A New Theory of Everything Based on Tensors! I had a look.
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- Опубліковано 10 лют 2025
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I got a lot of questions about a new theory of everything that supposedly explains dark energy and quantum physics by way of the "Alena Tensor". I had a look. It's not the worst idea I have had on my desk recently.
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#physics
I need that on a T-shirt.. "Always Start with the Lagrangian"
Go for it!
It's worth noting that Feynman's dissertation is a Lagrangian (least action) treatment of quantum mechanics.
@qwerty4324ify He was a fine man.
ALWAYS START WITH THE LAGRANGIAN. Boom.
Realize your potential
The grim smile on your face as you lit the paper up was priceless.
Without setting off the fire alarm! *swoon*
Well done.
Sabine: As usual, I had to watch this video four times before having even the vaguest idea what you were talking about. Not to worry; my degree is in Economics, so we're not expected to understand anything. Understand or not, I enjoy your videos immensely Thank you for the countless hours you put in for us dummies.
Happy you like it!
@@SabineHossenfelder Can you please do a video reviewing Sara Imari Walker's book "Life As No One Knows It: The Physics of Life's Emergence"? The book makes a lot of bold claims.
It’s been up for 18 minutes, and it’s 11 minutes long. Nice job with the time travel. 🎉
@@jrector666or perhaps it first came out to members.
@@SabineHossenfelderSABINE SHUT UP !!!!
This is what I come here for. Finally. No dumb animations and massively-annoying sound-effects, just a passionate/funny analysis+lecture, directly into the camera. Please, more like this. Burning up more stuff would be great too. @periodicvideos usually takes a torch to something in each vid, sometimes several somethings, and that's always fun.
No surprise here. This reminded me of the theory of everything that Feynman jokingly proposed. Let us add the left sides minus right sides of all physical equations. The sum will be zero. We give a fancy symbol to the sum, for example 💢. Then, we get 💢= 0, an equation that includes all known physics, but... adds nothing new 😂
Feynman had a good sense of humour! But as a pedant I must add, such equation would be wrong :P The reason is A + B = 0 has more solutions than A = 0 and B = 0. If we don't observe those this "generalisation" is broken.
"What I cannot create, I do not understand." -Feynman
Maybe a clueless master student can build a "useless machine", the "simplest robot" (a pendulum) and teach it how to "learn how to learn" about physics, by warping the state space to experience "Fuzzy" reasoning, while "standing on the shoulders of giants", and so, maybe then, a "theory of everything" is achieved, via humility and error 🔥🎩+💦=⛄Frosty, though it will probably talk to itself in Chinglish, or some 👽 alien language. Hopefully it's goal will be to teach us the "theory of everything" beyond just a mere answer of "42" 🎩🤠
@@cheshirecat111 yes, but the logical inverse of that is not true. A-B + C-D=0 does not imply A=B and C=D
@@Tablis0i don't know Feynmans joke, but I guess he was clever enough to add the norms of those differences (or some other related quantities like the squares of norms). Since norms are always nonnegative real numbers, their sum is zero if and only if each one is zero.
@@__christopher__ Yep, I found it, it is in the second volume of his lectures, end of chapter 25. He makes the joke to argue that supposed simplicity of a law is not enough, the language chosen must actually say us something about the phenomena described.
I just love how Sabine analysis other Physics Work. it also explains how people get lost in math, then get lost in physics by their own math.
How to Fry Baloney (ua-cam.com/video/tCp8Ri1qziI/v-deo.htmlsi=uhZwKLRjbkokko2o)
Why do circular slices of baloney have to be cut to remain flat after broiling or frying? How would a physicist use mathematics to describe what happens to circular slices of baloney that are not cut before heat is applied to them?
They made us learn tensors in our mechanical engineering curriculum as undergraduates, mostly so we could make sense of material stresses and strains in both solid and fluid mechanics. My physics undergraduate buddies were impressed I was conversant with the incantations for these arcane objects. Determining failure modes for structures often means "take the trace of this tensor and see if it's greater than something" or "take the largest principal component while holding a candle and chanting Timoshenko's name backwards!"
It's said that if you stand in front of a mirror at midnight by candlelight and chant "Ambitwistor" three times, the ghost of John VonNeumann will appear and solve a maths problem for you.
I feel like tensors are pretty simple overall. Am I alone in that?
It's rare to introduce where all this math is used and useful in engineering. Many equations are buried in computer aided drawing systems just waiting for a user to hit a go button.
Next time you drive over a bridge you may want to thank a mouse click?
@@SolidSiren "overall" is fascinatingly ambiguous phrasing.
@@SolidSiren3D tensors are a doddle.
I like to think that the damage on Sabine's right armrest is from countless hours of resting her elbow while facepalming Jean-Luc Picard style after each paper she reads
Some nice lace doilies might help.
She has to rotate the chair counterclockwise to get out of it and leave the office but the right arm rest rides under the desk and the desk is too low to clear it so it got damaged. That is my theory.
Uhn uh -----
I heard she got it in a knife 🔪 fight she got in when she was 5-------
That was when she was still working undercover-----
I think it was the bar fight where she defeated the "Colombian Drug Lords".
You can have your well placed Picard reference------
But I think we all know what was really going on_______
_______she was top-secret spying.
She's world famous for it----- that's why you never heard about it.
And yes her and Picard did know each other------ they were in StarFleet Academy Junior High together---- ???
That's ALL I know for certain,
because I'm making it all up as I go.
She's the one that really broke Jean-Luc's heart.
I'm pretty sure I didn't understand much of that but I have found a new reason to watch Sabine's videos: there will come a day when she sets papers on fire but will have forgotten to turn the smoke detector/fire suppression system off first.
A bit feeble - not so ? Sabine is quite serious about her work and why would she destroy is? Nihilist ?
I think that's a 200euro fine for the HRT to turn up and turn off the fire alarms...
@ Even staging jokes cost money and if not funny enough another 20E fine. so there ! Thanks for your note
It takes a lot of time and effort to produce these videos, especially to meet the quality your audience expects. Keep it going!
😊💯
Thank you🔥🐝
Thanks, happy you like it!
Maybe she can buy a new armrest for her chair! 😀
Thanks, Sabine. I've finally understood everything you said in the first 10 second. I am working on the rest now.
Yeh. I was so excited when I got to 10 seconds. I must be improving. Am I?
Yay! Tensors introduced to a broader audience!
I learned them in university, and at first, they looked scary. Instead of a scalar, you had to work with a matrix, but a couple of years later, I recognised the beauty of defining a real-life object using a matrix and a set of rules attached to it. Gradients, rotors, operators, different multiplications and differential equations in a unified notation format! They are not easy, but they can describe the uneven transparency of a chunk of a mineral, rotation of an object with no circular symmetry, and a lot of curved, deformed, uneven real-life stuff. Very useful mathematical construct!
Indeed, it's interesting that curvature naturally pops up in certain materials.
Something to note here: Not all tensors are matrices! While you can express a second degree tensor as a matrix you most definitetly know at least one other tensor that is in the simplest form a third degree. The levi-civita tensor ε_ijk. Using permutations you can actually generalize the concept of that tensor into even higher dimensions. It gets a bit more complicated but it is very useful while working with 4-objects in relativity.
@@derdotte Indeed, but as an AI programmer I know you can express any tensor as a multidimensional array. A matrix is a 2d array. You can express a vector as a simplified matrix with just one row or one column. In fact the dot product, cross product, scalar multiplication, and vector addition/subtraction can all be expressed as operations on a matrix.
Well, the unification of vector calculus is much more nicely done through differential forms than through tensors!
At least you avoid the horrible "debauche of indeces", as rightly pointed out by the great mathematician Elie Cartan 😁
Werent tensors introduced to broad audience when nvidia made RTX cards? I wouldnt call some old woman video "introducing to broader audience" lmao
Sabine's smirk when she sets the paper on fire at the end had me completely cracking up 🤣
I just want to know how she did that without setting off smoke alarms all over the building.
Thanks!
Thanks, happy you like it!
Good job 👍🏻 I’m impressed how clear and easy-accessible was the explanation and analysis, that’s a talent!
Can’t imagine anyone else who could release advance math episodes adapted fun version
I LOVE YOUR STYLE, @Sabine! I would love to have teachers and tutors with this both rebel spirit and strong commitment with solid science back in my student days!
Absolutely, you are right about this *theory of everything*, the wrong one.
Me as *theory of everything* meant, nothing about some particular science branches, or politics, or big tech, or any professions, but ABOUT OUR HUMANITY'S ethics, morality, humane conscious mind MUST RULE OUR HUMANITY'S LIFE on EARTH❤
Yes, as Sabine says, we HUMANITY doesn't NEED today ANY so called *geniuses* in any PROFESSIONAL fields, it's ABSOLUTELY not Emergency, WE DON'T NEED it today.
Because we HUMANITY'S got ENOUGH information CAPACITY in any PROFESSIONAL study subjects, ANYONE can be anything they want, but the ONLY ABSOLUTELY CRITICAL NECESSARY urgency is ONLY HIGHLY ETHICAL MORAL, HUMANE conscious mind ones MUST HAVE important jobs, careers, leadership roles in ANY Society's Structures!
That's what's called me is *THEORY OF EVERYTHING*.
For example if Hitler have been TRULY HUMANE SOUL, ETHICS MORALITY, then the WWII would have NEVER been happened, as you are from Germany & i like your accent.
Entire my life i was an EXCELLENT STUDENT in school, university & i was CEO of hospital & GP, Family Doctor, i was ALWAYS NICE to my patients, i was friend to everyone of them, i have NEVER cheated, lied, backstabbed anyone in my life, i have NEVER CORRUPT bribed anyone, i have ALWAYS been a law abiding citizen & VERY ethical moral professional & ABSOLUTELY not greedy, never conspired for BIG CAREER, power, fame, never will.
So that's why me is *theory of EVERYTHING*, as you have mentioned PHILOSOPHER Rousseau's *social contract*.
I meant it, NO ONE CORRUPT, GREEDY, POWER LOVING, ETHICLESS, MORALLESS, INHUMANE cruel character human NEVER SHOULD be allowed to work at ANY IMPORTANT positions, so that MUST WORK as *theory of EVERYTHING*, instead today's WORLD politics is/was as seen ONLY FOR WORST MORALLESS, ethicless INHUMANE PEOPLE'S job, career, social status, that's why EVERYTHING is WRONG.
We NEED THIS EMERGENCY as HUMANITY, the WORLD politics SUPPOSED TO BE THE BEST HUMANE QUALITIES PEOPLE, not garbage trash ones as today, understood, that's what's called me: theory of EVERYTHING & if i EASILY can live this way, why ANYONE ELSE CANNOT:)?!
A MUST😉🌏🙏
I love it when Sabine says that doesn't make sense to me, then I don't feel so dumb because most of it doesn't make sense to me.
"So much about being nice" XD I love it.
But reassurance about the impending revolution. Or resolution. Nice enough…
There was real joy in Sabine's face when she lit the flame. It was scary!
That delivery was of pure disdain.😂
Thank you, Sabine, Your videos can't be overrated!
That was a really nice conceptual explanation of why tensors are important!
Also, Feynman hated that conference and, at one point, shouted “NO!” loudly three times at a fellow physicist. He told his wife never let him go to a GR conference again.
I have a lot of understanding for that...
I’m trying to watch this, but I cannot get my head around tensor math. Differential equations is about the boundary for my understanding of math. Beyond that, it’s as if I’m a dog and you are talking me, “Yap yap yap Steve. Woof woof yap, Steve. Yip woof yap, Steve.” You’re talking to me (I hear my name….) but I have no idea what the hell you want!
@@stevenslater2669 Try the paper NASA/TM-2002-211716 "An Introduction to Tensors for Students
of Physics and Engineering" by Joseph C. Kolecki (2002), which is accessible online.
@@stevenslater2669 are you, by any chance, referencing the Far Side comic that compares what the dog's master says to what the dog hears? You made your point well in any case!
@@TerryBollinger😂
Thanks!
I am surprised that the paper passed peer review but didn’t stand a chance against the “Pen Of Doom” :-)
I didn't mention this in the video, but the authors have previously written several other papers on the topic. Once you get the first paper published, the later ones are easier. Actually the new paper is pretty much incomprehensible on its own and that probably helped getting it published.
@@SabineHossenfelder It might be interesting to feed it to one of the new AI models that can do math well to see how well it does in picking the paper apart.
@ I did with O1 and the article in Physica Scripta, it found multiple inconsistencies, also offered some good ideas how to fix them
@@ivaylovasilev2688
Curious, have you tried the communist one?
Just meme'ing but also, I could see it be better at this kind of stuff.
Sabine, the lighter absolutely kills me. Thank you, this is wonderful.
Sabine and the lighter approach
😂 now considering an entire series called "the lighter side of physics"
@@SabineHossenfelder Well the world is clearly going up in smoke so 'when in Rome' as they say lol. If only UA-cam enforced transcripts you could have battle after battle with your detractors!
@SabineHoss😂enfelder
@@SabineHossenfelder mmm, i could really need that hehe, i have a lot of gaps to fill in and wiki can be a bit dry on the humor side a veces jiji ❤🔥
Lighter side of physics - rotflol. But I'm also German so my word play comprehension is likely on a similar level as Dr. Sabine's is.
as a non physicist, these paper reviews where you give a brief overview of the topic and critique the paper itself brings the most entertainment and i enjoy it very much; even if i dont fully understand it.
This is one of your best videos in a while. No flashy stuff. And no talking down. Just straightforward. I like it better.
Your sense of humor always shines through. I love it. All the best from Texas
Thanks Sabine once again! nice that you explained so nicely. Although, I am only a PhD in medical imaging so I do not know much about tensors. I remember that while dealing with vectors, to develop the algorithm I was working with, I wanted to study tensor. Because vectors are also one type of tensor. But I could not find enough time to do so. Maybe, this video again motivates me to go back to studying tensors. :)
Greatest insight for me in this video is- “ always start with the lagrangian….”
One day you will find a theory of everything paper that actually works. I'm here for it.
I am keeping an eye out for it!
@@SabineHossenfelder Just make sure you don't burn it 🤣
Wasn't it 42?
@@SabineHossenfelder most of the modern theories of physics(mostly refering to quantum physics)aren't grounded by the objective truth, epistemological justification for quantum physics is rether poor just like big bang theory, a lot of science isn't provable empirically, Jay Dyer did a livestream on science and epistemological justification of modern science that claims its objectice even tho every now and then some "scientists" splis BS and then gets thesis and phd on theory that is false and absolutely unprovable even tho supposedly science was about empirical proof
Singularity? Based on what, how can you proove ans objectively observe it and how can you prove it to someone if you yourself don't have the actually scientifically verifiable (empirical) proof
Or she'll write it. 🙂
I absolutely love this paper review format. Thanks Sabine!
I didn't understand a word You said. I really enjoyed lighting up the papers. Thank You!
I'm actually surprised how well the camera captured this. I might burn some more things...
@@SabineHossenfelder 😂
@
😂😂😂😂😂@@SabineHossenfelder
We’re happy to contribute to your delinquency… 🤣😂🤣
whenever Sabine explains something it all boils down to a basic constant, "the physics of humor" or "the humor of physics". maybe humor is the missing link needed for our theory of everything (funny).
After watching this 5x, I formed the view that Sabine fully understands what she talking about...
😂Every of her vids makes a tiny little bit smarter though.
Gotta love how Sebine cuts various theories to shreds but does it ever so nicely! 👍👍
She doesn't just cut them, she burns them to ashes.
Oh god, Tensors... Makes me remember my second year at uni and a dread memory of the day I realised that there was a lot of maths that wasn't just tricky, but really very very tricky. I remember a lecturer, my mental image is that he was at least 120 and had one of those beards only 120 year old men can grow, talking about Dirac for at least an hour before he eventually got back onto the maths he was supposed to be helping us with. His descriptions of Dirac as some sort of mentally gifted maniac (maniacally gifted that is, not that he was a murderer or something), do give me a fond memory of how much the profs used to worship their heroes. Its a nice idea that there are still (or were 20 years ago when I was trudging to 3hr lectures written mostly in greek) some people who idolize genuinely clever people, and not just investment capitalists who self-proclaim themselves to be clever.
i'm so happy when i see the office table, love these paper review videos
Every fundamental physicist, before going to bed, check inside the cupboard to make sure that Sabine is not there
chirp gμν few times and see if she comes out of hiding
Yeah, like when a scary monster goes to sleep, has to check under the bed whether Chuck Norris hasn’t lurking there ...
LOLOLOL! LOVED IT! The fire at the end was… brilliant.
Very good review. Also, always focus on the Lagrangian first, eh? Makes sense. That has always made sense.
Holding a couple degrees in physics, I'm able to follow along with most of the content... but it's the burning of the paper for me. THIS is why I follow Sabine. 🤣
YEAASSS !!! Paper review is my fav format you do right now!!
Ah, that was a great journal club presentation and discussion, loved it. 🔥🔥🔥🔥🔥🔥🔥
I was totally lost until Sabine lit the paper on fire. I can understand that!
For the wonderful comment about starting from the Lagrangian
thank you!
Personal objective this week; Object to someone's action by declaring "You cant just go and chamge the energy momentum tensor!!" And observe their reaction 😅
Thank you for your content. This is the closest I'm ever likely to come to grasping these concepts.
love this video format. your sense of humour makes it work really well 👍
I just watch this channel to keep myself humble. Fantastic work as usual, I assume.
Sabine, I believe I can learn physics by hosmosis by watching your videos. While I don't learn, I can offer some compliments: congratulations, your image today is much better than when you published your first videos.
Now THAT is a thumbnail!❤❤❤
My first thought!
I like this "review by video" format. It would be very helpful in many fields.
The ending made me laugh out loud. The face. The tone of the voice. And then there was the burning.....
There is nothing wrong with the tone of this video. It actually made me laugh. Keep them coming!
Forget Deadpool and Wolverine. I want to see Sabine teamed up with John Wick.
I love these videos from the office with a very satisfying "paper work". And this chair. Very much reminds mine that I had to change for wooden firm one. Science facilities look the same throghout the world 😅
Understanding Tensors, Covariant Derivatives or Differential Forms and other Concepts like Topologie is the Key to understanding Physics. I always view my hard earned Ability to work with Tensors as the greatest tool of all I learned in Math in my whole Life.
Talking about the function of tensors in physics was incredibly insightful, you did a great job with this review!
Not gonna lie, that look of genuine enjoyment as you lit the paper on fire scared me a little.
For me - that was the best video of all I've seen you've done so far.
I wonder if you realize your significance. Confidence in science has been shaken. Your work publicly deflates Science-the-Industry and Science-the-Brand back down to a discipline--the simple and ruthless application of the Scientific Method. From my perspective, universities and companies have a conflict of interest resulting in overly-optimistic reports of theories and breakthroughs. I don't have the skills to judge the veracity of peer-reviewed publications. But I know that a paper that *you* find plausible, even in part, is worth reading. I suspect this might make you unpopular in physics social circles. I imagine hopeful young physicists approaching you with their new giant red balloon, and you're ready with the needle. Keep it up! You're appreciated.
Not really. Science has always had charlatans and bad scientists. That's why things need to be peer reviewed and can be changed whenever new evidence is found.
"So much for being nice." - My new motto! Thank you, Sabine.
I learned that scalar quantities have just a magnitude, e.g. mass. Vector quantities have a magnitude and a direction, e.g.momentum. Tensor quantities have magnitude and two directions, e.g. sheer stress.
Consider flow in a pipe with the cross-sectional area in the x-y plane and the direction of flow in the z-direction. The flowing liquid has momentum in the z-direction. Energy is required to maintain flow due to frictional losses with the walls of the pipe. In the case of laminar flow (not turbulent) the liquid against the walls is stagnant, the liquid at the center moves at maximum velocity. As you move out from the center the flow slows reaching zero at the wall. Thus z-momentum steadily declines as you move out toward the walls. The z-momentum is being transferred to the wall in the radial direction. This momentum transfer is mv/time = ma = force. This force is, the sheer stress, what decelerates the fluid as you go from the center to the wall. Sheer stress is a tensor that has a magnitude and two directions, one is the direction of momentum (z) and the other is the direction of transfer, radial or r.
1 min in, she roasts the paper so hard 😂
And then in the end does it literally 😂
Great advice, starting with the Lagrangian.
Wow! Thanks Sabine! Really good video explaining how physics is done and how you have to be really really careful. As Feynmann cautioned about not being a fool all along, and you are the easiest person to be fooled. Thanks! And please make these kinds of videos. ❤ all the best.
Im just glad the field is still active.
You are treasure that keeps om rewarding us all Sabine :)
“Let no one stand in your way, but your own self my dear.”
After all
“Being so bright as a star in the sky, causes all to look heavenly towards that light, then doubt its data universally.”
“The star needs not prove it exists or comprise its light by math or magic.”
Take care,
Jeremy
Wow. That was the best 5 minute introduction to tensors and GR I've ever seen. What's next quaternions?? I'd be careful about pissing off Alena, though!
That geometric mu nu stuff is something I had hoped to understand someday, but none of the texts I have from my failed undergraduate 50 years ago cover it. Same with anything on Riemann. I'm thinking of buying Susskind's theoretical minimum series of books to see if those can help.
Do the texts you've studied include Misner Thorne & Wheeler's Gravitation? They provide quite a lot of introductory material bringing these ideas to those new to all that stuff. Published something like 50 years ago, quite popular, but probably superseded at this time by other books and videos. Woefully old when it comes to gravitation waves - please ignore that chapter! But the math of tensors, metrics, curvature is still good.
What books have you found most useful?
I *love* this video. It is one of your _best._
Love you, Sabine. I teach physics in Portugal.
Loved it, as always! Thanks, Brilliant Sabine!
That's interesting. I've been exploring similar concepts in the context of extended Lagrangians, particularly those that incorporate higher-derivative terms or non-Riemannian geometry. My research has focused on understanding how such modifications can affect the dynamics of spacetime and potentially provide a framework for unifying gravity with other fundamental forces.
While I appreciate the attempt to explain dark energy and quantum physics through the 'Alena Tensor,' I remain cautious. Many theories have come and gone, promising to be the 'Theory of Everything,' yet ultimately failing to deliver on their promises. My experience has taught me to be skeptical of such claims, especially without rigorous mathematical backing and testable predictions.
I'm particularly interested in seeing the explicit form of the Lagrangian that incorporates this 'Alena Tensor.' How does it modify the Einstein-Hilbert action, and what new degrees of freedom does it introduce? Does it address the long-standing problem of renormalizing gravity, or does it simply shift the problem to a different sector? And, of course, the most crucial question: does it offer a natural and compelling explanation for the observed value of the cosmological constant, or does it merely introduce new parameters that need to be fine-tuned?
Until I see a concrete mathematical formulation and a detailed analysis of its implications, I remain unconvinced. However, I'm always open to new ideas and perspectives, and I'm eager to learn more about this 'Alena Tensor' and its potential contributions to our understanding of the universe.
I love this format, you know when Sabine is sitting down all hell will break loose :)
If a light bulb is the sun a stress map could be a tensor. A stress map represents how forces distribute across different dimensions, much like how tensors describe complex relationships in multiple dimensions.
Excellent description, very efficient and understandable,
02:20
_There are a lot of maths things which are not tensors._
However, scalars and vectors don't belong to this category because they are tensors of 0th and 1st stufe, respectively.
That's right. But mathematically nothing is preventing you from, say, combining 4 scalars to a thing with an index which would then not be a vector, if you see what I mean?
Things being able to be represented as tensors is an entirely different statement to actually being tensors.
e.g. Quaternions are absolutely not tensors but can be represented as such. An element of a vector space is absolutely not a tensor but may be represented as a rank 1 tensor. A group is absolutely not a tensor and cannot be represented by a tensor at all, although one can represent elements of groups by tensors and operate on them with other tensors to represent the group.
@@SabineHossenfelder
Depends on how generally the term 'vector' is used. What maths defines as a vector space over a field is any set for whos elements addition and multiplication with any scalar from the field is defined.
In applied maths, you even may find "vectors" which aren't even in the strict sense because their components are e.g. prices per amount of some compounds of, say, a cake you want to produce, and its scalar product with a "vector" representing the amounts of the compounds you need tells you the costs aside from your energy costs.
Love your channel, your mind. Love you. Wish I could grasp this material more easily.
That thumbnail is 🔥🔥🔥🔥🔥
I'm a new subscriber and wish I found your channel when you first started. We Canadians 🇨🇦 love your channel, and thank you for all your work and videos
Welcome
My teacher made paper chains ⛓️ out of my papers 😢.
I suspect the T originally just came from 'Tensor', but I like your explanation of a lack of coffee more.
Before she showed the paper, that visual diagram, that’s incoherent. And it has a typo lol. I was looking at it like, “I’m not usually dumb about this stuff” 😂 _What am I supposed to be taking from these random words and images??_ Read the abstract. “I… Still don’t get it” so happy when she said it’s BS. I’m not getting dumber tysm 😂
Thanks for the clarification! 👍 I always wondered, what these tonsils are for!
@9:09 the conclusion 😅😅
Some people just want to see the world burn. And rightly so!
When Sabine burns your paper on-camera, you've hit an entirely new level.
I can’t post a comment without spoiling the ending, so please just know that I LOVE❤ this video!
By the way, is this paper already reviewed and published or no? I’m thinking we need a video in which you lead a thesis review committee! I’m not sure what it’s called. You know: when you defend your dissertation…
I have a request: please have a look at protein engineering and consider whether that is physics, chemistry, math, or other?
Yes, the paper is reviewed and published. As well as several other previous papers on the same topic.
@@SabineHossenfelder …now I’m gonna cry. …D’oh! My tear ducts are dry from watching the US government go “blue screen…” Some are calling this a coup. I don’t care what we call it. Just, wow!
More paper review videos please! It's actually super helpful for me being in grad school.
Beep beep beep beep batteries in ya smoke alarm ‼️ 😅🤗👍🏽😂you rock 🙏
Sabine on fire😁
Doesn't matter since she saw a fire extinguisher on the wall and concluded that a solution exists.
Who knew deep physics had comedic opportunities. So interesting on so many levels. Thank you.
"Hey Sabine,
modern cosmology assumes the
universe expanded from a single point.
But relativity itself shows the 'edge of
space' IS the start of time. Isn't it
mathematically inevitable that we're
seeing the universe begin in real-time?
The big bang is not a point, it's a moment in time.
@@SabineHossenfelder Below 1.0 × 10-37 seconds, the concept of "time" made no sense, if I remember correctly. Or was it -43?
@SabineHossenfelder hey Sabine, to calculate G, it's length cubed over mass times time squared, all Planck
@SabineHossenfelder my model of the universe kicks ass. Seem to need no inflation, no dark matter, no dark energy, no exotic particles, no exotic physics, no ad hocs.
Solves flatness, homogeneity, isotropy, distribution, CMB, inflation, expansion, accelerating redshift, horizon problems, light, space, time, relativity, observer effect, wave-particle duality, spooky action, uncertainty, gravity, quantum fluctuations, galactic rotation, clustering, fillimenting, and lensing, the pioneer anomaly, the twin paradox, generates all constants, generates all dimensions, the cold spot, movement in a continuous environment, to name a few.
Let me know if you're interested in talking about it
This is your best category of your videos. I love it.
But maybe you could once every month make again a video like your old 20 min had been? That would be fantastic.
Well her very old ones were just about ten like the ones nowadays. Anyhow she puts morecontnet in five minutes like ohters in a boring hour.
If dark matter was just a math patch
and quantum fuzziness is just a
time-resolution error, wouldn't we need
a full first-principles cosmology to
replace Lambda-CDM? We've got one.
I REALLLY like these paper review videos!!!!
As someone who is actually pretty familiar with vectors and matricies, I find all the descriptions of "what is a tensor" infuriatingly unhelpful, including this one. It took me years for it to finally make sense to me even after I knew vector and matrix math (mostly from 3D rendering math, where every transformation is a 4x4 matrix). The actual helpful way to explain them to me would be to first explain vectors, the matricies, how vector/matrix operations allow to allow you to do certain types of transformations (specifically linear transformations) and from there explain that a tensor is a generalization of scalar->vector->matrix->(). And this also means that scalars - literally just numbers - are technically tensors, so are vectors, and matricies. Tensors are just a general term to capture all of that, and in computer terms are "just" high-dimensional arrays, with some useful transformation properties (and this is about where my understanding currently ends, and this is also where the actual interesting part about tensors begins). A matrix as a transformation makes perfect sense to me and I have a sort of geometric intuition for how it works for coordinates in space (and in 3d graphics there is an additional twist to it in that the fourth component of a vector is a scale factor, which allows you to do perspective transformation using a 4x4 matrix). I can clearly see how it generalizes to more dimensions of space (and can even visualize actual 4d space in my head). But I still have no clue what those 3 and higher order tensors do and how they work. And in cases where order ≥3 isn't even used, I don't see any reason to even use the name "tensor" except to confuse people less familiar with it. And SO MANY of the "tensors" in physics are just order 2... which is a matrix...
And very unfortunately all the math wikipedia articles are written in such a way that for as long as you don't understand it, they appear gibberish, and only begin to make sense once you actually understand it from other sources, and then what wikipedia says is "obvious:
So,you watched the video,and it made you feel tensor?
Tensors are the category of things that you can index with vectors. Given an indexing operator [], then A[i]=B means indexing by the vector i into tensor A, resulting in the tensor B. There are typically dimensionality constraints, and many choices of how to index, which give you transposition and slices and all sorts of other useful things. But if you see tensor, think indexing.
@@mrpocock This is no longer really tied that much to the video but I would love to get someone who actually has some understanding of it to explain at least a bit more in a way I may be able to understand. I think it really boils down to what ≥3 tensor could really do and how. Unlike with vectors and matricies, I don't know of any comprehensible to me way to tie "an 3+ dimensional array of numbers" to "there are somehow useful operations you can do on it beyond just extracting the individual numbers". All I know is the indexing.
With vectors and matricies I have a clear intuitive understanding of how a matrix can be used to apply linear transformations to vectors (again, going by my previous experience with 3d graphics), after for example a quick reading on Cauchy Stress Tensor (which turns out of a matrix), if I'm anywhere near understanding it correctly (which I may well not be and may be far off, also using very "informal" language because I'm not at all familiar with the physics terms, anything in quotes is a vague informal idea) is basically 3 vectors, each representing direction of sort of "stress/tension" on each of the 3 perpendicular planes. and if my intuitive guess is right (because I absolutely cannot deduce it logically from wikipedia) multiplying a vector and that matrix (in whichever order actually works here) results in (again informally because I have zero formal knowledge of this) a sort of "effective force/stress direction" on the plane perpendicular to the given vector (?). Please correct me if I got it completely wrong but given what I read that makes sense to me.
But for order ≥3... I actually know nothing beyond the indexing and _handwavy relations/transformations_. on one side I have those _handwavy explanations_, on the other - how to write them down, and no way to connect these two. And I think the simplest way for me would be to just follow it with actual example numbers in some small example case of order ≥3
Absolutely love the cover for this video 😁
Love your hair! Becoming more like the Relative Big E every day......
Marvelous hair
🤣 Du bist schon hart drauf...tolle Folge und wieder ein bisschen was gelernt. TOP!
New physics mantra: gee-myuu-nyuu, gee-myuu.nyuu, forty years and nothing new 🤣 All in good humor, I have utmost respect for science
For a quick crude intuitive notion of what tensors are, imagine you have a small stretchy object, maybe foam rubber, gelatin, or a patch of bubbles floating on water.
Pull on it in some direction and it moves that way. That's a vector.
Now pull on one end and pull the opposite way at the other end. If your pulls are outward, away from the center of the object, that's a tensor, a symmetric one. The stress tensor in mechanical engineering is just like this.
OTOH if you're pulling up, let's say we're pulling north, on the east side of the object, and pulling south on the west side, the object will rotate. That's an anti-symmetric tensor. As a practical mathematical concept, it's a rotation matrix.
In relativity, a "boost" - to make something move faster or slower or go sideways - is the same thing as rotation but "space-time" rather than "space-space" like a rotation. That's hard to explain further in a youtube comment. The capital 'F' you see in that paper Sabine shows is the electromagnetic tensor, which combines rotations (for magnetic fields) and boosts (for electric fields) into one 4 dimensional antisymmetric tensor.
Now imagine having a rod or cylinder of some material, like a can of soup or wood dowel or an common everyday battery (AA or D size, whatever) Twist one end. A twist is basically a rotation, which we already established is an anti-symmetric tensor made of two vectors. We need a third vector to say where we're applying this twist. Balance it out by twisting the opposite end in the opposite direction. We just made a rank-three tensor, anti-symmetric.
There are more examples I could give, but I'd be writing an article suitable for Medium or Substack, too large to fit in UA-cam comments, and I'd want to make illustrations. Someday...
so, the anti-derivative of forces under some geometrical constraints?
Excellent. You nailed it. Thanks. Including the humor also. 😂😀