2153: "Effects of High Altitude"

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Re: 2153: "Effects of High Altitude"

Postby gmalivuk » Wed May 29, 2019 5:29 pm UTC

kuri wrote:When it comes to measures of length or mass, the metric system deals with multiples of the basic units in an incomparably simpler manner. But regarding temperatures, I don't think that Celsius degrees are intrinsecally better than Fahrenheit (even if I think in Celsius because I grew up in a country that uses the metric system).

That's because the basic units are always arbitrarily chosen, unless you're using something like the Planck units, that are unusable in everyday life. So, the only meaningful difference IMHO (H stands for Humble :D) between the two systems is the way they deal with multiples of the basic units, and the metric system indubitably wins in this regard.

But this comparison is no more valid when it comes to temperature, because neither Celsius nor Fahrenheit have weird-looking multiple units. Moreover, both can be made more "natural" by translating Celsius to Kelvin and Fahrenheit to Rankine.

I think it is only a historical accident that the metric system came out packaged with Celsius and Kelvin rather than Fahrenheit and Rankine. But, if I was to choose which system to use for scientific purposes, I would have no doubt that meters and kilometers are more fitting than feet, yards and miles.

I'm just glad we finally freed temperature from the tyranny of water.
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Re: 2153: "Effects of High Altitude"

Postby Flumble » Wed May 29, 2019 5:48 pm UTC

Be honest y'all, the real reason we dislike fahrenheit is because everyone uses celsius except the USA and Liberia (and confused ovens). And fahrenheit is not qualitatively better (otherwise we should advocate it no matter how few people use it).


Since we're talking about temperatures again, I'll quote Simmon's superior scale again:
SCSimmons wrote:Fiddled around with possibilities for a bit. I thought milli-electron volts per molecule (of an ideal perfect gas) looked pretty handy for everyday purposes. The unit turns out to be just under 8°C and almost exactly 14°F, so it's not very fine-grained; reporting to tenths would give you comparable precision to what you see in weather forecasts, but the comfort categories can be that wide & still work well. I'll call this unit the Maxwell (M); he got a nice law named after him, but as far as I know, never a unit, the poor guy.

Code: Select all

M      °C      °F

30    -41     -41
31    -33     -27
32    -25     -13
33    -17       1
34    -10      15
35     -2      29
36      6      43
37     14      57
38     21      71
39     29      85
40     37      98
41     45     112


Water freezes at 35.2M and boils at 48.1M at standard pressure. And normal human body temperature is ... hold on, I know 98.6 °F is an outdated rule of thumb, let me look up the real number & variance ...

Huh. Normal human body temperature is ... 40.00 +/- .02 M. :shock: This must mean something, right? :)

(Not sure what he used for a conversion factor; seems like T_K=T_M*⅔/k (k in meV/K and a factor 3/2 for a monatomic gas), except with ⅔/k rounded to 7¾. So a more superior scale would just be meV or 10^-22J)

Whereas <0°C doesn't guarantee frost or anything (luckily the weather forecast includes things like "chance of frost" or "chance of slipperiness" when applicable), a max temperature of <35M or <37.5hyJ or <19.2 planks will get my hopes up for ice skating and snow. Which is really the only important thing about low temperatures. :mrgreen:­­

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Re: 2153: "Effects of High Altitude"

Postby PM 2Ring » Wed May 29, 2019 9:07 pm UTC

Let's not forget Felsius.

In Fahrenheit and Rankine, between the freezing and boiling points of water there are 180° or π radians. :wink:

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Re: 2153: "Effects of High Altitude"

Postby jgh » Thu Jun 20, 2019 1:05 am UTC

AndrewGPaul wrote:The only reason the current definitions of the second, kilogram and metre are "arbitrary" numbers of oscillations of caesium and whatnot is so that the values match the old definitions so no-one needs to remember a whole new set of constants and buy new scientific calculators. :)I suppose we could round everything to a more easily-remembered number, but that'd be awfully confusing.

The speed of light is so close to 3.00000000 x 10^thingy that when I become King of Earth that's what I'm going to redefine it as.

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Re: 2153: "Effects of High Altitude"

Postby gmalivuk » Thu Jun 20, 2019 5:26 pm UTC

jgh wrote:
AndrewGPaul wrote:The only reason the current definitions of the second, kilogram and metre are "arbitrary" numbers of oscillations of caesium and whatnot is so that the values match the old definitions so no-one needs to remember a whole new set of constants and buy new scientific calculators. :)I suppose we could round everything to a more easily-remembered number, but that'd be awfully confusing.

The speed of light is so close to 3.00000000 x 10^thingy that when I become King of Earth that's what I'm going to redefine it as.

That change would be equivalent to one minute per day, which is far too large to happen easily.
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Re: 2153: "Effects of High Altitude"

Postby jgh » Fri Jun 21, 2019 6:49 pm UTC

gmalivuk wrote:
jgh wrote:
AndrewGPaul wrote:The only reason the current definitions of the second, kilogram and metre are "arbitrary" numbers of oscillations of caesium and whatnot is so that the values match the old definitions so no-one needs to remember a whole new set of constants and buy new scientific calculators. :)I suppose we could round everything to a more easily-remembered number, but that'd be awfully confusing.

The speed of light is so close to 3.00000000 x 10^thingy that when I become King of Earth that's what I'm going to redefine it as.

That change would be equivalent to one minute per day, which is far too large to happen easily.

But it's about half a millimetre, so close to invisible.

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Re: 2153: "Effects of High Altitude"

Postby Pfhorrest » Fri Jun 21, 2019 6:55 pm UTC

jgh wrote:
gmalivuk wrote:
jgh wrote:
AndrewGPaul wrote:The only reason the current definitions of the second, kilogram and metre are "arbitrary" numbers of oscillations of caesium and whatnot is so that the values match the old definitions so no-one needs to remember a whole new set of constants and buy new scientific calculators. :)I suppose we could round everything to a more easily-remembered number, but that'd be awfully confusing.

The speed of light is so close to 3.00000000 x 10^thingy that when I become King of Earth that's what I'm going to redefine it as.

That change would be equivalent to one minute per day, which is far too large to happen easily.

But it's about half a millimetre, so close to invisible.

Half a millimeter per what? Half a millimeter per millimeter is a huge change. Half a millimeter per lightyear not so much.
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Re: 2153: "Effects of High Altitude"

Postby pogrmman » Fri Jun 21, 2019 8:07 pm UTC

Archgeek wrote:
ThirdParty wrote: 0°F isn't arbitrary: it's the freezing point of salt water. That makes it a temperature that can easily be created in a lab, as well as one that's relevant to many practical questions such as "should I salt my driveway to melt the ice on it?" Also, some of my favorite body parts--e.g. eyeballs--are made of salt water.

What molarity? Freezing point depression in a solution varies with concentration, after all.


0°F was initially defined as the coldest temperature that could be reliably obtained by a saturated salt/ice mix, so the concentration doesn’t matter. It’s just enough salt so that it doesn’t all dissolve.

100°F was his closest estimate of the human body temperature.

Pfhorrest wrote:Though IIRC Denver it not actually up in the mountains as it is right next to the foot of the mountains, no?

It is right by the base of the mountains. You have to go west to actually get into the mountains. It’s just that the Great Plains are like a giant, gentle slope upwards to the bottom of the Rockies and Denver is near the top of that slope.

kuri wrote:When it comes to measures of length or mass, the metric system deals with multiples of the basic units in an incomparably simpler manner.

It’a consistent, which is the best part of it. I’m not really sure if 10 was the best choice base to use, though: it makes fractional measures a bit inconvenient and makes things like the decimeter virtually useless on their own.

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Re: 2153: "Effects of High Altitude"

Postby gmalivuk » Sat Jun 22, 2019 12:30 am UTC

pogrmman wrote:
Archgeek wrote:
ThirdParty wrote: 0°F isn't arbitrary: it's the freezing point of salt water. That makes it a temperature that can easily be created in a lab, as well as one that's relevant to many practical questions such as "should I salt my driveway to melt the ice on it?" Also, some of my favorite body parts--e.g. eyeballs--are made of salt water.

What molarity? Freezing point depression in a solution varies with concentration, after all.


0°F was initially defined as the coldest temperature that could be reliably obtained by a saturated salt/ice mix, so the concentration doesn’t matter. It’s just enough salt so that it doesn’t all dissolve.

100°F was his closest estimate of the human body temperature.

[citation needed] for both of those claims, but the one about 100 especially.

And the amount of salt that wouldn't all dissolve changes with temperature, and 0F isn't the coldest freezing temperature for salt water.
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Re: 2153: "Effects of High Altitude"

Postby ijuin » Sat Jun 22, 2019 12:46 am UTC

Pfhorrest wrote:
jgh wrote:
gmalivuk wrote:
jgh wrote:
AndrewGPaul wrote:The only reason the current definitions of the second, kilogram and metre are "arbitrary" numbers of oscillations of caesium and whatnot is so that the values match the old definitions so no-one needs to remember a whole new set of constants and buy new scientific calculators. :)I suppose we could round everything to a more easily-remembered number, but that'd be awfully confusing.

The speed of light is so close to 3.00000000 x 10^thingy that when I become King of Earth that's what I'm going to redefine it as.

That change would be equivalent to one minute per day, which is far too large to happen easily.

But it's about half a millimetre, so close to invisible.

Half a millimeter per what? Half a millimeter per millimeter is a huge change. Half a millimeter per lightyear not so much.

I believe that he is proposing to keep the length of the second the same, but change the length of the meter to equal 1/(3*10^8) of a light-second.

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Re: 2153: "Effects of High Altitude"

Postby gmalivuk » Sat Jun 22, 2019 2:30 am UTC

Right, and 2/3 of a millimeter or so would be the adjustment. Which, again, is intolerably large for modern purposes.
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Re: 2153: "Effects of High Altitude"

Postby Pfhorrest » Sat Jun 22, 2019 3:02 am UTC

So to answer my question, half(ish) a mm per meter?
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Re: 2153: "Effects of High Altitude"

Postby gmalivuk » Sat Jun 22, 2019 12:18 pm UTC

Yeah.
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Re: 2153: "Effects of High Altitude"

Postby SuicideJunkie » Mon Jun 24, 2019 5:20 pm UTC

Alternatively, we can increase the speed of light slightly, and leave the meter as-is.
That would annoy even more people when GPS goes wonky.

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Re: 2153: "Effects of High Altitude"

Postby DanD » Mon Jun 24, 2019 6:57 pm UTC

sotanaht wrote:
cryptoengineer wrote:
sotanaht wrote:>the kilogram being completely arbitrary unto themselves.


As of a couple days ago, the kilogram has been redefined in terms of physical constants: the Planck constant, the speed of light and the resonant frequency of the caesium atom: https://www.sciencealert.com/tomorrow-the-definition-of-the-kilogram-will-change-forever-here-s-what-that-really-means

That doesn't make it any less arbitrary. The Kilogram is now defined as some bullshit multiple of something that's a thousand times harder to remember than 5280, and every other metric measurement is defined as something relative to the kilogram (and also some other constant, but the measures are all meant to be based on each other). Except for Celsius, which has nothing to do with the kilogram and the only scientific merit that it has is that it's fixed points are based on water in some slightly useful way. There are no funky unit conversions to mess up the system regardless of whether you use F or C and even converting to K is pretty straightforward. You can make an argument for the practicality of metric in other weights and measures, but purely for the purpose of temperature, the two systems are equivalent.


In case you missed it, the official foot and pound are based on the meter and kilogram, so no matter what, US Customary units are at least a few layers more abstract than the metric equivalent.

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Re: 2153: "Effects of High Altitude"

Postby jgh » Tue Jul 02, 2019 11:21 am UTC

gmalivuk wrote:Right, and 2/3 of a millimeter or so would be the adjustment. Which, again, is intolerably large for modern purposes.

So, squidge the length of the metre and the length of the second in opposite directions to split the difference. Good enough for government work. When surveying fields I use flat plane measurements, I only worry about lines on the surface of a spheroid if doing county-level work to millimetre accuracy.

2/3mm is less than the difference I get measuring due to the tensile strength of my measuring tape being insufficient to pull it tight enough to prevent gravity tugging the centre of the measuring tape down.

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Re: 2153: "Effects of High Altitude"

Postby ijuin » Tue Jul 02, 2019 1:11 pm UTC

That’s fine for work done by hand, but if you want functional GPS, then you need part-per-trillion accuracy. (one part per trillion is 86.4 nanoseconds per day, a time span in which radio signals will be off by 26 meters)


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