Uploaded June 2017 | Updated September 2026, 2 weeks ago
This is a corrected re-upload of a video from a couple of weeks ago. The original version contained one too many shortcut that I really should not have taken. Although only two viewers stumbled across this mess-up it really bothered me, and so here is the corrected version of the video, hopefully free of any more reupload-worthy mistakes. For those of you who already watched the previous version of this video, see whether you can figure out what required fixing :)
This video is all about convincing you that Liouville's number is really a transcendental number. I am presenting a proof for this fact that you won't find in any textbook and I am keeping my fingers crossed that people will agree that this is the most accessible proof of the transcendence of any specific number. Also part of this video is a nice way to create a clone of the real numbers using the Liouville's number as a template. This clone is a seriously paradoxical subset of the reals: it consists entirely of transcendental numbers (with one exception), just like the reals it is uncountably infinite AND of it is of measure 0, that is, it is hidden so well within the reals that in a sense it not even there.
The measure 0 extra video is at youtu.be/4ga58IP1iJU on Mathologer 2.
Liouville's original paper is here:
Liouville, J. "Sur des classes très-étendues de quantités dont la valeur n'est ni algébrique, ni même réductible à des irrationelles algébriques." J. Math. pures appl. 16, 133-142, 1851.
http://sites.mathdoc.fr/JMPA/PDF/JMPA_1851_1_16_A5_0.pdf
And if you are interested in having a look at this proof as it also appears in all the textbooks here is one possible reference:
http://people.math.sc.edu/filaseta/gradcourses/Math785/Math785Notes5.pdf
The proof that I am showing you in this video was inspired by Conway and Guy's take on the subject in their "Book of numbers". In particular, if you are familiar with this book you'll also recognise the 6th degree polynomial that I am using as one of the examples.
This week's t-shirt is from here: shirt.woot.com/offers/liars-paradox
You can download the comments of the original video as a pdf file here: qedcat.com/misc/comments.pdf.
Thank you very much for my friends Marty Ross for his feedback on a draft of this video and Danil Dmitriev for his Russian subtitles.
Enjoy!
This is a corrected re-upload of a video from a couple of weeks ago. The original version contained one too many shortcut that I really should not have taken. Although only two viewers stumbled across this mess-up it really bothered me, and so here is the corrected version of the video, hopefully free of any more reupload-worthy mistakes. For those of you who already watched the previous version of this video, see whether you can figure out what required fixing :)
This video is all about convincing you that Liouville's number is really a transcendental number. I am presenting a proof for this fact that you won't find in any textbook and I am keeping my fingers crossed that people will agree that this is the most accessible proof of the transcendence of any specific number. Also part of this video is a nice way to create a clone of the real numbers using the Liouville's number as a template. This clone is a seriously paradoxical subset of the reals: it consists entirely of transcendental numbers (with one exception), just like the reals it is uncountably infinite AND of it is of measure 0, that is, it is hidden so well within the reals that in a sense it not even there.
The measure 0 extra video is at youtu.be/4ga58IP1iJU on Mathologer 2.
Liouville's original paper is here:
Liouville, J. "Sur des classes très-étendues de quantités dont la valeur n'est ni algébrique, ni même réductible à des irrationelles algébriques." J. Math. pures appl. 16, 133-142, 1851.
http://sites.mathdoc.fr/JMPA/PDF/JMPA_1851_1_16_A5_0.pdf
And if you are interested in having a look at this proof as it also appears in all the textbooks here is one possible reference:
http://people.math.sc.edu/filaseta/gradcourses/Math785/Math785Notes5.pdf
The proof that I am showing you in this video was inspired by Conway and Guy's take on the subject in their "Book of numbers". In particular, if you are familiar with this book you'll also recognise the 6th degree polynomial that I am using as one of the examples.
This week's t-shirt is from here: shirt.woot.com/offers/liars-paradox
You can download the comments of the original video as a pdf file here: qedcat.com/misc/comments.pdf.
Thank you very much for my friends Marty Ross for his feedback on a draft of this video and Danil Dmitriev for his Russian subtitles.
Enjoy!



![How to build and solve a 4D Rubiks cubes in physical 3D (no simulator!)
I’ve been meaning to make this video about building and solving physical 4D Rubik’s cubes ever since Melinda Green sent me one of her brilliant physical 2x2x2x2s back in 2017! Why did it take so long? Well, this one was especially tricky to get right, and I think it’s probably the video that took me the longest to put together. I really hope you like this one :)
00:00 Intro
03:53 Warm-up
08:59 4d
14:13 Fancy moves
20:24 Solve
26:20 Melinda
31:27 Coding challenge
31:46 Whats next?
33:54 Gallery of animations
36:10 Thank you !
(New) Rensleys simulator of the 2d hedgehog https://renslay.itch.io/2d-hedgehog and my javascript port https://www.qedcat.com/2d_hedgehog/
Ed Collens amazing hedgehog simulator (now with full macro support, avoid Chrome browser, also see my macros for this simulator at the bottom of this blurb)
https://2x2x2x2.vercel.app/cube
Mitchell Mannings similarly amazing but quite different simulator (avoid Chrome browser)
https://rebelkeithy.github.io/TheHedgehog/
Burkards hedgehog simulator (just permutations, avoid Chrome browser)
https://www.qedcat.com/2x2x2x2%20hedgehog
Melindas 2x2x2x2 home page (go there straightaway !)
https://superliminal.com/cube/2x2x2x2/
Melindas YouTube page. Check out her 4D Twisty puzzle playlist.
https://www.youtube.com/c/melindagreen
Zasharan2 Melindas 2x2x2x2 simulator (now also with some macros for twisting corners of the 2x2x2 sides, swapping corners of the 2x2x2 sides, resolving the half-turn parity, and performing a monoflip, just in case you need them/would like to experiment)
https://zasharan2.github.io/2x2x2x2
A playlist of different ways to perform a gyro in Melindas puzzle
https://www.youtube.com/watch?v=d2Fh_1m0UVY&list=PLx1mIVtz33hJbAiFSsfsQ_IlAB1_fuAVc
Joel Karlsson animation showing the correspondence between a different unfolded version of the real 2x2x2x2 and Melindas puzzle. https://www.youtube.com/watch?v=QvhkGRUeGco
Everything about higher-dimensional twisty puzzles
https://hypercubing.xyz
MagicCube4D is a fully functional four-dimensional analog of Rubiks cube plus dozens of other beautiful 4D puzzles.
https://superliminal.com/cube/
Relevant Mathologer videos:
Cracking the 4D Rubiks Cube with simple 3D tricks (solving the 3x3x3x3 in MagicCube4D)
https://www.youtube.com/watch?v=yhPH1369OWc
Can you solve THE Klein Bottle Rubiks cube?
https://youtu.be/DvZnh7-nslo
A simple trick to design your own solutions for Rubiks cubes
https://youtu.be/-NL76uQOpI0
Hyperspeedcube, the name says it all
https://hypercubing.xyz/software/hyperspeedcube/
Piles of other simulators
https://hypercubing.xyz/software/
Grant Staten solves Melindas 2x2x2x2 in under a minute
https://www.youtube.com/watch?v=eIEu38wsjtM
The Unpopular Cuber solves the 3x3x3x3 using a simulator (the crazy action clip at the end of this video are a couple of seconds from this solve)
https://www.youtube.com/watch?v=2GPtYwmSeIU
Some mathematical articles worth checking out:
The Rubik tesseract by H. J. Kamack and T. R. Keane
https://udel.edu/~tomkeane/RubikTesseract.pdf
Rubiks Tesseract by Dan Velleman in Mathematics Magazine (1992), 65:1, 27-36. https://www.jstor.org/stable/2691357
n-dimensional sequential move puzzle https://en.wikipedia.org/wiki/N-dimensional_sequential_move_puzzle
Thank you very much to Melinda for all her help with this video. Also thank you to Vivian and Cristian from Monashs FutureLab for their help with 3d printing the connectors that hold the cubies in my hedgehog together.
Nice insight: Two swaps of the same adjacent cubies in one of the hedgehog sides results in a half-turn of the other side. Try in one of the simulators.
Music: Morning Mandolin by Chris Haugen
Enjoy!
Burkard
P.S.: Here are my macros if you want to use them in Eds hedgehog simulator (save as a .json file and import).
{
groups: [
{
name: Ungrouped,
macros: [
{
name: corner twist,
steps: Ly Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Lz Ix Lz Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ly
},
{
name: corner swap,
steps: Lz Ly Lz Lz Ix Lz Lz Ly Ix Ly Lz Lz Ix Lz Lz Ly Ix Ly Lz Lz Ix Lz Ix Lz Ix Ix Lz Lz Ly Ix Ly Lz Lz Ix Lz Lz Ly Ix Ly Lz Lz Ix Lz Lz Ly Ix Ly Lz Lz Ix Lz Ix Lz Ly Lz
},
{
name: halfturn parity,
steps: Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz
},
{
name: monoflip,
steps: Ly Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Lz Ix Lz Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ly xy Lz yx Ix Ly Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Lz Ix Lz Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Lz Ix Ly Ix xy Lz yx
}
]
}
]
} How to build and solve a 4D Rubiks cubes in physical 3D (no simulator!)](https://i.ytimg.com/vi/d-Yy-ILjM3k/mqdefault.jpg)






