Viktor Blåsjö
@viktorblasjo.bsky.social
History of mathematics.
Utrecht University: https://www.uu.nl/staff/VNEBlasjo
Podcast: https://intellectualmathematics.com/opinionated-history-of-mathematics/
Utrecht University: https://www.uu.nl/staff/VNEBlasjo
Podcast: https://intellectualmathematics.com/opinionated-history-of-mathematics/
Fact-checking Netz's mischaracterisations of Kuhn and Koyré: intellectualmathematics.com/blog/netzs-f...
November 7, 2025 at 6:04 PM
Fact-checking Netz's mischaracterisations of Kuhn and Koyré: intellectualmathematics.com/blog/netzs-f...
Drawing a circle with a rope. digi.vatlib.it/view/MSS_Vat...
November 3, 2025 at 1:45 PM
Drawing a circle with a rope. digi.vatlib.it/view/MSS_Vat...
Reposted by Viktor Blåsjö
Much of Euclid’s Elements is easily misunderstood. Some proofs seem to have logical gaps. Some constructions seem pointless, others seem needlessly convoluted.
Each of these provides a window into how the ancient Greeks thought about math and the philosophical role that geometry played.
Each of these provides a window into how the ancient Greeks thought about math and the philosophical role that geometry played.
Why ruler and compass? | Guest video by @bensyversen
YouTube video by 3Blue1Brown
youtu.be
September 18, 2025 at 2:24 PM
Much of Euclid’s Elements is easily misunderstood. Some proofs seem to have logical gaps. Some constructions seem pointless, others seem needlessly convoluted.
Each of these provides a window into how the ancient Greeks thought about math and the philosophical role that geometry played.
Each of these provides a window into how the ancient Greeks thought about math and the philosophical role that geometry played.
My new article, on why Euclid had to postulate that all right angles are equal: www.sciencedirect.com/science/arti...
There is no Euclidean proof of the fourth postulate
Gil-Férez et al. (2025) claim to prove Euclid's fourth postulate by strictly Euclidean means. In fact, however, they assume a principle that is neithe…
www.sciencedirect.com
July 3, 2025 at 7:07 PM
My new article, on why Euclid had to postulate that all right angles are equal: www.sciencedirect.com/science/arti...
Reposted by Viktor Blåsjö
Viktor Blåsjö's review of the book "Form & Number: A History of Mathematical Beauty" by Alan J. Cain, is now live at tug.org/books/review...
Book review: Form & Number: A History
of Mathematical Beauty, by Alan J. Cain
tug.org
May 10, 2025 at 7:03 PM
Viktor Blåsjö's review of the book "Form & Number: A History of Mathematical Beauty" by Alan J. Cain, is now live at tug.org/books/review...
What is mathematical beauty? tug.org/books/review...
Book review: Form & Number: A History
of Mathematical Beauty, by Alan J. Cain
tug.org
May 10, 2025 at 11:05 AM
What is mathematical beauty? tug.org/books/review...
My obituary of Henk Bos, who opened the eyes of so many of us to the history of mathematics: research-portal.uu.nl/ws/portalfil...
March 21, 2025 at 3:58 PM
My obituary of Henk Bos, who opened the eyes of so many of us to the history of mathematics: research-portal.uu.nl/ws/portalfil...
I believe Aristarchus did not make a "lousy measurement" (15:58). Rather, he deliberately underestimated the size of the sun, and showed that even in this worst-case scenario it is way bigger than the earth (i.e. heliocentrism wins). See arxiv.org/abs/2102.06595 §7.6.
New video! Terence Tao on how we measure the cosmos: youtu.be/YdOXS_9_P4U
Terence Tao on how we measure the cosmos | Part 1
YouTube video by 3Blue1Brown
youtu.be
February 8, 2025 at 9:10 PM
I believe Aristarchus did not make a "lousy measurement" (15:58). Rather, he deliberately underestimated the size of the sun, and showed that even in this worst-case scenario it is way bigger than the earth (i.e. heliocentrism wins). See arxiv.org/abs/2102.06595 §7.6.
Reposted by Viktor Blåsjö
I like this rant: I never found Gabriel's horn / Torricelli's trumpet to contradict my intuition, though it's a fun example. https://intellectualmathematics.com/blog/torricellis-trumpet-is-not-counterintuitive/
January 1, 2025 at 12:22 PM
I like this rant: I never found Gabriel's horn / Torricelli's trumpet to contradict my intuition, though it's a fun example. https://intellectualmathematics.com/blog/torricellis-trumpet-is-not-counterintuitive/
Reposted by Viktor Blåsjö
ICYMI there's a new episode of @viktorblasjo.bsky.social's podcast out this week, first new episode in over a year. A fun listen as always
Torricelli’s trumpet is not counterintuitive
There is nothing counterintuitive about an infinite shape with finite volume, contrary to the common propaganda version of the calculus trope known as Torricelli’s trumpet. Nor was this result seen as...
intellectualmathematics.com
January 1, 2025 at 10:03 PM
ICYMI there's a new episode of @viktorblasjo.bsky.social's podcast out this week, first new episode in over a year. A fun listen as always
Reposted by Viktor Blåsjö
Today I learned (ht Viktor Blasjo) how Huygens summed the reciprocals of the triangular numbers. He regrouped the series and showed that it equals the geometric series 1+1/2+1/4+... = 2, like so!
December 9, 2024 at 9:22 PM
Today I learned (ht Viktor Blasjo) how Huygens summed the reciprocals of the triangular numbers. He regrouped the series and showed that it equals the geometric series 1+1/2+1/4+... = 2, like so!
Reposted by Viktor Blåsjö
New Medieval Books: The Optics of Ibn al-Haytham Books IV-V www.medievalists.net/2024/08/new-... #books
New Medieval Books: The Optics of Ibn al-Haytham Books IV-V - Medievalists.net
A translation of a section from Ḥasan Ibn al-Haytham's work, Book of Optics, which was written between 1011 and 1021. It is a major work of scientific history, changing the way people understood eyesi...
www.medievalists.net
August 24, 2024 at 11:11 PM
New Medieval Books: The Optics of Ibn al-Haytham Books IV-V www.medievalists.net/2024/08/new-... #books
Reposted by Viktor Blåsjö
My book in the Cambridge Elements series on "Mathematical Rigour and Informal Proof" is out today! It's free to download for two weeks, so please share it widely with anyone who may be interested. 🥳🎉
www.cambridge.org/core/element...
www.cambridge.org/core/element...
Mathematical Rigour and Informal Proof
Cambridge Core - Philosophy of Science - Mathematical Rigour and Informal Proof
www.cambridge.org
March 1, 2024 at 12:22 PM
My book in the Cambridge Elements series on "Mathematical Rigour and Informal Proof" is out today! It's free to download for two weeks, so please share it widely with anyone who may be interested. 🥳🎉
www.cambridge.org/core/element...
www.cambridge.org/core/element...
Reposted by Viktor Blåsjö
🥁: Historian of mathematics, famous contrarian and "Intellectual Mathematics" podcaster @viktorblasjo.bsky.social is now on Bluesky! #histsci
January 2, 2024 at 10:49 AM
🥁: Historian of mathematics, famous contrarian and "Intellectual Mathematics" podcaster @viktorblasjo.bsky.social is now on Bluesky! #histsci