### The Domino Effect

This week's podcast is about falling dominos. Very large falling dominos. Everyone knows that a line of standing dominos creates a fun chain reaction when you knock the first one over; but did you know you can use increasingly larger dominos and get the same result? Theoretically, there is no limit to how large your dominos can get. Watch Stephen Morris of the University of Toronto knock down a domino that's over 1-meter tall, and weighs over 100 pounds:

Morris uses a size ratio of 1.5, meaning each domino is one and a half times larger than the last one. This is the generally accepted maximum ratio that dominos can have to successfully knock each other over.

But this month, Hans Van Leeuwen of Leiden University in the Netherlands, published a paper online showing that, theoretically, you could have a size ratio of up to two. That's in an ideal (and probably unrealistic) situation. But the team at the Dutch Science Quiz (which is a whole cool thing by itself) wanted to test the theory—and nab a world record in the process. So they built some really huge dominos (the largest is 26 feet high and weighs over 1000 pounds), and this is what happened: (sorry, this video takes a bit of time to load; the big domino demonstration is at 6:00. Before that is a lot of talking in Dutch).

Check out the podcast to hear more!

SOS!
We need to do this experiment for our science project.

Vibhu and Udai (from India)

### 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 ) Image Credit: St0rmz via Flickr 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?