Andrew Stacey
@mathforge.org
Mathematician: formerly academic (differential topology), currently educational (Head of Department in a UK secondary school).
Side interests in Maths & Programming & Art.
Website: https://loopspace.mathforge.org
Side interests in Maths & Programming & Art.
Website: https://loopspace.mathforge.org
Had a go at the great-granny knot in TikZ, @cubesart.bsky.social
February 9, 2026 at 9:17 PM
Had a go at the great-granny knot in TikZ, @cubesart.bsky.social
And in the second semester we will discuss whether our problem-2-category should be lax.
problem set? i'm sorry but we do 21st century mathematics in this classroom. here's your problem category
February 9, 2026 at 5:58 PM
And in the second semester we will discuss whether our problem-2-category should be lax.
Reposted by Andrew Stacey
A fun Sunday activity: designing and printing some more impossible cylinders. Here is one I call “Division by Zero.” 🤣
February 8, 2026 at 7:55 PM
A fun Sunday activity: designing and printing some more impossible cylinders. Here is one I call “Division by Zero.” 🤣
Reposted by Andrew Stacey
username checks out
A fun Sunday activity: designing and printing some more impossible cylinders. Here is one I call “Division by Zero.” 🤣
February 8, 2026 at 8:03 PM
username checks out
I usually see these reposted by a mathematician (you know who you are!) with a comment along the lines of "and also in mathematics". So I fully misread that first phrase!
In my defence, up to the first comma then "and also in math" works pretty well.
#mathsky #ITeachMaths
In my defence, up to the first comma then "and also in math" works pretty well.
#mathsky #ITeachMaths
Unsolicited writing advice, no. 8565:
No character can represent all of a group, an ethnicity, a culture. Every character is a complex result of upbringing, race, sexualtity, class, culture, age and many other factors. If you just write a character as "gay", or "Black", you're creating a stereotype.
No character can represent all of a group, an ethnicity, a culture. Every character is a complex result of upbringing, race, sexualtity, class, culture, age and many other factors. If you just write a character as "gay", or "Black", you're creating a stereotype.
February 8, 2026 at 5:27 PM
I usually see these reposted by a mathematician (you know who you are!) with a comment along the lines of "and also in mathematics". So I fully misread that first phrase!
In my defence, up to the first comma then "and also in math" works pretty well.
#mathsky #ITeachMaths
In my defence, up to the first comma then "and also in math" works pretty well.
#mathsky #ITeachMaths
Two regular hexagons inside a rectangle. What fraction of the rectangle is shaded?
I found this #geometrypuzzle in my sketchbook - I drew it last June, but I’m pretty sure I never got round to posting it. Better late than never!
I found this #geometrypuzzle in my sketchbook - I drew it last June, but I’m pretty sure I never got round to posting it. Better late than never!
February 7, 2026 at 10:37 AM
Made a stab at explaining intersecting planes in Y12 Further Maths, wasn't sure it was all that clear, then turned round to see that my students had made their own version.
#MathsToday
#MathsToday
February 6, 2026 at 10:17 PM
Made a stab at explaining intersecting planes in Y12 Further Maths, wasn't sure it was all that clear, then turned round to see that my students had made their own version.
#MathsToday
#MathsToday
Wasn't someone looking for examples of graphs for #CoreMaths recently?
February 4, 2026 at 9:06 PM
Wasn't someone looking for examples of graphs for #CoreMaths recently?
Reposted by Andrew Stacey
And it shows some obvious ways in which TV shows can do harm - both to individuals, many of whom were hoping this would finally 'prove' they were smart, and to society, when the myths are upheld by this kind of lazy and thoughtless design.
February 2, 2026 at 4:42 PM
And it shows some obvious ways in which TV shows can do harm - both to individuals, many of whom were hoping this would finally 'prove' they were smart, and to society, when the myths are upheld by this kind of lazy and thoughtless design.
Reposted by Andrew Stacey
Did you catch the new Channel 4 show #SecretGenius last night?
Alan Carr &Susie Dent teamed up with #Mensa to set puzzles for participants. The show helped to illuminate some of the issues with discrimination/inequality that are surfaced by trying to ‘measure’ intelligence. Some thoughts..
Alan Carr &Susie Dent teamed up with #Mensa to set puzzles for participants. The show helped to illuminate some of the issues with discrimination/inequality that are surfaced by trying to ‘measure’ intelligence. Some thoughts..
a man wearing glasses is holding a cup of coffee and laughing .
ALT: a man wearing glasses is holding a cup of coffee and laughing .
media.tenor.com
February 2, 2026 at 4:37 PM
Did you catch the new Channel 4 show #SecretGenius last night?
Alan Carr &Susie Dent teamed up with #Mensa to set puzzles for participants. The show helped to illuminate some of the issues with discrimination/inequality that are surfaced by trying to ‘measure’ intelligence. Some thoughts..
Alan Carr &Susie Dent teamed up with #Mensa to set puzzles for participants. The show helped to illuminate some of the issues with discrimination/inequality that are surfaced by trying to ‘measure’ intelligence. Some thoughts..
Reposted by Andrew Stacey
Still in ratio table mode. I remembered this @mathforge.org ;-)
January 30, 2026 at 8:44 PM
Still in ratio table mode. I remembered this @mathforge.org ;-)
My instantaneous reaction:
a) this is so cool
b) can I get that as a poster?
c) was that drawn using the knots package in TikZ?
I'll bet that many folks share (a) and (b), but (c) might be a bit niche ...
#mathsky #UKMathsChat #ITeachMaths
a) this is so cool
b) can I get that as a poster?
c) was that drawn using the knots package in TikZ?
I'll bet that many folks share (a) and (b), but (c) might be a bit niche ...
#mathsky #UKMathsChat #ITeachMaths
Project update:
Tanya and I have been writing up the results of this project and we've realized that all of the knots in this class of patterns are at most 6 "tangle moves" from each other and at most three tangle moves from what we're calling the "great-great-granny knot" (see alt text).
Tanya and I have been writing up the results of this project and we've realized that all of the knots in this class of patterns are at most 6 "tangle moves" from each other and at most three tangle moves from what we're calling the "great-great-granny knot" (see alt text).
January 30, 2026 at 7:03 PM
My instantaneous reaction:
a) this is so cool
b) can I get that as a poster?
c) was that drawn using the knots package in TikZ?
I'll bet that many folks share (a) and (b), but (c) might be a bit niche ...
#mathsky #UKMathsChat #ITeachMaths
a) this is so cool
b) can I get that as a poster?
c) was that drawn using the knots package in TikZ?
I'll bet that many folks share (a) and (b), but (c) might be a bit niche ...
#mathsky #UKMathsChat #ITeachMaths
So I'm growing increasingly in favour of "proof by generic example" as a teaching tool, rather than proof by algebraic manipulation. I think it makes the result more concrete.
#ALevelMaths #UKMathsChat #MathsToday
#ALevelMaths #UKMathsChat #MathsToday
January 28, 2026 at 8:18 PM
So I'm growing increasingly in favour of "proof by generic example" as a teaching tool, rather than proof by algebraic manipulation. I think it makes the result more concrete.
#ALevelMaths #UKMathsChat #MathsToday
#ALevelMaths #UKMathsChat #MathsToday
One of my students brought this to my attention:
www.cipherchallenge.org/111483-2/
Fame at last!
To clarify, I wrote all the solutions in my collection.
@cipher-challenge.bsky.social
www.cipherchallenge.org/111483-2/
Fame at last!
To clarify, I wrote all the solutions in my collection.
@cipher-challenge.bsky.social
Net loss - National Cipher Challenge 2025
Here is the solution to last week’s Sunday Puzzle as collated by Andrew Stacey from MathForge https://notes.mathforge.org/notes/published/four+squares+inside+a+rectangle+solution I am not sure if Andr...
www.cipherchallenge.org
January 26, 2026 at 10:26 PM
One of my students brought this to my attention:
www.cipherchallenge.org/111483-2/
Fame at last!
To clarify, I wrote all the solutions in my collection.
@cipher-challenge.bsky.social
www.cipherchallenge.org/111483-2/
Fame at last!
To clarify, I wrote all the solutions in my collection.
@cipher-challenge.bsky.social
Reposted by Andrew Stacey
New practice grid on rearranging scientific formulae added to the website this morning. Download it and much more at www.draustinmaths.com
#UKMathsChat #MathsToday
#UKMathsChat #MathsToday
January 25, 2026 at 11:01 AM
New practice grid on rearranging scientific formulae added to the website this morning. Download it and much more at www.draustinmaths.com
#UKMathsChat #MathsToday
#UKMathsChat #MathsToday
Teaching matrix mult, noticed that I mentally pick up the rows in the first and align them with the columns in the second before multiplying and adding, realised that that is actually the wrong way round: it makes more sense to pick up the columns in the second and align with the rows in the first.
January 24, 2026 at 12:34 PM
Teaching matrix mult, noticed that I mentally pick up the rows in the first and align them with the columns in the second before multiplying and adding, realised that that is actually the wrong way round: it makes more sense to pick up the columns in the second and align with the rows in the first.
January 24, 2026 at 12:34 PM
Teaching matrix mult, noticed that I mentally pick up the rows in the first and align them with the columns in the second before multiplying and adding, realised that that is actually the wrong way round: it makes more sense to pick up the columns in the second and align with the rows in the first.
But the trolls in Norway are so friendly now, and hardly ever eat people. Even if they got trip-trapity over their rickety-rackety bridge.
January 24, 2026 at 10:23 AM
But the trolls in Norway are so friendly now, and hardly ever eat people. Even if they got trip-trapity over their rickety-rackety bridge.
Eventually, everything ends up as an n-category.
January 23, 2026 at 10:14 PM
Eventually, everything ends up as an n-category.
Reposted by Andrew Stacey
What bothers me about Archimedean Solids is that I can't visualize the part that was removed from the Platonic parent shape. Here's a solution for the cuboctahedron: build the Platonic Solid parent cube around it and notice the shape of the negative space+
January 22, 2026 at 3:15 PM
What bothers me about Archimedean Solids is that I can't visualize the part that was removed from the Platonic parent shape. Here's a solution for the cuboctahedron: build the Platonic Solid parent cube around it and notice the shape of the negative space+
Trying to figure out which LaTeX package this is from.
January 20, 2026 at 9:26 PM
Trying to figure out which LaTeX package this is from.
In #MathsToday, picking off the little topics of Further Maths with Y13. Started with mean functions, ended with improper integrals. Last example was integrating 1/x from -1 to 1 so I got to finish the lesson with the immortal line:
"The limit does not exist"
#ALevelMaths #UKMathsChat
"The limit does not exist"
#ALevelMaths #UKMathsChat
January 20, 2026 at 8:48 PM
In #MathsToday, picking off the little topics of Further Maths with Y13. Started with mean functions, ended with improper integrals. Last example was integrating 1/x from -1 to 1 so I got to finish the lesson with the immortal line:
"The limit does not exist"
#ALevelMaths #UKMathsChat
"The limit does not exist"
#ALevelMaths #UKMathsChat
Reposted by Andrew Stacey
I am all for revolution.
Rip it up.
Start again.
Two GCSEs. One compulsory numeracy, one optional.
We won’t get it but it’s the biggest miss if we don’t.
I’m sick of killing kids souls with maths they will never understand. I didn’t come into teaching to make people feel stupid
Rant ends.
Rip it up.
Start again.
Two GCSEs. One compulsory numeracy, one optional.
We won’t get it but it’s the biggest miss if we don’t.
I’m sick of killing kids souls with maths they will never understand. I didn’t come into teaching to make people feel stupid
Rant ends.
January 19, 2026 at 6:59 PM
I am all for revolution.
Rip it up.
Start again.
Two GCSEs. One compulsory numeracy, one optional.
We won’t get it but it’s the biggest miss if we don’t.
I’m sick of killing kids souls with maths they will never understand. I didn’t come into teaching to make people feel stupid
Rant ends.
Rip it up.
Start again.
Two GCSEs. One compulsory numeracy, one optional.
We won’t get it but it’s the biggest miss if we don’t.
I’m sick of killing kids souls with maths they will never understand. I didn’t come into teaching to make people feel stupid
Rant ends.
The MAT is dead, long live the TMUA.
(Which always sounds in my head like "The Metropolitan Transit Authority")
#UKMathsChat #ALevelMaths
(Which always sounds in my head like "The Metropolitan Transit Authority")
#UKMathsChat #ALevelMaths
Big change from Oxford University!
For 2027 entry onwards they will use the TMUA (October sitting) for maths and not the MAT.
I am off to update SUMS magazine for current Year 12 students 😂
@meimaths.bsky.social
www.ox.ac.uk/admissions/u...
For 2027 entry onwards they will use the TMUA (October sitting) for maths and not the MAT.
I am off to update SUMS magazine for current Year 12 students 😂
@meimaths.bsky.social
www.ox.ac.uk/admissions/u...
January 19, 2026 at 6:41 PM
The MAT is dead, long live the TMUA.
(Which always sounds in my head like "The Metropolitan Transit Authority")
#UKMathsChat #ALevelMaths
(Which always sounds in my head like "The Metropolitan Transit Authority")
#UKMathsChat #ALevelMaths