Today’s Google Doodle (visit google.com to see it, or if you miss today, you can find it in their archive) celebrates Russian mathematician Olga Ladyzhenskaya. In recognition of her 97th birthday, the Doodle includes the Navier-Stokes equations, of which Ladyzhenskaya provided the first rigorous proofs of convergence using a finite-difference method.

### John Venn is 180

Today is the 180th Birthday of John Venn, inventor of the often-misused mathematical staple the Venn Diagram. In celebration, Google have made today’s Google Doodle be a playful interactive toy where you can select two categories and it’ll show you something in the intersection.

Here’s some of our other favourite Venn diagrams from the internet:

Enjoy Venn-day! I hope that your day is the middle bit of a Venn diagram where the two circles are ‘excellent’ and ‘enjoyable’.

### Google Doodle: The Witch of Agnesi

Today’s Google doodle (for those not in the know, the Google homepage alters its header based on the date, and on dates of special nerdy significance, they theme them around relevant birthdays/anniversaries) is about Maria Gaetana Agnesi, a female mathematician. Agnesi was born on 16th May 1718, making today her 296th birthday. This means you have four years to prepare for her 300th birthday bash, which I hear is going to go off big style.

### Happy Birthday Euler!

Today is Euler’s $-306 \times e^{i \pi}$th birthday, and Google have chosen to celebrate (despite ignoring several other prominent mathematical birthdays, including Erdős’s centenary – see the @MathsHistory twitter feed for a full list) by creating a Google doodle on their homepage.

For anyone who isn’t aware, this is when Google changes the image above the search box on the homepage at Google.com, so it still says ‘Google’ but using an appropriate image, which sometimes has built-in interactive elements. I thought it was worth pointing out some of the fantastic maths they’ve included in today’s doodle.