1867: "Physics Confession"

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Re: 1867: "Physics Confession"

Postby somitomi » Tue Jul 25, 2017 3:01 pm UTC

pkcommando wrote:
da Doctah wrote:
ManaUser wrote:
Pfhorrest wrote:Given the terrible, awful noise that MRIs make, I find it hard to imagine a cat possibly being happy while in one. You may as well ask a cat to be happy inside a vacuum cleaner.

Maybe use a deaf cat?


It's not the noise that bothers them, it's having to be put inside something. Anyone who's ever tried to put a cat in a bucket knows that they're actually twelve-legged creatures.

(This in spite of their well-documented propensity for getting inside things on their own. Cf. internet celebrity Maru.)

Also the issue of guaranteeing a cat will remain motionless for a specific amount of time, regardless of any other circumstances. Especially when you absolutely need them to remain still, as anyone who has ever tried to photograph a cat knows all too well.

You just need to wait for them to fall asleep, which in my experience happens anytime they voluntarily remain stationary for more than five minutes.
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Re: 1867: "Physics Confession"

Postby Heimhenge » Tue Jul 25, 2017 3:06 pm UTC

GlassHouses wrote:
orthogon wrote:Why is the rubbing necessary? What does that do?


Provide opportunities for electrons to jump?

Both of the objects are insulators, so charge cannot simply flow from hair to balloon etc. through a small contact area. In order to transfer a lot of charge, a lot of molecules of object A need to be brought into close proximity with molecules from object B, and rubbing is an efficient way to achieve that.

(Just guessing -- not a physicist)


Good "guess" GlassHouses. That exactly it. At the nano scale the surface of what may appear to be a "smooth" material has "hills and valleys" that stick, slip, stick during rubbing. This puts more of the substance in contact with the other increasing charge exchange. The friction can also cause microscopically local heating that releases even more charge via the process of pyroelectric emission.

But yes, even simple contact w/o rubbing will result in some exchange of charge. Many adhesives work via a similar principle. Try sticking and then removing a piece of scotch tape from anything it'll stick too. Then hold that tape near a small piece of paper (the tiny disc from a paper punch works well). You'll see that the tape attracts that piece of paper. At least until the charges on the tape are neutralized by ions in the air.

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Re: 1867: "Physics Confession"

Postby gmalivuk » Tue Jul 25, 2017 3:57 pm UTC

ucim wrote:
Pfhorrest wrote:The purpose of something is what it's good for.
I don't see it that way. To me, the purpose of something is what it's made for (or pressed upon to do). Intent is essential for something to have "purpose", though that intent need not be conscious.
So you're saying sweat doesn't in fact have the purpose to cool us down? Tears don't have the purpose to rinse our eyes? Stomach acid's purpose isn't to dissolve the food we eat?
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Re: 1867: "Physics Confession"

Postby Mutex » Tue Jul 25, 2017 4:08 pm UTC

somitomi wrote:
pkcommando wrote:
da Doctah wrote:
ManaUser wrote:
Pfhorrest wrote:Given the terrible, awful noise that MRIs make, I find it hard to imagine a cat possibly being happy while in one. You may as well ask a cat to be happy inside a vacuum cleaner.

Maybe use a deaf cat?


It's not the noise that bothers them, it's having to be put inside something. Anyone who's ever tried to put a cat in a bucket knows that they're actually twelve-legged creatures.

(This in spite of their well-documented propensity for getting inside things on their own. Cf. internet celebrity Maru.)

Also the issue of guaranteeing a cat will remain motionless for a specific amount of time, regardless of any other circumstances. Especially when you absolutely need them to remain still, as anyone who has ever tried to photograph a cat knows all too well.

You just need to wait for them to fall asleep, which in my experience happens anytime they voluntarily remain stationary for more than five minutes.

But it needs to be purring. While also held still inside an MRI.

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Re: 1867: "Physics Confession"

Postby Soupspoon » Tue Jul 25, 2017 4:23 pm UTC

gmalivuk wrote:So you're saying sweat doesn't in fact have the purpose to cool us down? Tears don't have the purpose to rinse our eyes? Stomach acid's purpose isn't to dissolve the food we eat?

I'd go along with that. There is an emergent property that excessive heat in the environment triggers mechanisms which promote sweating which happens to be a good way of cooling us down (it's not a mechanism used in dogs, they have a different response), which is thus selected for. But the sweat glands don't devote themselves to heat-mitigation, they dedicate themselves to perspiring on cue, the cue not even exclusively being tied to the need (or wish!) to disipate heat, though they are admitedly atuned to that outcome.

That it's a useful 'co-evolved response' to the ability to detect heat-imbalance means that it is highly-linked, but (as we know during cold-sweats - or feverish ones, depending on how you think of those) it's not a purposeful shadowing of the detected need to cool any more (and somewhat less) than a fridge's compressor has purpose in activating when powered up by wires that are externally fed that power by whatever system of thermostat and/or timer decides upon when that power is thus fed.
,
The same separation covers teary eyes and even stomach secretions. They're very good at working towards the apparent purpose (thanks, Evolution!) but I'd not go so far as to say that it demonstrates purposefulness. Somewhat ontological, I'll grant you, but we're back to the whole "why?" question dichotomy of "how come?"/"what for?", in many ways. And that level of philosophy is technically beyond my pay-grade.

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Re: 1867: "Physics Confession"

Postby gmalivuk » Tue Jul 25, 2017 4:47 pm UTC

Defining "purpose" so narrowly that no part of any organism has any purpose seems to remove most of the usefulness of having the word in the first place.
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Re: 1867: "Physics Confession"

Postby orthogon » Tue Jul 25, 2017 4:54 pm UTC

Heimhenge wrote:
GlassHouses wrote:
orthogon wrote:Why is the rubbing necessary? What does that do?


Provide opportunities for electrons to jump?

Both of the objects are insulators, so charge cannot simply flow from hair to balloon etc. through a small contact area. In order to transfer a lot of charge, a lot of molecules of object A need to be brought into close proximity with molecules from object B, and rubbing is an efficient way to achieve that.

(Just guessing -- not a physicist)


Good "guess" GlassHouses. That exactly it. At the nano scale the surface of what may appear to be a "smooth" material has "hills and valleys" that stick, slip, stick during rubbing. This puts more of the substance in contact with the other increasing charge exchange. The friction can also cause microscopically local heating that releases even more charge via the process of pyroelectric emission.

But yes, even simple contact w/o rubbing will result in some exchange of charge. Many adhesives work via a similar principle. Try sticking and then removing a piece of scotch tape from anything it'll stick too. Then hold that tape near a small piece of paper (the tiny disc from a paper punch works well). You'll see that the tape attracts that piece of paper. At least until the charges on the tape are neutralized by ions in the air.

To check I'm understanding: whilst the surfaces (made of different materials) are in close contact, it's energetically favourable for some of the electrons to move from one molecules of one material to those of the other. Rubbing just creates more opportunities for this "downhill" movement of charge to occur; it's not that the work done in the rubbing adds energy that allows electrons to move to higher energy configurations.

When the materials are subsequently moved apart, their charged state makes them attractive; work has to be done to separate them, and the resulting configuration has more energy than if the materials hadn't been charged. This energy can be released by discharging the system, which might happen spontaneously via a spark.
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Re: 1867: "Physics Confession"

Postby Heimhenge » Tue Jul 25, 2017 5:25 pm UTC

gmalivuk wrote:Defining "purpose" so narrowly that no part of any organism has any purpose seems to remove most of the usefulness of having the word in the first place.


Indeed. Been following this sub-thread and had to jump in to say you seem to be asking: What is the purpose of the word "purpose"? I've been switching sides back and forth as I read your discussion. But I think this is ultimately coming down to semantics, and whether "purpose" can only be of sentient origin, or whether evolution itself has a purpose.

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Re: 1867: "Physics Confession"

Postby mschmidt62 » Tue Jul 25, 2017 5:32 pm UTC

Another mystery which, in my estimation, physicists, chemists and engineers have failed to adequately explain is why the polyethylene bags at the supermarket are more easily opened when one's fingers are wet. I tried to do some research on this and several explanations have been put forward, but I don't see any definitive evidence that any one of them is the answer. A lot of websites will tell you it's because "adhesion," but that's like the triboelectric effect; it has little predictive power. You wouldn't expect water--or a damp surface--to be more attracted to a hydrophobic plastic bag. One paper I saw claimed that they had a "model" for water making the rough surface of the epidermis more flexible and thus increasing the contact area of the fingers against the bag, in the same way that a wet sponge will be harder to push across a kitchen counter than a dry one. But they gave no details of their model.

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Re: 1867: "Physics Confession"

Postby trpmb6 » Tue Jul 25, 2017 5:57 pm UTC

Heimhenge wrote:
gmalivuk wrote:Defining "purpose" so narrowly that no part of any organism has any purpose seems to remove most of the usefulness of having the word in the first place.


Indeed. Been following this sub-thread and had to jump in to say you seem to be asking: What is the purpose of the word "purpose"? I've been switching sides back and forth as I read your discussion. But I think this is ultimately coming down to semantics, and whether "purpose" can only be of sentient origin, or whether evolution itself has a purpose.


I don't think evolution itself can have a purpose. It's a series of random mutations that happened to benefit the organism in the environment it found itself at that time. Eventually certain adaptations may not be advantageous at all. To say evolution has a purpose is to say there is some higher-being pulling the strings to produce a desired result.

Edit: Along those lines, it seems to me that the word "purpose" inherently implies there is a concerted effort to achieve whatever that purpose is. Ie. for something to have purpose, it must first have been given a defining role by something sentient.

Lightning, for instance, has no purpose. It is simply the effect of some cause we don't fully understand.
Trees have no purpose. They are simply there because that's what the environment and evolution allowed. The fact that they produce oxygen as a byproduct of their existence does not imply that their purpose is to produce oxygen.

Whereas, the desk I am typing this on has the purpose of holding my computers, monitors and other equipment.

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Re: 1867: "Physics Confession"

Postby Peaceful Whale » Tue Jul 25, 2017 6:17 pm UTC

somitomi wrote:
pkcommando wrote:
da Doctah wrote:
ManaUser wrote:
Pfhorrest wrote:Given the terrible, awful noise that MRIs make, I find it hard to imagine a cat possibly being happy while in one. You may as well ask a cat to be happy inside a vacuum cleaner.

Maybe use a deaf cat?


It's not the noise that bothers them, it's having to be put inside something. Anyone who's ever tried to put a cat in a bucket knows that they're actually twelve-legged creatures.

(This in spite of their well-documented propensity for getting inside things on their own. Cf. internet celebrity Maru.)

Also the issue of guaranteeing a cat will remain motionless for a specific amount of time, regardless of any other circumstances. Especially when you absolutely need them to remain still, as anyone who has ever tried to photograph a cat knows all too well.

You just need to wait for them to fall asleep, which in my experience happens anytime they voluntarily remain stationary for more than five minutes.


A neat way to do that is to put a binder clip on the scruff of their necks. (The loose skin thatittens are picked up by) I've seen some vets do this for cat X-Rays. It doesn't hurt the cat (I think?) and it does work
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Re: 1867: "Physics Confession"

Postby Soupspoon » Tue Jul 25, 2017 6:24 pm UTC

mschmidt62 wrote:Another mystery which, in my estimation, physicists, chemists and engineers have failed to adequately explain is why the polyethylene bags at the supermarket are more easily opened when one's fingers are wet.

Is this true? Simulating the situation with a relatively fresh bag (not needing 'opening' any more, but it was only Friday when I realised I didn't have my Bag For Life so shelled out the nominal sum for the thin plastic thing, and I can create a small area of air-excluded area of self-stiction), and dry fingers are more grippy on the plastic than wet ones,

The most grip of all is if I let my (saliva-)wetted fingers dry for a few seconds (either in air or in contact with the plastic) at which point they become tackier to the plastic than the dry fingers. But dry fingers going straight for the pinch (of two flush-and-aligned) layers of plastic and twisting them to (re)create a gap is far quicker than licking my fingers and then (waiting for them to dry a bit + pinch to bag; either order) then applying the shearing motion.

And if shearing fails, due to cold and/or numb hands, or some reason thet might be actually something approximating grewasy, you just pull the handles apart (as aligned end-to-end of the polymer sandwich, not themselves one per layer so as to actually lever them apart) to wrinkle the plastic and protrude that mysterious little tab-fold up between the two layers and facilitate the raw separation by another means.

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Re: 1867: "Physics Confession"

Postby orthogon » Tue Jul 25, 2017 6:32 pm UTC

trpmb6 wrote:
Heimhenge wrote:
gmalivuk wrote:Defining "purpose" so narrowly that no part of any organism has any purpose seems to remove most of the usefulness of having the word in the first place.


Indeed. Been following this sub-thread and had to jump in to say you seem to be asking: What is the purpose of the word "purpose"? I've been switching sides back and forth as I read your discussion. But I think this is ultimately coming down to semantics, and whether "purpose" can only be of sentient origin, or whether evolution itself has a purpose.


I don't think evolution itself can have a purpose. It's a series of random mutations that happened to benefit the organism in the environment it found itself at that time. Eventually certain adaptations may not be advantageous at all. To say evolution has a purpose is to say there is some higher-being pulling the strings to produce a desired result.

Edit: Along those lines, it seems to me that the word "purpose" inherently implies there is a concerted effort to achieve whatever that purpose is. Ie. for something to have purpose, it must first have been given a defining role by something sentient.

Lightning, for instance, has no purpose. It is simply the effect of some cause we don't fully understand.
Trees have no purpose. They are simply there because that's what the environment and evolution allowed. The fact that they produce oxygen as a byproduct of their existence does not imply that their purpose is to produce oxygen.

Whereas, the desk I am typing this on has the purpose of holding my computers, monitors and other equipment.

Taking the argument to its conclusion, the desk is also a product of evolution. Genes chosen by natural selection built the person who built the desk. You're going to have to define sentience if you want trees on one side and desks on the other.
xtifr wrote:... and orthogon merely sounds undecided.

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Re: 1867: "Physics Confession"

Postby trpmb6 » Tue Jul 25, 2017 6:40 pm UTC

orthogon wrote:Taking the argument to its conclusion, the desk is also a product of evolution. Genes chosen by natural selection built the person who built the desk. You're going to have to define sentience if you want trees on one side and desks on the other.


It truly is a multi-faceted topic. I just found myself flipping my opinion by using the argument that the leaf of a tree has purpose. I am at a loss really.

Truthfully though, this is something humanity has struggled with for millennia.

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Re: 1867: "Physics Confession"

Postby Zinho » Tue Jul 25, 2017 7:27 pm UTC

trpmb6 wrote:. . . it seems to me that the word "purpose" inherently implies there is a concerted effort to achieve whatever that purpose is. Ie. for something to have purpose, it must first have been given a defining role by something sentient.

I think there's room in the definition of "purpose" to allow for absence of a sentient actor. There are lots of effects driven simply by physics where a state of balance is the eventual outcome, and it's common in such situations to refer to an out-of-equilibrium system as having a goal or purpose of regaining balance.

trpmb6 wrote:Lightning, for instance, has no purpose. It is simply the effect of some cause we don't fully understand.
Trees have no purpose. They are simply there because that's what the environment and evolution allowed. The fact that they produce oxygen as a byproduct of their existence does not imply that their purpose is to produce oxygen.

Lightning is the perfect example of what I mentioned above. It can be accurately stated that lightning serves the purpose of dissipating unbalanced electrical charges. I doubt there's anyone with a conscious goal of evening out the charges in clouds for the vast majority of lightning (barring the occasional Dr. Frankenstein).

Your tree example is more interesting; the purpose of photosynthesis (i.e. the reason why it's selected for in plants) is to transform energy in sunlight into a more useful chemical form, which is useful from an evolutionary standpoint as a survival strategy. I believe you could even say that a tree's purpose in sprouting leaves and photosynthesizing sunlight is to stay alive and grow, no sentience needed on the part of the tree. The fact that both oxygen and water vapor are released in the process is generally irrelevant to the survival of the tree.

This leads, however, to a situation where I think your stricter definition would apply; in a biodome such as Biosphere2 trees do have the purpose of creating oxygen from CO2 in the air. Knowing that something has a function and employing it for that function certainly gives the thing that function as a purpose, regardless of whether the function is there by design or not.

My point in making the above rant is that unless you don't understand my meaning in any of the sentences above, my use of the word "purpose" fits withing the scope of that word in the English language. Arguing that someone using it that way is wrong because their usage doesn't meet a stricter/narrower definition is misguided.

*EDIT*
trpmb6 wrote:It truly is a multi-faceted topic. I just found myself flipping my opinion by using the argument that the leaf of a tree has purpose. I am at a loss really.

And I'm ninja'ed. :P Feel free to ignore my rant entirely.
Last edited by Zinho on Tue Jul 25, 2017 7:31 pm UTC, edited 1 time in total.

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Re: 1867: "Physics Confession"

Postby Kit. » Tue Jul 25, 2017 7:30 pm UTC

gmalivuk wrote:Defining "purpose" so narrowly that no part of any organism has any purpose seems to remove most of the usefulness of having the word in the first place.

You can still use the word as a metaphor.

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Re: 1867: "Physics Confession"

Postby gmalivuk » Tue Jul 25, 2017 7:34 pm UTC

I think the question, "What's the eardrum for?" has more than a merely metaphorical answer.
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Re: 1867: "Physics Confession"

Postby ucim » Tue Jul 25, 2017 7:34 pm UTC

Purpose is a transitive property, and depends as much on the benefactor (or user). Purpose isn't a property of an object per se. A rock has no purpose, but if I put it on the end of a string and use it to find "down", I've given it a purpose (of a plumb bob). It (now) has that purpose to me, even though it's just a rock (to you). The rock wasn't created with this purpose in mind, it was me that gave it a purpose.

This illustrates two different kind of purpose - one that's inherent in the design and production of the thing (hammer) and another that comes from the use to which it is put (hammer as plumb bob).

Sweat glands are produced by the growing body in order to release sweat, in order to cool the body down. Evolution has found this to be effective; that is sufficient for intent. Sentience is not required. So, I'll go along with sweat's purpose being (among other things) to cool the body down. This is a purpose that was given (by the evolutionary process) to the sweat glands before they were created in any individual body. Ditto tears. Part of biology is trying to figure out the purposes that different parts serve, both in the "how" sense (by what mechanism does it accomplish the task) and the "why" sense (how did this mechanism get selected as the one to use).

It would be much more of a stretch to say that the "purpose" of a pile of rock that happened to fall where the river is narrow, is to dam the river, even if it does so effectively. It's a random event that does not lead to any "learning" in the system. Success here does not (coherently) lead to success there by the same mechanism, allowing the system to "learn" that this is a good way to dam rivers. Arguably though that is what happens with biological evolution - the system "learns" by trial and error how to make more complex beings that are better adapted. That's why I'm comfortable with purpose being applied there and not here.

trpmb6 wrote:I don't think evolution itself can have a purpose. It's a series of random mutations that happened to benefit the organism in the environment it found itself at that time.
Evolution doesn't have a purpose, but it's not just random mutations that happen to benefit... it's remembered random mutations that... That's the key part. That's what allows evolution to create purpose without having one itself.

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Re: 1867: "Physics Confession"

Postby Kit. » Tue Jul 25, 2017 7:45 pm UTC

gmalivuk wrote:I think the question, "What's the eardrum for?" has more than a merely metaphorical answer.

I don't think so.

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

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Re: 1867: "Physics Confession"

Postby gmalivuk » Tue Jul 25, 2017 8:04 pm UTC

If you want to call that a metaphor, there's still the question of when it's appropriate to use.

It looks like ucim believes it wouldn't be correct to talk about the purpose of the eardrum, literal or metaphorical.
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Re: 1867: "Physics Confession"

Postby trpmb6 » Tue Jul 25, 2017 8:11 pm UTC

Zinho wrote:
*EDIT*
trpmb6 wrote:It truly is a multi-faceted topic. I just found myself flipping my opinion by using the argument that the leaf of a tree has purpose. I am at a loss really.

And I'm ninja'ed. :P Feel free to ignore my rant entirely.



This is why I'm honestly struggling with this topic! If you start to really dig in and ask the why question, it begins to open your eyes and view from a different perspective. I guess my toddler has it right when he asks why over and over. (And full circle, boom.)

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Re: 1867: "Physics Confession"

Postby Pfhorrest » Tue Jul 25, 2017 8:25 pm UTC

trpmb6 wrote:
Heimhenge wrote:whether "purpose" can only be of sentient origin, or whether evolution itself has a purpose.


I don't think evolution itself can have a purpose. It's a series of random mutations that happened to benefit the organism in the environment it found itself at that time. Eventually certain adaptations may not be advantageous at all. To say evolution has a purpose is to say there is some higher-being pulling the strings to produce a desired result.

You're begging the question here, assuming that "purpose" can only be of sentient origin, and that evolution, in not being guided by any higher being, is thus not purposeful; while Heimhenge was asking whether "purpose" can apply to things that are not so directed by a thinking being, such as evolution.
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Re: 1867: "Physics Confession"

Postby trpmb6 » Tue Jul 25, 2017 8:34 pm UTC

Pfhorrest wrote:
trpmb6 wrote:
Heimhenge wrote:whether "purpose" can only be of sentient origin, or whether evolution itself has a purpose.


I don't think evolution itself can have a purpose. It's a series of random mutations that happened to benefit the organism in the environment it found itself at that time. Eventually certain adaptations may not be advantageous at all. To say evolution has a purpose is to say there is some higher-being pulling the strings to produce a desired result.

You're begging the question here, assuming that "purpose" can only be of sentient origin, and that evolution, in not being guided by any higher being, is thus not purposeful; while Heimhenge was asking whether "purpose" can apply to things that are not so directed by a thinking being, such as evolution.


Which I think we eventually discussed in latter posts. I now believe that "purpose" can apply to things that are not being directed by any 'thinking' being. The best example as discussed thus far, imo, was that lightning's purpose is to dissipate charged particles. (That is until we discover that Thor is really up there playing with his hammer because he's bored one night.)

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Re: 1867: "Physics Confession"

Postby ucim » Tue Jul 25, 2017 9:31 pm UTC

gmalivuk wrote:It looks like ucim believes it wouldn't be correct to talk about the purpose of the eardrum, literal or metaphorical.
You misread me. See my comments about sweat glands here, and compare with my comments about a pile of rock that happens to dam a river.

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Re: 1867: "Physics Confession"

Postby Kit. » Tue Jul 25, 2017 9:39 pm UTC

gmalivuk wrote:If you want to call that a metaphor, there's still the question of when it's appropriate to use.

It looks like ucim believes it wouldn't be correct to talk about the purpose of the eardrum, literal or metaphorical.

I think he can accept it if we also use the corresponding metaphor for "intent" (which "need not be conscious").

My point is that there are at least two different (although linked) meanings of "purpose", and each of them is good for its own domain. Whether it is appropriate to use a particular meaning of the word depends on the domain for which we are trying to share our knowledge - as long as all the parties in the communication can correctly determine the domain.

If we haven't agreed on the domain beforehand, it might be wise to avoid ambiguities and use words with more literal meaning. For the eardrum (or the tree leaf), the word "function" might suit well.

Ah, and about purr... it's the cat's analog of whisper. Not any purr means that the cat is happy.

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Re: 1867: "Physics Confession"

Postby gmalivuk » Tue Jul 25, 2017 9:49 pm UTC

ucim wrote:
gmalivuk wrote:It looks like ucim believes it wouldn't be correct to talk about the purpose of the eardrum, literal or metaphorical.
You misread me. See my comments about sweat glands here, and compare with my comments about a pile of rock that happens to dam a river.
Ah, I missed that post by clicking on the notification for the post below it where I was quoted.
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Re: 1867: "Physics Confession"

Postby ucim » Tue Jul 25, 2017 10:21 pm UTC

Kit. wrote:I think he can accept it if we also use the corresponding metaphor for "intent" (which "need not be conscious").
Yes, which leads to something else; that being that using the word "purpose" implying the more general form of "intent" is sometimes used to steer the listener towards the more specific (sentience required) form of intent as a hidden assumption, in the "design requires a designer" sense. It's bad logic; it's switching the meaning of a word (in this case the unused but implied word "intent") in the middle of a sentence. It's sneakier than usual in that the switched meaning is for a word that wasn't used, so it's harder to catch. But it's there.

Talking about the purpose of an eardrum does not imply a Creator and Master Designer of the Universe. But because of this, it's harder to talk casually about the purpose of an eardrum without the drumbeat of creationists.

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Re: 1867: "Physics Confession"

Postby morriswalters » Tue Jul 25, 2017 10:50 pm UTC

Maybe y'all should use better words. Ears drums and avalanches that block rivers are exactly the same. Matter arranged in different ways, acting in different ways on their surroundings. Any meaning happens somewhere else.

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Re: 1867: "Physics Confession"

Postby ucim » Tue Jul 25, 2017 11:37 pm UTC

morriswalters wrote: Ears drums and avalanches that block rivers are exactly the same.
I hope you're not a doctor. Or a civil engineer. :)

morriswalters wrote:...Matter arranged in different ways, acting in different ways on their surroundings.
Well, those differences are important. They give rise to concepts and such. The relationships between things are more important than the things themselves.

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Re: 1867: "Physics Confession"

Postby Plutarch » Wed Jul 26, 2017 12:03 am UTC

I'd be interested if anyone would elaborate on the ice-skate problem. Why did physicists once think they knew how they worked? And why don't they think that any more?

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Re: 1867: "Physics Confession"

Postby morriswalters » Wed Jul 26, 2017 12:37 am UTC

ucim wrote:I hope you're not a doctor. Or a civil engineer. :)
The world was spared those hazards.
ucim wrote:Well, those differences are important.
To me as well, but not to the rocks.

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Re: 1867: "Physics Confession"

Postby qvxb » Wed Jul 26, 2017 1:13 am UTC

Provide the statement musically, starting with "In my physics confession...".

https://www.youtube.com/watch?v=5nZnqtDdsws

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Re: 1867: "Physics Confession"

Postby Liri » Wed Jul 26, 2017 1:33 am UTC

Plutarch wrote:I'd be interested if anyone would elaborate on the ice-skate problem. Why did physicists once think they knew how they worked? And why don't they think that any more?

It was mentioned at the top of the thread, but briefly, that the pressure of the skate caused a thin layer of water to melt.
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Re: 1867: "Physics Confession"

Postby ucim » Wed Jul 26, 2017 1:33 am UTC

morriswalters wrote:To me as well, but not to the rocks.
The rocks don't have to know they have a purpose. (However, in the example I gave, the rocks actually did not have a purpose, though the eardrum did).

The argument actually extends into our future under AI robots. What will our "purpose" be?

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Re: 1867: "Physics Confession"

Postby Solra Bizna » Wed Jul 26, 2017 1:38 am UTC

Well, I, for one, now know more about the triboelectric effect. (In hindsight, I could have gotten most of this knowledge if I'd read the middle of the Wikipedia article instead of the beginning and end. :oops:)

Plutarch wrote:I'd be interested if anyone would elaborate on the ice-skate problem. Why did physicists once think they knew how they worked? And why don't they think that any more?

The explanation I was given as a child was that concentrating a skater's weight onto the small surface area afforded by the skates causes compressive heating of the ice, melting it into water under the skate and sharply reducing the friction. Here are just the problems I can remember:

  • Ice skates work just as well on ice at -1⁰C as they do on ice at -15⁰C or at -80⁰C.
  • Sleds and skis work quite well, too, in spite of having vastly greater contact area.
gmalivuk wrote:Defining "purpose" so narrowly that no part of any organism has any purpose seems to remove most of the usefulness of having the word in the first place.

I'm with gmalivuk on this one. I'm an engineer*, not a philosopher, so I'm more interested in a useful definition than an extremely specific, "correct" one.
* Today, anyway.

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Re: 1867: "Physics Confession"

Postby Pfhorrest » Wed Jul 26, 2017 2:56 am UTC

As a philosopher of the pragmatic persuasion, I too care about useful definitions, and think doing so is the correct way to do philosophy.
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Re: 1867: "Physics Confession"

Postby gmalivuk » Wed Jul 26, 2017 3:09 am UTC

Yeah, Ruth Millikan dabbles a bit in philosophy, as well, and reading some of her stuff in a philosophy class is where I first read the idea of a naturalistic or evolutionary account for things like function and purpose.
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Re: 1867: "Physics Confession"

Postby Pfhorrest » Wed Jul 26, 2017 5:41 am UTC

To be clear, I'm not backing a specifically evolutionary account of purpose. I think statements of purpose are tantamount to a kind of moral or ethical statement: to say that X is the purpose of Y is to say that X is why Y ought to be, X is what Y is good for. That could be in a purely subjective sense of "good" or "ought", or an objective one if there is such a thing. Sweat is good for cooling our bodies, so that's a purpose for sweat; the cooling of our bodies is why we ought to be able to sweat. Of course that last phrasing is tantamount to the inference "we ought to cool our bodies, therefore we ought to sweat", and so is only true if we ought to cool our bodies. You could then ask why we ought to cool our bodies, which is asking for a purpose again, the purpose for cooling our bodies; in that case, the purpose is to aid in our survival. You could then ask why we ought to survive, and so on until you somehow resolve the regress that you always get when you ask "why" over and over (whether that "why" is asking a cause or a purpose), and if you resolve the regress into some kind of ultimate purpose, that is tantamount to a statement of what the good is, what it is that we ought to be striving for. Or conversely if there are no "oughts" at all, then nothing has any purpose. If there are only subjective, agent-relative "oughts", then there are only subjective, agent-relative purposes. Not saying here which of those is the case, just that the nature of purpose tracks parallel to the nature of ethics, whatever it should be, because statements of purpose are ultimately statements about ethics; something only has a purpose if it ought to be (in some sense or another) for some reason, that reason being its purpose.
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Re: 1867: "Physics Confession"

Postby Kit. » Wed Jul 26, 2017 9:39 am UTC

Pfhorrest wrote:To be clear, I'm not backing a specifically evolutionary account of purpose. I think statements of purpose are tantamount to a kind of moral or ethical statement: to say that X is the purpose of Y is to say that X is why Y ought to be, X is what Y is good for.

I think we are leaving the domain of propositional logic here.

It is possible that the senses of "purpose" and of "duty" are linked in humans because they both have evolved from the same original sense of "goodness" (or whatever) and haven't diverged enough to fully separate yet. It might be possible to have a species that would roughly understand our idea of purpose and our idea of duty, but wouldn't see any "innate" connection between these two ideas.

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Re: 1867: "Physics Confession"

Postby niauropsaka » Wed Jul 26, 2017 10:19 am UTC

orthogon wrote:
Soupspoon wrote:Upon the lap of a person who is really uncomfortable around cats is probably the most likely place for a cat to be unilaterally happy to sit. This does not preclude the 'helpful' use of claws to both withstand and cause the movement of said lap.

I read once, many years ago, that humans narrow their eyes to indicate dislike, whilst for cats this is a friendly signal, and that's what causes the phenomenon you mention. I find the theory so appealing that I don't want to want to go and check it, as it's almost certainly disappointingly untrue.

I recognise the expression of which you speak. But I notice that in my art I use narrowed eyes (on humans) to indicate attraction and flirtatiousness, but not generally to indicate dislike, where I rely more on eyebrow, nose, and mouth movement. I'm not sure what this means, but I also have a cat.


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