@Shepard-Thomas
In college, I took a poetry class and once had an answer marked wrong on a test. Confident in my response, I reached out to the poet themselves, who affirmed I was right and even communicated this to my professor. Despite not being a fan of poetry, that moment made me quite proud!
@felixp535
That part about the circle rotating around the triangle was mind-blowing. You instantly understand why it's not the same if the circle rolls on a flat line or rolls on a curved line
@jebjim9391
MIND, BLOWN I did the math BEFORE you said "pause to do the math" and I got 3 and I was really confident in the answer. I was REALLY reacting when the answer varied by the 'perspective of the circle' And I was AMAZED when I saw the real answer. what, an, amazing video !! TY Veritasium
@forkmonkey
Another fun way to conceptualize the N+1 is to ask what happens if the circumference of B is 0. A still has to rotate around that point, one time. Great video.
@TupperWallace
The 1872 novel “Around the World in Eighty Days” had a plot that depended on this kind of situation. Phileas Fogg traveled around the world eastward, against the earth’s rotation. Though initially he thought he’d missed the 80 day deadline by some hours, in fact only 79 days had passed in London. One extra rotation had passed beneath his feet. He won the prize, married the girl and lived happily ever after.
@KevinJDildonik
To all the 1st posters: YouTube takes up to 15 minutes to gather data on a video before showing stats. Everyone in the first 15 minutes all think they're first.
@littlebrother82
I'm amazed that the SAT exam board actually admitted they were wrong and changed it. I took a trades exam a few years ago and argued about a question with the guy running it, demonstrating why the question was wrong, he admitted it was wrong, and still said nothing would change.
@stevedietrich8936
I came up with the answer, 3, in a second or two, and then wondered "how could that possibly be incorrect". I spent the next 18 minutes learning how. Great video!
@BjornHansen-n5w
Thinking about this yesterday and I realized the extra rotation becomes intuitive if you shrink the large circle down to a point, and rotate around that. Even though the diameter of the circle it's rotating around is zero, the "small" circle still has to make a full rotation to return to its starting point.
@Spondre
I loved the "I hope so" answer from Doug at the end. It highlights the most important lesson I learned during my education: "I might be wrong."
@bupdaddy1
This was the one SAT I took, and I remember the question that didn't have a correct answer, and it wasn't until today that I understood the right answer. I can die happy now.
@Darth_Insidious
I was confused for a second until I realized that if you set the radius of the big circle to 0, or in other words rotate the smaller circle around a point on its circumference, it takes 1 full rotation for the circle to end up back at the start.
@Tim3.14
One way to see the extra rotation -- shrink the inner circle to radius approximately 0, so it's like a thin wire. The circle still has to do a rotation to roll around the wire, even though the wire's circumference is negligible. (The rotation disappears from the "circle's perspective" because the "camera" does that one rotation along with it.)
@parnikajain6011
I paused the video and worked out an answer of 4, but since it wasn’t one of the answers, I figured I was wrong. Hearing you say that none of the options were correct and 4 was indeed the correct response from our point of view felt so validating. Can’t believe I even made the same diagram of the distance traveled by the center of the circle.
@jonathanbost8427
I paused the video with the question before the multiple choice answers came up. I debated with myself but decided the answer was 1 (because of the term "revolution"). I was disheartened when seeing the choices, deciding it must be 3, and then excited again when you said the answer was not an option. Then disappointed again when you said it was 4, and then excited again when you said 1 was a possible answer . . . a real rollercoaster of a video.
@ElectroBOOM
This was a great video! Blew my mind when I realized how I was wrong!! Good to know question wordings can be so important, eh?! 😁😉
@scottthacker9554
I have a 1st class degree in Physics and clicked on this thinking it would be simple algebra, I had a huge grin on my face whilst being explained to how I was wrong. I love these kind of videos, I love learning something new. Never stop learning!
@sonozaki7
this was the most genuine "everyone gets this problem wrong" without being a pure lie
@Cosmic9999
It will never fail to amaze me how seemingly simple questions can turn out to go against common sense when studied further, and then can be used to add to knowledge and laws that are used to greatly change or enhance our world.
@5MadMovieMakers