Thank you for not mentioning Descartes too early in the video. Most professors and teachers have a habit of (all too often) putting Descartes before the course.
My favourite Newton fun fact is that he wss appointed Warden of the Royal Mint, which was apparently meant to be mostly ceremonial but he took it super seriously and went undercover in bars and taverns to seek out counterfeiting operations, which he then attempted to prosecute.
that he managed to prosecute with terrifying effectiveness. Newton was every bit a genius as a Warden of the Mint and an investigator as he was a genius physicist.
@@acollierastro You should read Neal Stephenson's Baroque Cycle series. Historical fiction which in a broad way revolves around how things like modern financial systems came to be. Newton is a recurring character. Fantastic books.
Tangential to the off topic discussion at 38:45, I love the mention that we did not know how stars worked until relativity. My best friend and I each have half of a series of books called "The Books Of Knowledge" (which is just a great title). It is an encyclopedia published around 1912, but had significant content-altering revisions over time. I believe I have the 1940's edition. Point is, that while perusing the book, I came across a fascinating question in a Q/A section of the book which goes as follows: "When will the sun run out of oxygen," to which the answer was some flavor of ¯\_(ツ)_/¯. The question implies a belief that the sun is literally just a space bonfire, so there is evidence of the general public wondering about how tf the sun did its shenanigans even significantly after the 1920's.
There's another brain worm that suggests you can't actually smush atoms together, the repulsive force is too strong. All fusion is due to quantum tunneling.
You are a born public speaker. I'm very impressed with your presentations. Not many people can structure a talk with such focus and present it in such a relaxed way for 1h+ without ever stuttering.
Heh… I came here to say that I’m sold on what she’s telling us here in this vid - and it kinda blows my mind and makes me question myself, and how convincible I must be, cuz this isn’t anything I ever learned. 😏 Granted, I’m half past middle aged and went to a rural high school… heh but yeah, weird how I stayed engaged thru all of it either way. 🤷🏻♂️😏
Agree. I also find it fascinating that she expresses herself as much through her nose as through her mouth. Hahaha, just an observation of the nasal American accent.
I’m a research physicist and once was talking with a physics teacher/instructor and he started talking about relativistic mass. Since he taught it a lot and I never thought about it the kids (we were at a cub scout event) nearby probably thought that he understood things better. I was just kind of stuttering saying, “uhh, nobody thinks about mass like that anymore…it’s the old way” and he smoothly stated “no, mass increases with velocity and that’s why the speed of light can’t be reached.” The pyramid thing really helps to explain the situation. Enjoyed the video!
You were very kind about Brain Green docs. I watched one of his on String Theory and the only knowledge I gained from it was that strings are little multi-coloured circles that make wind-chime noises and float around your head.
Your videos are amazing. I'm a philosophy student whose biggest disappointment in life is not being a physicist, and these videos are some of the best I've ever watched.
Thank you sooo much!! I am 70 years old and have no formal background in either mathematics or physics but I enjoy reading about them and trying to get a handle on some general concepts and there is NOTHING more confusing than the myriad number of ways and definitions that seem to exist for similar concepts, in particular "energy". At least half my time is spent tracking down actual physicists to talk with them and have them clarify all of my misunderstandings and bad assumptions which are a result of sloppy use of language and educators trying to "dumb down" concepts and as a result teaching them incorrectly. Thanks for doing it right!!!
I still resent the Bohr model of the atom, after knowing about it for more than half a century. I feel that telling lies to children is a stop-gap, band-aid fix that covers a failure to understand the issues well enough to communicate them effectively. I feel that time dilation and length contraction are similarly poorly dealt with, leading to things like the Twins Paradox that really shouldn’t be pradoxical if the issues were properly laid out in the first place. Part of the problem is: of the people who are drawn to physics, only those who have a real affinity for mathematics at a high level of abstraction survive even fairly basic physics study and tend not to be great communicators to people who need more concrete examples, which turns out to be most people. Crude concrete examples are worse than abstraction, and I’m sure they kill the enthusiasm of a lot of children who might otherwise have brought more vitality-and better communication-to the subject. Yeah, this video hit a nerve. I’ve just recently discovered your channel, and so far I find it refreshing and enjoyable.
The Bohr model as it was laid out back then was pretty neat : you take the planetary model of the atom with circular orbits (which does not work because accelerated charges radiate), and you assume than the angular momentum of those electron can only take some multiple of a constant value (that happen to be the Planck constant), and you get a set of discrete energy levels. If you further assume that the electron can jump from one level to the other by absorbing or emitting photons, you can predict a bunch of spectral lines, reproduce the Rydberg empirical formula, and tie the associated constant to the electron mass and charge, coulomb constant, and Planck constant.
I think this all starts at simplification of Math. It is all very fixed and one-dimensional. Can we not teach kids probability and multi-dimensions from get go ? And then imagine what would those minds can come up with going forward !
@@denizersoz7012 yes! your correct! however the elite are INTENTIONALLY dumbing down the education system....they just want dumb simple taxpayers, moved business to china, the usa has been imploded many years ago, the falling has been taking 40 years....gen z cant change a car flat tire....and me and you hope to teach "n-dimensional" dynamics? i have seen hope in 1/100 genz rebels, they dont cell phone, 1 minute /day internet....despize social media.....research tech on thier own! there is hope!
10/10. I was lucky enough to have a professor in my sophomore modern physics class as an undergrad who really hammered this point home. Love hearing you talk about that physics life, I kinda miss it sometimes but then I remember how miserable I remember everyone in grad school being and how they really aren't that much better off now.
This video was very illuminating, thank you ❤ Btw regarding sickle cell disease: it’s believed that it’s been selected for since its appearance, because having 1 or both of the alleles of that gene as the SCD makes the subject resist malaria. And apparently the gene for SCD is recessive, so one can have 1 copy of it, not get the disease, and still not get decimated by malaria. :D
Because you still have phenotypically misshapen blood cells with one copy of the allele, but still enough healthy ones to not have it effect your health too significantly. It is why sickle cell is not selected for in areas without malaria because the heterozygous organism isn't as healthy as the homozygous dominant one.
@Waywardpaladin This is correct but (no offense) I think phrased somewhat awkwardly. All RBCs are diploid in humans and will all have the one sickling allele for beta-globin, and individual RBCs will vary in functional versus sickling Hb but generally sickling in heterozygotes only occurs under low oxygen conditions (such as when more oxygen dissolves into tissues during exercise or at high altitudes). The codominant phenotype under normal conditions is actually variable/patchy concentration of normal Hb, not sickling. This is because the allele is not causing the trait directly, the mutant protein subunit is, and alleles can be differentially regulated for stochastic or deterministic reasons. It's true that heterozygote advantage only exists for HbS in regions with diseases like malaria but it's worth keeping in mind that deleterious alleles are not magically cleansed from the population by evolution anyways and some combo of geographic isolation and drift can fix recessive alleles with deleterious phenotypes (e.g. Rh- maternal phenotypes predisposing infants to erthyroblastosis fetalis) in the absence of selective pressure. Hence stable extinction rates in the fossil record even after sexual reproduction gave an efficient way out of the Mullerian ratchet.
As someone who has consumed a lot of popular physics and has concocted a lot of crackpot theories (which I have NOT emailed to physicists and never really thought were true, but just enjoyed coming up with them), it's both exciting and kind of crushing to be shown in such ab entertaining way that you actually have to do the math... with the right formula no less. Thanks for the videos. Subscribed
"You know what holds the quarks together? Gluons...get it?" 46:10 Perfect delivery, I couldnt help but laugh out loud. Excellent Video once again, I learned a lot.
@WiseOwl_1408 Oh good, I'm glad other people are bored with this comment that makes no contribution to the topic at hand. Like yeah, we're all excited for the video. That's why we watch it. And Angela is fantastic.
I know it's a month later but small semantic point about evolution. Genetic mutations are random, selection pressures and environments not so much. If you have an accurate picture of a given environment and the selection pressures found in it, and the strength of those selection pressures, you can accurately predict the traits you would expect to see in a given population within that environment
(2 months later) I still think it is more accurate to say that evolution selects for what works; not what is optimal. Evolution is not able to "refactor" code, so you get workarounds like the vagus nerve: which takes a circuitous route through the body.
I came to the comments to make this comment (but found yours). I love this channel, but the evolution analogy was way off the mark and was fundamentally incorrect. Genetic mutations are random, but macroevolution is definitively nonrandom. Even the selection for a "negative" trait like sickle cell anemia is non-random, given that it increases resistance to malaria. It's not hard to imagine how this would be an evolutionary advantage in populations at malarial latitudes prior to modern medicine.
@@NME1012 IMO the analogy was well used if you consider 'evolution' and 'relativity' as two big categories and also popular concepts which are subject to a lot of interpretation and handling at the curricular level. We end up with fundamentally wrong nuclear beliefs as a result of such "teaching method" and that's what I think she's critizicing on this whole video.
Great video! I've been investing some time myself to convince several people (even with a BS in Physics) that there's only one mass and that the latter does not change for moving bodies, no matter the velocity, since m is an invariant of the Lorentz group. It's surprising how people feel it hard to change ideas they've accepted as totally true.
Fun fact: Sickle cell has been shown to be adaptive on a population level. Human with sickle cell trait (single recessive allele) are highly resistant to malaria. There is a high degree of correlation between environmental risk for malaria exposure, and prevalence of sickle cell in local populations.
Thank you for mentioning this so I didn't have to. Evolution works surprisingly well. We have enough time for it to work out well. Theres of course a number of situations where it doesn't due to how things were set up before (and as she mentioned, it didn't select for things after an individual has kids) but for the most part it makes good sense. Sickle cell effects you even in your teenage years too.
@@Norbal.And more recently an example of a different gene encoding a protein called ApoL1, which in certain variants makes people relatively resistant to trypanosomes that cause severe neurological disease (African sleeping sickness), but which markedly increase risk for adult onset kidney disease.
Biologist here. Evolution does not work by "correlations" but by "cause and effect." Organisms do not change by a 1 out of 1000 occurrence, that is anecdotal when it comes down to it. There are specific statistical models that drive this, which is why the p value of 0.05 is used to identify statistical significance. This is why the current "cancer debate" bothers me, as half brained doctors want to blame "genetics" to cause the vast majority of cancers. Less than 5% of all know cancers have a source of mutations, while the other 10% is found to have an organismal and environmental cause. Yes close to 85% of cancers we have no idea what is their cause, but more and more we have looked into evolutionary disease and how certain environmental factors drive this cause. I have met plenty of people who have never smoked in their lives, yet they develop lung cancer. Looking at data, the correlation of smoking is not a causation of cancer. Do not mistake "risk" for causation.
I appreciate these video's so immensely. It's like I'm at a tea time at a seminar and having a casual chat with a physicist. It's very real and personable.
The cool thing about these longitudinal vs transverse mass is that quasiparticles in condensed matter often have an apparent "mass" which can be broken down like this. It's weird, but it's great that it didn't just come out of nowhere.
When I decided to make a career pivot to physics, I was recommended to read T M Helliwell to get a foundation in special relativity. For those interested, great book. All you need is trig (and some patience). Helliwell is very deliberate in always using "m" to mean mass (the only mass), and avoids mentioning "relativistic mass" until an appendix (F) of the same name, which in short, says its discussion is not preferred.
@@MrMeltdown T M Helliwell also has a book titled "Special Relativity" on the topic of ... special relativity. The cover has Einstein riding a bike in space. Hopefully this helps!
I have a piece of paper that says I studied a lot of this stuff (and passed those courses) a while ago -- in the 70's, like last century. Your presentations are superb -- especially weaving in the history of how these things came about. Applause!
I've never ever heard of relativistic mass being taught as a literal thing, as in "this object *literally* gains more mass when moving fast" that's absurd. It's just a way of representing the situation, **as if** it had that mass, but of course it doesn't. It is outdated of course, usually just frame it in terms of inertia now. But there is nothing wrong with using relativistic mass as a mathematical tool. Honestly it's main issue people like Brian Greene explaining this in such a bad way, and skipping over details so important that no one actually understands what it's about anymore.
Fun fact: heterozygotes for the sickle cell allele are less susceptible to malaria, and the allele is enriched in malaria stricken regions. Certainly a steep evolutionary tradeoff, the immune system (including the immune system in a broader evolutionary context) is brutal. Neutral evolution and persistence of almost neutral deleterious alleles, especially lifetime traits that become harmful post reproductive age and experience damped selective pressure, is definitely super common. Interesting though that in this case, it is somewhat of a Red Queen situation, where population-level variation can maintain the species better than homogeneity. And while yes we certainly aren't evolving to get any smarter, parasites do tend to evolve in a specific way. If a pathogen is able to infect more people, or have an increased rate of transmission, then that strain will become more common. If a pathogen becomes too virulent, however, it loses some ability to spread from host to host (host dies or host can't move). Therefore, it will be outcompeted by strains that cause less host damage (at least, in the short term). Yes, rare genetic events occur by chance all the time that can do something completely unpredictable, such as recombination in a double infected cell (this is how we get pandemic-causing strains of influenza every century or so). But it is still true that pathogens tend to become attenuated to their host over time - especially following a shift in host range (like zoonotic leaps). Evolution is a certainly not a guided process, it's probability and statistics. But we understand broader trends, and are very successful at applying that understanding. For example, live attenuated vaccines are engineered via repeated passage. That is, you take a pathogen, infect a cell line with that pathogen, let it replicate, then collect it and do that again and again and again. You might passage it through a variety of cell lines, maybe even at a different temperature so it evolves to be more efficient at Not the human body temperature, depends on the pathogen. The live attenuated polio vaccine is still used in some places. Things don't evolve to be better, but when random variation in a population makes a thing more successful at making more of itself, more of that version of the thing will exist. Sorry i had to microbio info dump for a second, I love your content!!!
I don't know what y'all were expecting, but this is NOT the Roman Catholic "mass" I grew up with. Very weird take on transubstantiation. (Sorry, just trying to give you more "comments Bingo" material. ;-)
Here to say I was the perfect audience for your talk. MIT in the late 1960s required every undergraduate to take four semesters of physics 8.01 8.02 8.03 8.04 (many freshman who took AP Physics in high school got credit for 8.01). One of the three courses was closely based on Feynman volume 1. Soon after graduating I turned to teaching general science and high school physics (which provided not just a paycheck but also a Vietnam era draft exemption). So in the space of a few years I not only learned that mass increases with velocity, I taught it too!
Thanks for taking the time to clarify all this. As someone with an undergraduate in physics and who has just started teaching high school science, I can say there is a huge gap between understanding physics and understanding physics pedagogy. A lot of these 'lies' don't need to be told if students are given the tools to help understand the real complexity of reality. If you need to introduce misconceptions to 'simplify' the model, then you need to rethink how you are teaching that concept.
great video!! you will be pleased to know my ib physics teacher in high school was sure to teach us that things do Not get more massive at higher velocities As I recall though he didn't mention the E naught equation, though its been awhile
Newtonian gravity is taught so badly in schools, I remember my physics teacher telling us to multiply mass by 9.8 to get the weight on Earth, and I said "9.8 what?" and he said "Don't worry about it." Well I worried about it, and it made me think physics was dumb, until I started learning physics for fun later in life and realised actually it's kind of awesome & I probably should have been a physicist, d'oh. (Instead I did chemistry, found I was fascinated by particle physics but excruciatingly bored by hydrocarbons and dropped out) Perhaps there's an alternate universe me doing interesting research because that teacher had just said "It's the rate of acceleration in metres per second per second, but you don't need to know that for the exam" or something. Bit of a microcosm of the focus on passing tests over actual understanding that put off me education in general tbh. It's interesting to learn of the issues with relativity in higher education, there seems to be this pattern in science education of teaching kids wrong, revealing a slightly less wrong version with a smarmy flourish that they have to learn all over again a couple of years later, and repeat until grad school, rather than building a proper foundation.
In post-secondary electronics I started using units to check my algebra. If you get the wrong units: they are either equivalent, or you messed up somewhere.
I just found your channel. This and your other videos are great, I've got some catching up to do. Old engineer, not a physicist, but I still recall catching a glimpse of the wonder in quantum mechanics classes in grad school. Loved the shout-out to Reviewbrah at 39:52
There is a parallel with chemed. There's a bunch of literature exploring the widespread anthropomorphic misconception (students believe atoms "want" things and "strive" for things). The funny thing is that a good deal of this misconception comes from us teaching this way, because its easier for students to understand that "an atom wants to be stable" instead of introducing statistical thermodynamics early on (or at all).
I found your channel today off of reddit and I really like how data driven your thinking is. Will be looking forward to your next video, keep up the good work. I really liked your glass video, the mass video, the flouride video and the spider video; I learned a lot. As a hopeful first gen academic I learnt a lot binge watching your channel today. I also enjoyed(?) your videos on SA and women in science. I sympathise and I thought the videos were illuminating on a bunch of figures that I had no idea about. Any who, good luck with the channel, will be looking forward to the next video.
This unearthed a lot of buried physics knowledge I forgot about from almost 10 years ago. Maybe you'll find it reassuring that one of the things I remembered is that my undergraduate (lower division, even) physics class that covered special relativity made sure we knew that E=mc^2, as written, only applies to non-relativistic, massive particles. I think we then talked about the more rigorous E_0 definition, but that part I don't quite remember.
Just wanted to say (as an avid physics enjoyer, but not a student), that this 34:40 was the best explanation/calculation of time dilation and space contraction I've seen. I love your videos!
This is apropros of nothing, but I just discovered you, and earlier this week, I met the geology doppelganger of you. Just randomly out in the open mountains; we ended up talking through lightfall into the dark and then I helped her carry her equipment back to her car. She looks, acts, and talks very similarly to you, and even went to school in KY. I just find it amusing. I'm actually here to watch your video though, thank you.
I realize that you need to simplify and go fast. For interested viewers the "lifetime of the muon" that Angela talks about is what is called the "half-life." If one starts with a bunch of muons at rest then half of them will be left after 2.2 microseconds and after 4.4 microseconds there will be 1/4, after 6.6 microseconds there will be 1/8 and so forth in inverse powers of 2. Now, a 10 km distance is traversed in 33 microseconds at nearly the speed of light. That amount of time is 15 muon half-lives, which means that one out of 2^15 (=32,768) muons might survive to reach the ground if time dilation were not applicable - practically none but not exactly zero.
I love you! Every video has me in stitches. The way you land all those nuanced punches on chosen ignorance is amazing. You're a Warrior. (epic battle cry) FOR SCIENCE!!!!
Thank you. This is absolutely a misconception I had and I'm now irritated that I was knowingly taught the wrong information because I turned around and unknowingly spread that misinformation to other people.
The best way I've found to avoid misconceptions about evolution is to treat it as "survival of the adequate". As long as an organism is *adequately* adapted to its environment, it will survive and have progeny.
Main thing i got from this video is that cosmic rays are really just H+ ions, which makes so much sense. Totally reasonable that hydrogen nuclei get kicked out of stars (or whatever) and then fly through space until they get to Earth. All this time i was unclear whether these were photons, some kind of mundane particles, or exotic matter. I don't know why we have to mystify everything, so thank you for demystifying the mystery of cosmic rays.
Or He4. Rarely other ions. Can't be neutrons, free neutrons decay too fast. Electrons get captured too easily (high charge to mass ratio). High energy photons can also be a thing. Neutrinos we don't notice because they don't interaft with us enough.
GREAT video! I felt like it was specifically for me because I definitely fell into the camp of sorta-kinda-maybe thought relativistic mass was a thing until I watched that exact Don Lincoln video you referenced and then was still sorta confused after that. And I completely agree with you about the lies we tell to children. It doesn't make teaching much more complicated to caveat the things we say in a way that doesn't make it a lie. But the fact that you DID include a caveat makes it so that some day in the future when the kid is presented with more in-depth information that contradicts the lie, it's not a betrayal. It's just expanding on that caveat. Like I still remember how BETRAYED I felt in GenChem when my professor told us that ionic bonds and covalent bonds are not actually different phenomena. We've just divided a single phenomena into two regions based on electronegativity difference simply because compounds with electronegativity differences in excess of where we draw the line tend to have certain properties while compounds with electronegativity differences below that arbitrary line tend to have other properties. But compounds that are kind of close to that line can be blurry as to which side they belong on. Like that's why we say silicon dioxide (literally the most common compound in the Earth) makes covalent bonds (because the electronegativity difference between silicon and oxygen is not high enough to cross the arbitrary line we drew that divides ionic and covalent bonds), but it's NOT a molecular solid as we generally expect covalently bonded compounds to make. It makes crystals like ionic compounds. And just the other day I was subbing in an AP chemistry class in a local high school, and they were doing a practice AP test that asked them which would have a higher melting point: CO2 or SiO2, and a lot of them were confused because the answer didn't say anything about molar mass. Instead it mentioned that because SiO2 formed a matrix solid, it has a much higher melting point than CO2. And I wasn't sure what to do! Do I double down on the lie and just say something like, "you just need to know that SiO2 is a matrix solid because it's the most common substance on Earth." Or do I potentially damage their trust in their teacher and tell them she's been lying to them all along? I ended up deciding to explain the lie but with emphasis that the lie is useful to believe because it makes it very easy to predict behaviors and properties in lots of situations. It's just that in some few situations, it is helpful to know that it is a lie. But even knowing it is a lie doesn't mean you are going to know SiO2 is a matrix compound. That's still just something you have to know. But WHY it's a matrix compound instead of a molecular one is easier to understand because it's close to the line we've drawn to divide ionic from covalent bonds, so having a mix of covalent and ionic properties isn't all that surprising. But man, I had SO MUCH anxiety the whole time while I was explaining that thinking, "You're going to ruin their trust in their teacher forever!" But it just wouldn't be a problem if we just included the proper caveats in the first place. That same chemistry professor that first told me that ionic and covalent bonds aren't actually different did a good job of caveating other stuff like the Bohr model and some of the other quantum stuff you mentioned in this video that is relevant to chemistry (binding energies, etc). And I felt like knowing those caveats were there made it easier when I took Modern Physics to incorporate the spooky weirdness that that class got into.
As someone who is very much not a physicist but occasionally deals with acoustic physics for his electrical engineering work, I'd say my biggest gripe also is with the kind of strange and dogmatic behavior around causal determinism. Don't get me wrong, causal determinism is a fantastic modeling convention and seems to work really really well in many problem formulations and physical experiments, but it's always felt very handwavey to me that so many physicists just kind pretend that aleatory uncertainty is just this fundamentally unconscionable and that all random processes are fundamentally observable if we've got the "right sensors" to arbitrary degrees of precision.
Nice video! But it left me confused on one point. Why does the thermal energy (which I think is just a disordered form of kinetic energy) count towards an object's mass, while the overall kinetic energy of the object does not. Does this have to do with frame of reference? Like, do fast moving things appear heavier from some static "center of mass" frame? If so, how is this different from relativistic mass?
To put the question more succinctly: do things appear more massive as they move faster when viewed from some static frame? If so, it seems a little arbitrary to say that relativistic mass is fictitious. It seems more appropriate to say that the mass of an object depends on your frame of reference. To drive the point home, consider a planet orbiting a star. If we calculate the mass of the planet on its own, according to the video (if I understand correctly) we are not supposed to include its velocity. However, if we want to calculate the mass of the planet+star system we do include the kinetic energy of the planet. So the question is, from this frame(the star's frame), which mass do we use to calculate the orbit of the planet? If the answer is the relativistic mass of the planet, then it seems appropriate to look at the mas as genuinely reference frame dependent.
@@JohnShmidtt only object moving around 0.25c or faster begin a "relativistic" mass increase.....like, protons , electrons, nuclear collisions in a nuclear collider ect... planets and stars have velocities much slower than this...delta mass = 1/ [sqrt(v/c)]....nothing exciting happens until at least 0.1c.....
@@lunam7249 The "velocity squared" doesn't count towards the "E total combined energies", because it's always zero from anything's own inertial reference frame. The (mc²)² = E²-(pc)² version of this makes it clear that the extra velocity in the linear momentum gets subtracted from the extra velocity in the kinetic energy. So it all cancels out and the total mass remains constant. Remember, E=mv²/2 and p=mv classically. The stress-energy tensor makes this really clear. The 4-velocity in spacetime never changes. What you're calling "kinetic energy" or "linear momentum" is just an arbitrary chosen coordinate transformation into 3D space.
The teaching of kids using inaccurate or inadequate models is understandable, as you say - you have to start somewhere. Some ideas however, also leach into philosophy (being done by smart adults) and have devastating effects. Just one example is how the discovery of evolution informed some of the dumb theories of Nietzsche and others at the time, completely taking the biological theory out of the domain it lives in. Very good talk. My other bugbear is Newton's Third Law being popularly used as "every action has an equal and opposite reaction", and then people confuse that with equilibrium, because it always misses the part "of the same type".
That covid example wasn't very good, if I understand it correctly. "No one is guiding evolution" isn't true. Monitor the virus and try to limit its spread, and you exert an evolutionary pressure for variants that avoid detection. One way we detect it is by the symptoms it causes. It's not guaranteed to happen, but with each person carrying billions (trillions?) of viruses, it's likely I'd wager. (I'm no epidemiologist though.)
There are other pressures as well. Depending on how the virus is spread, if it kills it's host, that particular population probably has fewer opportunities to reproduce and spread.
I think the thing that freaks people out about the correct treatment is that the mass of a system of objects is *not* the sum of the masses of the objects. And if they don't know that, they get really confused. "Ok, objects get more massive if they're hotter because the molecules are moving around? But wait, we just said the molecules don't get any more massive because they're moving around!" And we're off to the races. But really, it's no more complicated than the fact that the length of a sum of vectors is not the sum of the lengths of the vectors. In fact it's the same thing, but with a slightly different geometry.
I think what might possibly have happened is that in the olden days immediately following SR, 'm' used to mean relativistic mass = m_0(1-v^2/c^2)^{-1/2}, so E really did equal mc^2 But over time physicists, or at least particle physicists, found that they almost never really wanted to refer to relativistic mass and they almost always wanted to rest mass. They were like "Writing this '0' subscript all the time really sucks. We're just going to write m instead of m_0. Einstein can sue me." Fast forward to today and all physicists (or at least particle physicists) now only use 'm' to mean rest mass, EXCEPT in E=mc^2 where they understand it in its old sense of relativistic mass. But if you only think of m as rest mass then it's true that E=mc^2 looks really funny, and I can see why you want to change it to E_0=mc^2. But IMHO this is just about conventions.
I really enjoyed the video, thank you for your work. I am not sure but I believe that sickle cell does have an evolutionary benefit. I remember reading that people with sickle cell are less likely to die from malaria.
That misses the point, which is that a debilitating disease nevertheless allows people to live fairly normal lifespans and pass the affliction on to the next generation. And males with sickle-cell often have low sperm counts and motility. Taken as a whole, the reproductive advantage is meager, but it's enough for the gene to flourish. Maybe Huntington's disease would work better as an example, as it develops later in life and so neither hinders nor enhances reproductive success significantly, except when carriers or potential carriers voluntarily abstain.
The fact that this was basically a one hour ramble for 10 minutes of content, and it was still comprehensible, disproves the 'for teaching' argument very Hardcore
Second time through this helpful video. One silly sidenote: my pet fancy mice know the concept of comparatively more, because they play fight if one gets a bigger piece of spaghetti until it is resolved to the appearance of same-amount-ness.
One of my favourite one panel cartoons depicts an obvious Albert Einstein standing before a large blackboard upon which two equations have been crossed out, the first E=ma2 and the second E=mb2. And he's utterly lost in thought. (I've no idea how to superscript the 2.)
Agreed. I get simplified models, but we shouldn't teach half-lies for "pedagogic reasons"; it's causes no end of trouble. The first problem is unlearning what you learned every time you step up to a higher level of learning, and this should be avoided as much as possible. The second is people who never advance to higher level of learning and carry a lie with them for a life time. Both are bad. Sure there's room for simplified models, but there's no reason to teach "E=mc2" when you can teach "E=mc2+pc2 but for now we will focus on the mc2 part which is a special case". And man, the amount of shit I have had to deal with because teachers has said "don't worry about that now" and "just learn the formula" instead of just fucking telling me the truth and let me know why, for now, we will use the simplified case or just use the formula... Maybe this is how some people learn effectively, but for me it has ruined my science education. I am very disappointed. And oh, Newton was a total cook. He spent his later years dong ALCHEMY. Man's a poster boy for Autism Spectrum Disorder; I recognise much of that weirdness in myself.
@@SisypheanRoller Oh, alchemy is still allowed today; it's still weird though. ;) Granted, the line between chemistry and alchemy was much blurrier in those days, but it's curious: being a religious scientist in those days was normal, but few scientists would delve into the occult with such fervor. He was odd though, unmarried for life, no friends, and described by his peers as mean, vindictive, anti-social, etc. So yea. He definitely seems to have been a cook. Reminds me of myself. We won't have to travel into the future to state the obvious; I'm pretty cooky too.
Philosophy person here, I haven't studied Descartes super in depth, but I have read enough on related topics that I _think_ I understand what he's saying in the quote. He's trying to come up with a theoretical definition (ontology) for "substance," and by "extension" here he basically just means physical mass, where a thing 'extending in length, breadth and depth' just means 'has length, breadth, and depth.' The first and third parts define "bodily substance" as anything and everything that extends along these three axes, claiming that when we talk about a "body" we really just mean an "extended thing"--and the bit about "thought" imagines that "thinking substance" is an ideal plain which goes with the material plain of "bodily substance," and that "thought" then defines "thinking substance" in the same way that "extension" defines "bodily substance." Newton's response claims that this leads to atheism because the facts that extension is a law of reality which must have always existed, and that we don't need to have an idea of God in order to understand extension, it therefore follows that we would be able to imagine extension existing without God. (I guess the secret, hidden premise is that God needs everything to ultimately relate back to Him.)
This channel has been a pretty interesting find for me. I was a Physics major in Undergrad. I did A LOT of internships, NASA, SSRL, LISA (very very different I know. Lot's of intern spots and not so many precocious undergrads willing to work for near-nothing. I came from relative privilege so accepting token salary to get in the door was on the table.) And... i didn't love it. I ground my way through the math and the mediocre professors. Loved the grad students and good professors... but I didn't love the science work I was seeing. And when I was in the NASA internship I really got to see what was on the PhD path. I didn't like what I saw, long years of obscurity and marginalization. I choose to jump to software. I look back at some of the study and work fondly. But the institution and the ... grind I couldn't justify. Love your videos, please keep it up.
I find that this very often causes serious confusion with general relativity as well. People ask the sensible (as far as they have been educated) question "What happens when a particle is moving so fast it's mass becomes to large enough it collapses into a black hole?" In terms of the actual theory, this is nonsense. Every particle is stationary in it's own reference frame, and collapsing into a black hole is definitely not something a particle at rest can do. It's also not something that can be relative. Whether some matter has collapsed into a black hole is something all accessible observers will agree on. (Observers inside the collapsing black hole may or may not agree; that's been an interesting sore spot in the theory for a while. Since they are unavailable for comment after the fact, physicists have uncomfortably decided it doesn't matter.) This misconception comes from the belief that mass actually increases due to motion, _and_ that gravity is due to mass. Neither of those statements are actually true, but that's not always been comminicated clearly. (For the record, the resolution to the paradox is that firstly, particles only have their intrinsic mass as argued in this video. Secondly, general relativity has gravity couple to the energy-momentum. Not even just the energy; the energy _and_ momentum. A particle moving very fast has a lot of both, which means that gravitational effects from the energy can be cancelled out by the almost-as-large effects from the momentum. I don't know all the details, because General Relativity, but given that General Relativity simplifies to Special Relativity in the absence of large gravitational fields (which are reference-frame-invariant), this is clearly what has to happen.)
I wrote some other (longer) comments on this video about this exact thing. Kinetic energy and momentum are functions of velocity... which is relative, and zero in an object's own inertial frame. The 4-velocity is invariant, and it's an arbitrary coordinate system choice you make to call part of the 4-velocity momentum (movement in 3-space) or kinetic energy (movement in time). Anyway, only energy internal to the object (or arbitrarily chosen hypervolume of spacetime) is what counts for gravity. You're always moving at the same speed through 4D spacetime, with different amounts of that speed in the time direction or a space direction.
Similar with Mendelian genetics! I can’t speak about genetics on the level she can about her field, but the understanding of recessive and dominant alleles and inheriting one allele from each parent and Punnett squares etc is a huge huge simplification and actually only true like two times ever (though the more I learn about biology the more I think that is true with every single biology/biochemistry rule)
Philosophy grad student here. Unfortunately, you got what Descartes is saying wrong. I would love to know where you got "the edge of space" thing from (since it's never mentioned in the quote you showed), but essentially what Descartes is describing is much simpler than any of that. What differentiates "matter", defined as extension, from such things as souls or ghosts or thoughts (in Descartes' conception), which are unextended, is that matter takes up space, quite literally. A thing made of matter physically occupies a particular spatio-temporal location at all times and how much space it takes up can ordinarily be defined by measuring its width, depth, length etc., i.e. its extension. Example: a body. As a result, two things made of matter, i.e. two extended things, cannot exist in the exact same place at the exact same time; each takes up space that cannot simultaneously be occupied by the other. The same isn't true for souls or thoughts, as Descartes imagined them, and if you think of a ghostly soul existing (as Descartes did) you can see why: it's not physical, so it could share its spatio-temporal location with another unextended thing or, more importantly to Descartes, with an extended thing. In other words, because souls are unextended they can exist in the exact same spatio-temporal location as the extended bodies that house them while remaining two separate things in nature (plus, a soul / the mind cannot be measured precisely because it's unextended). This stands in contrast to Aristotle for whom matter does not physically take up space (in his philosophy, it is a necessary part of physical things existing, but unlike the thing it creates, it's not itself physical in the extended/measurable sense).
Thank you for this video! I’m an engineer now and all I took away related to relativity when I studied basic physics in undergrad was that nothing goes faster than the speed of light. Adding the nought makes it make sense to me.
The problem with this, is that this mass (rest mass in fifty year old textbooks), if the only kind of mass, doesn't have any physical meaning. It is not "that which exerts gravity" (that would be energy - all of it). And it is not "that which resists acceleration" (that would be energy - all of it). And finally it is not... oh wait, that's all of them. Oh ok, it's "the energy content, at standstill of the center of gravity, of a system we can't be bothered to describe in more detail." I.e. no physical meaning, but fine for square cow exercises. So I guess it's alright for introductory textbooks. "Internal energy" of course, is not a concept in the Theory of Relativity (nor in any other fundamental theories in physics). At considerable relativistic speeds and great spacetime curvatures composite objects do not exist. The laws of physics cannot tell the difference between two molecules whizzing past each other in a closed weightless box (internal energy) and in open space (no internal energy, just two particles moving independently of each other), so the gravitational effects must be the same, though the "only one mass" is not. And no, you don't get heavier when you move faster, because... You are always at a standstill! That's the relativity part of the Theory of Relativity. The relativistic mass is a concept that only has meaning for someone else observing you, and if they want to swing a bat to accelerate you as you move by, they'll have to put in a lot more energy in the bat, the closer your speed is to the speed of light (even more than in Newtonian mechanics). Give it another couple of decades and the youtube videos will be all complaints about why people are still talking about mass when explaining physics. There is no mass! And that'll be fine. That is, after all, what the identity really means.
"I get existential dread when talking about particle physics" Coming from a person who works with dark matter "the unknowable thing invisible to all", that's very rich.
if it makes you feel better, when I went through undergrad we were never once taught relativistic mass, we were only taught the rest mass and we all understood E = m c^2 to be calculating a rest mass energy (without bothering with any subscripts)
WELL --- I do think Einstein did something amazing that the other scientists did not. Maybe I didn't say it well enough. HE THREW AWAY THE AETHER. He had a fundamental difference in how he interpreted the ideas that others were figuring out and from that he had his miracle year where he published 4 papers that changed every field of physics. He developed his own theory from his interpretation of space-time (though he didn't call it that, that was MInkowski) and from that theory he re-derived the previous results. That is amazing!!
@@acollierastro probably dumb question but didn't Newton do a similar thing, come up with something novel based on what previous people did? Also imagine getting famous for throwing things away.. Except Einstein throws out concepts I just throw out the trash :(
That's how science usually works. No individual invents all the individual new ideas AND connects the dots. Basically all breakthroughs in STEM occurred because many brilliant minds came up with various aspects of the breakthrough, and one or more additional brilliant minds puts the pieces together. Einstein ditched the Aether, and connected all of the existing dots with Relativity. Newton's breakthrough just added to what Kepler and others had already came up with. Darwin didn't come up with every aspect of Evolution. It can be thought of as a collaborative jigsaw puzzle. Many people contribute to building the puzzle's outline and filling in the details, but it only takes one or two people to add the last few pieces and figure out what the puzzle really is. All the big names just added the last pieces and described what they saw.
Brilliant. I just found your channel today and this is the third video I've watched; the first was your dunk on String Theory (funny and informative), the second was a hard-but-necessary-to-watch 2 hours (I'm sure you are aware of which one that is, and it sure as hell explains the continuing lack of women in the sciences) and then there's this excellent video. You've just gained an enormous fan. Kudos.
Yes: knots are speed, sea miles per hour to be precise (not land miles, sea miles are bigger, like 1.8 km). 60 knots however is a very high speed for a ship AFAIK, especially in 18th century.
The reason the names are weird is bc the descriptive options are so close to spiritual and religious ones you have to stray away from that foundation in an abstract way, like scribing out a word and making that scribble the new word. Also the vast options combined with varying imaginative skills.
I liked Prof Strassler's argument that well sure you *could* define mass as "relativistic mass" if you wanted to but why when then questions like "what is the mass of an electron?" doesn't have a single answer, and anyways we already have a term for that quantity and it's "energy". And for me at least, "mass is the internal energy of a system" just makes the fact that this is an *equivalence* so much more intuitive. I wish that's how it'd been taught to me.
Watched the video, thought I should read up on this stuff to get back into mental shape, be annoyed that I have to look up the name and paper... and it's there, linked in the description. My savior!
This reminds me a lot of math education. Everyone thinks math is basically numbers (or letters representing numbers) until abstract algebra and then boom.
Bodies have 3 reactions to force, weight (causing a body to move), inertia, and causing a gravitational field. ``Mass'', therefore, depends on the equation/model being used. Most models today ignore friction.
A teacher of mine, engineer, dumbed down physics to "make structural engineering easier to digest" in the first of 4 courses, leaving everybody confused and barely making it throught said courses.
I subscribed a couple days ago and so opened this particular video with much trepidation. I thought: "pleasepleaseplease let her reference Lev Okun as the proper way to define mass". So thanks; I extremely enjoyed your explanations, and might use some of your arguments. I especially like that you criticize other physics big names. Okun stated that "relativistic mass" is a pedagogical virus. You are absolutely correct to criticize the textbooks that propagate it. I teach a graduate course on accelerator physics and the first lecture on dynamics I always tell students : "m is mass. You will not see any reference to m_0. The '0' is redundant." Further, E=mc^2 with some re-definition of mass Destroys the connection of Energy to the Hamiltonian. One cannot derive the dynamics from it.
Since other people are posting Newton fun facts here's another: Before 1945 the University of Cambridge was counted as its own constituency in British parliament and the MP (Member of Parliament) for that constituency was determined by a vote from the University students and faculty. Isaac Newton was selected as one of these MPs from 1689-1690. He attended votes and debates but never said a word except once. Isaac Newton stood up amongst all of his peers and I like to imagine the other MPs were on the edge of their seats wondering what this modern genius was about to say. He drew his breath, turned to an usher and said something along the lines of: 'Can you open the window it's stuffy in here.'
Small point on sickle cell anaemia - it is a recessive genetic condition and while individuals with two sickle cell alleles have no evolutionary advantage, individuals with one sickle cell allele are less susceptible to malaria than individuals with zero sickle cell alleles. So there is an evolutionary pressure that makes having a single sickle cell allele advantageous, which is part of the reason why these traits are more common in parts of the world where malaria is endemic.
Sickle cell anemia actually confers a benefit to carriers of the mutation, as it provides resistance to malaria - the decreased oxygen carrying capacity is obviously bad, but minimally so in equatorial regions where elevations are closer to sea level (and therefore have higher O2 levels than at higher elevations).
on the bright side, my physics teachers and professors through my bachelors in geophysics have all made it a point to clarify e=mc^2 as not being the full equation, so i guess there's a lot of people who feel the same way you do about this mess, haha
Fun fact: Sickle-Cell Anemia is a devastating disease, but it is technically recessive. However, being heterozygous for sickle-cell (having one sickle-cell gene and one "healthy" gene) means your red blood cells live for less time, which means malaria can't live in your red blood cells and complete its life cycle. So technically, sickle-cell *carriers* are the reason that sickle-cell -- a very devastating and heart-wrenching disease -- continues to exist, is because carriers who don't express the sickled cells tend to get less malaria and thereby live longer and pass along *their* genes That said, yes it is evolving by not evolving to and I'm glad you make the distinction :)
