### OK Go Loves Potential Energy!!

There is nothing I can say to prepare you for the awesomeness of this video (which you very well may have seen already, because it has been EVERYWHERE and you are a very cool person who knows what's going on in the world):

The power of potential energy!

There is one particularly giggle-inducing moment when a gently rolling soccer ball releases an upright piano from its position 5 feet above the ground with a grand CRASH! It's a bit poetic how such a small thing can create such a large effect. Even though there are a few places where electronic devices are used, the entire machine keeps running without human intervention - without the addition of energy. It's continual motion relies on energy stored prior to the domino tip-off. Once again, with only a few exceptions, all of this energy is mechanical, not electrical. I think in this day and age we are used to relying on electricity as our primary energy source, and seeing mechanical energy put to work in such a creative way is a real treat. And once again, do not underestimate the awesome power of entertainment when trying to educate.

Energy is sometimes a tough thing to think about because it is not a physical thing you can hold in your hand; but it does exist in physical things. For example, I can take physical energy out of my muscles and put it into a bowling ball when I lift that ball above the ground. When I drop the bowling ball, the bowling ball passes the energy into the floor. I can't hold onto energy, but I can hold onto objects with energy. I can feel energy if I put my hand under that bowling ball as it falls. And if I secure the bowling ball in a sling above the floor, I can leave that potential energy there indefinitely, and release it with only the amount of energy it takes to release that sling. This goes for everything from marbles to pianos. When an object has the potential to release a lot of energy (like a piano dangling 5 feet above the ground) we call that potential energy. As the piano falls, the energy it is releasing is now called kinetic energy.

Systems want to be in the least energy state, which is why water always runs to the lowest point in a house and why the piano falls. In classical systems, gravity is often the dominating force that determines where the lowest energy state is. I will mention briefly how this relates to avalanches, which are another example of very small forces triggering massive results.

For the same reason a small soccer ball can destroy a piano, one skier can trigger a massive avalanche (see our other posts on Physics Buzz here and here). The snow on the side of a mountain has potential energy because it is lifted high above the valley floor. Rather than a rope or sling holding it up, the snow is held in place by frictional forces - the falling snow tends to stick together and stick to the mountain. But as the layers of snow grow, the weight of the snow drifts may over power those frictional forces, and an avalanche may occur naturally. Sometimes the weight of the snow drifts is almost, but not quite enough, to overcome those frictional forces. The snow drifts are like the piano held up by the rope. It only takes enough energy to undo the rope to send the piano crashing to the ground - but nature does not approximate. If the snow drift has almost, but not quite enough energy to overcome the frictional forces, it will remain still. The snow will stay on the mountain side.

But a soccer ball might happen along and trip the chord holding the piano, or a skier might go by and push on the snow drift. That little bit of energy might be enough to overcome the initial momentum and send the snow hurtling down the mountain. Initial momentum is the momentum it takes to get a system moving, which is a little more than it takes to keep the system moving. So if your car stalls, it takes one big push to get it rolling, but less energy to keep it rolling. Sometimes a system hangs delicately on the edge of having just enough energy to reach the necessary initial momentum, a very small outside force is enough to push it over the edge. And we can thank those classical laws for the Rube Goldberg machines we love so much.

Wired has a great story on the construction of the machine by Syyn Labs, a Los Angeles-based arts and technology collective. The article includes four "making of" videos which just might motivate you to get out your old Mouse Trap board game, or build your own, like this one from the Myth Busters (it's a holiday Rube Goldberg machine, which is out of season, but adds a bit of cheer to my rainy afternoon).

1. I love the OK GO video! There are so many great physics concepts in that video.

2. Science is the coolest.

3. Energy is sometimes a tough thing to think about because it is not a physical thing you can hold in your hand; but it does exist in physical things.

### How 4,000 Physicists Gave a Vegas Casino its Worst Week Ever

What happens when several thousand distinguished physicists, researchers, and students descend on the nation’s gambling capital for a conference? The answer is "a bad week for the casino"—but you'd never guess why.

### Ask a Physicist: Phone Flash Sharpie Shock!

Lexie and Xavier, from Orlando, FL want to know:
"What's going on in this video? Our science teacher claims that the pain comes from a small electrical shock, but we believe that this is due to the absorption of light. Please help us resolve this dispute!"

### The Science of Ice Cream: Part One

Even though it's been a warm couple of months already, it's officially summer. A delicious, science-filled way to beat the heat? Making homemade ice cream.

(We've since updated this article to include the science behind vegan ice cream. To learn more about ice cream science, check out The Science of Ice Cream, Redux)

Over at Physics@Home there's an easy recipe for homemade ice cream. But what kind of milk should you use to make ice cream? And do you really need to chill the ice cream base before making it? Why do ice cream recipes always call for salt on ice?