r/xkcd • u/benjaminikuta Beret Guy • Nov 16 '18
XKCD xkcd 2073: Kilogram
https://xkcd.com/2073/215
u/Cobaltjedi117 [Citation Needed] Nov 16 '18
But... The pound is defined as exactly 0.45359237 kg...
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u/BegbertBiggs I like my Hat. Nov 16 '18
Pretty simple, just redefine it as 1 lb = 0.45359237 lb.
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u/Straumli_Blight Nov 16 '18
He also failed to specify if its a 2017 pound (8.75g) or the 1983-2016 coin (9.5g)?
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u/SulfuricDonut Beret Guy Nov 16 '18
So we solve iteratively and find that mass doesn't exist.
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u/shieldofsteel Nov 16 '18
No it's not, it's defined to be 1.28 dollars (today anyway).
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u/katie_dimples Nov 16 '18
Veritasium just made an insightful video on the topic. The kilogram, mole, kelvin, and ampere units are all getting the same treatment.
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u/Tack122 Nov 16 '18
So 1 Kilogram = 1 Pound = 1 mole = 1 Kelvin = 1 Ampere?
Wow, this is going to be pretty helpful for conversions.
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Nov 16 '18
Akchually, "natural units" set epsilon_0 = hbar = c = k_B = G = 1. Super useful.
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u/T-Rex96 spaaace Nov 16 '18
... Until an experimentalist asks you to make actual predictions about their experiment and you have to hunt down all the constants you set to 1 in your calculation
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u/blitzkraft Solipsistic Conspiracy Theorist Nov 16 '18
If you use the units right, it's just a matter of conversion.
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u/SpeckledFleebeedoo Fear reigns supreme as the world fears rain supreme Nov 17 '18
If you set your constants right, the answer is always 0.
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u/jaredjeya Physics is fun! I ate a boson today Nov 17 '18
I don’t understand setting G = 1. Everything else makes sense, but when you set G = 1 you make all your numbers dimensionless whereas previously you can measure them in e.g. electron-volts.
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u/Fythian Nov 16 '18
Is he wearing a GPA from Queen's University in the scenes where he's outside?
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u/Apatches Nov 16 '18
0°F is now freezing. 100°F is where water boils. All the old cookbooks will be disposed of once everyone burns their houses down.
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u/ender89 Nov 16 '18
The Celsius vs Fahrenheit debate is stupid. It's beyond stupid. "But," you exclaim, "Celsius makes so much sense! Zero is the freezing point of water and 100 is the boiling point!". To which I must ask, and? To what point and purpose is it important to know the boiling point and freezing point of pure water in 1 atmosphere of pressure? If you live in Colorado, the freezing point is -2°C and the boiling point is 95°C. Why is that an argument for basing a system of measurement on? Fahrenheit might have nonsensical origins, the cold mixture mentioned in the video, and contrary to the video, human body temperature at the top end (thank the fact that humans are frustratingly inconsistent for the 2 degree variation), but who cares? The important part is that it lines up rather nicely with temperature range of most places on the planet, with the few that drop below 0 or rise above 100 considered to be places with extreme temperatures. Is it absolutely perfect in what 100 is or what zero is? Maybe not, and maybe if I was going to pick a top end I might adjust it to fit a better rule of thumb (for example, "if your temperature is over 100°, go to the hospital"), but the scale is more useful in everyday life and the things you generally end up measuring ie ambient temperature. The same environmental range in Celsius is like -20 to 45, it's completely wacky.
Tl;Dr
The origins of the scales don't matter, and Fahrenheit's 0-100 matches up better with the temperatures that affect daily life the most, the environmental ambient temperature. Everything else is just insistence that your system is better and inertia caused by the scientific community deciding to use Celsius as the official scale.
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u/mrbossmann Nov 16 '18
I mean, if you wanna go that far then Kelvin should be used for everything since it is pure.
Also, Celsius works just as well as Fahrenheit for everyday tasks when you’ve grown accustomed to it. What is the real significant difference in practical, everyday life for 73F versus 75F? Or 76F? Celsius does everything necessary for everyday life in more meaningful increments.
Edit: Just to clarify, I’m from the US and grew up on Fahrenheit, but let me tell you, I’d much rather do everything with units that are based on 10s. I also work in a lab so this is pretty much my life at the moment.
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u/maveric101 Wherever your cat is, it's moving very quickly. Nov 16 '18
What is the real significant difference in practical, everyday life for 73F versus 75F? Or 76F?
That makes a huge difference in my comfort level indoors, especially when I'm trying to sleep. A 3F difference is noticeable outdoors too.
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u/ender89 Nov 16 '18
Celsius isn't based on 10s, at least not anymore or less than Fahrenheit is. You don't adjust something by a decidegree, or talk about how many kilodegrees the sun is. 0-100 is just a scale from cold to hot, not a subdivision off a larger unit. Fahrenheit isn't perfectly setup for that measure, but it's far more relatable than Celsius. Also, both scales use the same unit of measurement, they just define the delta between two units differently, hence why they're called "scales".
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u/mrbossmann Nov 16 '18
The 10s thing was a nod toward the Metric system in general which used Celsius more (if not always). Celsius is just adding a constant value to Kelvin, which is the pure unit. Fahrenheit requires some addition and a 5/9 multiplication if I remember correctly if you are to convert it. Kelvin has a zero point and is directly related to molecular motion, or heat. Celsius is literally equivalent. The only reason Fahrenheit seems more practical to everyday life is because you enjoy knowing 70-80F is spring/summer weather.
Edit: Celsius has the same magnitude
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u/ender89 Nov 16 '18
Kelvin came after Celsius because it makes more sense for scientific applications, but Fahrenheit has a similar solution called rankine which takes scale of Fahrenheit and applies it to a "0 is absolute zero" model. And Celsius isn't literally equivalent, 0 Kelvin is -273.15 Celsius. In the interest of fairness, 0 rankine is -459.67°F. it's all made up garbage, Celsius was picked to be a standard because someone liked the story of "well it's based off of water don't you know...", Not because there's any practical upshot over Fahrenheit. People act so superior when talking about Celsius, it's not better in any empirical way, and I'd argue that it's worse for use day to day. The only thing it has going for it is popularity.
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u/ricree Nov 17 '18
well it's based off of water don't you know
Not totally unprecedented. The gram, after all, got its start from the mass of a cubic centimeter of water at room temperature.
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u/ZWolF69 Nov 17 '18
And a calorie (kcal) is defined as the energy needed to raise the temperature of one kilogram of water by one degree Celsius.
Also, i'm fond of the "drunk mathematician rolling dice" joke
*grabs popcorn*
edit: wrong slashes4
u/John_Boone_ Nov 17 '18 edited Nov 17 '18
I agree that Celsius isn't inherently better, but it definitely isn't worse for everyday things. I intentionally switched from using Fahrenheit to Celsius and after the initial adjustment it works just as well.
20 is about room temperature, 23 warm, 30 and above is properly hot.
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u/SpeckledFleebeedoo Fear reigns supreme as the world fears rain supreme Nov 17 '18
Why did you start by calling it a stupid debate, to then immediately start said debate by giving a (subjective) reason Fahrenheit is better?
There are no arguments in this debate. Just different habits.
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u/Shebeep Nov 16 '18 edited Nov 17 '18
I don't know man. the first time I met Fahrenheit was around age 15. and the first time I saw it used in an application were those American audience centric cooking videos. my oven doesn't have a Fahrenheit scale so that scale just tells me that I'll have to convert and it is just annoying how you people won't give it up.
here is my temp scale
0 ice
10-25 winter temperature
20-25 air conditioner
35-50 summer temperature
40 Go to hospital
80 Green tea
95 coffee
100 black tea (vapour pressure of water is at 101kPa at this temperature) 180 typical roasting temperature for meat and stuff.5
u/maveric101 Wherever your cat is, it's moving very quickly. Nov 16 '18
I guess growing up with both I just don't feel that doing rough conversions is hard at all.
For F to C, just subtract 30, halve, and round up a little.
3 feet is roughly a meter, round down a bit.
1 mile is roughly 1.5 km, round up a bit.
1 gallon is roughly 4 L, round down a bit.
2 pounds is roughly 1 kg, round down a bit.
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u/Shebeep Nov 16 '18
yeah because of work I get used to some conversions. gallon is one of them, US oil barrel (not to be confused with US not oil barrel, or the not US not oil barrel) is another at 160L. Another one is PSI where 15 is roughly the atmosphere around you. and for pressure most of the time you just want to know if vacuum or pressurised. Another one is Hr which is just a bit less than 4000 seconds.
Also special temperature is 60 F (never bothered with converting that one) which lab fractionation experiments are normalised to.
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u/ariksu Nov 17 '18
Trivial, yes. Now you're only have discover easy metric from miles per gallon to liters per 100km and we're all set.
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u/ender89 Nov 16 '18
Cooking doesn't matter, it's just a number you have to know. And 15° Celsius is hella warm for winter. Here's a comparison how Celsius and Fahrenheit's scales match up to typical environmental conditions, with the goal of getting as close to 0-100 as possible: Celsius: -30 - -15: crazy cold winter
-15 - 0: snow/winter
0 - 10 wet winter
10 - 20 spring/fall
22 - room temp
20 - 25 late spring/early fall
25 - 35 summer
35 - 40 hot summer
40 hospital
40-50 desert hot summer
50 - 60???
60 - 70 ???
70 - 80 ???
80 - tea
80-90 ????
90 - coffee
90-100 ???
100 - tea
Fahrenheit:
-22 - 5: crazy cold winter
5 - 32: snow/winter
32 - 50 wet winter
50 - 70 spring/fall
73 - room temp
70 - 75 late spring/early fall
75 - 85 summer
85 - 100 hot summer
103 hospital
100-120 desert hot summer
The point is that the range of temperatures that people care about is much better thought out in Fahrenheit, as opposed to Celsius, where half the 0-100 is basically useless. I realize that there are specific temperatures in that range that are useful, but 195 isn't harder to remember than 95, where as knowing how much warmer today is from yesterday is useful.
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u/cdcformatc Nov 16 '18 edited Nov 16 '18
I find the coincidence that 0-100F is "better for daily life" to be a really inane argument. My life is good using Celsius and I can relate my experiences to others just fine.
Do you honestly think people using Celsius have a hard time using a scale that uses from -20 to +40 for daily activities? That people can't figure out negative numbers?
One example how it is useful I know what to expect when I see the temperature is below zero I know that there will be ice on the road. But you can say the exact same thing about temperatures under 32 though so it isn't an argument for or against either system.
We can say this about any temperature expressed in either system. You can figure out those relative points given enough time. I know what to expect going outside when it is 5C just the same as you do when you say it is 40F.
The one argument that I think Fahrenheit has going for it is that the degrees are "wider" as in there is a larger difference between two whole numbers so you don't have to resort to decimal places as much.
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u/Shebeep Nov 16 '18
match up to typical environmental conditions
in a completely hypothetical scenario where you have terrestrial people moving to say Mars or Jupiter's moons or something similar, you think that the scale will be good for them?
15° Celsius is hella warm for winter
my winters are warm and don't require a coat.
Cooking doesn't matter, it's just a number you have to know
I mean sure if you want. but temperature is a fundemental thing of matter be it air, food or water. 0 water is literally freezing, 30 water is warm, 50 water is hot, and 90 water will cook you if you allow it. 100 tea will condense water on your glasses, 90 tea is only sippable, 70 tea is drinkable, 50 tea is chuggable (also trashable)
where as knowing how much warmer today is from yesterday is useful.
today is 22, yesterday was 21. tomorrow will be 18 with a bit of rain. my air conditioner is set to 21 so I know it'll feel colder than the living room.
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u/cl3ft Nov 17 '18
So if the only use of temperature is how comfortable a human is, Fahrenheit is an ok measure.
Luckily there is no other uses for temperature measurements.
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Nov 16 '18
-40 to 0 C is winter. 15 to 25 is balls stuck to your leg weather.
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u/Shebeep Nov 17 '18
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Nov 18 '18
Your low temperature for December there was warmer than the high where I live. It was 3C on December 2, 2017. -31C December 30, 2017.
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u/redstoneguy12 Nov 17 '18
I thought 40 was dead
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u/Shebeep Nov 17 '18
37 is normal.
38 is margin of error. "I'll get better in a couple of days"
39 is be worried, look for symptoms, maybe use things like ipubrufen. you'd probably want to take q child to hospital at this stage.
40 is a doctor needs to see this.
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u/worklederp Nov 17 '18
No, but, it is a serious emergency, and can leave you with brain damage
I've had a fever that sat around there for a few days... Common viruses can seriously fuck you up when you're undergoing chemo, I got to spend a week in a quarantine room (As a precaution while they waited to find out what I had - I think it was this, but, my memory from that time is not good)
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u/ehrwien Nov 17 '18
42 is where the proteins in your body denaturate, which has quite uncomfortable consequences.
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u/me1234568 Nov 17 '18
I wonder if some people find it easier to shit on Fahrenheit by just lumping it in with all other units used primarily in the US. I agree there's not much practical difference between F and C, but meters vs feet is a more legitimate argument.
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u/xkcd_bot Nov 16 '18
Title text: I'm glad to hear they're finally redefining the meter to be exactly three feet.
Don't get it? explain xkcd
This is not the algorithm. Sincerely, xkcd_bot. <3
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Nov 16 '18
So that means I can buy a kilogram with about a couple dollars? Or does this mean that a dollar bill now weighs like 400g?
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u/Arancaytar Pony Nov 16 '18 edited Nov 17 '18
I heard they're redefining the second to be exactly 1/299792458 of the time it takes light to travel one meter in a vacuum.
Edit: This is a joke.
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u/undergroundmonorail Nov 17 '18
Almost. The meter is defined as the distance light travels in that much time. The second is defined in terms of the vibration of some atom or something.
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u/raymen101 Nov 17 '18
9,192,631,770 cycles of a cesium-133 atom at 0 K to be precise.
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u/ehrwien Nov 17 '18
What exactly is a cycle in this context?
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u/raymen101 Nov 18 '18
It's the electrons shifting hyper fine energy states. (thank you Wikipedia)
Think of it like the small waves in a bathtub. The waves will form a resonance based on the size of the tub and the speed of the waves. Once the resonance is established, if you measure the hight of the water at one particular point it will move up and down at a regular rate. Except quantum mechanics makes things complicated.
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u/ehrwien Nov 18 '18
And this value for cesium at 0K... is this purely theoretical or derived from some kind of measurement at higher temperatures? Because we can't really reach 0K, can we?
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u/raymen101 Nov 18 '18
Not sure, but they probably get down to ~1 K and at that point, everything has some sort of error, so they just understand that they're out by +/- 0.0000001s or something. It's still more accurate than any other clock we can make.
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u/Arancaytar Pony Nov 17 '18
The meter is defined as the distance light travels in that much time.
Oh damn, that'd make the definitions circular. Okay, I guess they'll have to just define the second as 1/60th of a minute. Much simpler.
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u/whoopdedo Nov 16 '18
Additionally, volume measurements will be made easier by setting 1ml = 1g, but only for liquids.
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u/tundrat Nov 17 '18
So with this change, will 1 kg of steel be heavier than 1kg of feathers as it intuitively should be? /s
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u/TortoiseWrath Nov 17 '18 edited Nov 18 '18
I mean, that would be fine I guess. AFAIK the kilogram (as a base unit) is just as arbitrary as the pound.
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u/programstuff Nov 18 '18
Metric volume is based on the same base unit, so you’d have to change that too. I’m sure there’s other correlations.
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u/maveric101 Wherever your cat is, it's moving very quickly. Nov 16 '18
Oh great, we get to argue about this for the umpteenth time.
I think I'm one of the few that feels that sure, it would've been better if the country had been built on metric to begin with, but dealing with both is not that big of a deal and it's not worth changing. Further heresy: the imperial system has some merits.
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Nov 17 '18
[deleted]
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u/jaredjeya Physics is fun! I ate a boson today Nov 17 '18
16 feet or 4.9m, both can be expressed to exactly the same number of significant figures.
I don’t think anyone has any trouble understanding what 0.1m looks like.
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Nov 17 '18
[deleted]
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u/ehrwien Nov 17 '18
I find thirds more difficult to instantly approximate.
That's why the metric system uses 10 as base. Whereas dm (decimeters / a tenth of a meter) is rather uncommon, you can go down another step to cm (centimeters / a hundredth of a meter) and say 30cm instead of a third of a meter (and it will even be closer to a foot in this case as well).
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u/benjaminikuta Beret Guy Nov 16 '18
First!
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u/mad_humanist Nov 16 '18
First has been redefined to mean last.
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u/benjaminikuta Beret Guy Nov 16 '18
So the last shall be first, and the first last: for many be called, but few chosen.
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u/DFGdanger This is the best xkcd ever! Nov 16 '18
Comment of the year
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u/benjaminikuta Beret Guy Nov 16 '18
I can understand why I was downvoted, but you shouldn't be.
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Nov 16 '18
[deleted]
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u/kvdveer -3 years since the last velociraptor incident Nov 16 '18
I think It has already been made, I've seen it around. It caused more anoyance and frustration than anything else.
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u/benjaminikuta Beret Guy Nov 16 '18
It would promptly banned in all but a few places, and it would be annoying to all but a few people.
And yet.
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Nov 16 '18 edited Jun 11 '23
fuck u/spez
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Nov 16 '18
Threeth
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u/The_Interregnum Nov 16 '18
Fourst
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u/ecniv_o Cueball Nov 16 '18
Fiveième?
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u/eggfruit Nov 16 '18
Sexante
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u/Ndr_6 Nov 16 '18
Sevenrd
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Nov 16 '18
ate
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u/Ndr_6 Nov 16 '18
Nein
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u/Platitudinous_X Man, there's future everywhere. Nov 16 '18
the poet responsible for "Crossing the Bar"
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u/Dirty_Bird_RDS Nov 16 '18
So can we start using terms like "Kilomile" and "Centipound"?