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I got: "We only use 10% of our brains. Modern neuroimaging has shown that we use most of our brain." In the 90's I thought this was not in fact, but urban legend, the whole time.

Also: "Christopher Columbus discovered America. Indigenous peoples had been living in the Americas for thousands of years before Columbus arrived." I didn't realize that it was implied no one was here when he came.

The first two paragraphs are definitely wild, but I guess you've sorta nerd sniped me with the third paragraph.

It sounds like the professor was talking about the concept of work, in a physics sense. In this sense, work being done on an object is effectively just the difference in energy of that object between a start and end point. When you lift an object, it gains gravitational potential energy due to being higher up (it has farther to fall). If you lift it by the same amount, the amount of energy it gains is the same regardless of whether you do it quickly, slowly, or walk around the room and end up back in the same spot. The end result for the object is the same, so the amount of work done on it is considered to be the same. Obviously, in a common sense, some require more exertion than others--that's just not part of what's considered to be work on the object in that sense.

My physics professor discussed the difference between "work" in the physics sense and "work" in the common sense. As best I can recall (it's been years now), his demonstration was basically that he held something out at arm's length and said something like "it's not moving and not gaining any or losing any potential energy, so as far as physics is concerned, no work is being done on it. But the muscles in my arm certainly don't feel that way!" In both cases, you're actively exerting a force to counter the force of gravity, with the end result being that the object doesn't move, and so its energy stays the same. Thus, no work is done on that object as far as physics is concerned.

~~I'm not sure this extends to planking, though--your body is the object, in that case, and you're expending chemical energy to maintain that position. It's all a matter of what you include in the analysis, I guess.~~ Reading up on it, the concept of work in physics only seems to be concerned with forces and motion; I guess that makes sense, since it is physics. With that in mind, I guess planking would also be considered doing 0 work (again, in a physics sense).