Jon Clarke writes, “As an avid cyclist and physics teacher, I had a tattoo a few months ago on my calf, and wondered whether that would fit with your archive. Having been given a cycle computer a year ago, I was frustrated and surprised that no matter how hard I cycled–on a level road without a tailwind or fast-moving large vehicle to shadow–I could never reach the UK speed limit in built-up areas (30mph). After some thought, I concluded that the dominant effect, and therefore limitation, was the power required to overcome aerodynamic drag for turbulent flow.”

In this tattoo, v is the speed of a bicyclist, and P is the rate at which muscles have to do work in order to overcome air resistance. If you double your speed, you have to work eight times harder. It is, in other words, a tattoo of human limitation.

You can see the rest of the Science Tattoo Emporium here or in my book, Science Ink: Tattoos of the Science Obsessed.

Originally published June 30, 2013. Copyright 2013 Carl Zimmer.

As you can tell from my recent posts, I am a bit obsessed about cancer–or more specifically something you might call the natural history of cancer. Cancers in the animal kingdom can get very strange–even giving rise to what I would call new species. Earlier this month, I gave a public talk in San Francisco as part of the International Evolution and Cancer Conference. The video is now up. I hope you find these strange cancers as spookily fascinating as I do.

In case the slides are hard to see, I’ve uploaded them via Slide Share:

A number of the newest cancer drugs can give a few months of extra life to people in advanced stages of the disease. The drugs attack the cancer cells with pinpoint accuracy and wipe out the tumors. And then, months later, the tumors come right back. In my “Matter” column today, I take a look at the work of cancer biologists and evolutionary biologists to understand how this rebound happens, and how doctors might stop it. Check it out.

Originally published June 27, 2013. Copyright 2013 Carl Zimmer.