10 ms·
Well, Actually – Physics Answers
- nayuki 6y agoThe author Sabine Hossenfelder also has a YouTube channel where you can find more physics content: https://www.youtube.com/channel/UC1yNl2E66ZzKApQdRuTQ4tw https://www.youtube.com/channel/UC1yNl2E66ZzKApQdRuTQ4tw
- jasonlfunk 6y agoI thought all of these were interesting except number 3. The rest were common “misunderstandings” in popular culture. #3 seems more like internal physicist pedantry.
- lucb1e 6y agoTo be honest I found most of them to be fairly pedantic. I knew all except number 8 (Lorentz contraction is new to me), but all of them are of the style "might seem that way but technically..." I didn't dislike the article though, that's not really what I mean to say. Was conveniently to the point and I can just lookup more about Lorentz contraction if I want to :)
- TeMPOraL 6y ago#3 pops up when you start reading up on meteorology. I was quite recently surprised by this myself, when some article on climate I was reading started talking about gravity waves... The only one I didn't like was #6 - I think it may be wrong. Not just because of language use (words gain multiple meanings over time; dieting!weight != physics!weight), but also because, while weight is indeed a force (a vector), it's also proportional to mass - so if you lose mass, you also lose weight.
- StavrosK 6y agoRight, but when you lose weight you don't necessarily lose mass. You may have just gone to the moon (or Everest, I guess).
- TeMPOraL 6y agoFair enough.
- andi999 6y agoOr simpler boarding an airplane. If I remember correctly the effect is around 0,5% which can be measured with a normal scale.
- StavrosK 6y agoI don't know if you can measure that, the airplane would have to be flying perfectly level (to at least within 0.5%).
- andi999 6y ago0.5% is around a pound for a lot of people.. should be ok, isnt it?
- StavrosK 6y agoIt's not the magnitude of the measurement, it's that if the airplane is descending at 1 degree when you measure, you'll get around 1% less weight than your actual mass. If the airplane is descending at 90 degrees, you weigh nothing.
- avalys 6y agoMost of these are silly pedantry of the type that, IMO, turns people away from math and science by making it seem like you have to be interested in pointless, inconsequential distinctions and “gotcha” factoids to be good at science. Unfortunately material like this also makes up a substantial fraction of what passes for science education in the US.
- human 6y agoSabine is known for that kind of sense of humour. She is actually critical of the scientific elites.
- avalys 6y agoOh, is this a parody? It is a little too close to the source material, hah.
- 2pEXgD0fZ5cF 6y ago"Today I will tell you how to be just as annoying as a real physicist. And the easiest way to do that is to insist correcting people when it really doesn't matter" The video is pretty nice in that it teaches interesting facts and at the same time criticizing the behaviour you mentioned (I agree with you). The video itself is named "How to talk like a physicist", so the blog post linked here could be a bit misleading in that regard if one does not know Sabine Hossenfelder already.
- wruza 6y agoI don’t think that “annoying” is not figurative here and I do not agree. Instead of being fed with eli5 explanations as I was in my childhood, these people and articles uncovered an entire world of hard, real physics to my layman curiosity that I still try to grasp. It was not what turned me off physics, it was what drove me into it. If someone cannot stand pedantry, chances are they’ll be fine with explanations that are simply wrong and nobody will point that out. See a root comment on light speed in medium itt, for example.
- anonytrary 6y ago> 2. “The Speed of Light is constant.” Well, actually, the speed of light is constant, it just takes time to ping-pong around a lattice/gas. Photons hit particles, get absorbed, and re-emitted, which causes an effective slowdown at a larger scale. A gas is just vacuum with particles floating around in it. When photons travel between those particles, they are traveling at c. The effective slowdown is determined by the lattice/gas, and we denote this slowdown with the refractive index... > 7. “Light is both a particle and a wave.” Well, actually, it’s neither. Light, as everything else, is described by a wave-function in quantum mechanics. A wave-function is a mathematical object, that can both be sharply focused and look pretty much like a particle. This is a great example of how quantum mechanical analogies don't work if over-analyzed. A great professor of mine once told me that you can't look too far into classical analogies for quantum mechanics -- you will end up coming to the wrong conclusion. At the end of the day, understand the math. As someone else in the comments said, most of these are pedantic gotcha's. I thought the one about water being blue was the only one that actually surprised me as something people thought was true.
- wruza 6y agoPin-ball theory is a common misconception, afaik. https://qr.ae/pNSdj9 https://qr.ae/pNSdj9 (quora answer with sixty symbols video link in it; explains reasons for every debunked version of why)
- Bjartr 6y ago> it just takes time to ping-pong around a lattice/gas. Photons hit particles, get absorbed, and re-emitted Well, actually the speed of light, specifically the rate of propagation or phase velocity, is not slower in mediums because of absorption and re-emittance. Instead, a photon is affected by feedback loops between its oscillating electric field and the charges of atoms it is passing near, without being actually absorbed by the atoms. Paraphrased as best I could from: https://en.wikipedia.org/wiki/Refractive_index#Microscopic_explanation https://en.wikipedia.org/wiki/Refractive_index#Microscopic_e...
- randallsquared 6y agoOkay, but I would expect the main takeaway is that, for the purposes of things like tachyons and black holes and CTCs, the "speed of light" is still c, not whatever speed one measures in various non-vacuums. The only assertion of which I'm aware that the apparent speed of light in a medium is what really matters for relativity was Ron Mallet's work: https://www.phys.uconn.edu/~mallett/main/papers.htm https://www.phys.uconn.edu/~mallett/main/papers.htm . I don't believe there's been any experimental confirmation of it, though.
- 8bitsrule 6y ago"Science is the belief in the ignorance of experts. When someone says ‘science teaches such and such’, he is using the word incorrectly. Science doesn’t teach it; experience teaches it." The Pleasure of Finding Things Out, p.187 https://philosophynow.org/issues/114/Richard_Feynmans_Philosophy_of_Science https://philosophynow.org/issues/114/Richard_Feynmans_Philos...
- wruza 6y agoThe amount of simplified and not well-actual information we are crammed with in our lifetime is enormous (not only in physics). So much bullshit that isn’t even wrong and it lives happily in our minds for decades. Once I realized this, I tried to re-explain many things by studying them in ways that are accessible to a full-time employed layman. You may find it annoying and/or pedantic, but I’m very grateful to such authors, popsci enthusiasts and participating scientists for helping me on that hard path. Thank you all, guys!
- s_gourichon 6y agoAre you Sabine? Else please provide a link to what you write, thanks.
- wruza 6y agoNope. Neither can I provide a link because that’s just my own experience and it wasn’t documented before. (I didn’t notice that this could sound as author’s comment, sorry)
- TeMPOraL 6y agoYup. The list over[0] is a good place to get started. It may be annoying[1] to correct people on such stuff, but it is important. Misinformation established at social/cultural level affects us all. If you ever wonder where these people afraid of microwave ovens or infrared thermometers come from[2], it's this: many misconceptions adding up to an invalid mental model of the world, which makes them susceptible to further scares[3] they hear or read. -- [0] - https://en.wikipedia.org/wiki/List_of_common_misconceptions https://en.wikipedia.org/wiki/List_of_common_misconceptions [1] - Probably as annoying as hearing someone spout these misconceptions once you know the correct answer. [2] - And behind each such person there's dozens if not hundreds people who harbor similar beliefs, but won't admit to them. [3] - It's not just conspiracy theories, either. There is plenty of established businesses that just sell this kind of bullshit, usually as a part of an ad delivery vector. For instance, all the health and lifestyle magazines general population reads are a major source of annoying health-related misinformation.
- larkeith 6y ago> "Water is blue because it mirrors the sky." Seeing that people believe this was quite unexpected, at first - it's such an obvious phenomenon looking down into any slightly deep body of water. But on reflection, it makes sense: many (most?) people in the world might live most or all of their lives without going beyond the shorelines of a sea, ocean, or larger lake/river. It's a good reminder to always be critical of the assumptions you make, and how much they depend on your own context. (If you ever get the opportunity, visit Crater Lake. The drop from blue to midnight to pitch is beautiful.)
- simonh 6y agoDid you read the whole answer, including the bit at the end? >...So the major reason the oceans look blue, if they do look blue, is indeed that they mirror the sky.
- StavrosK 6y agoI contest that, the sea looks blue in overcast days too.
- marcosdumay 6y agoHum... The sea color changes a lot depending on the sky condition. In overcast days it's way more likely that it will be green than blue. (And, of course, after it rains there is a good chance the water will actually be green, but it's a different timing and a different shade of green.)
- yodelshady 6y agoWell actually, the Earth clearly isn't round, as anyone who has been near a hill or large body of water can attest. Assuming you're not travelling very far, a "bumpy Flat Earth" geometry works quite well, and didn't your lecturer tell you physics about using "models that work quite well"? That said, one of the things I've enjoyed about travelling a decent way North-South is how the night sky feels different. I do wonder how many Flat Earthers have had that opportunity.
- Koiwai 6y agoI won't call a basketball 'not round' because it has a rough surface, would you? The highest mountain or deepest canyon on earth are roughly 10 km above/below sea level, compared to the radius of earth it's way smoother than a basketball. As for the flat earthers, you assumed they would accept another concept that stars are very far, if they resides not far above us, that could kinda explain that. For the record I'm not a flat earther, please do not downvote me because of the previous paragraph.
- function_seven 6y agoI still stay the Earth is round, but not because of the relative roughness or smoothness of the surface. Oblate spheroids are round in the same way my dinner plate is round!
- j7ake 6y agoIn the end it depends on what you want to predict from your assumptions that tell you whether it’s okay to assume a ball is round or the roughness matters. Would you call a golf ball round? Depends. If you want to calculate how a golf ball travels upon being hit by a golf club, then you’re going to get more predictive results if you consider the dimples in the golf ball. If you only want to calculate the number of balls you can fit in a bag, by all means ignore the roughness. Just as in the flat earth debate: it’s perfectly reasonable to assume flat earth when planning your bike trip, but the assumption breaks down when you want to fly large distances. For me it is all about knowing which models and abstractions are useful in which contexts rather than philosophising what is “real”.
- ummonk 6y agoRe 6 well actually, when people say they've lost weight, they're talking about the magnitude of their weight as measured; this just so happens to be proportional to mass since gravity + centrifugal force is relatively constant on Earth. As to 8, well actually when referring to objects one would by default use a reference frame where those objects are approximately at rest. E.g. a reasonable reference frame would be one where the aforementioned center of mass is at rest. So it's reasonable to say the Earth and Sun are 8 light minutes apart.
- falseprofit 6y ago4. Since when are oblate spheroids not “round”? Is “round” really a synonym for “shaped like a perfect sphere”? 5. One reason we might not see quantum effects at a large scale is that they are small. Another reason might be that the effects are large, but we are entangled with the system we are observing.
- beloch 6y ago"Today I will tell you how to be just as annoying as a real physicist. And the easiest way to do that is to insist correcting people when it really doesn’t matter." We primarily say "Well, actually..." to each other, and it's pretty much unavoidable. Physics is a diverse, complex, and difficult field. People working in any given niche have to make a plethora of simplifications and assumptions about peripheral stuff just to make it manageable. It's a bit like how computer scientists usually don't worry about the solid-state physics of a logic gate, how a CPU is designed, or how compilers are written when they're writing a program. Yes, it's the foundation their work is built upon but, most of the time, they can safely ignore it. When we say "Well, actually...", some of us are letting our insecurities show by trying to one-up everyone else. Some of us (probably a lot of us actually) are obsessive about certain things that fall within our bailiwick. We have difficulty staying silent when somebody smooths over something wonderfully crinkly that we can't resist talking about. Mostly, we're just pointing out things that we find genuinely interesting. This serves a valuable purpose. Sometimes the simplifications and assumptions we make bite us in our posteriors. When we talk to other physicists, mathematicians, etc. outside (or within) our own specialties, sometimes the "Well, actually..."'s lead to important realizations. Most of the time, it doesn't really matter. Well, actually, sometimes it really does matter!
- ttiurani 6y agoVery OT (and hope this is not frowned upon) but just want to say thank you for introducing me to "bailiwick". As a non-native speaker I will make it my goal for 2021 to use it in a sentence!
- SftwreEngnr 6y agoPerson use big words smart!
- inglor_cz 6y agoInterestingly, both Jersey and Guernsey are officially bailiwicks headed by bailiffs until today. https://en.wikipedia.org/wiki/Jersey https://en.wikipedia.org/wiki/Jersey https://en.wikipedia.org/wiki/Bailiwick_of_Guernsey https://en.wikipedia.org/wiki/Bailiwick_of_Guernsey
- figassis 6y ago> 6. “I’ve lost weight!” Well, actually weight is a force that depends on the gravitational pull of the planet you are on, and it’s also a vector, meaning it has a direction. You probably meant you lost mass. Most people expect to not leave the earth, so for all purposes, losing mass is the same as reducing the earth's effect on one's body, which is what people feel. We don't feel mass, we feel weight, so if we feel lighter, we've lost weight.
- cambalache 6y ago> weight is a force...and it’s also a vector, meaning it has a direction Well, actually this is redundant. All forces are vectors.
- corty 6y agoWell, actually, the zero-vector has no direction and every direction.
- raverbashing 6y agoI think n.8 is too nitpicky even for that kind of list. Of course if you're talking about the Earth-Sun distance you are taking one of them as the reference. If you're in a different frame, then you should do the math for it. But I think at the surface of the sun (if you could stand there naturally) the time/distance is still around 8min (happy if someone does the math) - Note that the statement says 8min, not 480.000s which would be metrologically wrong.
- maffydub 6y agoOn "Black Holes have a strong gravitational pull.”... > For a black hole you keep falling towards the center, cross the horizon, and the gravitational pull continues to increase. I've always struggled with "crossing the horizon". - From the perspective of an observer falling into the black hole, I understood that the event horizon falls away from you, so you never reach it (maybe you get "closer", though - not sure). - From the perspective of an observer away from the black hole, time appears to slow down for the object falling into the black hole, so it never crosses the event horizon. Am I right? What does it mean to talk about crossing the event horizon if this never happens from either of the observers' perspectives?
- PopeDotNinja 6y agoIt would have to cross the event horizon eventually, or the black hole would be this black dot that never grows and is surrounded by the worst traffic jam in galactic history.
- marcosdumay 6y agoYet, GR is adamant on giving us no possibility of ever seeing anything fall into a black hole. So, how exactly does that work? And yeah, I am aware we've watched things falling into black holes, although I'm not sure how much different the "it's frozen just before the horizon" scenario would look like.
- MauranKilom 6y agoThe light emitted by said object would get more and more red-shifted. That's a consequence of "time would appear to pass slower and slower".
- marcosdumay 6y agoIt's not like we can observe light from near the horizon anyway. An active black hole is a hellish place to observe anything. What observations we have come from gravitational waves.
- phkahler 6y agoThe distance from earth to sun is actually 8 CVS receipts.
- spodek 6y agoI saw the point of the video was to call out the annoying habit of correcting with pedantry, focusing on words instead of meaning, showing off how smart you are at the expense of meaningful communication -- the opposite of "yes, and". It's incredibly annoying to talk with people like that except if you like being a pedant back. So it has its place, but it undermines teamwork. I see it as a property of nerds, which I say as a nerd myself with a PhD in physics. I still do it and feel the tug to, but I've worked hard to learn to listen and reflect with more empathy and generosity.
- ltbarcly3 6y ago>> The difference between a black hole and a star is that if you fall onto a star, you’re burned to ashes when you get too close. Well, actually, the difference is that all non-black-hole masses have spacial extent, so if you get 'too close' you are now inside the object and the gravitational attraction decreases if you continue to move closer to the center of the object, since you are now inside the 'newton shell' of some of the mass. There is no place you can be relative to any non black hole where you can find a gravitational field as strong as what you would find near the event horizon of every black hole (which is always equal to any other black hole, and is basically by definition the strongest gravitational field that can be found anywhere). Black holes do have stronger gravity than non black holes.
- cwmma 6y agoThe Earth is an oblate spheroid Well actually it's a Geoid, which is defined as something the shape of the earth and is approximately slightly pear shaped. That being said I do GIS stuff professionally and 90% of the time just pretend the earth is spherical.
- rory_h_r 6y agoGood physicists know what level of abstraction to use for any particular question. Too high and you gloss over what's interesting and too deep and you miss the forest for the trees. This is why the the Feynman Lectures are invaluable resources even if you already know the material.