I wasn’t claiming that the hypothetical physicists made a valid inference—just the opposite! And FWIW, the shaking (cycling of tension level in the relevant muscles) can’t provide net energy to the object because you apply as much work to it on the up movements as it applies to you on the downward movements. The reason you expend energy while holding it in place is because of the muscle adjustments that your body must undergo to maintain an upward force on the object, which indeed involve “force through a distance”—it’s just that body-energy-consuming forces through distances do not include force through a distance on the object you’re holding. [1]
In the scenario I was trying to describe, the physicists have made the mistake incorrectly identifying the correct way to map their models onto a system in a way that accounts for all relevant factors. The more “epicycles” you have to add on to get the model to work (no pun intended), the more questionable its claim to relevance—hence the parallel to (how I understood) AlexMennen’s point.
(And for the record, I don’t consider the refutation I gave of the hypothetical physicists to be “adding epicycles” because it simply uses independantly-established knowledge from another field, rather than an ad-hoc fix only applicable to this case, thus showing consilience with biology.)
[1] Added footnote to say: Rather, the kind of “work” here shows up in the expansion and contraction of muscles.
Edit2: Hey, what’s with the comment deletion? I had a neat reply to you all written up and then you disappeared the thing I was responding to! :-(
Sorry. I deleted my comment because it sounded too obvious. (For onlookers, I said the energy gets spent due to shaking of the arm.)
And FWIW, the shaking (cycling of tension level in the relevant muscles) can’t provide net energy to the object because you apply as much work to it on the up movements as it applies to you on the downward movements.
Of course it doesn’t provide net energy to the object, but it still takes energy away from you. You spend it on the upward movements, but don’t reclaim it on the downward movements because that would involve resynthesizing ATP or whatever. So it becomes heat. Likewise, braking your car doesn’t cause refuelling (except when it does).
In the context of the hypothetical physicists, it does not help them resolve their confusion to point to the hand shaking. Their mistake is in only counting the work done by the hand to the object. Once they’ve made that mistake, telling them that the hand shakes would not change their minds, since it doesn’t show net work being done by the body in that respect, which is why I made the comment you quoted.
The mistake could only be corrected by pointing out the incorrect model of how humans generate lifting force.
So while your point is correct, and perhaps obvious, one should also remember that it doesn’t address the specific mistake I criticized.
Huh? When you’re holding something, you expend energy because your hand shakes. The longer you hold it, the more it shakes.
I wasn’t claiming that the hypothetical physicists made a valid inference—just the opposite! And FWIW, the shaking (cycling of tension level in the relevant muscles) can’t provide net energy to the object because you apply as much work to it on the up movements as it applies to you on the downward movements. The reason you expend energy while holding it in place is because of the muscle adjustments that your body must undergo to maintain an upward force on the object, which indeed involve “force through a distance”—it’s just that body-energy-consuming forces through distances do not include force through a distance on the object you’re holding. [1]
In the scenario I was trying to describe, the physicists have made the mistake incorrectly identifying the correct way to map their models onto a system in a way that accounts for all relevant factors. The more “epicycles” you have to add on to get the model to work (no pun intended), the more questionable its claim to relevance—hence the parallel to (how I understood) AlexMennen’s point.
(And for the record, I don’t consider the refutation I gave of the hypothetical physicists to be “adding epicycles” because it simply uses independantly-established knowledge from another field, rather than an ad-hoc fix only applicable to this case, thus showing consilience with biology.)
[1] Added footnote to say: Rather, the kind of “work” here shows up in the expansion and contraction of muscles.
Edit2: Hey, what’s with the comment deletion? I had a neat reply to you all written up and then you disappeared the thing I was responding to! :-(
Sorry. I deleted my comment because it sounded too obvious. (For onlookers, I said the energy gets spent due to shaking of the arm.)
Of course it doesn’t provide net energy to the object, but it still takes energy away from you. You spend it on the upward movements, but don’t reclaim it on the downward movements because that would involve resynthesizing ATP or whatever. So it becomes heat. Likewise, braking your car doesn’t cause refuelling (except when it does).
In the context of the hypothetical physicists, it does not help them resolve their confusion to point to the hand shaking. Their mistake is in only counting the work done by the hand to the object. Once they’ve made that mistake, telling them that the hand shakes would not change their minds, since it doesn’t show net work being done by the body in that respect, which is why I made the comment you quoted.
The mistake could only be corrected by pointing out the incorrect model of how humans generate lifting force.
So while your point is correct, and perhaps obvious, one should also remember that it doesn’t address the specific mistake I criticized.
Edit2: Hey, what’s with the comment deletion? I had a neat reply to you all written up and then you disappeared the thing I was responding to! :-(