### Friday Fermi Problem: Settlements in Space

What if something happened to our planet that rendered in inhabitable? We used up all of our resources, let's say. Or for whatever reason we feel the need to abandon our terrestrial home and settle in space. What would that new home look like?

Above is a painting done in the 1970s by an artist named Rick Guidice. The painting, commissioned by NASA, depicts the imagined Sanford Torus. It's a doughnut-shaped space station that rotates to provide Earth-like gravity for its inhabitants.

Here's today's Fermi question: Let's say we built the Sanford Torus for real. (It looks like a nice enough place to live.) Using the painting to guess the dimensions of the station and the settlements inside, how many of these stations would we need to house all of the people of the world?

1. OK, my guess is 100000 stations.

2. I'm guessing that the interior diameter of the tube is 400'. I'm also guessing that the diameter of the station is roughly 1 mile. By my calculations, this gives roughly 5280*2*pi*400 = 13.27 million sq ft. Using the population of Indianapolis as a reference (it's my hometown and kinda looks like the area shown in the tube), that's a population of 781,870 in an area of 371 sq miles. This means that each person has roughly 13.27 thousand sq feet. Which means that each station will hold 1000 people. With a world population of 7 billion, that means we'd need 1 million of these stations to hold everyone.

3. Correction of my above post: We'd need *7* million of these stations to hold everyone.

4. Wow , amazing the imagination is just great, specially the painting ones. very creative, i hope nothing such happens .but still i guess we are ready if something happens like this

CTCA Arizona

### 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?