \frac{\lambda_{red}^2 - \lambda_{obs}^2}{\lambda_{red}^2 + \lambda_{obs}^2} \right) .\]
Red light has a wavelength ($\lambda_{red}$) of about 650 nm, and green light has a wavelength ($\lambda_{obs}$) of about 550 nm. Plug everything in and you get

\[v = \frac{24}{145} c \approx \frac{1}{6} c . \]
So you'd have to be driving at one-sixth the speed of light, or 50 million meters per second, or over 100 million mph. In one second, you'd encircle the Earth once and then some. But assuming you could push your car that fast, you could run a red light and legitimately tell the cops that it looked green to you.

Then again, they'd probably have a hard time catching you anyway. Plus, the actual green lights would look blue, which would just be really weird.

Turkey building an accelerator

I'm flying off to Turkey soon -- inshallah, a lot of our students would add here -- so this caught my attention just the other day (physics alert):

Turkey plans an accelerator center

Over the last ten years, Turkish physicists have been working diligently to build a national accelerator center, which would serve as a core science facility and offer increased opportunities for Turkish students. It would be the first accelerator facility in the country, and only the second in the Middle East.

After much planning, excitement is building over the construction of the first phase of the project, a testing and research facility called the Turkish Accelerator and Radiation Laboratory at Ankara, or TARLA for short. Scheduled to be completed in 2012, it will be an Infrared Free Electron Laser, capable of producing an intense laser beam of infrared light for research in a wide variety of sciences ranging from physics to chemistry to biology and medicine.

For everyone reading this who isn't a giant physics nerd, what they ("they" being Turkish physicists) are building is a research facility to boost a beam of electrons to incredibly high speeds. Once the electrons are up to full speed, they get shaken slightly from side to side as they zoom down their otherwise straight path. Shaking the electrons makes them emit infrared light, and done enough times, the light comes out of the other end as a powerful infrared laser beam. If it sounds kind of expensive and useless at first, it's worth mentioning that a lot of advances in the biological, chemical, material, and medical sciences in the past half-century have come from related research at accelerator labs around the world. (To preempt the inevitable suggestion, it's not a nuclear fission facility. Or a black hole factory.)

It's a dorky thing to say, but it's really awesome -- to me, anyway -- to hear about basic research continuing to spread like this across the globe. Hopefully it'll be finished in the near future, and hopefully they'll be able to make good on their plans to expand the accelerator.