Category: computer science

This disturbs me, because the natural numbers …

This disturbs me, because the natural numbers shouldn’t start at one.

We’re down in the weeds, but these are good we…

We’re down in the weeds, but these are good weeds.

Real numbers don’t exist.

Real numbers don’t exist.

A wall of lava lamps in a San Francisco office…

A wall of lava lamps in a San Francisco office currently helps keep about 10% of the Internet’s traffic secure. Internet security company Cloudflare uses a video feed of the lava lamps as one of the inputs to the algorithms they use to generate large random numbers for encryption. The concept dates back to a 1996 patent for a product called LavaRand. The idea is that using a chaotic, unpredictable source as a seed for random number generators makes it much harder for an adversary to crack your encryption. 

With lava lamps, a lot of that chaos comes from the fluid dynamics involved – without perfect knowledge of thousands of variables, it would be impossible to simulate the lava lamp wall and get the same outcome as the real one – but there’s also randomness that comes from the measurement. People walking by, shifts in lighting, and random fluctuations of individual pixels all help make the video feed unpredictable. For those interested in the details of how Cloudflare uses their lava lamps, the company explains things for both technical and non-technical readers. You can also check out Tom Scott’s video for a good overview. (Image and video credit: T. Scott; submitted by Jean H.)

American Mathematics Society | Mathematical MomentsI’m…

American Mathematics Society | Mathematical Moments

I’m substituting for a 9th- and 10th-grade math teacher, and she has a number of neat posters on her wall, ranging from the application of mathematics to robotics, to its role in black hole physics, to its cultural impact on the NBA.

Here’s the description of the poster set, which comes from the AMS:

The Mathematical Moments program promotes appreciation and understanding of the role mathematics plays in science, nature, technology, and human culture.

The AMS has many, many more online, many of which are accompanied by podcasts, shorter versions, and translations into a variety of languages. Pictured are:

Check them out and enjoy!


sketchplanations: Idempotence. A term I’d always found…



A term I’d always found intriguing, mostly because it’s such an unusual word. It’s a concept from mathematics and computer science but can be applied more generally—not that it often is. Basically, it’s an operation that, no matter how many times you do it, you’ll still get the same result, at least without doing other operations in between. A classic example would be view_your_bank_balance being idempotent, and withdraw_1000 not being idempotent.

HTs:  and Ewan Silver who kept saying it