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Richard Feynman on education in Brazil

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Re: Richard Feynman on education in Brazil

#31

Post by ignifero »

palish wrote: post #29
kalid wrote: post #18

I love this story because as Feynman puts it, there's a difference between knowing the name of something and really knowing it. Since we're on the topic of light -- despite going to a great school and taking several physics courses, I suffered from a severe misconception until about a month ago. Maybe you have it too. Think about a light wave. You might imagine a diagram like this: http://betterexplained.com/wp-conte…

Very informative, thank you! Something I've been mulling over for awhile now is... what does it mean to represent a color with numbers? That is, every pixel on our monitor is RGB 0 through 255. But what about in physics? Well, "color" is a photon whose wavelength falls between 400nm (short wavelength; intense energy; "ultra"-violet; and violet = blueish; therefore 400nm = "the blue side" of the EM spectrum; this is h…

EM radiation can have any wavelength. Color is the visible spectrum in which our retinal cones and rods respond when EM is shone upon them (actually, they cease responding, but that's another matter). We have 3 kinds of cone cell receptors sensitive to different parts of the visible spectrum. Color is the perception generated further down in our brain from the combination of these incoming signals. Screens were designed to be visible, that's why it makes sense to have 3 colors of LEDs. Light wave frequencies do not add up, i.e. you can't add 2 green beams to create an ultraviolet.

Re: Richard Feynman on education in Brazil

#32

Post by ignifero »

microarchitect wrote: post #8

The problem boils down to just one thing. The teachers don't understand what they're teaching themselves, so they confuse memorization and repetition with learning. The students who are good at this are rewarded because they do better in the exams, and slowly but surely all the joy of understanding science is beaten out of a student. I can relate to this personally. Until I started college, I really understood what I…

It's also a matter of opportunity. People in the US consider opportunity a given. It's not so in most of the world, people may choose to educate themselves, even forcibly via repetition, because there may not even be other things to do, and it's better to have some kind of education than no education. The exceptional kids of course do not follow that rule, they'll make it no matter what.

Re: Richard Feynman on education in Brazil

#33

Post by palish »

ignifero wrote: post #31
palish wrote: post #29

Earlier quoted context omitted.

Very informative, thank you! Something I've been mulling over for awhile now is... what does it mean to represent a color with numbers? That is, every pixel on our monitor is RGB 0 through 255. But what about in physics? Well, "color" is a photon whose wavelength falls between 400nm (short wavelength; intense energy; "ultra"-violet; and violet = blueish; therefore 400nm = "the blue side" of the EM spectrum; this is h…

EM radiation can have any wavelength. Color is the visible spectrum in which our retinal cones and rods respond when EM is shone upon them (actually, they cease responding, but that's another matter). We have 3 kinds of cone cell receptors sensitive to different parts of the visible spectrum. Color is the perception generated further down in our brain from the combination of these incoming signals. Screens were desig…

My point was that you can't add two RGB values and expect to get a meaningful physical result --- you can't multiply them either, as far as I know.

This has vast implications for computer graphics. Video games, for example.

"Light wave frequencies do not add up, i.e. you can't add 2 green beams to create an ultraviolet."

The light wave frequencies do add up --- if you add 2 "green" beams, then you get a more intensely bright green beam. The hue changes only slightly.

Re: Richard Feynman on education in Brazil

#34

Post by ignifero »

palish wrote: post #33
ignifero wrote: post #31

Earlier quoted context omitted.

EM radiation can have any wavelength. Color is the visible spectrum in which our retinal cones and rods respond when EM is shone upon them (actually, they cease responding, but that's another matter). We have 3 kinds of cone cell receptors sensitive to different parts of the visible spectrum. Color is the perception generated further down in our brain from the combination of these incoming signals. Screens were desig…

My point was that you can't add two RGB values and expect to get a meaningful physical result --- you can't multiply them either, as far as I know. This has vast implications for computer graphics. Video games, for example. "Light wave frequencies do not add up, i.e. you can't add 2 green beams to create an ultraviolet." The light wave frequencies do add up --- if you add 2 "green" beams, then you get a more intensel…

RGB values can be added to create other colors, just like painters mix colors (just divide the sum by 2 to avoid saturation), because the R, G and B colors were arbitrarily selected from the beginning to match what the artists were familiar with.

In the case of combining beams, what changes is the intensity of the beam, the frequency spectrum does not change at all (there is two photon excitation, but that's a completely different phenomenon).

Re: Richard Feynman on education in Brazil

#35

Post by palish »

ignifero wrote: post #34
palish wrote: post #33

Earlier quoted context omitted.

My point was that you can't add two RGB values and expect to get a meaningful physical result --- you can't multiply them either, as far as I know. This has vast implications for computer graphics. Video games, for example. "Light wave frequencies do not add up, i.e. you can't add 2 green beams to create an ultraviolet." The light wave frequencies do add up --- if you add 2 "green" beams, then you get a more intensel…

RGB values can be added to create other colors, just like painters mix colors (just divide the sum by 2 to avoid saturation), because the R, G and B colors were arbitrarily selected from the beginning to match what the artists were familiar with. In the case of combining beams, what changes is the intensity of the beam, the frequency spectrum does not change at all (there is two photon excitation, but that's a comple…

You are missing my point.

From a physical standpoint, it makes no sense to add two RGB colors.

It makes sense to add two lengths. (1 inch) + (1 inch) = (2 inches).

It does not make sense to add two RGB colors. The result is not a meaningful physical quantity. In the same spirit, (7.8 earthquake) + (8.3 earthquake) != (16.1 earthequake).

This is a big problem for those of us who are trying to reproduce how nature looks on the screen of a computer. (In my case, realtime graphics.)

For the case of the combining beams of light, the only time that the hue wouldn't change is if you have two lightbulbs that emit precisely the same EM waves --- the same frequencies and the same intensities for all emitted waves. This is practically impossible. Therefore, the hue of the combination is never exactly the same. Just because you can't perceive the difference, doesn't mean there isn't a difference.

Re: Richard Feynman on education in Brazil

#36

Post by Jach »

kalid wrote: post #18

I love this story because as Feynman puts it, there's a difference between knowing the name of something and really knowing it. Since we're on the topic of light -- despite going to a great school and taking several physics courses, I suffered from a severe misconception until about a month ago. Maybe you have it too. Think about a light wave. You might imagine a diagram like this: http://betterexplained.com/wp-conte…

Personally I think the whole wave-particle business shouldn't be touched upon until the student understands that in reality those things are just complex vectors in a configuration space, not a little ball bouncing around. Equivalently you can think of them as outlined in Feynman's QED (which anyone interested in physics should read), as arrows. The word "wave" shouldn't ever be mentioned in introductory quantum mechanics.

Then once that's over, you explain to the students this: http://www.youtube.com/watch?v=_7OEzyEfzgg it's a duality of interpretation, not reality, we use wave mathematics for simplified calculations. Plus if you interpret it as a wave (as Feynman shows) you run into problems with experimental results not coming out as expected that a particle interpretation doesn't have problems with. (And for some reason I can't think of color in terms of waves, it makes much more sense if I think of it in terms of the energy of a photon with the brightness as a function of how many photons there are, which then ties back to a probability point of view where it's obvious that it's brighter where there's probabilistically more photons.)

http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ remains for me the best introduction to thinking sanely about the subject without becoming confused from the get-go as you start talking about waves vs. particles.

Re: Richard Feynman on education in Brazil

#37

Post by ignifero »

ignifero wrote: post #34
palish wrote: post #33

Earlier quoted context omitted.

My point was that you can't add two RGB values and expect to get a meaningful physical result --- you can't multiply them either, as far as I know. This has vast implications for computer graphics. Video games, for example. "Light wave frequencies do not add up, i.e. you can't add 2 green beams to create an ultraviolet." The light wave frequencies do add up --- if you add 2 "green" beams, then you get a more intensel…

RGB values can be added to create other colors, just like painters mix colors (just divide the sum by 2 to avoid saturation), because the R, G and B colors were arbitrarily selected from the beginning to match what the artists were familiar with. In the case of combining beams, what changes is the intensity of the beam, the frequency spectrum does not change at all (there is two photon excitation, but that's a comple…

Sorry if i am being dense but you got me confused. It makes sense to add 2 rgb vectors from a perceptional standpoint: you add a red color on a green color you get a yellow. It also makes sense from a physical standpoint: the resulting frequency spectrum will have peaks near both red and green, thus what we perceive as yellow. If instead you mean that "red" is not a physical quantity, i totally agree, it's just a name for a range of frequencies.

It seems to me in computer graphics you also have to deal with other color problems such as light dispersion, the blue shift due to light scattering in the atmosphere, maybe even doppler effects :), but it's still valid to combine colors linearly for short distances, for example a green and yellow lightbulb would look yellow from a reasonably far distance.

In the example you give below, RGB 128 can be considered halfway between black and white, just not in terms of frequency, but in terms of freq. distribution (also, RGB is a 3dimensional space). As for the earthquakes, you 're right, the amplitude of the resulting wave would be the product of the original waves. Sorry for the rambling, i think it's a fun subject.

Re: Richard Feynman on education in Brazil

#38

Post by Jach »

rbanffy wrote: post #22
ojosilva wrote: post #17

Just for clarification: Richard Feynman, Nobel physicist wrote this piece about his experiences teaching in Brazil in... 1950. So I don't think this is a very precise account of education in Brazil nowadays, but it sure does sound like education there (and almost anywhere else) in the 50s -- my mom tells me she would read out loud to herself until dawn the day before an exam, as she was taught auditory learning. This…

It's soul-crushing to read this, isn't it? Every day I am confronted with former students who have been taught like this. I took fluid dynamics 3 times, until I found a teacher willing to teach it instead of just letting us memorize the whole thing. When you really understand a subject, it's like hitting the light switch and realizing you were in a dark room. I feel for those who live their professional lives in dark…

I let slip to one of my engineering teachers whose wife also teaches physics at the school that I desired Feynman to teach me electricity and magnetism since I feel the class has just been equations thrown at me and horribly contrived situations with "story" elements* that don't add to understanding. I believe he said something like "Well, there's limits with Feynman too" and I said "Yeah, he's dead." So I have to make due with the Feynman Lectures Volume 2, which is excellent but clearly designed for students with a different background in math and physics. (It's still way better than Giancoli.)

Ah well, that's often the case in college due to pacing and how it's structured. You do enough to pass the class and if you care you'll go further and reach understanding over the summer.

In addition to Feynman's excellent lectures (there are more than the other poster linked) there's also a lot of general videos on the nature of science, what it means to be scientific, and about Feynman himself. The Pleasure of Finding Things Out is one of my favorites: http://www.youtube.com/watch?v=srSbAazoOr8

* When you find a Karate Girl who can jump kick a charged pole into a perfect semi-circular arc without transferring any charge to herself let me know.

Re: Richard Feynman on education in Brazil

#39

Post by Stormbringer »

ignifero wrote: post #32
microarchitect wrote: post #8

The problem boils down to just one thing. The teachers don't understand what they're teaching themselves, so they confuse memorization and repetition with learning. The students who are good at this are rewarded because they do better in the exams, and slowly but surely all the joy of understanding science is beaten out of a student. I can relate to this personally. Until I started college, I really understood what I…

It's also a matter of opportunity. People in the US consider opportunity a given. It's not so in most of the world, people may choose to educate themselves, even forcibly via repetition, because there may not even be other things to do, and it's better to have some kind of education than no education. The exceptional kids of course do not follow that rule, they'll make it no matter what.

To say that there is no opportunity in places like Brazil and India is to blame someone else for your not taking the initiative.

Even in the UK and US the vast majority of the students don't really take advantage of the education system. And those who do are often ridiculed by those that don't.

There is just as much pressure to slack off and underperform in the west as there is to do rote memorisation in Brazil or to cheat on the exams in India.

The system is never to blame for you not taking the opportunities that are there. The system is not to blame for your slackness.

So long as you never take responsibility for your results, you will get crap results.

Those guys you see in India who are rich and successful, I guarantee you they didn't sit around pissing and moaning about how because the system is bad there are no opportunities. They grabbed a big double handle of life's balls and went out and made their own opportunities.

Re: Richard Feynman on education in Brazil

#40

Post by palish »

ignifero wrote: post #37
ignifero wrote: post #34

Earlier quoted context omitted.

RGB values can be added to create other colors, just like painters mix colors (just divide the sum by 2 to avoid saturation), because the R, G and B colors were arbitrarily selected from the beginning to match what the artists were familiar with. In the case of combining beams, what changes is the intensity of the beam, the frequency spectrum does not change at all (there is two photon excitation, but that's a comple…

Sorry if i am being dense but you got me confused. It makes sense to add 2 rgb vectors from a perceptional standpoint: you add a red color on a green color you get a yellow. It also makes sense from a physical standpoint: the resulting frequency spectrum will have peaks near both red and green, thus what we perceive as yellow. If instead you mean that "red" is not a physical quantity, i totally agree, it's just a nam…

What I'm saying is that RGB(128,128,128) is not halfway between RGB(0,0,0) and RGB(255,255,255), in the same way that a 4.0 earthquake is not halfway between a 0.0 earthquake and an 8.0 earthquake.

The scale is non-linear.

As far as I can see, the only true linear space is frequency space --- aka "EM spectrum" space.

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