1867: "Physics Confession"

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Solra Bizna
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1867: "Physics Confession"

Postby Solra Bizna » Mon Jul 24, 2017 5:24 am UTC

Image
"You know lightning, right? When electric charge builds up in a cloud and then discharges in a giant spark? Ask me why that happens." "Why does tha--" "No clue. We think it's related to the hair thing."

When I was younger, I was given the pressure-melting explanation for ice skates and I took it at face value. More recently, I learned that explanation doesn't work. But I thought we at least had a good answer for the hair-on-balloon / lightning thing. A quick Googling doesn't uncover much. (I couldn't find the Dinosaur Comic about science not knowing the answers to things, either. Edit: Found it. It was one comic to the left of the one I gave up at.)

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Re: 1867: "Physics Confession"

Postby Heimhenge » Mon Jul 24, 2017 6:11 am UTC

We do have a good answer for the hair/balloon/lightning thing ... it's called the tribolectric effect. What's wrong with that? Too empirical?

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Re: 1867: "Physics Confession"

Postby rhomboidal » Mon Jul 24, 2017 6:19 am UTC

If we don't fully understand how lightning works, I'm cool with Wrath of Thor to fill the gaps.

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Re: 1867: "Physics Confession"

Postby orthogon » Mon Jul 24, 2017 6:34 am UTC

rhomboidal wrote:If we don't fully understand how lightning works, I'm cool with Wrath of Thor to fill the gaps.

The god of the spark-gaps?
xtifr wrote:... and orthogon merely sounds undecided.

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Re: 1867: "Physics Confession"

Postby taemyr » Mon Jul 24, 2017 8:18 am UTC

Heimhenge wrote:We do have a good answer for the hair/balloon/lightning thing ... it's called the tribolectric effect. What's wrong with that? Too empirical?


Beware ontic dumping;

If you answer "Why does static charge build up when rubbing a ballon on hair?" with "because of the tribolectric effect" - you are begging the question. The definition of the tribolectric effect is the electric charge buildup when certain materials come into contact.

So you have to go at least one step further before you in any way can say to have answered the question; ie. "Because the elecrochemical potential in the materials differ and this difference will tend to be canceled by charges moving between materials that are in contact."

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Re: 1867: "Physics Confession"

Postby somitomi » Mon Jul 24, 2017 8:26 am UTC

rhomboidal wrote:If we don't fully understand how lightning works, I'm cool with Wrath of Thor to fill the gaps.

I like to think it has to do with Tesla1 somehow.

1: I mean the Serbian-American inventor, electrical engineer, mechanical engineer, physicist, and futurist
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Re: 1867: "Physics Confession"

Postby cellocgw » Mon Jul 24, 2017 10:21 am UTC

Physics can be made a lot less scary if you replace all instances of "why" with "how."
I should know, seeing as I actually have an ABD in Physics. :D

The problem with "why" is that sooner or later that devolves into philosophy, or worse, religion. "How" at least lets us stop with a useful model for predicting outcomes.
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Re: 1867: "Physics Confession"

Postby Rossegacebes » Mon Jul 24, 2017 11:10 am UTC

Physics can be made a lot less scary if you replace all instances of "why" with "how."


In general the "why" questions are much clearer if we replace "why" by "how come" or "what for", depending on the information required. Dictionaries explain that this information is either "reason" (that is, how) or "purpose" (what for). "Why is there a rainbow?" may be rephrased as "What are the phenomena/mechanisms that explain how a rainbow is produced? (and then you go with optics, refraction and caustics), or "What is the purpose of the rainbow?", to which you may answer depending on your favourite set of beliefs.

In physics, and generally in science, "why" should be always interpreted in the first way. The second choice, purpose, posits that there is a being with free will and power of decision.
Last edited by Rossegacebes on Mon Jul 24, 2017 11:50 am UTC, edited 1 time in total.

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Re: 1867: "Physics Confession"

Postby da Doctah » Mon Jul 24, 2017 11:14 am UTC

cellocgw wrote:Physics can be made a lot less scary if you replace all instances of "why" with "how."


The word why in English (unlike many other languages) has two distinct meanings, which can be abbreviated "what for" (what purpose is served by the thing being explained) and "how come" (what caused the state of affairs being explained). Because the same word is used for both, many people have trouble telling them apart, but here's a simple illustration:

If you ask "why is the remote control in the freezer?", a "how come" answer might be "because I had it in my hand when I went to fix myself a snack during a commercial, and I must have set it down in there". A "what for" answer might be "because keeping it cold makes the batteries last longer".

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Re: 1867: "Physics Confession"

Postby morriswalters » Mon Jul 24, 2017 12:01 pm UTC

Why is the word by which your toddler will teach you the concept of infinite regression. The appropriate exit condition for this state is, because mommy/daddy said so.

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Re: 1867: "Physics Confession"

Postby cellocgw » Mon Jul 24, 2017 12:14 pm UTC

morriswalters wrote:Why is the word by which your toddler will teach you the concept of infinite regression. The appropriate exit condition for this state is, because mommy/daddy said so.


We preferred the phlogistonical " because the Why-monster will get you"
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Re: 1867: "Physics Confession"

Postby RAGBRAIvet » Mon Jul 24, 2017 12:28 pm UTC

Arthur C. Clarke's Third Law says "Any sufficiently advanced technology is indistinguishable from magic".  That will work for any other unexplained (or unexplainable) natural phenomena as well.

    ● "If clouds are water vapor and water is heavier than air, then why do clouds stay in the sky?"
    ● "What causes lightning?"
    ● "How does a salmon know exactly which stream to swim back to?"
    ● "When do the leaves know it's time to change color in the fall?"
The answer is simple ..... it's magic.

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Re: 1867: "Physics Confession"

Postby trpmb6 » Mon Jul 24, 2017 12:46 pm UTC

morriswalters wrote:Why is the word by which your toddler will teach you the concept of infinite regression. The appropriate exit condition for this state is, because mommy/daddy said so.


I find this comical because my wife and I went through this exact sequence with our toddler last week. Immediately after saying "because daddy said so" I stopped, looked at my wife and said, "Oh God. Mom was right."

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Re: 1867: "Physics Confession"

Postby cellocgw » Mon Jul 24, 2017 12:47 pm UTC

RAGBRAIvet wrote:Arthur C. Clarke's Third Law says "Any sufficiently advanced technology is indistinguishable from magic".  That will work for any other unexplained (or unexplainable) natural phenomena as well.

    ● "If clouds are water vapor and water is heavier than air, then why do clouds stay in the sky?"
    ● "What causes lightning?"
    ● "How does a salmon know exactly which stream to swim back to?"
    ● "When do the leaves know it's time to change color in the fall?"
The answer is simple ..... it's magic.


Yes it is: It's magic . I hereby swear by all things 1190 that's NOT a rickroll.
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Re: 1867: "Physics Confession"

Postby orthogon » Mon Jul 24, 2017 1:09 pm UTC

taemyr wrote:
Heimhenge wrote:We do have a good answer for the hair/balloon/lightning thing ... it's called the tribolectric effect. What's wrong with that? Too empirical?


Beware ontic dumping;

If you answer "Why does static charge build up when rubbing a ballon on hair?" with "because of the tribolectric effect" - you are begging the question. The definition of the tribolectric effect is the electric charge buildup when certain materials come into contact.

So you have to go at least one step further before you in any way can say to have answered the question; ie. "Because the elecrochemical potential in the materials differ and this difference will tend to be canceled by charges moving between materials that are in contact."


It reminds me a bit of mathematical functions like erf or si, which are defined as the result of integrating something else. This feels like cheating to me. I can't put my finger on why they are any less deserving of names than functions like exp, sin or cos, but if it's ok for mathematicians to do it, why couldn't I answer all my A-Level maths integration questions with "oi1(x), where oi1(x) is the orthogon integral, defined as the integral of <whatever the question asked me to integrate>?
xtifr wrote:... and orthogon merely sounds undecided.

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Re: 1867: "Physics Confession"

Postby DanD » Mon Jul 24, 2017 2:24 pm UTC

orthogon wrote:
taemyr wrote:
Heimhenge wrote:We do have a good answer for the hair/balloon/lightning thing ... it's called the tribolectric effect. What's wrong with that? Too empirical?


Beware ontic dumping;

If you answer "Why does static charge build up when rubbing a ballon on hair?" with "because of the tribolectric effect" - you are begging the question. The definition of the tribolectric effect is the electric charge buildup when certain materials come into contact.

So you have to go at least one step further before you in any way can say to have answered the question; ie. "Because the elecrochemical potential in the materials differ and this difference will tend to be canceled by charges moving between materials that are in contact."


It reminds me a bit of mathematical functions like erf or si, which are defined as the result of integrating something else. This feels like cheating to me. I can't put my finger on why they are any less deserving of names than functions like exp, sin or cos, but if it's ok for mathematicians to do it, why couldn't I answer all my A-Level maths integration questions with "oi1(x), where oi1(x) is the orthogon integral, defined as the integral of <whatever the question asked me to integrate>?


For the same reason that math(s) classes require you to show your work. They don't actually care what x is in 2x=4. They care that you understand why it is 2.

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Re: 1867: "Physics Confession"

Postby sociotard » Mon Jul 24, 2017 2:53 pm UTC

I was really shocked when I found out we're not sure how Cats purr. the guy explaining it said nobody had gotten around to sticking a happy cat in an MRI. Really? that just seems like an easy thing to satisfy curiosity for. (says the guy who doesn't even know what an MRI scan costs, or how to justify sticking an allergen producer in a piece of medical equipment)

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Re: 1867: "Physics Confession"

Postby Pfhorrest » Mon Jul 24, 2017 3:38 pm UTC

Rossegacebes wrote:The second choice, purpose, posits that there is a being with free will and power of decision.

It actually doesn't, that's a common misconception. The purpose of something is what it's good for. Some agent's purpose for the thing is what that agent finds it to be good for. An agent-independent purpose only requires that there be some objective sense of "good"; the rest is simply a question of what good something does, whether it was intended to do that by an agent or not. (There's a whole other argument to be had about whether an objective sense of "good" is possible, but given that it is, things can have purpose without having been made intentionally by an agent to serve that purpose).

Your point about rephrasing things into two possible questions can be boiled down to basically the is-ought divide: "why [is] this?" and "why [ought there be] this?"

Also interestingly, Ancient Greek had a similar thing, which is why in ancient philosophy they speak of four kinds of "cause", only one of which is our modern sense of that word; they're actually four different answers to Ancient Greek's four different senses of "why is this?" (The "efficient cause" and "final cause" are the two we're talking about here, the former being the usual modern English sense of the word "cause" and the later being more "purpose". The other two, "material cause" and "formal cause", are basically answers to "what is this made of?" and "what are the criteria for this to be this?").
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Re: 1867: "Physics Confession"

Postby ucim » Mon Jul 24, 2017 3:59 pm UTC

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. A hammer's purpose is to drive nails - it was designed and made for that task. If somebody picks the hammer up and bashes a skull with it, then at that moment, the purpose of the hammer (in the hand of the wielder) was to bash a skull. The wielder's intent gave the hammer another purpose, one not intended by the maker of the hammer. A hammer is also good as a plumb bob and as ballast; however that's not its purpose.

I do agree that is/ought is another way of looking at the two ways "why" is used.

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Re: 1867: "Physics Confession"

Postby Rossegacebes » Mon Jul 24, 2017 4:06 pm UTC

Pfhorrest, I think that your are re-defining purpose, blending it into usefulness.

On the other hand, I find your explanation of the four versions of cause in ancient Greek philosophy quite enlightening.

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Re: 1867: "Physics Confession"

Postby Solra Bizna » Mon Jul 24, 2017 4:07 pm UTC

Heimhenge wrote:We do have a good answer for the hair/balloon/lightning thing ... it's called the tribolectric effect. What's wrong with that? Too empirical?

The fact that we have a name for it doesn't help on its own.

"Why does an ice skate on ice have almost no friction in the direction parallel to the skate?" "Because it does."

"Why does static buildup occur when I rub my hair with a balloon?" "Because it does, and when it does we call it the triboelectric effect."

One does have to accept a "because it does" explanation if one goes deep enough in any physics question. But I'm a lot more happy, subjectively, when the eventual "because it does" explanation is at least one or two levels "deeper" than the original question, or regards a question of fundamental forces/particles.

"Why are some things one color, and other things another color?" "The most common way that things acquire their color is for those things to absorb some wavelengths of photon and scatter others. Photons that are scattered enter our eye and contribute to our perception of the thing's color." On its own, that explanation does require me to accept a "because it does" regarding the wavelength-dependent behavior of photons when interacting with common objects, but such an explanation also leaves me with more information, and is made of pieces that can be used to explain / predict other situations. Therefore, it's more satisfying to me.

Now, if we had a working model of triboelectric charging that would let us precisely predict whether a given pair of materials would exhibit the effect, and to what degree...

sociotard wrote:the guy explaining it said nobody had gotten around to sticking a happy cat in an MRI. Really? that just seems like an easy thing to satisfy curiosity for.

I imagine the difficult part would be maintaining the "happy" status of the cat during the process of forcing it into a confined space full of loud noises.

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Re: 1867: "Physics Confession"

Postby Soupspoon » Mon Jul 24, 2017 4:12 pm UTC

da Doctah wrote:If you ask "why is the remote control in the freezer?", a "how come" answer might be "because I had it in my hand when I went to fix myself a snack during a commercial, and I must have set it down in there". A "what for" answer might be "because keeping it cold makes the batteries last longer".
In either case, "Because there's a freezer surrounding the remote control" is of equal accuracy and of equal utility. But not of a utility equal to the accuracy. ;)

sociotard wrote:I was really shocked when I found out we're not sure how Cats purr. the guy explaining it said nobody had gotten around to sticking a happy cat in an MRI. Really? that just seems like an easy thing to satisfy curiosity for. (says the guy who doesn't even know what an MRI scan costs, or how to justify sticking an allergen producer in a piece of medical equipment)

There's allergen-free cats, these days. But can one ever know if a cat in an MRI scanner is happy, unhappy, either, neither or both..?

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Re: 1867: "Physics Confession"

Postby Pfhorrest » Mon Jul 24, 2017 4:14 pm UTC

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.
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Re: 1867: "Physics Confession"

Postby orthogon » Mon Jul 24, 2017 4:19 pm UTC

Solra Bizna wrote:"Why are some things one color, and other things another color?"

Let's not go there...
xtifr wrote:... and orthogon merely sounds undecided.

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Re: 1867: "Physics Confession"

Postby HES » Mon Jul 24, 2017 4:20 pm UTC

Don't MRI's also require quite a high level of stillness? I recall dogs having to go through extensive stay-still-despite-scary-noise training for some other study. Cats aren't so malleable.
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Re: 1867: "Physics Confession"

Postby orthogon » Mon Jul 24, 2017 4:45 pm UTC

Pfhorrest wrote:You may as well ask a cat to be happy inside a vacuum cleaner.

Asking a cat to be happy seems like a futile exercise anyway. They're far too aloof to deign to be actually happy about something. If pushed, they might admit to having, on occasion, been not entirely displeased with the state of things.
Soupspoon wrote:There's allergen-free cats, these days.

I'd heard about that, but I have trouble believing it. I'm so horribly allergic to them that my eyes puff up and I start to wheeze just looking at a lolcat on the intertubes. Do they really work, or are they just effective against nocebo allergies?
xtifr wrote:... and orthogon merely sounds undecided.

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Re: 1867: "Physics Confession"

Postby Soupspoon » Mon Jul 24, 2017 4:54 pm UTC

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.

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Re: 1867: "Physics Confession"

Postby orthogon » Mon Jul 24, 2017 5:00 pm UTC

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.
xtifr wrote:... and orthogon merely sounds undecided.

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Re: 1867: "Physics Confession"

Postby morriswalters » Mon Jul 24, 2017 5:02 pm UTC

orthogon wrote:I'd heard about that, but I have trouble believing it. I'm so horribly allergic to them that my eyes puff up and I start to wheeze just looking at a lolcat on the intertubes. Do they really work, or are they just effective against nocebo allergies?
It depends on why you are allergic.
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.
You are just heated cat furniture which can be intimidated.

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Re: 1867: "Physics Confession"

Postby Zinho » Mon Jul 24, 2017 5:05 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. A hammer's purpose is to drive nails - it was designed and made for that task. If somebody picks the hammer up and bashes a skull with it, then at that moment, the purpose of the hammer (in the hand of the wielder) was to bash a skull. The wielder's intent gave the hammer another purpose, one not intended by the maker of the hammer. A hammer is also good as a plumb bob and as ballast; however that's not its purpose.

I do agree that is/ought is another way of looking at the two ways "why" is used.

Jose

Emphasis added. This discussion is verging on a Platonic analysis of a hammer, i.e. "what is the essence of a hammer?" To me, this becomes a question of identity rather than purpose - in the case of a plumb bob, a hammer can be hung from a string and be used as a plumb bob (or, rather, used in place of a proper plumb bob); however, it doesn't become a plumb bob in the process. A hammer doesn't have a proper place to attach a string, nor does it have an indicator point that indicates the point on the ground directly below the top of the string. At best, the hammer becomes a makeshift plumb bob when used as one.

Similarly, when used to bash a skull instead of driving nails the hammer is being used as a club. In this case, it has all the necessary features to be a club; I'd agree that a hammer is a club when used as one, and that depending on the intent of the user it can be both a hammer and a club simultaneously.

Incidentally, 2nd Amendment activists get bent out of shape over this nuance; they are constantly berating lawmakers for making certain knives illegal based on their features (number of cutting edges, blade length, method of deployment, etc). The lawmakers insist that the presence of features that enhance the utility of a knife as a weapon make the knife into a weapon inherently. The 2A folks insist that any tool can become a weapon if used as such, so further legislation is redundant once there is are laws against assault and murder. I believe their argument goes beyond is/ought to say that "can be" != "is"; that is, a knife is only a murder weapon once it has been used for murder, not before.

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Re: 1867: "Physics Confession"

Postby ManaUser » Mon Jul 24, 2017 6:43 pm UTC

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?

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Re: 1867: "Physics Confession"

Postby Heimhenge » Mon Jul 24, 2017 7:01 pm UTC

Solra Bizna wrote:
Heimhenge wrote:We do have a good answer for the hair/balloon/lightning thing ... it's called the tribolectric effect. What's wrong with that? Too empirical?

The fact that we have a name for it doesn't help on its own.


Totally agree. One of my favorite Feynman quotes is (and I paraphrase) "Just because you know the name of something doesn't mean you know jack about it." I realize the tribolelectric effect is not 100% explained or even operates consistently. Still, we're a LONG way from having to say "because it does" for things like balloons sticking to the wall after being rubbed on hair.

Taking it just one level deeper I could say "because different materials, when rubbed together, have differing propensities for acquiring and holding electrical charge, and the resulting imbalance of charge causes an electrostatic force of attraction.

To take it another level deeper, I could say that the reason for different materials having differing electron affinities is the structure of the energy levels in the molecule or atom in which those electrons reside.

From there we'd be into quantum mechanics at the next level, trying to explain why the energy levels are what they are. That's getting pretty close to "because it does."

So my contention is there's nothing wrong with giving "the triboelectric effect" as an answer any more than, say, "soap bubbles are round because of surface tension." As long as I can go a few levels deeper in response to "but why?" I feel I've given a fair answer. Saying "because it does" too early in the process deprives the asker of valid scientific information.

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Re: 1867: "Physics Confession"

Postby SuicideJunkie » Mon Jul 24, 2017 8:23 pm UTC

Heimhenge wrote:So my contention is there's nothing wrong with giving "the triboelectric effect" as an answer any more than, say, "soap bubbles are round because of surface tension."
It seems to me that "the triboelectric effect" is tightly self-referential and vague, while "surface tension" is a more generally applicable, straight forward idea and thus far better.

eg:
Keeping in mind the triboelectric effect, can you predict what will happen if I rub cardboard on shag carpet?
Keeping in mind surface tension, can you predict what will happen if I touch two water droplets together?
Keeping in mind gravity, can you predict what will happen if a teapot is dropped halfway between the Earth and Moon?

PS:
Wikipedia even notes "The triboelectric effect is not very predictable, and only broad generalizations can be made."

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Re: 1867: "Physics Confession"

Postby da Doctah » Mon Jul 24, 2017 8:41 pm UTC

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.)

SuicideJunkie
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Re: 1867: "Physics Confession"

Postby SuicideJunkie » Mon Jul 24, 2017 8:56 pm UTC

In that case, we simply need to design an MRI made of cardboard!


If Star Trek has taught us anything, the solution to the problem lies in reversing the polarity, and that definitely applies to Psychology.
The main problem may be that we're trying to get the cats into the MRI, instead of trying to keep them out.

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Re: 1867: "Physics Confession"

Postby ucim » Mon Jul 24, 2017 9:33 pm UTC

SuicideJunkie wrote:If Star Trek has taught us anything, the solution to the problem lies in reversing the polarity
I see what you mean.
SuicideJunkie wrote:Keeping in mind the triboelectric effect, can you predict what will happen if I rub cardboard on shag carpet?
Keeping in mind surface tension, can you predict what will happen if I touch two water droplets together?
Keeping in mind gravity, can you predict what will happen if a teapot is dropped halfway between the Earth and Moon?
Keeping in mind the triboelectric effect, can you predict what will happen if a teapot is dropped halfway between the Earth and Moon?
Keeping in mind surface tension, can you predict what will happen if I rub cardboard on shag carpet?
Keeping in mind gravity, can you predict what will happen if I touch two water droplets together?

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Re: 1867: "Physics Confession"

Postby Wolfkeeper » Tue Jul 25, 2017 12:08 am UTC

taemyr wrote:
Heimhenge wrote:We do have a good answer for the hair/balloon/lightning thing ... it's called the tribolectric effect. What's wrong with that? Too empirical?


Beware ontic dumping;

If you answer "Why does static charge build up when rubbing a ballon on hair?" with "because of the tribolectric effect" - you are begging the question. The definition of the tribolectric effect is the electric charge buildup when certain materials come into contact.

So you have to go at least one step further before you in any way can say to have answered the question; ie. "Because the elecrochemical potential in the materials differ and this difference will tend to be canceled by charges moving between materials that are in contact."


Yes, but why does it do that? What moves the charge?

I believe that the latest explanation in the literature seems to explain it. When you rub your hair on the balloon, there's an electrochemical reaction (like a battery/cell) that moves the electrical charge. Because they're insulators that charge has nowhere to go so it builds up, basically like a capacitor on the balloon.

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Re: 1867: "Physics Confession"

Postby orthogon » Tue Jul 25, 2017 6:17 am UTC

Why is the rubbing necessary? What does that do?
xtifr wrote:... and orthogon merely sounds undecided.

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Re: 1867: "Physics Confession"

Postby GlassHouses » Tue Jul 25, 2017 11:20 am UTC

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)

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Re: 1867: "Physics Confession"

Postby pkcommando » Tue Jul 25, 2017 12:56 pm UTC

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.
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