XKCD: It's more than a comic

Because a liter is a unit of volume, and the density of water changes with temperature.

I think it's because the density changes slightly with temperature, so if you scoop up a litre from a tub of cold water and a litre from a tub of hot water, you won't have precisely the same mass of water in them.

edited 20th Apr '18 12:45:08 AM by Medinoc

Note that the difference is tiny - you need pretty accurate instruments to be able to notice the difference.

Oh, and tiny differences do matter for high precision. Take mass, for instance. To properly measure mass, you need to account for what the value of gravity is for your elevation. You need to account for bouyancy in the air. You need to account for temperature, humidity, dust, and oxidation. But that's at very high precision.

That's because when you think you measure mass, you usually measure weight. That is why scales have to be calibrated for different geographical locations. But remember those old-style scales that use counterweights instead? Those actually measure mass. More pedantically, it measures whether the weight of your article is less or more than that of the counterweight. Weight depends on mass and gravitational (and inertial) acceleration, but that should be reasonably constant between the two ends of your scale. Of course precision is limited by the friction of the device, magnetic forces if either the article or the counterweight is made of a ferromagnetic material, wind etc., but you cannot measure the wavelength of whatever radiation without expensive lab equipment either.

Inertial scales can also measure mass while ignoring weight. It depends on how many figures of precision you require.

I'm all over the place with which measurements I use. For most things, it's metric, and I never use ounces. But I know my height in feet and iches, not metres, and my weight in pounds, not kg, and I use cups and teasppons for baking, not litres. I only understand weather temperatures in Celsius (Fahreinheit tells me nothing), but I'm pretty sure my oven is in Fahreinheit.

I consider metric better, because of the ease of conversions (especially when dealing with multiple dimensions), and Celsius is easy for weather wher you're used to it. 0 is where water freezes (and thus the point we're you're likely to get snow rather than rain, and the point where there starts to be frost outside in the morning). Below -20 means there's danger of frostbite, below 0 is cold, 0 to 10 is cool, 10 to 20 is moderate, 20s is a nice summer day, 30s is unpleasantly hot, 40 or above is unbearably hot.

All depending on your subjective preferences for temperature, of course.

edited 20th Apr '18 9:43:26 AM by Galadriel

Clutter

I absolutely can 100% relate I've got so many amiibos and figures of anime girls all over my shelf and dresser at this point that it's going to hit critical mass sooner or later.

It reminded me of this.

Below -20 is when I'll think about putting two shirts on under my jacket (usually it's just the jacket over a t-shirt if it's below 0). 0 is good because if I'm hosting a party, people can put their drinks on the balcony instead of the fridge, and it probably won't freeze (unless it's there for several hours and has a low alcohol content). 10 degrees is t-shirt weather, where wearing a jacket makes it unbearable (unless it's raining or very windy). 20 degrees is a very warm, but still tolerable summer day. 30 means you'll avoid going outside if at all possible. If it's 25 for two or three days, the news and newspapers will talk about ways to stay safe in the heat, and elderly people will start dying if it goes on for more than a few days.

40 degrees is not something I'd normally experience. It's not warm enough for a sauna, though - that starts at about 60 degrees, but 80-100 is normally good temperature for a sauna. (Some people like to go 120-140, but you're not in there for more than 5-15 minutes at a time if it's that hot. At 80-100 degrees you can hang out there for a while.)

So basically,

Yes. My point was that Celsius does provide usable, intuitive information about the weather if you're used to it.

I'm still not understanding how a person can even survive a sauna at a temperature (100C) where the water in all your tissues should be boiling.

Saunas are not 100C, more like 90-95. That's not yet boiling, and you sweat like hell. But I think BestOf is more of an authority on that subject than me.

edited 20th Apr '18 1:10:50 PM by petersohn

Wow, Finland is cold.

I mean, I knew already, but that drives the point home.

The thermometer is at 100 degrees if we say it's 100 degrees in the sauna. Apparently, the layer of sweat on the skin, as well as the fact that the air is mostly still, is what keeps your body from boiling (plus you're not in there for hours at a time, and the body does regulate its temperature). It's hottest when you throw water on the stove, obviously, and you're supposed to do it according to the preferences of the people in there. Some like to use a lot of water and feel very hot all the time, and then go out (dip in a lake or take a quick shower) before coming back in. Others like to sit there for a while, only throwing water occasionally.

Kids often play a prank on each other where they tell the victim to try what it feels like to blow a bit of air on your skin. As you might guess, it really burns - and no one falls for it more than once (which is why only kids can get anyone to try it on themselves).

There's actually a competition for who can stay in the sauna longest with the temperature well above 100 degrees. Several years ago, that competition got some notoriety because a Russian contestant actually died (someone else still won it by staying there even longer). That, of course, is not a good idea: the sauna is supposed to be enjoyable, not an endurance test.

10 degrees is most certainly NOT considered t-shirt weather over here, that would be more like 20. 25 would be a warm summer day. And no one wears just a t-shirt and coat at 0.

You must live way up north.

62nd parallel, approximately. A few degrees to go to the Arctic Circle. It's about the middle of Finland, latitudinally. (Is that even a word?) On the East-West axis, I live well in the East.

Still about the sauna: one way to look at it is this: assume you had a container full of water at room temperature, and a boiling kettle. Suppose you were to submerge your container of water in the boiling water. Would it boil immediately? No, because it takes time for the temperature of water to change. The conducting material also matters.

Air is a good insulator. The air in a sauna tends to be quite dry, exept immediately after the water's been thrown on the stove (it boils instantly, with a hissing sound). That's why, even if the sauna is at 120-140 degrees (although something like 80-120 would be more common), you won't instantly die. It's not the same as being submerged in a vat of water of that temperature.

Take this as a reference. I went to the sauna with my brother yesterday. We had some beer with us, and while you'd normally drink it after the sauna, or when you're taking a break from it, we decided to bring it with us. The problem with that is that because it's in a metal can, it gets hot quite quickly. On the other hand, the beer in it is mostly water, which means it retains its temperature well. That means you can have an opened can of beer in the sauna, which might be at 80 degrees, for about 10-15 minutes and it'll still be at least cool, if not cold. The more you drink of it, though, the less liquid there will be compared to the (warm) metal - so as you drink it, it becomes warmer at an ever accelerating pace. That means you have to sip it until you're about half way through the can, and then have the rest in a few gulps or it will be warm. Alternatively, you can enjoy it for a while and then go out of the sauna to finish it, which is what we did.

Another way to look at it would be to compare it to changes in temperature in the other direction. Let's say your normal body temperature is about 35 degrees (rounding to the nearest 5 - something like 36 or 37 is actually closer to the truth, while 40 is a fever bad enough that you should think about going to the hospital if it continues for more than a few hours). Going to a room that's at 80 degrees, then, means the difference between your internal temperature and that of the room is about 45 degrees.

Now, let's go the same amount - 45 degrees - colder than your normal temperature. That's just -10, no big deal. If it was -10 outside, I could go out there in the nude and stay there for hours and it wouldn't do me any sort of damage. It might be a bit uncomfortable, but that's it. -20 or -30 is quite a lot worse, but it's still not as if I'd die or anything if you put me out there for a few hours. I wouldn't like it, but if I got to take a nice, warm shower and have a cup of tea after I'd be fine.

You don't stay for hours at a time in the sauna, even if the session does take an hour or more. You preriodically step out and cool with drinks or rolling in the snow or a cool shower or a vat of water or something like that. Then you go back in. 15-20 minutes at a time is about normal, with about 2-3 breaks. Your skin will be hot and you'll sweat a lot, but the internal temperature of your body doesn't rise significantly, and it's all back to normal quite soon after you're done.

As a Canadian, I agree with Best Of's assessment on below-zero temperatures but I'd shift all the above-zeros upwards by another five or ten degrees to get his expected reactions. 15-ish degrees for t-shirts (10 is windbreaker weather), 20 degrees is normal summer, 30 is tolerable, anything above that is to be avoided.

As a Brit I’m probably the next layer south (so my equipment is 15 degrees higher than Best Of’s), it’s been in the high 20s here the law few days (29 yesterday) and we’re all complaining about the heat, I still put a jacket on but don’t want to (I just need inside pockets is all), I stopped wearing a hoodie under my jacket this week, last week I switched from a coat with a hoodie to a jacket and hoodie.

I’ve been realy appreciating having a cold room at work recently.

edited 20th Apr '18 7:40:44 PM by Silasw

Does the sauna actually get hotter when you throw water on the stove? I thought it just feels hotter because the humidity increases suddenly. And humidity is a huge factor in your feeling of temperature.

Let's do a little math. I may be wrong with the actual number, but water's specific heat is around 4.2 kJ/(kg*K). It means that it takes 4.2 kJ of energy to heat up 1 kg of water by 1 K (or 1 C). It is pretty large in contrast to most other materials, especially metals. In contrast, its boiling heat at 100C is around 2200 kJ/kg. It's the reason that when you cook, the water reaches boiling temperature relatively fast, but it takes a lot more time to actually boil off. Evaporation heat at lower temperatures is even greater. This makes evaporation a very efficient method of cooling.

When you are in a sauna and the air is dry, you can evaporate sweat pretty quickly, keeping you cool. If you pour water on the stove, then humidity increases and evaporation becomes much slower, thus your body has a much harder time keeping itself cool.

People living in tropical climates have the exact opposite experience. They think its freezing when its 15 degrees and will go for the double layers and coat at 10.

That's probably it. It does feel like the steam sort of makes a round around the sauna - those sitting closer to the stove tend to feel it first.

Those of us in a steppe climate (The Great Plains or Central Asia) can tell you that you acclimate to both heat and cold within a month or so. Meaning that 10°C in October feels very different from 10°C in February.

I can attest to that, as well. We've got about +5 right now, and it does feel quite hot outside. A few weeks from now, at +5 I'd be saying it's a bit cool.

I can't get used to the climate in Estonia. for a while I had gotten used to freezing temperatures, but then a few weeks ago it reached 20 degrees. Now 5 degrees feels too cold to hang out outside

Autumn's late in coming here and I'm very much enjoying an overcast day, even if it's barely dipping below 20 Celsius.