You can see this phenomenon in American football where the pretty good quarterbacks often become great coaches but the very best quarterbacks rarely do. The pretty good ones got good by being very detailed students of the game, memorizing thousands of plays and watching as much game film as possible... the absolute elites like Joe Montana often just had the ability to see an open receiver 30 yards away and throw the ball with 4 inch accuracy to the point that he would have run to during the ball’s flight.

Alternate explanation: Most quarterbacks aren't the best in the world. Statistically speaking, coaches who are former quarterbacks will typically come from this group.

Who are the great quarterbacks that have struggled at coaching?

My best guess is that the spoils of being a great quarterback are so great, and the retirement job offers are so lucrative that they simply don't want to take the steps required to learn to coach.

For example a pretty good QB turned great coach like Jim Harbaugh took a job as an assistant coach Western Kentucky after he retired, and subsequently moved up the coaching ladder. I struggle to see a great QB taking a road like that when they have so many other options.

For varying definitions of great ...

All 5 HOF QBs who coached in the NFL have losing records.

Norm van Brocklin, HOF QB who could never coach another HOF QB (Fran Tarkenton)

Bart Starr

Otto Graham

Sammy Baugh

Bob Waterfield

But yeah basically as soon as broadcasting and endorsements became a post foot all career option, all the top QBs went that route.

I don't think this is always true.

Some of the best books and courses I've taken were from people who are experts at what they do. The keyword there is "are", not "were".

There's just an extra level of insight you can get from someone who is in the trenches doing real work, rather than trying to learn from someone who never really did the thing for real but happens to be an "armchair expert".

I think this is especially true for software development material and it's one of the reasons why I continue to do freelance work while creating video courses on the side. If I stopped consulting then I would become rusty in my craft if all I did was come up with course material.

An example of this would be DHH's books. Would you rather learn business from DHH (someone involved in a ridiculously successful business that operates today), or a college professor who likely never ran a really successful business but knows a ton of theory about it but also has 30 years of teaching experience?

I would argue DHH's advice in his books would be more valuable, even if he happens to be a less skilled teacher on paper.

Pardon my ignorance but who is DHH?

David Heinemeier Hansson, creator of Ruby on Rails, cofounder of Basecamp.

http://david.heinemeierhansson.com/

Teaching like any learned skill requires significant commitment and practice. Those who "do" like Einstein aren't prepared to carve out 1000s of hours from their scientific research, where their passion lies, to learn and practice how to teach well. I'm quite sure that if Einstein loved teaching as much as research he would learn to be an outstanding teacher.

The notion that there's a "do <-> teach" continuum is just silly. OK, Einstein was great at "do" and lousy at "teach". How about Feynmann?

Feynmann was not exactly what you'd call "statistically representative".

Teaching requires a set of distinct skills which are different from researching. Naturally not everyone is equally gifted or developed in all areas.

One of the most valuable skills in life is the ability to adapt your mental models and present ideas at an audience-appropriate level. It is useful in teaching; it is also useful in leadership, sales, design...

As an exemplar, I submit Akamai CTO and MIT professor Tom Leighton.

https://www.youtube.com/watch?v=L3LMbpZIKhQ&list=PLB7540DEDD...

This is all true, but learning to teach takes time and one has less time for research.

Too much presenting moves one into extrovert mode where one has many "ideas", but no proofs or execution.

I rarely see a top presenter actually doing anything.

Feynman really is an exception, and there are rumors that his classes were too good -- the students would think they understood everything, but actually did not.

This is also what I experienced when reading his books (which are superbly written).

Sure, Feynmann was pretty special. But the title of the article is "Those who can Do, Can't Teach", which is clearly false given the presence of at least one counterexample. It's possible to make any statement "true" if you don't accept the counterexamples because they are not "statistically representative". :)

It is also hard to formalize and convey to someone else what one already knows: https://en.wikipedia.org/wiki/Tacit_knowledge

The formulation I like is the "curse of knowledge".

https://en.wikipedia.org/wiki/Curse_of_knowledge

But overcoming the "curse of knowledge" is exactly what makes for good teachers, good designers, good communicators, and so on!

This idea that you better you are at "teach", the worse you are at "do" and vice versa is A) a sharp dig at academia, and B) a result of the cognitive dissonance we feel when someone is extraordinarily good at something valuable but has underdeveloped teaching skills.

If it is indeed true, then Feynman is probably the biggest exception to it.

This topic is plenty debatable.

Many people I meet who are excellent at their jobs are lousy teachers. They tend to have instinctive grasp of things which doesn't transition well in teaching.

But people who are good but not great at their jobs tend to be the best teachers. One of the reason is that these guys tend to have detailed notes and learned through experience.

As the article mentioned Einstein as a teacher, I think it’s worth asking about his writing too. I think his actual papers are very good at explaining the theory and indeed better than many textbooks. I think a good way to start learning eg special relativity is to get a copy (available online) of Einstein’s first paper on special relativity and read it. The paper has to explain it for people who have never really seen such a thing before. Obviously a certain level of mathematical ability is required to understand the paper and maybe this is more than required by a modern textbook. A modern textbook may also explain things in a different way with eg 4-vectors and lots of spacetime diagrams.

Suppose that there are 1% of people in a field who are considered great at doing and 2% who are great at teaching, then just from expectation without additional knowledge the vast majority of great teachers won't be great at doing.

Also, if the percentage of people who are great at both is higher than 0.02% but lower than 1%, there is a positive correlation between teaching and doing, but it is not a perfect correlation. I suspect this is the case.

Why? Both doing and teaching something well often require clear and systematic thinking. However, there are also disparate skills required for each and only those with time, inclinations, and opportunities to practice both skill sets could become great at both.

I faced the consequences of this first hand. In the Abstract Algebra class we were recommended a very standard book by one of the giants in the field and I suffered the entire semester depending on that one book. I should have switched a little too early. I learnt it the hard way and advise anybody to look for alternative resources or more explanations once you start seeing a lot of text such as "and the rest is left as an exercise for the reader" without much explanation irrespective of the field you are in and regardless of the big name attached to a source. At times an obscure blog is able to explain a difficult concept much more easily.

Now that I think about it, the worst CS teachers I've had were the ones who taught part-time while working in respected positions in industry, or had a strong industry resume behind them.

Previously I had wondered why some of my best CS professors in university didn't go for a private sector job where they could be earning 1.5-2x doing programming instead of teaching it, but now I realize they would've been mediocre programmers instead of great teachers.

Nonsense. All the great teachers I had were also great practioners. I like to see myself also there. Rhetoric is trainable.

The irony that he cites Harvard Physics is the vanguard of rethinking how to teach Physics, and possibly the root of this article come from Harvard Physicist Eric Mazur: https://www.youtube.com/watch?v=LIFL0K184kg

They say the best teachers struggled with the subject.

Does this work the other way around?

People tell me I'm an excellent teacher, but I'd consider myself a mediocre developer...

The title is a play on the old saying "Those who can't do, teach".

Whether this is actually the case or not is debatable.

Back in junior high one of the classes was marooned into doing a skit on a school event day. The punchline of the skit was an extended version of the saying - "Those who can, do. Those who can't, teach. Those who can't teach, teach PE. And those who fail at that, end up as head masters."

The head master at the time was an ex-PE teacher.

Being a good dev requires long term commitments and delivering.

Teaching is a serie of small sessions, each connected but still, they have their own close little finish line.

So if you are a procrastinator or have a hard time finishing, you may be a good teacher and yet a mediocre dev

Maybe I'm a good teacher because I'm a mediocre developer?

I mean, people are bad-to-mediocre when they begin to learn something per definition, so when I teach them, I teach them from their perspective? :D

I actually would see teaching as the longer term project without the small wins you can expect in programming.

When you end a lesson, you win. Always. There are very few ways to lose at a teaching moments if you are good at it.

I can code for several days before having something that will make someone smile.

As the child of two teachers I vehemently disagree with what I consider your inaccurate and wholly unsupported supposition.

Except i'm a dev and a teacher.

And i have yet to met a teacher who's anywhere close to have the deadline challenge a dev has.

Somebody not learning is a failure but that's life. A line of code not working on time, well, that's the entire product not shipping.

> My renowned astrophysics professor taught us how the universe seemed to be expanding, but never bothered to explain what it was expanding into (still waiting for someone to demystify that one).

Wow... and this person went to Harvard??

I want to know the answer too.

I always thought the universe is expanding to a larger universe. I never thought that it could be expanding to something else.

There's no notion of spacetime outside the universe. The spacetime is the universe.

Two assumptions:

a) the universe is infinite. In this case it doesn't expand into anything, the things inside of it just stretch apart.

b) the universe is finite. In this case it expands into something, but because we're trapped inside spacetime, we can't answer this scientifically.

The wording "expanding" adds more confusion than it helps. See [1] for the discussion about this topic.

[1]: http://curious.astro.cornell.edu/ask-a-question/104-the-univ...

I think it’s like the universe being a balloon (infinite or not) and inflating it. The space between any two points on the balloon increases over time. And at the Big Bang the space was basically 0.

Think of it another way: All matter in the universe is getting smaller. But the universe have the same size, so distances between everything increase.

the universe doesn’t expand into something bigger. It’s like multiplying the set of the real numbers by two, the set doesn’t become bigger and its boundaries do not change.

I think you or someone understands this subject should write a detailed comment in this thread that explains this to software folks like us. I appreciate the help.

I doubt a renowned professor would use expanding instead of inflating. likely the student got stuck on the balloon metaphor.

Explaining what is/was "around" the big-bang was never done properly in most physics courses I've taken, and for a good reason: you need to understand the notion of local space metric before you can get that - as the theory currently stands - there is basically nothing outside of the expanding universe.

There are some things humans will simply never be able to come into contact with or fully comprehend. Such things include the 4th dimension, the concept of infinity, and the concept of nothingness. The universe and what lies outside of it, unfortunately involves all of these concepts, so while there may or not be nothing beyond the universe, because we cannot measure this or engage with this, it is only effectively nothing and not literally nothing.

Is the universe infinite? Debatable.

What’s the answer? Curious.

It's not expanding, separate points are growing further apart.

Any metaphor you hear about a balloon or fabric or things like that is an overly simplified version of complicated mathematical models of the universe.

Are electrons getting larger? Are atoms getting larger?

Long story short, no and that's because forces are only applicable in certain situations and not others, and in this case gravity, electromagnetism, and similar subatomic forces are binding the atoms we know and preventing them from "expanding". I'm not an expert and this is just my simplified version of a simplified version.

Here's more to read about it:

https://www.quora.com/Astrophysics-If-the-universe-is-expand...

https://medium.com/starts-with-a-bang/ask-ethan-if-the-unive...