Richard Feynman on Physics: 4-part lecture series (videos) | Hacker News Reader

Richard Feynman on Physics: 4-part lecture series (videos)

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I've read the Feynman lectures on physics, but I had no idea there was actually a series of videos as well.

Great find.

I have collected some Feynman lectures as well. See this:

http://freescienceonline.blogspot.com/2008/12/richard-feynma...

Just a question, does anyone know how to download these videos to watch offline?

I just finished watching the first lecture, it was very enjoyable as is typical of Feynman lectures, but what I'm confused about is the metaphor that he chose to give as an explanation for the reason the probabilities are the way they are.

Isn't another interpretation of that experiment (what I thought was the current default interpretation), that as you increase the distance between the two surfaces you have light rays reflecting back, and because of the distance (not the time it takes an arrow to spin as in the video), the two light rays become out-of-phase, and therefore you get constructive and destructive interference?

Secondly, I was also confused as to his insistence that "light is a particle", hasn't it be established that light has properties of both particles and waves? Certainly Feynman doesn't deny that, so why would he make that statement so insistently? The wave-length of the light "particle" is very important in calculations, and while this characteristic of light wasn't denied in the lecture, it certainly seemed to be ignored amidst the talk of "little spinning arrows"...

I know nothing about physics - I took a class in high school, and that's it - but there are a couple of explanations:

1) These are old lecture and the whole particle/wave thing, while known, was just thought of differently back in the 1960's. 2) My guess - he's making a generalization to set up for a "blow your mind" moment later in the lecture series.

I know nothing about (1), but I do (2) all the time when I teach.

One of the things I do is that I try to simplify the building blocks of whatever I teach early on. I simplify things and I repeat them both verbally and visually, doing everything I can to drill my students with these facts. Then, later in the class, I show the exception cases. This does two things: 1) it gets their attention and 2) it reminds them of the general rule. I love doing this because you can immediately see comprehension in students' faces and it re-establishes my control over the classroom. (Anyone who's taught knows that a dialogue in a lecture room is doomed to failure; you're the teacher - you're in charge.)

My guess - again, I know nothing about physics and nothing about Feynman - is that he's making a tactical decision in how he presents material to maximize student learning over the totality of the lecture course.

That is what I thought might be the case as well, but if you watch the lecture, you'll see that he takes the time to insist that he's not giving his audience a watered-down explanation to "help" them understand.

To address your second concern, all quantum particles (this includes photons) have wavelike properties (including wavelength), and thus can show wavelike effects, such as interference. For example, a ray of light contains a huge number of photons and obeys certain wave equations, but if the intensity is decreased enough, the light is found to impinge in discrete units, which have been named photons.

When Feynman says light is particles, he means that it comes in discrete units, not that it behaves as a stream of tiny billiard balls with classical behavior.

I'm aware of this, but this is the exact sort of caveat that he failed to mention in his lecture, despite promising his audience that he would tell them exactly his understanding of the situation.

I also have a question about the first lecture. He mentions that the probability of a particular event happening is given by adding arrows/vectors head to tail, and then getting the area of the circle with radius equal to length of the resulting arrow. Would this not enable you to have a probability greater than 1?

It certainly would, good point, that's yet another issue with his metaphor.

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