Updated: 2021-Sep-25 14:17 UTC. Entries: 20. Based on tweets of Mathematicians on Twitter. Feedback: @TrueSciPhi.

Mathematicians' tweets from past 7 days most retweeted *per follower*:

1. One retweet per 13 followers:

I'm almost in awe at Rowling's confidence in herself as a writer that she would set for herself the task of explaining why the heroes of her story didn't stop the Holocaust. https://t.co/f7ukd2CPz5

— Kameryn J.W. 🦄 (@KamerynJW) September 22, 2021

2. One retweet per 23 followers:

高校数学の教科書には、「〜〜を数学的帰納法で証明せよ」という問題がある。

— Iwao KIMURA (@iwaokimura) September 23, 2021

解答例「n=1のときは明らかに成り立つ。n=kで成り立つと仮定してn=k+1で成り立たないとすると、帰納法で証明できないので、問題に反して困る。よってn=k+1でも成り立つ。帰納法により任意のnで成立する。」

3. One retweet per 27 followers:

he’s hard at work pic.twitter.com/IViDipxfoD

— frobunnius (@frobunnius) September 21, 2021

4. One retweet per 28 followers:

it wasnt a meteor that ended the reign of the dinosaurs https://t.co/su2v1AXmuF

— frobunnius (@frobunnius) September 22, 2021

5. One retweet per 32 followers:

I was on a train for the first time in ages last Sunday.

— Kit Yates (@Kit_Yates_Maths) September 18, 2021

It struck me that, in the same way we have a quiet carriage, couldn’t we have carriages for people who want to wear masks and carriages for people who don’t?

6. One retweet per 40 followers:

100,000 kids off school with confirmed or suspected covid.

— Kit Yates (@Kit_Yates_Maths) September 21, 2021

What happened to children’s education bring a top priority.

This is an abject failure of policy.

Our children deserve better.https://t.co/7dI36Zuo9X

7. One retweet per 55 followers:

CHARTS OF LARGE CARDINALS

— Andrés E. Caicedo (@AndresECaicedo1) September 23, 2021

A Thread

The ladder of large cardinals is ubiquitous in modern work in set theory, with the consistency strength of many statements being calibrated by its rungs. Here I collect published charts of fragments of the hierarchy.

1/

8. One retweet per 58 followers:

We are creating a Data Science + Mathematics degree/major and I am pleased that it requires two ethics courses.

— Kay L. Kirkpatrick \🥄\ (@kay314159) September 22, 2021

9. One retweet per 59 followers:

It absolutely beggars belief that some U.K. scientists are still gaslighting us with “schools just reflect community transmission” BS.

— Kit Yates (@Kit_Yates_Maths) September 23, 2021

Rates in older people are typically going down, but in school-age children they are rising.

How do you square that? pic.twitter.com/FYKcpy8B5r

10. One retweet per 64 followers:

There are simple things we could have been doing to prevent kids catching covid in schools.

— Kit Yates (@Kit_Yates_Maths) September 22, 2021

Masks, isolation, efficient contact tracing, bubbles, ventilation, vaccination.

Where are the CO2 monitors that were promised? Not in my kids’ school for sure.

11. One retweet per 70 followers:

When we teach calculus, we *at once* introduce (at least) 5 new concepts (limits, tangent lines/slopes, derivatives, area, integrals), all intertwined together. There's no reason for this! Most of these ideas can be introduced *much* earlier, one at a time. Here's an attempt at.. pic.twitter.com/mWed3rS9sn

— Alex Kontorovich (@AlexKontorovich) September 23, 2021

12. One retweet per 72 followers:

Know any new(ish) faculty in the math. sciences who want great professional development and a supportive community? #MAAProjectNExT applications are open! Anyone already in a position should apply by Oct. 15th. @maanow @amermathsoc @TheSIAMNews @tpsemath https://t.co/uHUoTzwJXm pic.twitter.com/sz1b8Sjvtk

— Dave Kung (龚仲孝) (@dtkung) September 23, 2021

13. One retweet per 78 followers:

Just saying “we should treat covid like any other respiratory virus” won’t magically make covid just like any other respiratory virus.

— Kit Yates (@Kit_Yates_Maths) September 24, 2021

14. One retweet per 80 followers:

hanging out with my little gamer pic.twitter.com/xtaqpo2AKE

— frobunnius (@frobunnius) September 19, 2021

15. One retweet per 82 followers:

just came out from nap time pic.twitter.com/uz4VyiX7Qg

— frobunnius (@frobunnius) September 18, 2021

16. One retweet per 82 followers:

he looks like a dignified statesman pic.twitter.com/MpBMPkOg1O

— frobunnius (@frobunnius) September 20, 2021

17. One retweet per 82 followers:

Oh good everything’s back to normal. Nothing to see here. https://t.co/2nXAwmUXnt

— Kit Yates (@Kit_Yates_Maths) September 23, 2021

18. One retweet per 89 followers:

Some videogames pretend to be spherical, but they are not! They are just the old flat plane but with stereographic projection. Easy to tell because we cannot have a hex or square grid on a sphere (a beautiful math fact). (1/5) pic.twitter.com/xtDGDJXkko

— Zeno Rogue (@ZenoRogue) September 18, 2021

19. One retweet per 91 followers:

Question: Why do we attribute calculus to Newton and Leibniz? For instance the fundamental theorem of calculus was already known to Isaac Barrow (Newton's teacher). Other concepts date back even earlier, e.g. in ancient Greece and India there were calculus concepts already.

— Anton Hilado (@anton_hilado) September 21, 2021

20. One retweet per 97 followers:

"Mathematics is the ultimate language! It is cold and concrete and precise!"

— Anton Hilado (@anton_hilado) September 23, 2021

Meanwhile mathematicians: "If we assume this conjecture we don't know how to prove, we then see that this is greater than or equal to this, up to some fudge factors. The proof is easy to see."