Starting the Discussion

Intern Ankit Ahuja and designer Kitt Hirasaki have launched the first of our planned summer improvements to the Khan Academy video discussions.

Now from every user’s profile page, you can view their history of questions, answers, and comments, as well as the discussion badges they’ve earned.

To view your own discussion history, visit your profile page and go to the “Discussion” tab.

Khan Academy has some amazing and involved contributors, and we hope to have many more! Check out some of their profiles:

So the next time you watch a video, ask or answer a question!


Happy Tau Day!

You may have heard of (or even celebrated) Pi day on 3/14, but how about Tau day? What is Tau, you ask? In 2001, Bob Palais published the article “π Is Wrong” in which he argued that the beloved constant π is the wrong choice of circle constant. He instead proposed using an alternate constant equal to 2π, or 6.283… to represent “1 turn”, so that 90 degrees is equal to “a quarter turn”, rather than the seemingly arbitrary “one-half π”.

Two years ago today, Michael Hartl published “The Tau Manifesto” echoing the good points made by Palais and building on them by calling this “1 turn” constant τ (tau), as an alternative to π. Tau is defined as the ratio of a circle's circumference to its radius, not its diameter and is equal to 2π. 

Tau is approximately equal to 6.28, so that makes today (6/28) tau day! Aside from eating twice as much pie as we would on 3/14, we’ve found another way to recognize tau day: Thanks to Emily Eisenberg, one of our awesome summer interns, all of our exercises that can be answered in terms of pi can now be answered in terms of tau too!

All the hints and explanations still use pi, and of course we still accept answers with pi, but for those of you in the know, you can now use this secret feature to answer with tau!

Try it out for yourself, and let us know what you think!

To learn more about the difference between Pi and Tau, check out some of our videos:


iPad App

In mid-March, we launched the official Khan Academy iPad app. If you haven’t yet downloaded it, you can download the app for free from the App Store.

Using the app, you can view all 3,200+ videos available on the Khan Academy website, including all of Sal’s videos as well as art history videos by Beth Harris and Steven Zucker, math videos by Vi Hart, and cryptography videos by Brit Cruise.

For every video with English subtitles, the app includes an interactive transcript which allows you to read along with the video or go to a specific section if you want to rewind or jump ahead. If you log into your Khan Academy account, all of your progress is automatically saved so you can earn energy points and badges for the videos you watch.

Best of all, using the app, you can download videos so you can watch them anywhere without internet access, such as in an airplane or on a long car ride – you can either download a single video or all the videos in a single topic.

Currently, practice exercises are not available from within the iPad app but we hope to have them available in a future release; for now, you can do exercises directly on the website.

If you haven’t yet tried it, download it for free. We hope the app is a great tool for both students and teachers – enjoy!


Parents can now create accounts for their children!

Developer Ben Komalo has made it possible for parents to create accounts for their children who are under 13.

Parents, to create an account for your child, visit:

Child accounts have several safety features:

  • The parent who creates the child account becomes the child’s permanent coach.
  • The child cannot enter certain information (e.g.. email, full name) in their profile, nor make their profile public.
  • The parent has the option of disabling the child from adding other people as coaches. (See What is a coach? for more details on coaching.)
  • The parent manages the child’s password and can change it at any time for any reason.
  • The child cannot post public messages in discussion forums.

FAQ articles about child accounts:


Share your Khan Academy badges on Facebook in style

As of today, you can now share your Khan Academy badges on Facebook using the new Open Graph protocol. In normal speak, it means that you’ll get richer, more interesting displays of your badges on Facebook if you choose to share them, like so:

So, how does it work?

Say your name is Mary Littlelamb, and you earn a couple of badges:

If you click on the “Share” button,

This dialog will pop up asking for you to grant us permission to post on your behalf. In order to share the badge on Facebook, you must click “Allow”. Otherwise, we can’t share it. =(

After a short delay (hopefully not too long; we have to wait for Facebook to confirm that the publish action went through), the badge will appear in your Facebook Timeline!

If you miss the opportunity to share from a badge notification dialog, you can also share from the “Recently Completed Activity” section of your Khan Academy profile page.

Just hover over the badge you want to share, and the same share links will appear in gray:

After sharing several badges, a neat Khan Academy “Badges earned” section will appear in your Facebook timeline:

You can edit or remove this view.

If you’ve shared more badges than can fit in the display case, you can customize which ones get shown by clicking on “View Individual Stories”.

On the resulting page, you can change the settings for individual badges.

Here, Mary wants to make sure “Addition and subtraction” shows up in her Timeline.

Back on Mary’s Timeline, we can see the changes were put into effect. Woohoo!

At the end of it all, Mary’s friends will be able to see her activity in their Facebook Newsfeed. Way to go, Mary!

If you click on a badge, you’ll end up at a page more info about what it takes to earn the badge, as well as a ginormous list of all the badges you can earn on Khan Academy.

Happy sharing!

Stephanie, Desmond, and Marcos