j_bertolotti

Associated Professor of Physics at the University of Exeter.
Scientific visualizations (grouped under the hastag #PhysicsFactlet).
He/lui/on. All opinions are my own fault.

Public Key

npub1a4ywuu668ac6558wk53ng6nsykluuag9zpwm64nhgmjpeucc5n6skrazsc

NIP-05 Address

j_bertolotti@mathstodon-xyz.mostr.pub

Profile Code

nprofile1qqsw6j8wwddr7ud22rht2ge5dfczt07ww5z3qhda2em5dequ7vv2fag7j6eqh

Author Public Key

npub1a4ywuu668ac6558wk53ng6nsykluuag9zpwm64nhgmjpeucc5n6skrazsc

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Last Notes

2025-01-24 11:10:38

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@nprofile…yu7x
https://media.mathstodon.xyz/media_attachments/files/113/883/018/208/883/008/original/80b43cc30b979be6.png

2025-01-13 16:35:33

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@nprofile…dp56 I tried both, but couldn't come up with a simple formula where the frequency was position-dependent, the line was nice (continuous and infinitely differentiable) and didn't take forever to compute 😉

2025-01-13 09:45:35

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@nprofile…dp56 This looks a LOT better than my rudimentary "sinusoidal Mario". 😃
Do you have a legible code I can take a peek at for inspiration?
https://media.mathstodon.xyz/media_attachments/files/113/820/394/283/285/852/original/b7e0a8d340328ab1.mp4

2025-01-13 07:45:27

In a rational world insurance companies would be at the frontline, lobbying for pro-environmental policies to minimise the number of people dying, getting sick or having their house burnt down.Just to avoid having to pay.
And yet...

2025-01-09 11:21:49

#PhysicsJournalClub
"Blending Optimal Control and Biologically Plausible Learning for Noise-Robust Physical Neural Networks"
by S. Sunada et. al.
Phys. Rev. Lett. 134, 017301 (2025)
I am not a big fan of generative AI, especially in the form it is sold and advertised today, bvut I think that there is a lot of cool and potentially useful research been done in the field of Machine Learning. In particular I am very interested in approaches where most of the heavy lifting is left to Physics, i.e. the Physical system naturally does stuff, and you exploit it for Machine learning, instead of spending a ton of resources and energy to create and manipulate the whole neural network.
In this paper the authors borrow ideas from different sub-fields to put together a training method that doesn't really need to know much about what the Physical system is actually doing, and doesn't need an accurate control of the Physical system either.
I admit I understand no more than 10% of what they say (Machine Learning is definitively not my field), but it looks interesting and promising!
https://doi.org/10.1103/PhysRevLett.134.017301
#MachineLearning #Physics

2025-01-07 17:20:42

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@nprofile…36ju This is not very different from what any EU citizen has to do to enter the US for a short visit.

2025-01-07 10:17:47

#PhysicsJournalClub
"Testing the necessity of complex numbers in traditional quantum theory with quantum computers"
by Jarrett L. Lancaster and Nicholas M. Palladino
Am. J. Phys. 93, 110 (2025)
In classical electrodynamics the use of complex numbers is only due to to its convenience for calculations. Nobody wants to remember all those pesky trigonometric identities, so we use complex numbers to simplify calculations and take the real part at the end. You need to be a bit careful when calculating stuff like the Poynting vector, but this is well addressed ion any half-decent undergrad-level textbook.
But for quantum mechanics the problem is less obvious. On one hand we only ever measure real quantities, but on the other hand the imaginary unit appears explicitly in the Schrödinger equation, and no textbook I am aware of ever even mention the possibility that quantum numbers might be just a calculation convenience like it is in classical electrodynamics.
The question is subtle enough that you are going to find no shortage of well-read Physicists claiming that it is "obvious" that complex numbers are necessary for quantum mechanics, or that it is "obvious" that you could just use real numbers if you wanted.
This paper makes a pretty good job at explaining the problem, going through some of the history and explicit calculations, up to constructing explicitly a real-valued version of QM.
The second part, where they make an "experiment" on a IBM cloud quantum computer is (imho) less interesting, and their conclusion that you need indeed complex numbers not really supported by the evidence, but your mileage might vary 🙂
https://pubs.aip.org/aapt/ajp/article/93/1/110/3327097/Testing-the-necessity-of-complex-numbers-in
#Physics #QuantumMechanics #ITeachPhysics

2025-01-06 19:21:26

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@nprofile…fa4k I am missing the experimental evidence of black holes somewhere in that list. Not sure where one would put the exact date, but when I was a student it was still not obvious at all that black holes were real 🙂

2025-01-06 12:44:03

#PhysicsFactlet
Schematic of the epicycle model, as requested by @nprofile…fa4k (see https://mathstodon.xyz/@johncarlosbaez/113652794327730499 for his thread on the topic).
Apart from having (hopefully) more colorblind-friendly colors, this one is in the #PublicDomain instead of being copyrighted.
#Physics #Astronomy
https://media.mathstodon.xyz/media_attachments/files/113/781/438/824/005/821/original/f1bd725d46a98b4c.mp4

2025-01-01 12:54:07

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@nprofile…yu7x We finally got the killer application for LLMs! 🥳

2025-01-01 12:25:11

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@nprofile…yu7x What I am reading is that there is a small but nonzero chance of every day being Saturday/Sunday!

2024-12-31 20:51:13

Yearly repost.
Happy new year!
https://media.mathstodon.xyz/media_attachments/files/113/749/384/904/279/638/original/b0fab2a802e22787.png

2024-12-21 15:21:31

I recently started replaying Katamari Damacy (my 6y/o finds it hilarious) and I have to say I didn't remember the soundtrack to be so good!
(I don't understand a single word of Japanese, so I have no clue what the lyrics say, and it is probably better this way.)
#videogames #katamari

2024-12-13 08:15:43

Does anybody knows where I can find reliable numbers on how mouch energy (and/or CO2 equivalent) a generative AI like chatgpt consumes per prompt?

2024-12-07 18:57:02

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@nprofile…yu7x The "science" feed is largely pointless. The "Physics" feed is marginally better. Still, nothing beats curating who you are following and looking at the feeda once in a while to check if there is someone there worth following you didn't know about.

2024-12-02 17:41:36

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Scientist types as #DnD classes (part 2):
Paladin: Science is important, you get it. But why nobody else seems to care about the ethical implications of what they are doing? Things are bad, there are so many injustices around, and nobody seems to care. It is maddening!
Bard: You love giving talks (the bigger the audience the better) and the wide eyes of kids during your demonstrations. Everything else is secondary and you are happy somebody else is doing all the heavy lifting in the lab so you can talk about it.
Monk: All those tools are great and useful, but they are also a crutch, separating you from the essence of the problem and preventing true understanding. Nothing beats getting your hands dirty if you want to reach true knowledge.

2024-12-02 09:59:07

Scientist types as #DnD classes:
Fighter: The best way to approach any problem is to do an experiment first and ask questions later (assuming there is any question left to ask). Very high volume of fire, but needs a constant stream of money to pay for fancier and fancier equipment.
Wizard: You dive deep into the mathematical foundations of your discipline. So deep you lost contact with reality a long time ago, but it doesn't matter, as you only speak with other wizards, who also lost contact with reality a long time ago.
Cleric: Never the first nor the last author. Your name is always somewhere in the middle, like an afterthought. But it is to you that the rest of the party always comes back to for help every single time they get in troubles.
Druid: You really care about the impact you make, and find the mathematical formalism at the foundation of your discipline a waste of time. So you developed a more intuitive approach, and rely a lot on your gut feelings.
Sorcerer: You are naturally gifted, and thus you never had to really study to be successful at what you do. You are a raising star, but true wizards look down on you as a shallow amateur (while at the same time envying you).
Thief: You are somewhere. Everybody knows that. But no one seems to be able to say where or doing what. Officially you are working for the good of the collaboration, and since everything seems to be working out everyone assumes you are doing your part.
Warlock: You are not as gifted as a Sorcerer, nor you put as much effort in as a Wizard. What you have is an extremely powerful patron, who grants you visibility, and the money you need to carry out your research. All for the small price of your soul.

2024-12-01 21:45:43

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@nprofile…fa4k I assume you know @nprofile…kppt and his blog (in particular the series "From τὰ φυσικά to physics": https://thonyc.wordpress.com/from-%cf%84%e1%bd%b0-%cf%86%cf%85%cf%83%ce%b9%ce%ba%ce%ac-ta-physika-to-physics/ )

2024-11-27 17:29:27

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@nprofile…ucsf
Any hack that works will be, sooner or later, formalized, given a name and rise to "method" status.
@nprofile…j07c @nprofile…dpz7

2024-11-27 11:10:51

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@nprofile…yu7x That smells of sunk cost fallacy 😜

2024-11-27 10:53:29

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@nprofile…yu7x Not your point, but t a certain point you will stop seeing them, as all the light they reflect/emit will be redshifted out of the visible range 🙂

2024-11-26 20:13:57

"Zoom is now an AI-first work platform"
Does anybody know of a half-decent videocall app that is not infested by AI? I need one.
https://www.theverge.com/2024/11/25/24305942/zoom-communications-rename-ai-first-company

2024-11-24 16:12:17

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@nprofile…yu7x @nprofile…e5g0 @nprofile…fa4k @nprofile…cnse @nprofile…j7pr
This whole thread is a beautiful representation of the best social media have to offer in terms of scientific discussion.
Thank you to all the people involved, I love it! 🤩

2024-11-22 10:08:08

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@nprofile…e5g0
As far as I understand GR, even long before you actually arrive at the proper horizon things will get very dark, as only the light moving in a narrower and narrower cone will be able to escape.
@nprofile…fa4k @nprofile…j7pr

2024-11-14 15:30:54

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@nprofile…vrgz To be on the safe side, send the homework to the prof together with the screenshot, so you can truthfully claim you did everything you could.

2024-11-14 07:59:44

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@nprofile…gx3z
Raccontamela meglio questa, che non la conosco.
@nprofile…v78a

2024-11-07 17:08:56

#PhysicsFactlet
Not a great animation, but I made it for a lecture, so I am sharing it 😃
Electric (red line) and magnetic (black lines) fields of the TE₁,₁ mode propagating in a rectangular waveguide.
https://media.mathstodon.xyz/media_attachments/files/113/442/792/383/115/367/original/b39316eccad673f1.mp4

2024-11-06 15:45:38

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@npub19qm…sn8k A felony is only a felony if you are poor.

2024-11-06 07:58:34

One day we will have to face the fact that a whole lot of people actually really like the idea of fascism.
And no, I have no idea if anything can be done about it.

2024-10-17 15:24:30

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@npub1c9m…9xjd All the "repeated things that were just untrue about the relationship between DM and player" were likely true when this was written (especially for the intended target audience, who was very used to wargames).

2024-10-16 10:50:09

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@npub1ky2…ghvc I 'd argue that the half-way point when arguing with a flat-earther is a curved surface like a paraboloid.

2024-10-01 07:07:28

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@npub1ky2…ghvc Whoever told you as a kid that you can't gain superpowers just lacked imagination 😉

2024-09-27 08:41:58

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@npub1c4s…aqv4 Physicists "put things into formulas" all the time. That is not the problem.
We just shiver in horror at the thought of having to parse something written in "definition, lemma, lemma, theorem, corollary" form 😉

2024-09-19 18:11:35

My main problem with the Copenhagen interpretation of #QuantumMechanics is that, if you ask 10 Physicists what the interpretation actually is, you are going to get 11 different (and largely mutually exclusive) answers. #Physics

2024-09-18 18:35:28

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@npub1c4s…aqv4 Not an answer to your question (apologies) but... who asks professional copy-editing for a master thesis? 😲

2024-09-18 09:11:07

#PhysicsFactlet
Game of life, played on a Klein bottle (still very much a work in progress)
#ITeachMath #ITeachPhysics
https://media.mathstodon.xyz/media_attachments/files/113/157/771/803/076/458/original/c050450a911b3cf3.mp4

2024-09-12 12:26:19

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@npub1t76…4l63 I don't watch a lot of anime, but whrn I watch some I do it dubbed, as the lip sinc is less precise anyway.

2024-09-02 10:25:50

Currently preparing a 90min tutorial about scientific animations for #EOSAM next week.
I really hope that people will ask a lot of questions / make a lot of comments, because if I have to fill 90min with animations, the presentation file will be huge! 😅
https://www.europeanoptics.org/pages/events/eosam-2024/program/tutorials-1698149154.html

2024-08-29 08:17:47

Dear editors of academic journals, please repeat with me: "Asking someone to create an account on your system, just for the privilege of doing unpaid work for you (i.e. review a paper) is bad, and you should feel bad."
#Academia #AcademicJournal #PeerReview

2024-08-26 10:22:05

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@npub1knz…c73p On the other hand, you can do statistical mechanics of classical electrodynamic waves, and it is a fun topic in of itself 🙂

2024-08-26 08:49:46

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@npub1knz…c73p I like to call it a "wave" 😉

2024-08-26 08:32:03

Dear AAA game developers: what about allowing us ageing players to increase the UI font size?

2024-08-11 13:23:38

Watching a ton of #Godot tutorials made me realize that I will never be able to make a game (and gave me a new level of respect for those who are able to). But it also made me realize that I would really like to go back to making "Create scientific animations with #Mathematica" videos.
If only I had the mental space... 😞

2024-08-09 09:40:46

Dear digital artists: just out of curiosity, what would be the rough price of a 30-40 frames of animation of a stickman?
Not sure at all I really need it, but wondering what kind of money we are talking about.
#pixelart

2024-08-05 08:44:38

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@npub1knz…c73p I really hope students in the UK understand "sinusoidal", because it is how I call them during my lectures 🤣
(Straight from the Italian "sinusoide")

2024-08-05 07:52:08

#PhysicsFactlet
Temporal coherence can be a bit confusing the first time you encounter it, so I made a small animation that might help teachers to explain it to students.
#ITeachPhysics #Optics #Physics
https://media.mathstodon.xyz/media_attachments/files/112/908/307/324/990/564/original/3ff0d7abd5eb1a5b.mp4

2024-08-02 13:33:21

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@npub1knz…c73p Similar style to Aeon Flux, but instead of being a sequence of mostly disconnected shorts, it tells the (obviously VERY modified) story of Alexander the Great. An absolute masterpiece.

2024-08-02 13:21:39

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@npub1knz…c73p I love Aeon Flux, but I love Reign: The Conqueror even more. It was so good!

2024-07-31 13:00:30

EXTREMELY naive question (I have no experience and likely none of the required technical skills): how hard/expensive would it be to host a #PeerTube instance for scientific talks? Any legal headache, beside getting people authorization?

2024-07-24 14:30:05

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@npub1knz…c73p Will play with it tomorrow 🙂

2024-07-24 13:26:27

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@npub1knz…c73p Me too, and I have already waited 5 years waiting for it (and nothing happened in this space).

2024-07-17 10:20:25

#PhysicsFactlet
If you ever studied any Physics in school you probably know that the trajectory of an object thrown in a uniform gravitational field will be a parabola.
But if the drag (e.g. due to the atmosphere) is not negligible, the trajectory will be much more skewed, and it will fall almost vertically after reaching its maximum height.
#Physics #ITeachPhysics
https://media.mathstodon.xyz/media_attachments/files/112/801/321/308/356/559/original/29a465550a69ee36.mp4

2024-07-10 14:24:03

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@npub1pqp…e753 Made tons of them throught the years. What are you interested in specifically?

2024-07-08 09:01:24

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@npub1c0f…mp03 I'd like to hear the contorted chain of reasoning that led someone argue that Sweden have low taxes, France (especially Paris, as it is in the picture) has big houses, and Italy has high wages.

2024-07-07 16:18:58

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@npub1knz…c73p Have long train trip tomorrow. Will try to read the article and will probably come up with questions.

2024-07-07 15:00:40

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@npub1knz…c73p I hereby propose a collaboration to visualize these mechanical models to explain where they come from and how they connect to the more famous equations 😉

2024-07-05 13:30:15

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@npub1knz…c73p methanol and hexane. Simplest, not overly dangerous mixture we found in the literature when looking for a nice Friday-afternoon experiment to run

2024-07-05 08:28:54

In order of total number of votes:
Labour: 9.6M
Conservative: 6.7M
Reform: 4M
LibDem: 3.5M
Green: 1.9M
SNP: 0.7M
Independent: 0.6M
(Everybody else seems to be below 0.2M)
And now for the depressing thought: Reform is the 3rd party by number of votes. It seems the UK is well in line to follow exactly the same pattern as most of Europe did in the past decade, and see the far-right swallow the center-right, with a very weak center-left unable to stop them winning the next elections.

2024-07-03 11:52:34

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@npub1knz…c73p Great! Let me know when you plan to take a trip in this general direction and we can arrange your visit!

2024-07-03 11:14:08

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@npub1knz…c73p How willing are you to travel to south-west England to come here to give a talk? 😃

2024-06-26 13:12:19

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@npub1knz…c73p Not exactly what you are looking for, but something like \addcontentsline might be going in the right direction.

2024-06-18 08:41:09

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@npub1knz…c73p If you ever need help with figures (for the "Lectures on Classical Mechanics" one), you only need to ask 😉

2024-06-14 18:07:50

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@npub1skv…aky3 Why use hares and lynxes when the original model was developed to describe fishes (+fishing)? 🤔

2024-06-14 06:48:17

[PhD position, short deadline]
If you are interested in doing a PhD on #OpticalComputing and #MachineLearning, me and MickaelMounaix have now a open position!
Apply or contact us for more info.
Boost appreciated for reach.
https://scholarships.uq.edu.au/scholarship/quex-phd-scholarship

2024-05-27 14:29:48

#PhysicsFactlet
The human eyes have "only" 3 different colour receptors, so multiple spectra can be perceived as the same colour.
(And this without considering all the ways the signal is processed before you actually "see" it.)
#Optics #Colour #Color #Vision
https://media.mathstodon.xyz/media_attachments/files/112/513/522/771/769/803/original/9295946366e480c0.mp4

2024-05-04 10:40:02

Keeping in mind I don't really have the time or mental space to truly learn it, and I definitively don't have the skills necessary to actually make a game: any advice for a #Godot beginner tutorial?

2024-05-02 14:20:52

This one is way above my level, but I'd love to hear the opinion of @npub1knz…c73p 🙂
https://arxiv.org/abs/2405.00071

2024-04-02 13:30:31

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@npub1ky2…ghvc Agreed in principle, but if you take the classical limit and you end up with photons in your theory, something has gone badly wrong 😉

2024-02-27 11:04:15

Find a job you love and you will realize you actually love only a small fraction of it, while most of your time is spent doing the parts you don't like at all.

2024-01-22 11:33:44

Listening to R.E.M. while marking exams, after I haven't listened to them in years.
And asking myself why I haven't listened to them in years.

2024-01-04 14:28:08

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@npub16nf…q6as
Have been preaching the same (mostly from the perspective of Physics) since forever
https://www.nature.com/articles/s41567-019-0625-2
@npub1g8r…r5v6

2023-12-04 18:22:47

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@npub1te7…3dzs The article begins by saying the paper has been published in PRX, but the link at the end is to a paper in Nature Comm. 🤔

2023-11-22 15:04:32

#PostdocJobs
If you are interested (or know anyone who might be) to work with me on optical computing, and have experience with fs lasers, take a look at https://jobs.exeter.ac.uk/hrpr_webrecruitment/wrd/run/ETREC107GF.open?VACANCY_ID=818524h2kW&WVID=3817591jNg
(and contact me!)
#Optics #Physics

2023-11-17 15:59:50

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@npub178r…qekt Naive question from someone who understand optics but not photography: what is the purpose of the polarizer here?

2023-10-25 10:41:13

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@npub1sdk…0kgj Agreed. But the whole point of GURPS is that, while you have options for everything, you only really need a small subset of it for your specific campaign. Who cares about magic if you are running a cyberpunk adventure? Who cares about vehicle combat if you are running a fantasy adventure?
Take what it is useful to you, and leave the rest for when you will play in a totally different setting.
(And it helps that all those rules actually make sense together, so switching genre requires only minor adjustments.)

2023-10-25 06:48:08

One of my most controversial opinions is probably that #GURPS is actually easier (and less crunchy) to run than #DnD.
#ttrpg

2023-10-19 10:18:48

I have added to my personal webpage a brief high school math-level introduction to what tensors are, with the hope to make them a bit less scary to people encountering them for the first time:
https://jacopobertolotti.com/TensorsIntro.html
#ITeachPhysics #ITeachMath #Tensors

2023-10-17 13:06:42

@npub1hyk…3p33 is a constant source of quotable sentences, but I think my new favourite is:
"Geometry hates cars. You can't bargain with geometry."
(from https://pluralistic.net/2023/10/17/care-work/ )

2023-09-08 12:25:55

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@npub1z2q…3yuf
It opens instantaneously for me using Firefox on Ubuntu.
@npub1ez3…xnxl

2023-08-03 17:50:28

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@npub1znz…8l64 Super-naïve question: does wishlisting on Steam helps the developers? (I technically have an account on Steam, but I have never used it for anything)

2023-08-01 06:41:05

Haven't seen much discussion on the recent room-temperature superconductivity claims here on Mastodon (am I following the wrong people?), but before the hype hits you, here is the current state of affairs:
* Two experimental attempts to replicate the result have found nothing (https://t.co/D1gmAEOvzx, https://t.co/u5qIEv7aB7)
* One numerical result shows that the suggested material should have flat eletron bands, which are consistent with (but do not prove) superconductivity (https://t.co/2m0ojMOTLr).
Until we have independent experimental replication, any hype is premature.
(h/t @npub1s3g…9zjt)
#Physics

2023-07-29 16:17:39

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@npub1znz…8l64 I can find one in any electric appliance shop in both Italy and England, so I assume they are still very common.
I actually gifted one to my parents (after their old one broke) just a couple of years ago.

2023-07-28 09:36:28

Dear #WebComic authors, I am begging you, put a #rss feed to your webcomic. I really want to read them, but without a rss feed you are creating an unnecessary barrier.

2023-07-20 12:41:49

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@npub1knz…c73p Well, not that we have one unit for the x-axis and one (different) unit for the y-axis, I guess what we really need is a unit for the z-axis.

2023-07-07 09:05:55

Just a reminder of how dangerous trusting machine learning to reconstruct an image is.
(from https://doi.org/10.1038/s41592-020-01048-5)
https://media.mathstodon.xyz/media_attachments/files/110/671/987/015/728/790/original/874118efdd89b71b.jpg

2023-06-26 12:42:34

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@npub1znz…8l64 Not the point of your post (which I largely agree with), but I would really like the possibility to search within my own posts.

2023-05-07 07:35:26

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@npub16y5…ym3t I remember how a previous writers strike completely destroyed Heroes, one of the most promising series of its age.

2023-05-05 06:38:43

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@npub1pqk…z65u
To be fair, even by specifically googling it, it is not easy to find a decent explanation of what calckey&co are, and why one should bother.
And this is a problem common to a lot of the fediverse: there are a lot of options out there, but for a newcomer it is almost impossible to learn about it (and I am speaking from personal experience).

2023-05-02 10:32:22

Short story time:
When I was doing my PhD, we had in the lab an old Argon laser (which we used to pump a Ti:Sapphire, for those familiar with lasers). If you have never seen one, Argon lasers are massive, can output a ton of power, and eat a crazy amount of current, so much that the laser had its own dedicated industrial pentaphase plug.
I don't remember how many Amperes of current flew in those cables. What I remember is that, when you turned on the switch in the morning, the change in current (from zero to whatever the steady state value was) was enough to make the cable shake.
This happens because the electromagnetic field inside and around the cable stores momentum, and so it kicked the cable when building up.
I am not sure that laser still exists, and I have never been able to find a video of a cable shaking when the current is switched on, but it would be great to have such a video when teaching electrodynamics (and in particular how momentum and angular momentum can be stored in an electromagnetic field).
#ITeachPhysics #Physics #Electrodynamics #Laser

2023-03-21 16:30:11

Nobody can accuse #[0] to be realistic, but among the flying dragons and magic spells, its weirdest feature is probably hiw gravity works.
You jump down from several km high up in the sky, and if you are high level enough, you can just splat on the ground, stand up, and walk away with just some minor bruises.
Even weirder, if you have two massive bodies, each of them has its own gravitational field, but if they touch, only the heaviest one determines where gravity is pointing!
Sometimes I thinknit would be fun to get a group of other Physicists, and play a campaign where you have to live with the consequences of such weird rules 😉