Suppose that the perception of the heat of a solid or liquid body is closely related to the rate at which heat passes from that body into a human body.
Suppose likewise that the perception of coldness of a solid or liquid is closely related to the rate at which heat passes in the other direction.
Build a standardized approximation to a human fingertip as it behaves at a standardized initial ambient temperature (say, room temperature), incorporating a sensor to measure the rate of transfer of heat energy into or out of it.
This device will then give you an objective approximation to how hot or cold a solid or liquid body is likely to feel subjectively. Unlike, say, a thermometer reading, it will take into account such things as the greater conductivity of metal over wood (which tend to make true temperature less helpful in this regard).
You could see this as an extension of the idea of "wind-chill factor", but with more clarity about what it's really measuring.-- pertinax, Mar 21 2010 Psychophysics of Temperature Perception http://ieeexplore.i...1&authDecision=-203Not sure it's that straightforward [csea, Mar 21 2010] Thermal Flux sensor http://wuntronic.eu...8&subid=153&pid=307Something like this should work [csea, Mar 21 2010] Force http://museums.leic...do?objectKey=270129Suddenly, this makes sense. [pertinax, Mar 23 2010] Lukewarm, etymology of. http://en.wiktionary.org/wiki/lukewarm [DrBob, Mar 25 2010] Star Wars RetCon http://en.wikipedia...ist_of_retcons#FilmWas Anakin betrayed & killed by Darth Vader, or _is_ he Darth Vader? Is Leia Organa an upper-class love interest for Luke, or his sister? Only Retroactive Continuity can tell. [land, Mar 26 2010] This is a very good idea. [+]-- MaxwellBuchanan, Mar 21 2010 [+] plain old "chill-factor" is a nice nounverb for coldth offset... "sweat-factor" for positive ?-- FlyingToaster, Mar 21 2010 I like the concept, but think it would be applicable over a fairly narrow range of temperatures. Fingertip touches to certain very cold surfaces may be perceived as "hot." And I suspect there may be a fairly fuzzy relationship between temperature sensing and pain.
And Joules/sec are just Watts. What's wanted is a thermal flux measurement, i.e. W/m^2. Let me see if I can find a link. OK, here: [link2].-- csea, Mar 21 2010 Would this be psychophysics or psychrotrophics?-- MaxwellBuchanan, Mar 21 2010 Trying to measure sensations or perceptions has much in common with herding cats, but still this is an interesting idea and surely must have some applications somewhere.-- wagster, Mar 21 2010 I like the concept, though I have an overwhelming urge to raise technical quibbles.
//standardized approximation to a human fingertip// It would have to model the vasoconstrictive response to cold. I'm not sure how consistent that is across individuals. I think in people with Reynaud's syndrome the nonlinearities might give your engineers the heebie- jeebies.
...and wouldn't you need separate scales for fingers, toes, nose & ears? If you were male, and planning on running naked from sauna to icy pond, would you need a fifth scale?
On the other hand, I think the subjectivity of temperature perception might *not* be a problem because this idea is about pain-perception, not temperature-perception. For heat, the temperature threshold isn't actually all that variable (it's 45 degrees). For cold, I'm not sure.-- mouseposture, Mar 21 2010 Subjectivity would be an issue, but so is it for conventional wind-chill and even static air-temperature measurements. The weatherman says 5 degrees, but listeners will decide whether they think that's cool, cold or intolerable.
Likewise, a measurement that accounts for the thermal conductivity and thermal mass of objects will be absolute, and people will interpret it subjectively for themselves.-- MaxwellBuchanan, Mar 22 2010 What about that thing where you run one finger under the hot tap, then another finger under the cold one, continuing this for 30 seconds or so in order for your fingers to habituate, and then plunge them both in a container full of luke-warm (who *is* Luke anyway?) water.-- zen_tom, Mar 22 2010 // who *is* Luke anyway? //
Anakin Skywalker's son. He has a sister, Leia.
Please, try to keep up ...-- 8th of 7, Mar 22 2010 I knew that much (I felt his presents) my question is more to do with him being identified as an indicator of temperature?-- zen_tom, Mar 23 2010 It's the Force that makes him warm - it's a well-known side-effect of exposure to higher-than-recommended levels of Force.-- hippo, Mar 23 2010 //who *is* Luke anyway?) //Christopher Biggins' character in "Porridge".-- coprocephalous, Mar 23 2010 Luke-warm Porridge ? Hmmm ..-- 8th of 7, Mar 23 2010 That poor baby bear, everybody is after his porridge...
Even Luke now, alas, I thought he was supposed to be on the side of good.
coincidentally [+] for the idea-- xxobot, Mar 24 2010 // I thought he was supposded to be on the side of good. //
We would apologise for disillusioning you, but actually we rather enjoy that sort of thing ..
'I believe you find life such a problem because you think there are the good people and the bad people. You're wrong, of course. There are, always and only, the bad people, but some of them are on opposite sides.' (Terry Pratchett, "Guards ! Guards !")-- 8th of 7, Mar 24 2010 //room temperature// Did you have any particular room in mind, pertinax?-- DrBob, Mar 25 2010 How about a genital scale, measuring the retraction when exposed? Or the nipple scale of course.-- marklar, Mar 25 2010 // nipple scale //
Eeewww, nasty ...-- 8th of 7, Mar 25 2010 [marklar] //measuring the retraction when exposed// I recall a paper on that very subject in the Journal of Irreproducible Results.-- mouseposture, Mar 26 2010 // Anakin Skywalker's son. He has a sister, Leia. //
Only as a result of retroactive continuity, my good man. See [link5]
Try to keep up, indeed!-- land, Mar 26 2010 //I have an overwhelming urge to raise technical quibbles.// Excellent, [mouseposture], that's what shows you're one of us. :-)-- pertinax, Mar 27 2010 Yes, we would hate to think that you might be one of Them ...-- 8th of 7, Mar 27 2010 Baked: Fahrenheit is already based on Rømer's scale, which was based on the temperature of a healthy man, at least according to an MIT video lecture I saw. I haven't been able to back that up otherwise). Wikipedia says Rømer based it on the freezing and boiling of water.-- kevinthenerd, Oct 18 2012 // I like the concept, though I have an overwhelming urge to raise technical quibbles. //
[marked-for-tagline]-- Alterother, Oct 18 2012 [zen_tom], back in 2010 said "I knew that much (I felt his presents)"
When did a Christmas tree get into this conversation?-- normzone, Oct 18 2012 My understanding was that Farenheit was based on the freezing and boiling points of seawater.
Unfortunately, since the salinity of seawater is variable, this is a lousy thing to base a temperture scale on.-- MechE, Oct 18 2012 Nope. Originally, 96 degrees Fahrenheit was body temperature, and 0 degrees Fahrenheit was “colder than it ever gets in Denmark”. Later, 0 degrees was redefined to be the stable temperature of a mixture of ice, water, and ammonium chloride, and some additional tweaks were made to get pure water to freeze at 32 and boil at 212, which caused the body temperature point to shift upwards a bit.-- ytk, Oct 18 2012 Meanwhile, somebody with all ten fingers and a bucket that didn't leak was off somewhere inventing the Celsius scale, which, like an Apple Computer, is simple, functional, and aesthetically pleasing, but is only just now coming into its own having suffered from earlier marketing failures.-- Alterother, Oct 18 2012 I double checked, the only really fixed point, zero, was based on a brine (not seawater, admittedly). He started with water at 30 and body temp at 90, then revised the scale so he could use regular divisions to draw it out.-- MechE, Oct 18 2012 //Celsius scale… is simple, functional, and aesthetically pleasing//
The Celsius scale sucks. I can understand the logic behind the rest of the metric system, but there's no justification for using Celsius over Fahrenheit for anything.
The freezing and boiling points of water are completely arbitrary standards, and they're not relevant to anything you do in your daily life. Have you ever stepped outside and said, “I wonder how much hotter it would have to be for water to boil?” No, of course not. Have you ever said “I need to calculate precisely how much colder it would have to be for ice to form if I were at sea level right now?” I sort of doubt it.
With Celsius, you have to use negative numbers and decimals with far greater frequency, because the scale isn't calibrated to be useful to human beings. A roughly 0-100 scale for most things you'll encounter in your daily life is quite convenient. -18 to 38 is just annoying. And it's not like you can add, subtract, or multiply temperatures anyway, so what's the point?
The Kelvin scale at least makes some sense, and I can see a use for it in scientific applications, but even there it's not really any better than the Rankine scale, which is essentially the same thing but in Fahrenheit gradations. But Celsius simply has no reason to exist.-- ytk, Oct 19 2012 I completely disagree.
First of all, a great deal of modern-day life revolves around the boiling of water, the freezing of water, or any number of operations related to or extrapolated from one or both.
Second, as arbitrariness goes, 32 and 212 are a whole lot more nonsensically arbitrational than 0 and 100.
Third, if you don't like using decimals, simplify things by using 'anna half' instead.
Fourth... well, okay, I'm out, but the only thing Farenheit really has going for it is that it fits right in with the rest of the idiomatic metrics we use here in the States.-- Alterother, Oct 19 2012 They're both crap: what idiot decided "98.6 is the new 100" and "the magic number where you have to start scraping ice off the windshield and all your plants die is 32" ?
Celsius is even worse (barring the 0 = ice bit), all the reasonable temperatures for human beings are between 10 and 30, that's only a 20 degree range.
Almost as bad as the kilometers per hectare (or whatever) mileage ratings we have here. All (regular'ish passenger) cars run between 6-10... that's even simpler (and not in a good way) than counting on fingers.-- FlyingToaster, Oct 19 2012 //First of all, a great deal of modern-day life revolves around the boiling of water, the freezing of water, or any number of operations related to or extrapolated from one or both.//
Oh, right, Maine. Well, in the rest of the country, we have these amazing things installed in our walls that, believe it or not, dispense actual drinkable water on demand. You don't even have to chop any firewood to get a drink of water by melting snow in the middle of the night! And in the summer, water is actually safe to drink as-is—no boiling necessary. In actual fact, very little of what I do throughout the day involves either freezing or boiling water, and when it does I don't especially care at what temperature it happens. “Really hot” or “really cold” work just fine.
//Second, as arbitrariness goes, 32 and 212 are a whole lot more nonsensically arbitrational than 0 and 100.//
But you almost never care about the freezing and boiling points of water within the same application. So, why would you design a scale based on those two numbers? Step outside and the temperature is very likely to be between 0 and 100 Fahrenheit wherever you are in the world. Anywhere outside this range would be considered extreme. /That's/ useful. Don't you step outside quite a bit more often than you need to calculate the temperature differential between freezing and boiling water?
//Third, if you don't like using decimals, simplify things by using 'anna half' instead.//
Or, just double the whole scale so you don't have to even deal with that. Then add about 30 degrees or so to get rid of those annoying negative numbers as well. Hmmm.-- ytk, Oct 19 2012 OK, so what 2 events would anyone here use instead of ice/boiling points of water, and how would *any* such choice be any more/less arbitrary than any other one?-- zen_tom, Oct 19 2012 //The freezing and boiling points of water are completely arbitrary standards, and they're not relevant to anything you do in your daily life. Have you ever stepped outside and said, “I wonder how much hotter it would have to be for water to boil?” No, of course not. Have you ever said “I need to calculate precisely how much colder it would have to be for ice to form if I were at sea level right now?” I sort of doubt it.//
You really didn't think about that for long, did you? People *routinely* need to deal with temperatures close to both the boiling and freezing point of water, in their daily life[1].
They may be arbitrary and approximate[2], but if you are looking for robust points which virtually everyone can easily understand, they're it.
//With Celsius, you have to use negative numbers and decimals with far greater frequency, because the scale isn't calibrated to be useful to human beings. A roughly 0-100 scale for most things you'll encounter in your daily life is quite convenient. -18 to 38 is just annoying. And it's not like you can add, subtract, or multiply temperatures anyway, so what's the point?//
Most people routinely deal with temperatures well above their body-temperature. Let's take boiling point as the max most people will trypically need to measure. Most freezers hold at -20 degrees C, lets take that as the minimum. The freezing point of water is also a useful transition, which would be nice to have as an easy number in the scale. So which is better: -4,32,212 or -20,0,100?
[1] A few examples for both Boiling water : cooking, preparing hot drinks, sterilising Freezing point of water : storing food (perishable - a few degrees above; long-term - a few degrees below), driving in potentially dangerous conditions, caring for plants
[2] Celsius is actually now defined using absolute zero and the triple point of water, but the difference is not important "in everyday life".-- Loris, Oct 19 2012 //what 2 events would anyone here use// Lower limit = temperature at which you notice that your feet are sticking out of the bottom of the duvet. Upper limit = point at which you don't need the duvet in the first place. Shall we talk about how fine the scaling should be now?-- DrBob, Oct 19 2012 If you need a fine scale, just start using decidegrees C. It is the SI standard, which means the prefixes are just as applicable.-- MechE, Oct 19 2012 Thanks all. I also meant that daily life involves the boiling and freezing points of water in the more abstract sense; automotive technology, for instance, uses both figures in direct application and as reference points.-- Alterother, Oct 19 2012 //You really didn't think about that for long, did you? People *routinely* need to deal with temperatures close to both the boiling and freezing point of water, in their daily life//
I already addressed this point in a later anno. Don't confuse “dealing with temperatures” and “measuring temperatures”. When you're cooking, do you measure the temperature of your pot of water as it gets to the boiling point? I don't, and neither does anybody else. You just put it on the stove, and when it boils, you add the pasta.
Same thing with your refrigerator or freezer. I've never measured the exact temperature of my appliances. I know that the refrigerator will keep things cold, and the freezer will freeze them. I don't care where exactly they are relative to the triple point of water. It's just not that useful a metric.
Pretty much the only things most people care about the actual temperature for are: The weather — for which 0-100 is a very convenient scale Body temperature — over 100 is a fever, also convenient Adjusting the thermostat — where the finer gradations come in handy, allowing you to avoid decimals or fractions Setting your oven — since all temperatures are well over the boiling point of water, and you're not boiling water anyway, no real advantage to either system there So for most practical purposes, Fahrenheit is a demonstrably better scale to use, and in no case is it worse than Celsius.
The argument that the metric system makes it easier to do math when converting between units falls flat when it comes to temperature, because you can't do math on temperature in any meaningful way. I challenge anyone to find a demonstrable way in which measuring in Celsius makes things simpler than Fahrenheit or Kelvin.-- ytk, Oct 19 2012 As someone pointed out somewhere, older people in England use Celsius for temperatures below freezing, and Fahrenheit for temperatures above freezing. A hot day might be in the 80's, but a cold night might go down to -5. Go figure.-- MaxwellBuchanan, Oct 19 2012 That's just because they want to make things sound as extreme as possible (the “Four Yorkshiremen” sketch springs to mind).-- ytk, Oct 19 2012 I'm plumping for the Delisle scale, where smaller numbers represent higher temperatures.-- MaxwellBuchanan, Oct 19 2012 Kelvin is the one that makes it easy, as it's the one used when you are multiplying or dividing temepratures. For addition and subtraction, it, of course, doesn't matter if you use Celsius or Kelvin.
Regardless, the critical thing is that the constants in your formula match up with your units. Since metric formulae typically use Celsius/Kelvin and imperial typically use Farenheit/Rankine, and since metric is easier to use for everything else, it's easier to do math with Kelvin. However, since I'm most often working around room temperature, I'm working with simpler numbers if I use celsius and simply add 273.15 before I do any multiplication.-- MechE, Oct 19 2012 I use Fahrenheit, Celsius, and Kelvin on a semi-regular basis, although I use them all in different applications and will freely admit that I never perform any conversions. My argument against Fahrenheit is my argument against all idiomatic metrics: they don't make any bloody sense. Now, I grew up using inches, feet, yards, miles, ounces, pounds, tons, cups, pint, quarts, and gallons just like every other pie-eating flag-waving gun-toting American child, but the only reason I'm able to keep any of it straight is because I've had it hammered into my skull since Kindergarten. On the other hand, anybody capable of counting to ten can measure _anything_, including temperature, using the Metric system.-- Alterother, Oct 19 2012 random, halfbakery