### Friday's Siesta Fermi Problem Solution

Fermi Problem Solution:

First, according to a doctor at the siesta competition, less than 30 percent of the contestants actually fell asleep. To make our lives easy, we'll say 100 people (roughly 28 percent) fell asleep.

Next, we'll assume that it took the average napper 10 minutes to fall asleep. Normally, people might average a longer drifting off time, but we're assuming these people are expert nappers capable of falling asleep quickly.

Multiplying those two numbers together, we can say that the total amount of napping done in the contest was 1,000 minutes.

Assuming each of the nappers works an office desk job, each would ordinarily burn 102 kilocalories (kcals) an hour at work. Over ten minutes, those 100 office workers would burn a combined 1699 kcals. Since a person burns about 61 kcals an hour while sleeping, we guess a collective 1016 kcals were burned by the nappers.

By subtracting the number of kcals burned while sleeping from working, we know that the net energy the nappers conserved was about 683 kcals, or 2.9 million Joules.

That's enough to power the average U.S. home for an hour!

### 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?