[HN Gopher] Veritasium: The SAT Question Everyone Got Wrong [video]
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Veritasium: The SAT Question Everyone Got Wrong [video]
Author : goplayoutside
Score : 254 points
Date : 2023-12-26 20:04 UTC (1 days ago)
(HTM) web link (www.youtube.com)
(TXT) w3m dump (www.youtube.com)
| krackers wrote:
| This was also the infamous amc 2015 "clockblock" question
|
| https://artofproblemsolving.com/wiki/index.php/2015_AMC_10A_...
| CrazyStat wrote:
| I remember having the same question (probably with different
| sized circles) in our local high school math team competition
| ca. 2002. I got it wrong.
| genocidicbunny wrote:
| I distinctly recall having to solve a version of this in my
| 2nd grade math class. Only about half the class got it right.
| lostmsu wrote:
| The title sort of spoils it as it becomes obvious you need to
| look for some issue with the trivial number solution.
| anamexis wrote:
| I think any video about it would spoil it, because you wouldn't
| make a video about a trivial number problem.
| orenlindsey wrote:
| The guy who figured this out (who Veritasium interviewed) is
| crazy smart.
|
| Also, a lot of kids math problems (middle school and below) are
| super vague. I get that they're designed to teach a concept, but
| they could do it in a more exact/precise (idk what the word is)
| way.
| dudeinjapan wrote:
| I think you are looking for the word "cromulent".
| plibither8 wrote:
| Did you just learn this word too from another recent thread
| on HN? I did, haha!
| mewpmewp2 wrote:
| Considering how little educators are paid, I'm amazed as to how
| much they have been able to come up with and do already,
| though.
| makeitdouble wrote:
| The vagueness is seen as a feature, not a bug. The kid is
| supposed to read between the lines and find out what the
| problems are really about.
|
| That's straight how my teachers would explain it to us, and you
| see that line of thinking in the "problem solving" bits where
| the text is intentionally made harder to decrypt.
|
| Reading skills and shared background assessments are baked into
| most math tests, even if that's not the focus of it.
| peyton wrote:
| I'm thankful I was doing competition math by that age and had
| access to more rigorous materials than these "readiness"
| assessments.
| kuroguro wrote:
| I think vagueness is kindof ok in math/physics questions - if
| you think about it there's usually and interpretation that
| makes more sense, but I doubt most of them are made that way
| on purpose.
|
| Where I really hate to see it is humanities e.g. psychology
| tests/surveys - if after reading a question I immediately
| think of 3 different interpretations I just think it's a bad
| test. And if I spend any more time thinking about it I get
| almost nowhere.
| makeitdouble wrote:
| > there's usually an interpretation that makes more sense
|
| Yes, I see it as "background" part, or "common sense"
| perhaps.
|
| I's funny when for instance you have grocery questions
| about little Jimmy having 3 bags with 4 buns in each, so
| how many sausages does he need to make hotdogs with all the
| buns ?
|
| That's cute and straightforward as long as you know what a
| hotdog is, which is common sense for the question writer.
|
| I don't think that's something that needs to be (or can be)
| changed, as long as school and exams are seen as a
| formative step, and not a single chance you'll have to make
| a decent living. Kids in the later group will have a hard
| time either way.
| Aeolun wrote:
| > That's cute and straightforward as long as you know
| what a hotdog is, which is common sense for the question
| writer.
|
| Even if you don't know what a hotdog is, it's indicated
| you use sausages and buns to make them. The most
| straightforward method of doing that would lead to the
| correct answer.
|
| There may be kids that figure that's too simple and
| assume they need two or three sausages per bun, but those
| will be the minority.
| lupusreal wrote:
| Most sandwiches are made with two pieces of bread. Buns
| happen to be two-pieces-in-one, which isn't disclosed in
| the question. Somebody who has passing familiarity with
| sandwiches but not hotdogs or buns specifically might
| think it takes two buns to make one hot dog.
|
| Thankfully I think _most_ questions usually aren 't like
| this. Cultural loading in questions is a popular excuse
| for discrepancies in testing outcomes but those
| discrepancies have a nasty tendency to persist even when
| tests are redesigned. Usually there's something else
| going on which causes the outcome discrepancies,
| particularly bad parenting.
| whoopdedo wrote:
| Which is a big problem I have with these sort of tests. A
| problem that exists in most I.Q.-like assessments. Rather
| than evaluating how well the student is able to use their
| brain it's instead filtering those who were coached to think
| the same way as the test writers. That creates homogenity
| which is why I believe there are cultural divides in test
| results.
|
| Like the Cold War era stories where spies use seemingly
| innocuous or nonsensical code phrases to identify each other.
| "The sparrow flies at midnight. Calculate the velocity it
| would need to reach Berlin in 7 days."
| mhh__ wrote:
| Practically I think that just means that the kids end up
| getting taught vast quantities of "exam technique" rather
| than content.
|
| I taught myself the essence of calculus when I was 14 or 15 -
| there were holes in my knowledge but it took I'd estimate 5
| years for regular education to catch up to the intuition I
| built then (on a houseboat on the Thames even, sounds
| romantic except for the fumes)
| refulgentis wrote:
| I was homeschooled through 6th grade, entering regular
| school, it was striking just how "slow" everything seemed.
|
| Conversely, I struggled immensely for a year and a half,
| once my 3 year lead on material ran out.
|
| The difference in quality and speed in something you're
| self-motivated to do and are doing at your own pace, versus
| something you're being told to do at someone else's pace,
| even with the same person in both cases, is quite
| astounding.
|
| Or maybe that's the viewpoint of someone with ADD, and most
| people can keep steady progress _and_ lead balanced lives.
| I'll never really know.
| dev_hugepages wrote:
| I don't think you're alone, i have the same "issue"
| makeitdouble wrote:
| Yes. Kids moving countries hit that wall at full speed, and
| have to learn the exam system and quirks on top of the
| actual content.
|
| The interesting aspect to me was how they need to take a
| step back and look at it as a set of made up conventions,
| when they might have just absorbed it as universal truth
| otherwise.
| atoav wrote:
| Depends on the kid. Don't you think? For some the
| repetition is the only chance they get to find a pattern.
|
| I think where "traditional" education truly sucks tho
| (unless you are blessed with a gifted teacher), is giving
| you an overwiew of how the pieces fit together and what is
| behind each of them.
| irjustin wrote:
| This has been a huge contention point of Common Core and why
| so many kids had such huge problems with the overall test.
| Hard questions that seem/potentially-are vague, but are hard
| questions first.
|
| Personally, I'm a big fan of what Gates was attempting to do,
| but I have teachers in my family who couldn't get rid of
| Common Core from their schools fast enough. Debates with them
| were never good and me, not being an operator, wouldn't dare
| tell them how to do their jobs.
|
| But, I understand difficult, standardized testing isn't a
| good answer, but really how do you get a whole nation to up-
| skill?
| csense wrote:
| De-centralize and de-nationalize schooling. It's clear the
| feds have no idea how to make the education system work.
| Let the states have ~50 different curricula, or individual
| schools to have ~hundreds or ~thousands of different
| curricula. Even if they're bad on average, some of them
| will probably figure out how to make an actually good US
| school by sheer luck. Once we have that, the others have a
| model to copy.
| kemotep wrote:
| I haven't been in public school in 15 years but there was
| 2 public school districts, a public-private magnet school
| associated with the State University and a Private
| Catholic school with radically different curriculum in my
| hometown. Even between the two high schools in the same
| district there was different courses and funding because
| of the property taxes funding specific schools and one
| school was on the nice side of town.
|
| As far as I understand, most public schools are
| decentralized, at least the State level, if not further.
| Are you claiming that is not the case currently?
| irjustin wrote:
| > De-centralize and de-nationalize schooling. It's clear
| the feds have no idea how to make the education system
| work. Let the states have ~50 different curricula, or
| individual schools to have ~hundreds or ~thousands of
| different curricula. Even if they're bad on average, some
| of them will probably figure out how to make an actually
| good US school by sheer luck. Once we have that, the
| others have a model to copy.
|
| Sadly, we already know what works, individualized/custom
| attention that exposes the kid to a lot of fields. A
| worse way to put it, more money == better education. And
| this is largely true even if specifically wrong.
|
| But once you try to scale that up, everything falls
| apart.
| rtsil wrote:
| > Once we have that, the others have a model to copy.
|
| That is a bold expectation. Some schools will have an
| incentive to just have as much pupils pass the exam by
| lowering the bar, other will be incentivized to just
| teach the bare minimum, others won't have enough money if
| the model of excellence is expensive (and it probably
| will be).
|
| And the model that applies to, say, a child who grew up
| with college-educated parents won't necessarily apply to
| the child from a blue collar family.
|
| That is just to say that this is a hard problem. My
| intuition is that the only way to achieve the best
| education (excluding the case of hypergifted people)
| seems to be by throwing money at it through personalized
| education and tutoring and solving the child's other life
| problems, i.e. the wealthy kid model, but obviously
| that's not realistic when it comes to mass education. But
| maybe mass education (at the level we seem to expect from
| it) isn't realistic.
|
| Or maybe we should reduce the number of subjects taught
| in school to math, language and physical education.
| chongli wrote:
| The problem with trying to make a good school is that
| strong students pretty much teach themselves and their
| performance far exceeds any effects from good teaching
| methods. If any school starts to show decent results then
| word gets around and it becomes a magnet school. Magnet
| schools attract wealthy and high-performing students,
| which totally swamp the effects of the teaching method
| you're trying to study.
| lupusreal wrote:
| Good teachers unfettered by standardized course plans,
| when dealing with brilliant students, keep pace with and
| support those students. If this attracts even more
| brilliant students, all the better! Then the brilliant
| students will also support and motivate each other
| leading to even better outcomes. This is an ideal
| situation unless you're one of those Harrison Bergeron
| people who wants to cap high achievers so they don't
| leave the dummies in the dust.
|
| We really should be prioritizing the brightest students,
| because their brilliance has the best payoff for all of
| society. Better to have 100 students who are genuine math
| wizards and are prepared to continue building on what
| they know than to have 10000 students who _sort of_ learn
| basic calculus then forget all of it, with those previous
| 100 lost in the noise and never given the resources to
| reach their potential.
| zozbot234 wrote:
| On the contrary, standardized course plans are actually
| the most effective way to provide truly reliable
| instruction at all levels in a mass lecture/group
| education format. One key reason why those 100 math
| wizards don't all become PhD's is that math instruction
| at both school and university level leads to the
| proliferation of random gaps in learning where some
| content just wasn't reinforced effectively. Since math
| instruction generally builds on previously-learned math,
| once you accumulate enough of these gaps you hit a wall,
| and will need remedial instruction (often sought via
| autonomous self-teaching, of course) to make any
| progress. The dynamic is structurally the same between
| the "dummies" and the "math whizs", all that changes is
| the level at which the problem arises.
|
| Focusing on a standardized course plan that the student
| is able to learn, memorize and ultimately repeat
| effortlessly makes it easy to ensure that absolutely
| everything was reinforced properly.
| thfuran wrote:
| >Let the states have ~50 different curricula,
|
| There are several states in which that would be
| absolutely disastrous.
| snowwrestler wrote:
| Congrats: what you're asking for is exactly how things
| work now! The feds do not set currricula, each state does
| independently. Common Core is an opt-in, state-led
| initiative, which was based on the idea of examining the
| latest research and practices in education across the
| country, and adjusting curricula to match.
| anigbrowl wrote:
| Except that as soon as someone says 'hey X works, here's
| the data to prove it's all the rent seekers who have
| gotten happy with the alternatives will fight against its
| adoption. When I was younger I used to buy into the
| 'laboratories of democracy' concept, now I think it's
| more like 'meth labs of bureaucracy.'
| throwaway2037 wrote:
| I am not defending "Common Core", but why didn't this
| happen before Common Core existed?
|
| Also: Many highly advanced nations have a national-level
| curriculum. What is different and why does it work?
| tsimionescu wrote:
| > Even if they're bad on average, some of them will
| probably figure out how to make an actually good US
| school by sheer luck. Once we have that, the others have
| a model to copy.
|
| How could anyone know that, if each school has its own
| curriculum and exams? If you got 4 gold stars out of 5 on
| your reading comprehension and I got three palm leaves
| out of 4 at literature interpretation, which one of us is
| getting a better education?
| hoten wrote:
| The ones who get into better colleges.
| tsimionescu wrote:
| The there is a de facto national curriculum, defined by
| the good college entrance criteria.
| EnigmaFlare wrote:
| Schools and teachers have ways to make sure improvements
| don't happen. These include - same pay regardless of
| performance, not hiring or firing based on performance,
| and teachers don't want to learn or do anything
| differently, especially if it's even slightly harder than
| what they already do. They're not really professionals
| that improve or have any career growth besides management
| and accumulating number of years experience. Schools
| don't care either, nor do governments bother to
| incentivize them to care.
|
| Except in, say, China, where none of that applies and
| education works great.
| lupusreal wrote:
| > _Schools and teachers have ways to make sure
| improvements don 't happen. These include - same pay
| regardless of performance, not hiring or firing based on
| performance, and teachers don't want to learn or do
| anything differently, especially if it's even slightly
| harder than what they already do_
|
| You can just say unions, no need to beat around the bush.
| Anyway, I don't really agree. Of course some teachers are
| stuck in the mud, but other teachers are eager to try new
| things and improve outcomes. If unfettered by
| standardization they would be eagerly experimenting with
| new approaches to teaching their subjects. And if school
| funding weren't reliant on teachers "teaching the test",
| then schools would find ways to reward these teachers
| because it makes the administration look good to have
| passionate and proactive teachers.
| doikor wrote:
| > Except in, say, China, where none of that applies and
| education works great.
|
| Yup the school system plagued by epidemic cheating where
| cheating is even accepted to some level (you are an idiot
| if you don't cheat).
| dr_kiszonka wrote:
| I always found that "feature" annoying because students who
| knew the material well could fail questions testing its
| mastery due to imprecise instructions. (My personal pet peeve
| is not making it clear whether "or" is inclusive or
| exclusive.)
| hahajk wrote:
| I can't think of a situation in which "or" would ever be
| used in an exclusive sense unless it was explicitly called
| out as an XOR or included "but not both".
| tsimionescu wrote:
| "Is it A or B?"
|
| "Do you want the burger or the ribs?"
| monkeydreams wrote:
| > The vagueness is seen as a feature, not a bug. The kid is
| supposed to read between the lines and find out what the
| problems are really about.
|
| Pity the poor child who is capable of thinking both
| inductively and reductively. Such lax testing standards
| reminds me of the story of the WWII cryptographer in
| Cryptonomicon who is asked to work out how long a ship would
| take to travel down the river, comes up with a new theory of
| fluid dynamics, and flunks the test.
| BeetleB wrote:
| > The guy who figured this out (who Veritasium interviewed) is
| crazy smart.
|
| Eh. I knew about it before I took the SAT. It was in various
| brain teasers books.
| mlcrypto wrote:
| The perspective from inside the circle was mind blowing. Can that
| be an analogy to relativity & time?
| emmet wrote:
| Such a clever way of showing the mechanic! Tried to picture it
| in my head first and then he just did it for me
| pmayrgundter wrote:
| None of the explanations gave me an intuition for it except the
| circle rolling down a straight line with the same length as its
| circumference.
|
| A roll down the line will rotate the circle once. Coming back the
| same. But rolling around one corner will add half a
| circumference, and another half for rolling around the other. So
| you get 2 * 0.5 extra circumferences, and so + 1 C. Somehow that
| helps with the other polynomials for me too. Super cool.
| KMag wrote:
| Do you mean polygon, or did I miss something relating to a
| polynomial solution?
| jeffbee wrote:
| To me the intuitive explanation is that if they were gears,
| with shafts fixed in a block, the small wheel would turn 3
| times per turn of the big wheel, but in the given scenario the
| small gear also has to go around the big one, hence the R/r+1
| solution.
| Aeolun wrote:
| Yeah. I think that's the intuition I have about this too. It
| rotates once by virtue of going around, and three times by
| virtue of the size of the big circle.
|
| If you imagine a very tiny circle it'd still rotate a full
| time.
| HarHarVeryFunny wrote:
| Yes, but that line of thought doesn't really help when the
| small disk is rolling around the inside of the large disk,
| not the outside.
| krackers wrote:
| Triangle is probably easier to see (120 deg rotation when you
| turn the corner). Then you can see that the key is the sum of
| exterior angles, and this holds as you increase num sides. In
| the limit, you get a circle.
| beautron wrote:
| Oh wow! Hadn't heard it like this before, but now I like this
| way the best. I can finally _see clearly_ where that "extra"
| rotation comes from.
| cm2187 wrote:
| Having watched the video, yours is the only intuitive
| explaination that talks to me.
| jodrellblank wrote:
| The best intuition for me was the YouTube comment that said to
| imagine the rolling coin/circle is picked up on its edge, in
| 3D, rolling like a unicycle wheel. It turns forwards to roll
| and measure distance, and it turns sideways to travel around
| the circular path. i.e. "N" rotations for circumference
| distance on one axis (the straight line distance) plus one full
| rotation on a different axis around the circle. When the coin
| is lying flat, both have to happen on the same axis.
| haltist wrote:
| This is the right way to think about it. You get half at the
| beginning and half at the end so overall you get an extra
| rotation.
| wodenokoto wrote:
| For my inner eye, I can see that the circle will rotate half a
| circumsphere to get around the corner.
|
| But I can't really explain why. It's the same distance.
|
| I get that when a road turns left, it's longer on the right
| side, but these are lines that have no width and so there's no
| stretch and by definition we've kept the length the same.
| treyfitty wrote:
| What corner? What shape only has 2 corners?
| ec109685 wrote:
| A line (which is really a rectangle in this case).
| drc500free wrote:
| What makes sense to me is to think about something that DOESN'T
| roll.
|
| Suppose I start in Greenwich, walk - without rolling - down the
| prime meridian to the south pole, up the international date line
| to the north pole, and back down the prime meridian to Greenwich.
|
| How many rotations do I go through? One. I get a full rotation
| because I've followed the earth's curvature all the way around
| the globe once, even though I'm walking straight without rolling.
|
| So the answer is "how many rotations due to rolling" plus "one
| bonus rotation for passing around the curvature of the circle."
| jagthebeetle wrote:
| That intuition makes a lot of sense to me, especially if I
| picture the person's frame of reference.
|
| Kind of reminds me (a layman) of winding numbers. I suppose
| there are topologically inspired variations of this problem
| that might be even more "paradoxical" (or perhaps just silly).
| If you moonwalk the second half, you undo your rotation? Or if
| you follow specially designed subterranean tunnels, you can end
| up doing 0 or negative rotations!
| lordnacho wrote:
| The way I thought about it was to ask what happens if you just
| have a coin going around a point, which would be the natural
| end point of reducing the size of the second coin. That of
| course would give you 1, so a good first hypothesis is that the
| total is just however many spins the two coins go, plus 1.
| arketyp wrote:
| The video demonstrates the 1:1 coin size case and speaks
| about the curvature of the line it rolls on, but your thought
| experiment makes it a lot clearer. As the size of the other
| coin goes to 0, the amount "gnawed off" of the rolling coin
| will also go to 0 while obviously still rotating a full
| revolution.
| jodrellblank wrote:
| I like this; it gives me a good way to think about the "from
| the circle's view" - Earth center looking out at you sees your
| feet close and your head far away, always; you don't rotate at
| all.
| HarHarVeryFunny wrote:
| Yes, but that intuition doesn't seem to work for the case where
| small disk is rolling around the inside of large one, not
| outside. What's the intuition for why we then subtract one
| rotation rather than adding one ?!
| HenryPrickett wrote:
| Very basically, to go the same direction, a small disk on the
| inside and the outside of a large disk need to spin opposite
| directions. When you're on the outside, your spinning
| direction agrees with the direction you go around the circle
| (i.e. the rotations add). When you're on the inside your
| spinning direction is the opposite of the direction you go
| around the circle (the rotation subtracts).
| ahepp wrote:
| It's concave rather than convex? It's bending into itself
| instead of away from itself?
| 7734128 wrote:
| You're intuitively rolling the other way. Going on the
| surface means that you're falling forwards while going inside
| means that you're falling backwards.
| icegreentea2 wrote:
| I think you can always arrive at the correct answer by
| tracking the distance traveled by the center of the rolling
| object.
|
| In the original SAT question, the center of the rolling
| circle is 4r from the center. That means it travels an arc of
| 8pi. Then assuming no-slip, that works out to 4 rotation.
|
| In your case, rolling on the inside, the center of the
| rolling circle will only be 2r from the center. Using the
| same logic, this yields 2 rotations.
| HarHarVeryFunny wrote:
| Yes - the relationship between distance traveled by center
| and number of rotations (= distance/diameter) is a nice
| generalization, although the guy in the video went so fast
| that I didn't understand his derivation of this
| relationship (related to speed, etc).
| bearmode wrote:
| This is definitely the easier way to understand it. Imagine
| a point in the centre of the circle that is traveling. Draw
| the line that point takes, and then calculate using the new
| circle.
| charcircuit wrote:
| >How many rotations do I go through?
|
| 0. Walking in a circle is different from spinning. They are 2
| separate things that should be counted separately.
|
| Adding them together should be a type error.
| thaumasiotes wrote:
| > I get a full rotation because I've followed the earth's
| curvature all the way around the globe once, even though I'm
| walking straight without rolling.
|
| I don't follow. You aren't walking straight without rolling.
| You're constantly turning to keep the angle from the center of
| the earth to your head, as measured through your feet, fixed.
| This is not a necessary part of moving around the earth; you
| could maintain a constant orientation to e.g. the earth's axis
| of rotation instead. The one rotation that you're imagining
| isn't due to your travel around the earth; it's due to the
| rolling that you're pretending you aren't doing along the way.
|
| I tried defining a parametric equation for the position of a
| point on the rim of the small outer circle; if it has radius r,
| and it starts at coordinates (3r, 0) lying tangent to a circle
| of radius 3r centered at the origin, and it takes 2pi units of
| time to roll around the larger circle, then its position at
| time t is (4r cos t, 4r sin t) - (r cos 3t, r
| sin 3t)
|
| (unless I've made a mistake...?)
|
| We then need to define what a "revolution" is. If we define it
| in what appears to me to be the obvious way, as having been
| completed whenever the vector from the center of the outer
| circle to the point that we're tracking on its rim is parallel
| to its initial value of (-r, 0), then this parameterization
| makes it clear that the zeroth revolution of the outer circle
| ends at time t = 0, the first ends at t = 2pi / 3, the second
| ends at t = 4pi / 3, and the third ends at t = 6pi / 3. Since
| the maximum value of t is 6pi / 3, it appears that there cannot
| be more than three revolutions.
|
| However, I find the argument compelling that we should be able
| to get the number of revolutions by dividing the distance
| traveled by the center of the circle - 8pi - by the
| circumference of the circle, 2pi. This clearly tells us that
| there must have been four revolutions.
|
| What was wrong with the parameterization approach?
| bobby_table wrote:
| The way I think of this is: If instead of having a small circle
| rolling around a larger one, think of a circle with ANY non-zero
| radius rolling around one with a zero (or really really small)
| radius. You'll always end up with at least one rotation,
| regardless of how small the other circle is. So +1 makes sense.
| saberdancer wrote:
| The way I thought about it, you have to roll around the larger
| one and you have to roll around yourself (+1). So if they are
| two same size circles, it's 1 for the other and 1 for yourself.
| If the other one has 3 times bigger radius, it is 3 for the
| bigger one and 1 for yourself. Etc.
|
| Not sure if it is mathematically accurate but it seemed to make
| sense to me.
| jncfhnb wrote:
| I think the explanation is kind of messy tbh.
|
| People are going to have one of two interpretations. If a coin
| rolls around another coin, is the distance traveled equal to the
| edge along the the static coin? Or is it the distance traveled by
| the center of the rotating coin?
|
| If it's defined by the former, the answer is 3 because the
| circumference is 3x as long as that of the traveling coin. If
| it's defined by the latter then it's 4 because the circumference
| of the base coin buffered out by the radius of the traveling coin
| is 4x as long that of the traveling coin.
|
| I vote 3 personally
| orenlindsey wrote:
| The point is that the question is vague and is open to multiple
| different "correct" answers. SAT questions should only have one
| correct answer, with no possibility of any others.
| jncfhnb wrote:
| The point is that the question is sort of interesting and the
| history is just fluff for YouTube clicks and video length.
| The context is irrelevant.
| HarHarVeryFunny wrote:
| It's not just that it was poorly worded, but rather poorly
| conceived/analyzed. Apparently they had wanted the right
| answer to be "3", and therefore basically asked the wrong
| question (which would been a bit awkward to word!).
| medler wrote:
| It depends on the viewer's perspective. From the coin's point
| of view it rotates three times, but to an outside viewer it
| rotates four times. I think the outside viewer's perspective is
| far more intuitive, so four is really the "most" correct answer
| to me.
| jncfhnb wrote:
| Perhaps. But I think the most intuitive is noting that a
| coin's perimeter should touch the other coin exactly one full
| time during a rotation.
| omeze wrote:
| Yea, I think the difference between "how many rotations" and
| "how far is the center of the small disk traveling" is pretty
| big. I was completely lost as to how you "add one" until I
| watched what the video called a "rotation". It would have never
| occurred to me to call the coin being upright a rotation... the
| Art of Problem solving question in another comment thread was
| more clearly worded for that scenario
| HarHarVeryFunny wrote:
| The question wording was about "revolutions" of the small
| disk. The distance traveled by the small disk center (= 4x
| it's own diameter) was only used as a way to calculate the
| number of revolutions, but I'm still not getting the
| intuition for how each diameter of distance traveled by the
| disk center equals one rotation regardless of the shape of
| path followed (it's obvious for a flat line of course).
| jncfhnb wrote:
| If a coin rolls such that its complete perimeter touches
| the other surface exactly once it will move the distance of
| its perimeter. In this case the total distance is 3x the
| perimeter so the edge answer is 3. Shape doesn't matter.
|
| If you're wondering how many times the traveling coin 360s
| you have to account for the fact that it is rotating both
| because it's rolling and because it's going around the the
| other thing. You can simplify this by just imagining it's
| the edge again, but the edge is going along the radius of
| the inner and traveling coin (3+1).
|
| Dumb it down. How far does a point travel? X units. X units
| / coin perimeter = coin rotations required to travel X.
| Ergo the only question is whether the distance traveled is
| along the perimeter of the 3r coin or if it's based on the
| center of the traveling coin (3+1).
| jodrellblank wrote:
| (as I commented elsewhere) I found it useful to picture a
| unicycle; a straight line track means the wheel rolls
| forwards the same distance as the length of the track.
| Curve the track around to the right into a circle and when
| the unicycle rolls forward in a straight line it's getting
| away from the track (at a tangent) - it would have to slide
| sideways to get to where the track is. That is some extra
| movement for the curved track compared to the straight
| track which has to be accounted for somewhere, somehow, and
| of course the unicycle _turns right_ while rolling forwards
| to follow the curve in the track. When it gets back to the
| start, it must have done 1 complete turn to the right as
| well as all the rolling forwards. As long as the track is
| simple (no loops, bridges, crossings), e.g. a square with
| rounded corners, going around and back to the start needs
| the left and right turns to balance out to get to 1
| complete turn - too much turning right spirals in, too much
| turning left spirals out, only a balanced amount of left
| and right turning that ends up as 1 complete turn can meet
| up back at the beginning.
|
| Seeing the turns in two axes made it clear to me that the
| forwards rolling is always the length of the track because
| changing the shape doesn't change the length, and the
| sideways turn is always one for any simple loop or it
| wouldn't be a circuit. That fixes your question " _how each
| diameter of distance traveled by the disk center equals one
| rotation regardless of the shape of path followed_ " - you
| say it's obvious for a straight line, and curving the line
| can't change the length of the line, the extra rotation to
| go round a circuit must be one, so there's nothing which
| can vary.
|
| (If you lie the unicycle down on its side, the 1 complete
| turn to the right needed to follow the curve around to the
| start doesn't go away, it has to happen, and now it has to
| happen in the same axis as the rolling forwards happens so
| it's much less clear (to me). If the only thing the wheel
| can do is roll forwards, this extra movement from earlier
| to avoid getting away from the track can only be extra
| rolling - the extra one turn for the loop, spread over the
| N turns for the distance).
| snowwrestler wrote:
| The text of the question did not ask about distance, it asked
| about revolutions.
|
| "In the figure above, the radius of circle A is one-third the
| radius of circle B. Starting from position shown in figure,
| circle A rolls around circle B. At the end of how many
| revolutions of circle A will the center of circle A first reach
| its starting point?"
| jncfhnb wrote:
| Indeed. But distance is a much more intuitive way to think
| about the problem than frames of reference of the rotations
| imo.
|
| Are revolutions the coin rotating 360 degrees or are they the
| complete perimeter rotating across the other coin and touch
| the other one exactly once.
|
| The problem is intended to be mapped onto a distance
| perspective and figured out that way. So it's very much
| distance.
| natdempk wrote:
| I felt the same way, the question is pretty ambiguous, there
| are two readings, one corresponds with a somewhat "unintuitive"
| answer provided, and another doesn't, but is maybe more
| intuitive to some people, and yet "everyone got it wrong". I
| think its a bad question because the terms aren't defined
| clearly, but the "everyone got it wrong besides these people"
| framing is also not really true imo. I also didn't see why the
| original answer isn't considered defensible because from the
| view inside the circle, each of the 4 "rotations" doesn't look
| like a rotation because you don't start and end them from the
| same view.
| xorcist wrote:
| Does the video spoil the solution too or is it only the question?
| orenlindsey wrote:
| Well, there's not really one solution. Watch the video to see
| what I mean.
| fsckboy wrote:
| the video starts out with the question and then says you can
| pause if you want to work on it. Then it the next thing it says
| is something about the answer.
| sillysaurusx wrote:
| There is an intuitive way to see why this is true.
|
| Picture a circle rolling around the outside of another. Easy to
| picture, right? Even if it's not clear how many times it rotates,
| you can still visualize it.
|
| Now imagine the outer circle has to spin around the _inside_ of
| the first circle.
|
| Stack two quarters, and try to spin the top quarter around the
| inside of the bottom quarter.
|
| You can't do it. There's no room. If they're identical size, the
| top quarter can't spin "around" the inner edge of the bottom
| quarter.
|
| Now put a penny on top of a quarter. Spin _that_ around. Not
| along the outside, but along the inside of the quarter. You'll
| see the penny is tracing a very tight circle. There's not much
| room.
|
| Now put the penny next to the quarter and spin it around the
| outer edge of the quarter. It goes easily. Plenty of room.
|
| If you do the naive calculation, you'd get the same answer for
| both cases. But clearly there's a difference.
|
| The difference is more apparent if you imagine the coins had
| little teeth, like gears. If you go around the outside, it'll go
| just fine. But if you hollow out the quarter and put teeth along
| the inside, and try to spin the penny around in that, you'll find
| that it doesn't make anywhere close to a full rotation each time
| you go around.
| whoopdedo wrote:
| This becomes even more apparent when you turn the circumference
| of the fixed circle into a straight line. (As the video
| suggested but didn't show in the same way.) The center of the
| rolling circle will trace a line parallel and equal length to
| the fixed line, whether above or below it. If you reform the
| circle the outer line will be too short to form a complete
| circle, and the inner line will overlap itself.
| medler wrote:
| The application to sidereal time is where this really gets
| interesting. It's far from a trivial question of semantics or a
| mathematical trick. It's something astronomers have known about
| for ages, since the amount of time it takes for the Earth to make
| one rotation is different from the perspective of distant stars
| than from the perspective of the sun.
| whartung wrote:
| Indeed. This was my favorite part of the video. The discussion
| of the problem and SAT part are interesting, but when it delves
| into the sidereal time aspect, it just flies off into a
| direction where never saw coming and presented some fascinating
| aspects I'd never had need to consider.
| fsckboy wrote:
| what is perplexing to me is that I've been thinking about the
| sidereal problem for the last or so
|
| ...(because I heard on a podcast that the earliest sunset
| occurs more than a week before the solstice and the latest
| sunrise occurs after the solstice, but still the solstice is
| the shortest day, and they said something about the tilt of the
| earth and I was thinking that was not explanatory, so I've been
| idly noodling about it)...
|
| and I just got this problem wrong! didn't even occur to me :)
| in my defense, the thumbnail for this video does not state the
| question so I wasn't sure what I was supposed to do, but guided
| by the multiple choice I selected 3
|
| but talk about having my brain primed for the question... doh!
| TarasBob wrote:
| The way I think about it is imagine the circle in the middle is
| very tiny compared to the circle that rolls.
| medler wrote:
| I like this perspective as well. If the coin is rotating around
| a point (radius 0), the point on the coin edge touching the
| point will not move at all, yet the coin will make one rotation
| before returning to its original position.
| js2 wrote:
| This is an 18 minute video about an SAT problem from 1982. If
| you're not sure you want to commit to it, here's a
| contemporaneous NYT article:
|
| https://www.nytimes.com/1982/05/25/us/error-found-in-sat-que...
|
| (Gift link.)
|
| And a recent Scientific American article:
|
| https://www.scientificamerican.com/article/the-sat-problem-t...
|
| (Both of these are linked from the video description itself.)
|
| I'll bet Marilyn vos Savant wouldn't have got this one wrong[1].
| :-)
|
| [1]:
| https://web.archive.org/web/20130121183432/http://marilynvos...
| hightrix wrote:
| Thank you so very much. Reading this article was so much more
| valuable to me as I would have never watched an 18 min video to
| show a single question that needed 1 paragraph to discuss.
| jjnoakes wrote:
| The video does go further - it contains some interesting
| content around how this concept relates to the earth's orbit
| around the sun, the discrepancy between the duration of an
| earth day and a 360 degree rotation about the earth's axis,
| and why astronomy days are not the same length as earth days.
| jraph wrote:
| Yeah, the SAT question is almost an excuse to speak about
| this things, and you also get to see an interview with one
| of the concerned candidates. Very enjoyable video.
| 2muchcoffeeman wrote:
| There's also an interesting note about when the specified
| answers in the question would have been right, the point
| of view of the centre circle.
| jjnoakes wrote:
| I actually didn't think that part belonged in there.
| Considering a rotating point of view seemed contrived to
| me.
| 2muchcoffeeman wrote:
| Surely the intended meaning of the question belongs in
| the discussion?
|
| You're right, it's contrived. But I automatically tried
| to compare lengths too. So it's a good lesson in making
| sure that your simplification of the question still does
| what the question asks.
| jjnoakes wrote:
| I'm not convinced that the intended meaning was to
| consider a rotating reference frame. I think it was
| simply an oversight that the straight-line answer and the
| around-a-circle answer aren't the same. A rotating
| reference frame is one way to explain that oversight, but
| it isn't the only one.
| fnordpiglet wrote:
| Also note you can speed it up. I usually watch YouTube on 1.5
| speed, so this is a 12 minute video for me ;-)
| alister wrote:
| The New York Times says:
|
| _The choice was given among these answers: (a) 3 over 2. (b)
| 3. (c) 6. (d) 9 over 2. (e) 9. ''The answer to this question
| should have been 4, not 3. Daniel B. Taylor, the College
| Board's executive vice president for operations, said as a
| result of the flawed question, he anticipated score adjustments
| of 10 points, up or down._
|
| I'm wondering how they corrected the scores since the correct
| answer was not in the list of choices. I'm assuming that they
| simply excluded the question -- so if there were 154 questions
| in total, they recalculated as if there were only 153
| questions. I'd like to imagine that the three students who
| reported the error got an extra boost to their scores, but
| probably not.
| chatmasta wrote:
| According to the video, they rescored all 300,000 affected
| tests after excluding the question.
| sverhagen wrote:
| I found the notion pretty shocking how deeply the rescoring
| affected people. If the test writers couldn't even get it
| right, why fault the test takers. I get it... rules... but
| it still feels unfair at some angle.
| perryizgr8 wrote:
| They should have done max(old_score, re_score) for all
| test takers. That's the only fair way. Although I don't
| know if SAT grades on a curve, which wouldn't play well
| with this method (I think?).
| SkeuomorphicBee wrote:
| That is not a fair way, for two reasons:
|
| 1. You can't award a bonus question to a subset of
| people, that is not a fair way of running a standardized
| test. You can't score some people as x/154 and some at
| x/153.
|
| 2. The old score was just plain wrong, so using it in any
| way is unfair.
|
| The truth is no one got that question right because there
| was no right answer available. None of those available
| answers is "righter" than the other so it is not fair to
| assign a higher score to one of them like you proposed.
| Those people that got a higher old_score also got that
| question wrong, so their old_score is as wrong as any,
| and awarding them this unearned extra point would be
| unfair.
|
| The only two fair options would be: to annul the whole
| test and make everyone retake; or the one taken where
| they annul that one question pretending it never existed
| and score based on the remaining questions (with each
| remaining question now being worth a fraction more). And
| this later option is in fact very fair, I don't think
| there is any real argument against this being fair.
|
| It does suck that people were initially informed a wrong
| score and then later were disappointed with their real
| score. On this line I find it absurd that the SATs don't
| have the recourse period before they release the scores,
| and instead just releases the tentative scores as if they
| were real. This would all have been avoided if they heard
| the recourse and annulled the question before publishing
| results (as pretty much any serious exam around the world
| does it).
| thaumasiotes wrote:
| > I found the notion pretty shocking how deeply the
| rescoring affected people.
|
| The effect of noise on your score is supposed to be
| around 30 points. A 10-point effect is too small to
| measure. How can that be "shockingly deep"?
| SkeuomorphicBee wrote:
| Nothing unfair about it, the truth is everyone got that
| question wrong (because there was no right option
| available), so they didn't fault the test takers, instead
| just annulled that one and scored everyone based on the
| actual questions, it is as fair as it can be.
|
| It does suck for the people who though they had that one
| right, it is distressing to be shown one score and then
| later find out that the real score is lower. That should
| have been avoided by having an official recourse window
| before publishing scores, so when problematic questions
| are annulled then people only see their actual final
| score (in my country a recourse window is standard for
| all public exams).
| huytersd wrote:
| If they annulled the question, why would the score drop?
| Shouldn't the scores be renormalized around the new
| number of questions, the easiest way being to just give
| everyone the points for it?
| ToValueFunfetti wrote:
| At least one of the three answered the question "correctly",
| so they would have gotten a _worse_ score after rescoring,
| provided they answered anything else incorrectly.
| ramraj07 wrote:
| While I share your disdain for unnecessarily long YouTube
| videos, Veritasium often (not always) gets a pass from me. I
| have been instant clicking pretty much every video he's
| released in the past few months and always came out having
| learned a lot and satisfied.
|
| The only other channel I would give the same pass is neo.
| jraph wrote:
| > The only other channel I would give the same pass is neo.
|
| Nice, thanks for the mention, I'll check this out. At first
| sight, typically looks like stuff I would enjoy.
| ramraj07 wrote:
| I would start with their Thai Cave rescue video. I scratch
| my head how this guy is not on tv.
| drdrey wrote:
| his Kowloon Walled City is incredibly well made
| corethree wrote:
| First 10 seconds into the video I know one major reason
| working against him. He has a bit of lisp. Personally I
| don't mind, but I'd be lying if I said his videos would
| be better without it.
|
| Fortunately we have youtube.
| EE84M3i wrote:
| It's almost 2024. He seems to do very well on YouTube and
| has a lot more freedom in his niche. Why would he want to
| be on TV?
| alt227 wrote:
| TV presenting pays very well in comparison to Youtube.
| Plus all you have to do is turn up and read a script, as
| opposed to filming and editing a video to high production
| standards, or having to pay somebody out of your ad
| revenue to do it for you.
| holoduke wrote:
| Is someone still watching tv? Nobody in my neighborhood
| watches linear tv anymore. Already for many years. Maybe
| some elder people?
| alt227 wrote:
| Pretty much everyone I know in the UK watches linear TV,
| old and young.
|
| According to last years research, over 50% of people are
| still watching linear TV via broadcast or cable:
|
| https://arstechnica.com/gadgets/2022/08/for-the-first-
| time-e...
| lotsofpulp wrote:
| That is mind boggling. In the US, I know no one under the
| age of ~50 that watched linear TV. Even the 50+ year olds
| are using their phone and watching YouTube/Whatsapp
| videos while "watching" linear TV.
|
| Live sports are the only exception, but I would say that
| is down big time also (as Nielsen indicates). Or rather,
| a series of gambling ads interspersed with a sporting
| event.
|
| Overall, I don't think Nielsen is able to properly assess
| which screen has people's focus.
| TaylorAlexander wrote:
| You may be interested to see this critique of Veritasium
| which cooled my views on the channel significantly since I
| saw it:
|
| https://youtu.be/CM0aohBfUTc
| gnicholas wrote:
| Given the length of the video (50+ mins), could you give us
| a TLDR? What aspects of the channel does the critique take
| aim at?
| nojs wrote:
| He claims Derek's Waymo video was a paid PR piece and too
| favourable to the company. He also spends 2 minutes
| explaining why you need Surfshark VPN
| ramraj07 wrote:
| Which is obvious to anyone with half a brain though. So
| what. We have discretion to choose which of his videos to
| watch. I doubt he got paid by the laws of thermodynamics
| to make his entropy video.
| j4yav wrote:
| Sure, but there are lots of good science content creators
| out there and I'd rather just watch one where I don't
| have to worry about it. The Waymo video is over the top
| credulous, even for something they were being paid to
| review. In general, the idea of building a channel based
| on "the element of truth", establishing yourself as an
| educator, and then shamelessly selling your credibility
| in that way is kind of a turn off. At least I'm not going
| to see you as credible in the same way anymore, and
| others feel the same.
|
| That said, the channel is more popular than ever so who
| knows.
| moffkalast wrote:
| He's just in the pocket of Big Physics! /s
| gnicholas wrote:
| So it's just about the one video? It's not about
| technology reviews in general, or any of the math stuff
| (like what was linked in the video above)?
| hoten wrote:
| This guy does hour long videos on many large popular
| YouTubers. I tried watching one but it was so. drawn. out.
| Is he just creating controversy from nothing?
| beaned wrote:
| Yeah, pretty much.
| deaddodo wrote:
| He's like Turkey Tom, but instead of just recapping
| YouTubers/YT Drama, which is already the reality TV
| version of YouTube content, he wants to treat it like
| hard hitting journalism. Which means he overinflates and
| exaggerates everything.
| jnsaff2 wrote:
| The thing that put me off veritasium was the electricity
| video which was immediately controversial.
|
| Looking at just the video he left the feeling that all
| electricity being taught is completely wrong while actually
| he was talking about some edge case and failed to put it
| into the proper context. He did not mention at all that the
| proportion of what he was talking about was essentially
| irrelevant unless you are an electronics board designer.
| ploxiln wrote:
| EE details relevant to electronics board designers are
| kinda important and interesting, and I have a lot of
| sympathy for "technically correct". But that veritasium
| video was a _trick_ question, and a misleading video. It
| subtly shifted between ideal model to real-world effects
| to smugly show how most skilled EEs are wrong about
| electricity, but Derek knows the truth.
|
| In a simplified circuit model it would work like a
| circuit, in a as-real-world-as-possible model it would
| always be dominated by interference. In a carefully-
| segregated-semi-real model, it would be less than 1% on
| after 1/c seconds, would you really call that on? If it
| was, then 100% on would be way too much current!
|
| So many minutes spent _without_ explaining that the real
| world is very complicated and EEs apply different models
| to different situations as appropriate, and it 's silly
| to say that only the field matters not the electrons
| because of course the electrons cause the field while the
| field moves the electrons, and the original question is a
| trick because it's an idealized thought experiment which
| tries to trick you into applying the wrong model but
| that's silly because it's _an idealized thought
| experiment_ which wouldn 't work in the real world so
| it's only purpose is to exercise a simplified model ...
|
| Great fodder for a series of viral-y videos from multiple
| youtubers though. (electroboom's response was pretty good
| IMHO)
| quailfarmer wrote:
| Hah, that video really ticked me off at the time.
| Technically true, but only in the least meaningful way
| possible.
| moffkalast wrote:
| Yeah I really liked the AlphaPheonix video[0] where he
| actually built the thing in a field and explained the
| entire effect properly.
|
| I'm not entirely sure if Derek didn't really understand
| what he was presenting in that video or deliberately
| based it on a really misleading bullshit gotcha to troll
| people and stir debate for clicks, and neither reflects
| very well on him.
|
| [0] https://www.youtube.com/watch?v=2Vrhk5OjBP8
| sixothree wrote:
| His latest video on open ended wires is very much worth a
| watch.
| moffkalast wrote:
| That one was absolutely amazing, it (and the electric
| current maze solving one) brought my intuition for
| electricity to a whole new level.
| Jackson__ wrote:
| The one that I really couldn't stand was the "How to slow
| aging" one, in which he interviews a man, who in my
| opinion clearly had some sort of cosmetic surgery done on
| himself to appear younger. He talks about how to reverse
| aging in mice, and then randomly claims he actually
| reversed aging _in himself_.[0]
|
| For anyone following science in mice, this seems like an
| extremely huge red flag. That together with the cosmetic
| surgery and a clear financial incentive for the him to
| lie here, seeing as he is selling a book about it, was
| triggering just about every bullshit detecting neuron in
| my brain.
|
| Veritasium however seems perfectly fine with it, and
| still posted the video.
|
| I haven't ever seen anyone else bring this up, so if
| anyone wants to share their own hot take on this, I'd be
| interested to know :)
|
| [0] https://www.youtube.com/watch?v=QRt7LjqJ45k
| antihipocrat wrote:
| In response to all the controversy he made a follow up
| video [0]. In the video he recreated the experiment,
| explaining the effect in a more technically correct
| manner and also apologised for not doing so on the
| original.
|
| He also made it clear that the light globe in the
| original video did not receive enough current to light
| up.. it was hooked up to an alternative power source and
| an oscilloscope and upon receiving any signal above
| baseline would switch on the globe.
|
| [0] https://youtu.be/oI_X2cMHNe0?si=uprU-oZfk3ahKgx0
| logiduck wrote:
| When i watched that follow up video and he didn't
| apologize he only said that he wasn't clear enough. In
| most responses like the other above linked criticism he
| doesn't apologize either and just gives out a long list
| of reasons why he's right. In the electricity follow up
| video it really seemed like he was saying more along the
| lines of "I was always right, you just weren't smart
| enough to understand what i was _really_ saying because i
| was unclear ". So I wouldn't say that he apologized, just
| doubled down and accepted fault with the lack of clarity
| but without saying sorry in any way.
|
| It really put me off his channel for a long time. I still
| watch his channel to be fair and get a lot out of it, but
| his videos hit different after seeing him double down on
| criticisms and contorting controversy instead of just
| saying sorry.
| antihipocrat wrote:
| Of all the many episodes I've watched, it's the only
| episode that I felt was misleading.
| teekert wrote:
| Yeah the induction thing. That also left a sour taste in
| my mouth. I also don't like his correction where he sort
| of tries to proof he was bit right
| dghughes wrote:
| > He did not mention at all that the proportion of what
| he was talking about was essentially irrelevant unless
| you are an electronics board designer.
|
| If you want to get that detailed most people would freak
| at conventional vs electron flow. The + wire is actually
| where the negative electrons are emitted. But as
| electricity was developed people didn't know that but it
| all works out so it was left as is. For physics or any
| other scientific experiments electron flow is used.
|
| Even the term "negative" is a can of worms it could have
| been called green or red or yellow not "negative". It
| comes from Ben Franklin and accounting terms.
| class3shock wrote:
| I would add I felt the wind powered car video was
| similar. I started watching him years ago as he had an
| amazing video looking at a silicon sphere being made to
| use as a new mass standard. In recent years though his
| videos seem to increasingly confuse subjects (for me)
| instead of clarify them.
| _fizz_buzz_ wrote:
| The Veritasium video is kind of weird. The example is good
| and interesting and when I watched I thought he would then
| introduce the concept of transmission lines (as taught in
| EE classes). It would make things clearer and gives an
| explanation and also maybe some intuition to problems like
| that. Instead he starts talking about the poynting vector,
| which makes things even more abstract and weird (and also
| he is slightly misleading about the poynting vector,
| especially for the DC case). It seems like he is trying to
| make things weird for the sake of weirdness and not trying
| to explain anything.
| dghughes wrote:
| Derek Muller from Veritasium replied to the video it seems
| there was some behind the scenes communication which the
| video author (Tom Nicholas) ignored but replied to in a
| long comment. It seems to to create sensationalism. He got
| 2.1M views so I guess it worked.
| arijun wrote:
| Just watched the video--it has the same failings as most
| other debunking videos (e.g. Thunderf00t): in order to get
| views he must show that what he is debunking is _very_
| wrong, and so manufactures gotchas. It's a little ironic
| that his video accusing Veratasium of lacking nuance is
| completely lacking nuance itself. Although admittedly, he's
| not wrong that Veratasium is lacking nuance and is too
| breathless in his praise.
| js2 wrote:
| I intended no shade on Veritasium and my comment that the
| video is 18 minutes long wasn't an expression of disdain,
| merely a statement of fact. Rather, my intent was to offer an
| alternative for folks who prefer to read instead of or before
| watching a video.
| jahnu wrote:
| I appreciated it. Most of the time I would be interrupting
| my music or silence or disturbing those around me if I
| played videos. Friends send me links to video after video
| and I just can't even review whether they are worth my time
| because of the above issues. At least text I can quickly
| scan to get a sense. I really regret how video has come to
| utterly dominate.
| addicted wrote:
| Thank you for sharing the articles.
|
| I did not want to watch a video and preferred reading about
| this irrespective of the length of the video.
| AtlasBarfed wrote:
| The video used modern social media length dragout
| techniques that make virtually all modern podcast like
| media so tiresome to listen to.
|
| "You won't BELIEVE what everyone got wrong"
|
| Here's the trumped up drama from people involved.
|
| Here's an interview
|
| Here's a restatement of the cliffhanger
|
| Oops the author dropped enough info that I can read the
| Wikipedia article in 30 seconds. End streaming media.
|
| The amount of "good podcasts" that are ultimately a
| Wikipedia page drawn out over 20-30 minutes is just
| ridiculous.
|
| "Good tv" like a good john Oliver show or Frontline is
| chock full of information, further avenues of research if
| interested, and dense.
|
| Geewhiz podcasts like these seem like the result of YouTube
| algorithmic game theory result rather than an improvement
| to the access and organization of info that Wikipedia
| represented.
|
| I'm cranky this morning, sorry
| RuggedPineapple wrote:
| That's not modern, that's been media since time
| immemorial. Geraldo spent 2 hours talking about what
| could be in Al Capone's vault only for them to finally
| open it up and it was empty. Magazines would print
| stories in serial format so you had to buy the next
| issue.
|
| Writing and structuring to fit the length you want/need
| has been the norm for a century or two at least before
| social media came about. Hell, there's evidence that
| Shakespeare padded out a couple of his plays to fit the
| 4-pages per folio printing techniques of the time so that
| there weren't blank pages at the end.
| runlaszlorun wrote:
| Geraldo's vault! Haven't thought about that in a good
| while...
| hasmanean wrote:
| Or the camera in the great pyramid...3 hours of opening a
| door, entering a tunnel only to find another door.
| hasmanean wrote:
| Veritasium is much better than Shakespeare. If you
| dropped his videos 500 years ago it would have caused a
| minor revolution.
| lotsofpulp wrote:
| > "Good tv" like a good john Oliver show or Frontline is
| chock full of information, further avenues of research if
| interested, and dense.
|
| I have seen John Oliver state errors or misrepresent
| data/leave out information in favor of the
| comedy/supporting a particular viewpoint. A good HN
| thread with people knowledgeable about the subject or in
| the field about a John Oliver episode will usually be
| full of more information.
| peterleiser wrote:
| This is the same reason I can't watch Dateline, where
| telling the story linearly and with just the facts would
| actually take about 3 minutes.
| hasmanean wrote:
| This is a general problem. If you want to get a good answer
| to a certain class of problems (especially in the diy
| domain, and now even math problems), YouTube videos are the
| best. But you have to watch 20 minutes. This is not
| scalable.
| lotsofpulp wrote:
| For me , 99% of the time, obtaining information from a
| video is less time efficient than a written piece. I
| almost always ignore video links.
|
| After reading the NYT article, I would say there was no
| need for me to spend an additional 15min watching the
| video.
| js2 wrote:
| For the shade tree mechanic and/or handyman, YouTube is a
| tremendous boon. A few years ago I needed to replace the
| cooking elements in my double-oven and I found repair
| videos on Vimeo[1]. So I built a dolly and pulled my oven
| out[2]. It takes all the fear and uncertainty out of a
| repair you've never done before.
|
| Videos have all the tips and tricks missing from
| conventional repair manuals and shop guides.
|
| For academic material, I prefer the written word. For
| repairs around my home? I'll go to YouTube.
|
| [1] https://vimeopro.com/fisherpaykeltechnical/training-
| videos/v...
|
| [2] https://i.ibb.co/fkL0r3Q/IMG-2416.jpg
| otteromkram wrote:
| > [...] often (not always) gets a pass from me.
|
| Thank you for clarifying what "often" means.
|
| Say, how can you tell which ones should get a pass?
|
| Is there a way the less intelligent folks (like myself) could
| get a notification for when you decide to watch or not watch
| one of Veritasium's latest creations?
|
| Do you feel more intelligent after watching that video? If
| so, could you share some of the techniques you used to
| capitalize on passive learning?
| elbasti wrote:
| Question: the outside circle is a tire made of rubber, which
| wears down at a known rate.
|
| Which tire wears down more:
|
| A tire that rolls around a circle of circumference D.
|
| A tire that rolls down a flat surface, total distance D?
| johnfn wrote:
| Well, surely these are the same. Right? Haha of course they
| are. This is silly. Right? RIGHT?!?
| Aeolun wrote:
| Just because it's spinning more does not mean it wears out
| faster though.
|
| Maybe tires are more resistant to rolling on curvatures?
| scotty79 wrote:
| I'd say they are less resistant to going on positive
| curvatures. It's like a bum that goes deeper into the tire,
| deforming tire more which should result in more wear than
| driving on even surface.
| elwell wrote:
| What if the large circle rotates at the same rate that the small
| circle 'orbits' it?
| jhncls wrote:
| The coin around coin problem has its own wikipedia page, although
| some people want to delete it:
|
| https://en.wikipedia.org/wiki/Coin_rotation_paradox
| jhncls wrote:
| The same paradox is also featured prominently as part of a
| Mathologer video [0] and an article in Scientific American [1].
|
| [0]: https://youtu.be/oEN0o9ZGmOM?t=523s
|
| [1]: https://www.scientificamerican.com/article/the-sat-
| problem-t...
| alister wrote:
| I love the Wikipedia animations -- they are usually extremely
| helpful -- but when I'm trying to read the article, I find them
| distracting. I usually move another window on top to obscure
| the animations so I can concentrate on the article. But there
| must be a better way. Is there a hotkey to stop animations? For
| Firefox in particular?
|
| EDIT: I don't want to stop animations permanently with
| about:config; I just want to pause and un-pause.
| caditinpiscinam wrote:
| > although some people want to delete it
|
| I hope they don't. The argument for removing it is basically
| that if you understand geometry, then the conclusion is
| obvious; but since this is an area where most people's
| understanding of geometry is incorrect (myself included, before
| today), the article is valuable. I don't see how it's different
| from articles on other mathematical paradoxes (Simpson's
| paradox, for example).
| ecshafer wrote:
| My answer to this after reading the question was 1, because by
| definition it is one revolution. So I thought that was trick, and
| the answer essentially is none of the above. But there is a lot
| more nuance here than just that with multiple definitions of
| revolution versus rotations, and sidereal time is where this
| answer can get weird.
| HarHarVeryFunny wrote:
| The only ambiguity there would be revolution/rotation about
| what center - the small disk's own center or the center of the
| large one. It seems pretty obvious they are expecting you to
| calculate something, so assuming this is a trick question and
| the answer is 1 would seem a risky interpretation, and anyways
| wasn't one of the answer options.
| matt-attack wrote:
| But isn't that precisely the distinction between rotation and
| revolution already provides? When I first read it I thought,
| well they used the word revolution so clearly the answer is
| 1. If they had stated "rotations" then the answer is
| obviously 4.
|
| It's pretty ridiculous they couldn't use the right word when
| the distinction was taught back it elementary school during
| the discussion of the motion of the earth.
| HarHarVeryFunny wrote:
| But why is it _obviously_ 4 ? Is it equally obvious that if
| the small disk was rolling around the inside of the large
| disk then the answer would be 2 ?
|
| If you already know the relationship between distance
| traveled by the center of the small circle and number of
| rotations, then of course both answers (for outside of
| circle, or inside) are obvious, but the inside case doesn't
| seem intuitive.
|
| btw, it seems they were intending "3" to be the right
| answer, but the wording isn't even close to what it'd have
| to be for that to be the right answer!
| gumby wrote:
| Interesting: I took the SAT in 1982 and don't remember this
| problem. They don't give you your % right, just percentile and a
| mysterious score between 200 and 800 for some reason. Does 800
| mean 100%?
| hatthew wrote:
| anecdata from years ago: 100% is 800, and leaving one question
| blank is 780.
| zdw wrote:
| I got an 800 on the Math portion of the SAT, but the results
| also said I missed a question (this was mid-90's), so maybe
| that one was thrown out?
|
| (1480 combined, did a prep class but didn't pay much attention
| to the language bits)
| gumby wrote:
| Back in 1982 our school's entire SAT prep was: "bring only #2
| pencils. Sharpen them before you come. Fill the bubble
| completely and don't leave any other marks. If you can
| eliminate one answer, it's worth picking one randomly, else
| skip the question." I don't remember that there was any SAT
| prep culture like there is these days. Nobody had heard of
| ACT -- perhaps it didn't exist yet.
|
| There were apparently about 50 of us in my year at MIT who
| had 800/800, and apparently that was pretty standard. I don't
| think I was the only one in my HS class of 39.
| calfuris wrote:
| The scaled scores are intended to be directly comparable, so
| the mapping from raw score to scaled score depends on the
| difficulty of the questions on the particular test that you
| took. On a sufficiently hard section, you can miss a question
| and still get an 800.
| gnicholas wrote:
| When I took the SAT a couple decades later, there were multiple
| sittings per year. Is it possible you took it at a different
| time? You should be able to check the news coverage and see
| which sitting it refers to.
| ad404b8a372f2b9 wrote:
| It's odd to me that anyone would come up with 3, to me it was
| immediately very apparent from the diagram that the closest
| answer was 9/2.
| HarHarVeryFunny wrote:
| I guess if you're smart enough to realize that 4 is the right
| answer, but isn't one of the choices, then the next question is
| "what were they thinking?", which is why 3 would be the smart
| guess to get your answer marked as correct.
| pbj1968 wrote:
| I'm no genius, but I used to score well on such tests as a
| youngster. I was handed an IQ test circa ~1996 and got about two
| thirds through it before I found a question where none of the
| responses were correct. I brought it to the teacher's attention.
| "There is no way you could possibly be right, this test was
| reviewed first!"
|
| Anyway, blame it on photocopy errors or whatever, but the answers
| were wrong. Still mad about it.
|
| I took another one ~2007 when I was looking to be a marketing
| person for a construction equipment rental company. This one was
| about 30 questions over 60 minutes. I got to question 26, which
| was some extraordinarily complicated question about how many cuts
| would it take to chop down a large board into the pieces you
| needed. After I wasted several minutes methodically writing this
| out, I realized the true test was realizing it was a time waster
| question one should skip. 27-30 were far simpler and then the
| buzzer ran out on me.
| pedrosorio wrote:
| > Still mad about it.
|
| Why?
| fsckboy wrote:
| they told him it was an IQ test but it was actually a
| psychological profile to diagnose his anger issues
| mrfox321 wrote:
| For the same reason why he brought up his iq tests in the
| first place.
|
| Because he self-identifies with some definition of iq.
| pbj1968 wrote:
| Not at all. The authority figure simply could not live in a
| world where the question was wrong. A better response, in
| his role as a school teacher, would have been to tackle the
| question in depth as a class or otherwise show me how I was
| mistaken. But given as I was immediately dismissed I'll
| never know for sure.
| az226 wrote:
| Might not even have been a gotcha. They interlace draft
| questions all the time. They don't count toward your score.
| WalterBright wrote:
| I approach tests by going to the next question if the answer
| isn't immediately solvable. Then, when reaching the end, I go
| back and spend more time on the ones I hadn't solved. That
| maximizes the score.
|
| I apply that technique everywhere. For example, when working
| the bug list, I'll solve the easy problems first, and the
| toughest last. That also maximizes the score, as the bug
| submitter's only care is if the bug is fixed, not how hard it
| is to fix.
| nick__m wrote:
| Almost completely off topic but you are good example of
| nominative determinism !
| WalterBright wrote:
| In the Air Force, my dad's assigned office mate was Major
| Smart. A line of my ancestors were the Dumbles.
| LanceH wrote:
| While in the Marines, I knew of a Major Hazzard and a
| Captain Justice. I really wanted to be there when they
| first met.
| remram wrote:
| Given a fast enough supply, this means you never look at the
| difficult bug reports at all.
| WalterBright wrote:
| It also clears the mind if one clears out the easy ones
| first. It's like when I feel like working on the car, the
| first thing is clean the garage.
|
| (If the reports come in faster than they can be fixed, of
| course one can never catch up regardless of the algorithm.)
| sverhagen wrote:
| In (software) engineering you want to take on enough of the
| hard stuff early on, to make sure you're not painting
| yourself into a corner with naive solutions...
| WalterBright wrote:
| There is always the concern that one has made a
| fundamental error. Can't worry about it too much, though,
| or one will never get anywhere.
| dsego wrote:
| I applied this to school tests but not in my work, well
| sometimes, if I'm procrastinating and need a few quick wins.
| But for timed tests, it's essential to skip something you're
| struggling with and get some points on the other questions.
| anigbrowl wrote:
| _the true test was realizing it was a time waster question one
| should skip_
|
| I remember something similar on the LSAT. Odious practice; if
| you get a wicked problem in a professional context, you don't
| have the option of just blowing it off. Of course, you could
| say it's about learning to prioritize with limited resources,
| but that's meta-gaming the applicants and selecting for corner-
| cutters. There's a place for corner cutting; in emergency
| situations it's sometimes the right thing to do. The problem is
| that selecting for corner cutters also incentivizes exploiting
| the system for less noble motives.
| kleene_op wrote:
| I don't see the problem with a corner cutter question located
| around the end of a test.
|
| It filters people into:
|
| - those who don't manage time efficiently by investing too
| much energy on a problem.
|
| - those who did cut the corner and as a result got an edge
| with a few more questions solved
|
| - the genius ones, who solved everything, in whatever order
|
| If the objective of a test is classifying candidates and time
| management is one of the metric considered, then this kind of
| testing pattern absolutely makes sense.
|
| I was one of those who never cut corners and just focused on
| the problem at hand until failure, and now that I am working
| and need to get things done I wished my teachers trained me
| that skill.
| contravariant wrote:
| Worst one I ever saw was a question to prove something that
| was vacuously true if you got the preceding question correct.
|
| People spent ages trying to find their mistake. I was one of
| the first to finish because I quickly concluded I wasn't
| going to find the mistake (after checking a mere 3 times).
| chunsj wrote:
| Why should we take the meaning of revolution in this problem not
| as the contacting point to meet the circle again, but just as the
| pointing the same direction? I think this is the source of
| confusion here.
|
| I'm not the native speaker of English and I might take the
| meaning of "revolution" very absurdly here. Just curious and I
| have to ask this. :-)
| scotty79 wrote:
| He mentions that the word revolution has specific meaning in
| astronomy which doesn't make any sense in the context of this
| problem.
| vood wrote:
| I'm surprised that only 3 people reported the error.
|
| While problem is not trivial, my initial reaction was "it can't
| be 3, it's too obvious". And it seems that a lot of people in the
| comments here do get to the right answer on their own.
|
| So, why not hundreds of reports?
| crazygringo wrote:
| > _my initial reaction was "it can't be 3, it's too obvious"._
|
| The SAT has math questions ranging from easy to hard-ish.
| Plenty of the questions have very obvious answers.
|
| Unlike the AP Physics 2 exam, for example.
| belltaco wrote:
| I did a eyeball ball park estimate and figured the closest answer
| was 9/2 and was right.
| goodpoint wrote:
| Yes, it's pretty easy to just imagine the rotation and guess
| it's somewhere around 4. The last part of the rotation is more
| difficult to imagine.
| scotty79 wrote:
| Second part of the video is way more interesting, where he
| discusses how this toy problem actually relates to how we define
| what a year is depending on whether we look at the stars or at
| what's on Earth.
| less_less wrote:
| One interesting thing that's not in the video: there is a real
| application beyond the astronomy one, a scenario where you would
| want to roll one object around another object, and care about how
| many rotations it makes.
|
| https://en.wikipedia.org/wiki/Epicyclic_gearing
|
| These are used for car differentials, bicycle gear hubs, pencil
| sharpeners, and many other applications.
| stormdennis wrote:
| I don't revolve once every 24 hrs, the earth does.
| freediver wrote:
| Explaination that works for me is that if you were rolling it
| around a spot (zero diameter) you would need one full revolution.
| tim333 wrote:
| Tldr it was a four choice multi choice question but the all the
| options were wrong because the people setting the test got it
| wrong.
|
| So I'm not sure everyone got it wrong, just that they weren't
| confident enough in a rushed test to cross out A,B,C and D and
| write in the correct answer!
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