A cool, portable and literally manual protractor. <;-)

Seen in *Physics-Astronomy.com* FB page.

Educational
Learning resources for teachers and students

**Hadwiger–Nelson problem** yields to (relatively) amateur mathematician *Aubrey de Grey*.

Image caption: *This 826-vertex graph requires at least five colors to ensure that no two connected vertices are the same shade*. High-res.

All you need is to do a bit of thinking and a certain order when counting. After (and only after) solving it you can check your answer out in this twitter thread, where you can also check that on the Internet there are many people who prefer to blindly ask Google than think by themselves, which eventually leads to big mistakes.

1. Vincent van Gogh was born on March 30, 1853, in Holland. He was named after his grandfather and his stillborn brother who died one year before Van Gogh was born.

2. Van Gogh was 27 years old when he painted his first piece.

3. When Van Gogh first began painting, he used peasants as models. He would later paint flowers, landscapes and himself, mostly because he was too poor to pay the models.

4. Van Gogh suffered from temporal lobe epilepsy, a chronic neurological condition characterized by recurrent, unprovoked seizures.

5. In a short period of ten years, Van Gogh made approximately 900 paintings.

6. During one of his seizures, Van Gogh attempted to attack his friend Paul Gauguin with an open razor. This ultimately resulted in Vincent cutting off a piece of his own ear – but not the whole ear as is often rumored.

7. Van Gogh created his most famous work The Starry Night while staying in an asylum in Saint-Remy-de-Provence, France.

8. Vincent Van Gogh visually depicted turbulence, an incredibly complex (and still unsolved) mathematical principle in several paintings during a particularly chaotic time in his life.

9. Vincent shot himself in a wheatfield in Auvers, France, but did not die until 2 days later at the age of 37. His brother Theo, at his side when he died, said that Vincent’s last words were “La tristesse durera toujours” which means “the sadness will last forever.”

10. Vincent only sold one painting during his lifetime and only became famous after his death.

Happy Birthday, Vincent van Gogh.From the TED-Ed Lesson The unexpected math behind Van Gogh’s “Starry Night” – Natalya St. Clair

Animation by Avi Ofer

In order to celebrate Pi Day, we TED-Ed nerds are bringing you 3 fun facts about our favorite irrational number!

1. Pi is infinite! To write it out, you’d begin with 3.14159 and continue on….forever! That’s why, instead of trying to write out an infinite number of digits every time, we just refer to it using the Greek letter, Pi.

2. Pi is an irrational number, or a number that can never be expressed as a ratio of 2 whole numbers.

3. Scientists have used Pi to calculate the density of our entire universe, which has infinitely less stuff in it than the total number of digits in Pi.From the TED-Ed Lesson The infinite life of pi – Reynaldo Lopes

Animation by Igor Coric

This is probably the cutest video I watched in weeks. You won’t get the answer to the question, but will get a nice explanation of why **String Theory** is useful in the way to decipher the deepest secrets of nature.

If you have one hour available, I think this lecture is a good homenage to **Joe Polchinski** who passed away a couple of days ago.

For people interested in this top theoretical physicist, check out e.g.:

– *How will Joe Polchinski be remembered?* (Quora,

– *Memories of a Theoretical Physicist* (ArXiv – PDF)

– *Joe’s Little Book of String* (KITP – PDF) – Graduate level

– *String Theory*, his famous text book (Amazon, Vol1, Vol2) –

Graduate level

**R.I.P.**

A fascinating overlap of apparently far fields, Mathematics and Biology, sometimes through Physics (see e.g. *mathematical biophysics*), sometimes directly through pure mathematics (as it happens in *statistics*, *automata theory* or *algebraic biology*, for example). I suggest this informative wiki entry as a good introduction: **Mathematical and theoretical biology**. All the info about the activities in the links included below:

The year of Mathematical Biology 2018is a joint venture of theEuropean Mathematical Society (EMS)and theEuropean Society for Mathematical and Theoretical Biology (ESMTB). The main objectives are to celebrate the huge increase and importance of applications of mathematics to biology and life sciences in the last years and to foster the feedback loop between life sciences and mathematics for years to come. Applications of mathematics in Biology are completely opening new pathways of interactions and they are a huge source of new mathematical problems.

Lava lamps. The system used by **Cloudflare** to generate random numbers used in turn to encrypt web traffic of their customers, about 10% of the Internet’s traffic.

Intrigued? See also:

- Lavarand (Wikipedia article)
- Google Patents:
*Method for seeding a pseudo-random number generator with a cryptographic hash of a digitization of a chaotic system*