Happy Mole Day to you all! No, we're not celebrating the burrowing mammal or even the chocolate-accented Mexican sauce. Mole Day commemorates Avogadro's number -- 6.02x10²³ -- a way to measure infinitesimal things like atoms and ions. It's celebrated from 6:02 a.m. to 6:02 p.m. on October 23rd. Get it? Here's what our chemists concocted this week:

• Faces of the Flickrverse: Tagging has always been the fun part of Flickr, making it a cinch to find photos of anything from fungus to flugelhorns. This week, People in Photos made its debut, letting you add people to your photos, find photos of people you know, and manage which photos you're in. If you're tagged, you'll get notified in your activity stream. If that sounds at all creepy to you, never fear - you've got plenty of privacy power. Opt out, opt in. More on the Flickr blog.
• Teach your phone to yodel: Sure, your mobile can probably mimic the sound of crickets, a dog bark, a vintage telephone, or sonar. But can it yodel? Now it can. In support of our Yodel Studio promotion, which seeks the world's best new yodelers with a chance to be featured on our homepage and in our global marketing campaign, we've cooked up yodeling ringtones. And not just your government issue yodel. We're talking hip-hop, a cappella, R&B, reggae, and bluegrass yodels. Download them here or text YODEL to 49737 in the US, 56263 in India, and 83338 in the UK. Oh, and don't forget to submit your yodel and/or vote for your favorites. The deadline is November 8th.

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Nicki Dugan
Blog Editor