By Hamish Johnston
I’m a bit of a connoisseur of the art of stone skipping. That’s because I grew up a stone’s throw from the western end of Lake Ontario, which thanks to its shale shoreline has the best skipping stones in the world. As a result, I was fascinated to read a piece on the Figure One blog about entitled “Frisbee meets fluid: Skipping stones takes spin and skill”.
The world record for successive skips is 51, and in her blog, Amanda Alvarez shares a few tips for improving your technique. I’ve spent many an hour initiating my children into the art of skipping, so here are my top tips. First, stone selection is crucial. Ideally, it must be flat, thin and about the size of your palm. But it can’t be too thin, because it will tend to flip over when it hits the water. Second, you need angular momentum, and lots of it. The stone really needs to be spinning when launched, which requires a flick of the wrist (the tricky bit). Spin is important because conservation of angular momentum stops the stone from flipping over when it hits the water. Finally, the trajectory is important; you need to crouch down and launch the stone as parallel as possible to the water surface. According to Alvarez, physicists in France reckon that the ideal angle of contact between stone and water is 20 degrees.
According to legend, Lake Ontario is home to a Nessie-like monster called Kingstie, so be careful if you are skipping stones from its shores. But Kinsgtie would be a flea next to the latest incarnation of Godzilla, which will be hitting the cinemas this year. For some reason there are several similar posts across the blogosphere about how the legendary monster has grown over the years and the biophysical implications.
My favourite is on Deep Sea News, where the biologist Craig McClain has a nice graphic showing how Godzilla has shot up from about 50 m in 1954 to 150 m in the latest film. He discusses this rapid evolution in terms of “Cope’s rule”, which quantifies how living organisms have tended to become larger over time. In other words, three billion years ago the Earth only supported single-cell organisms but now we have redwood trees, blue whales…and Godzilla. Using data from a previous post on the biophysics of Godzilla-like Kaiju creatures, he also calculates the amount of urine the latest Godzilla would produce: the monster could fill an oil tanker in four days.
Godzilla calculations are a walk in the park compared with the mind-boggling feat of simulating 13 billion years of cosmic evolution, right from the largest scales of the cosmic web down to individual galaxies. Which is why astronomer Mark Vogelsberger, who works on the “Illustris” simulation, is rather jubilant, saying that “until now, no single simulation was able to reproduce the universe on both large and small scales simultaneously”. The computer simulation began a mere 12 million years after the Big Bang and was run until it reached the present day, when astronomers counted more than 41,000 galaxies in the cube of simulated space 350 million light-years across.
Illustris took five years in total to develop, includes both normal matter and dark matter using 12 billion 3D “pixels”, or resolution elements. Actual calculations took three months of “run time,” using a total of 8000 computers running in parallel. Indeed, if the team had used an average desktop computer, the calculations would have taken more than 2000 years to complete! Take a look at the video above and make sure you have a play with the simulation yourself on the Illustris website.
Finally, physicsworld.com reader Phil Edwards has send us a link to a short piece he has written about Erwin Schrödinger on his Trivia Happy:) blog. It’s called “Erwin Schrödinger was not a morning person”. Thanks Phil, and if any other readers want to suggest a link for next week’s Red Folder round-up, please get in touch.