What-If 0132: "Hotter than Average"

[Rombobjörn]

Hotter than Average

... and entering the domain of the underworld.

[fisian]

"What is the average temperature of all water on the Earth’s surface, and how does that temperature compare to 39°C?" Was that even answered? One should not simply take the average earth surface temperature, one should exclude the areas that are frozen. Or do we count ice as water? This should make a large difference, right?

[krabcat]

i dont think it actually answered the question. the question was essentially "what is the average temp of all water on earth's surface" since the ocean contains most of the water on earth i figured it was safe to use that as a proxy for all water. the numbers i could find said that the surface water was at about 17C but deeper water was closer to 0-3C on average there is more deep water than surface water so i estimated the average would not be much over the 0-3 number. then i found The World Ocean. Columbia Encyclopedia. 28 May 2007 which flat out said that the average was 3.9C

[keithl]

The questioner asked about water at the Earth's surface, not in the depths. If the subject was "all water", the vast majority of water is between stars, with an average temperature of approximately 3K (Kelvin, not Celsius). The ocean surface also approximates atmospheric temperature, a little cooler because evaporation removes some heat.

However, "hot" can also mean radioactive, like this new Japanese spa. 私の寿司とのガイガーカウンターをお願いしてもいいですか？

[Andries]

The map of average groundwater temperatures does seem to answer the question. At least for the US.

But what is this F I keep seeing in these charts?

[Carlington]

I think F is for Farads, which makes sense if you think about it.

[DreadArchon]

Then i found The World Ocean. Columbia Encyclopedia. 28 May 2007 which flat out said that the average was 3.9C

Good to know. Thank you, helpful user.

[Rombobjörn]

The questioner asked about water at the Earth's surface, not in the depths.

So how deep into oceans, lakes and rivers does "the surface" go? Should we calculate an average of the actual surface temperature? The questioner wanted to compare the average to the 39 °C of the hot springs tub, but I bet that temperature was measured in the middle of the tub, not on its surface, so that would be a meaningless comparison.

I think one reason why Randall didn't answer the question was that the question was badly asked.

[Mikeski]

the question was badly asked.

It also has no "what if" quality at all. It's simply a "what is" question, with a single-number answer. Randall's eight-paragraph answer didn't even wrangle an "if" question out of the concept.

[Andries]

That is true of a very significant portion of what ifs. From Yoda's power output onwards.

[cyanyoshi]

Hey man, sometimes to answer a question, you have to, like, not answer the question. Man.

[Copper Bezel]

I for one appreciate the variety and unpredictability. The final new What-If in the book was excellent for this reason. Playing with a concept > following a formula.

[rmsgrey]

It's not the best What If, but then, it's also not the longest, and didn't go up earliest in the week either.

As filler when the alternative is missing a week, I'm okay with it.

[chalkie]

As a surface-dweller, any sign which told me "YOU ARE LEAVING THE DOMAIN OF THE SUN" would certainly make me sit up and think "crap - this is serious now". I live in a narrow temperature band of around -5°C to 30°C*, and in my house I can easily tell the difference between 19°C and 21°C. When I consider leaving the domain of the Sun I start thinking in terms of a range starting in single-digits of K to many thousands of K. Either would kill me, and I would regards that outcome as sub-optimal.

* Air temperature

Also, I found this:
"When immersed in 39°C water, your heart rate will increase by 12 per cent, which can cause problems if you have a heart condition," says Mike Maynard, chairman of the Hydrotherapy Association of Chartered Physiotherapists.

edit:
And being a trout, I like an even narrower water-temperature range than that.

[Showsni]

Maybe the sign was trying to be even deeper than that. Perhaps it was trying to say that, in general, water is one of the substances that is hotter than the average of the temperature of all substances in the universe.

Could that be true? Is water generally more likely to be warmed up than a random given substance?

What is the average temperature of the universe? How different is the average when measured as an average over space (say, measure the temperate in each cubic centimetre then find the average temperature of a cubic centimetre in the universe) as opposed to an average over substance (measure the temperature of each molecule in the universe then find an average temperature per molecule)?

[Whizbang]

Where does the spring fall on the hot/crazy scale?

[Klear]

HYDROLOGY CANNOT HELP YOU

[gmalivuk]

The questioner asked about water at the Earth's surface, not in the depths.

I think ocean water is typically considered surface water, as opposed to groundwater or water deep in the mantle. Surely you've heard something like, "3/4 of Earth's surface is covered by water," which I think is more commonly said than "3/4 of Earth's surface is water."

[january1may]

Maybe the sign was trying to be even deeper than that. Perhaps it was trying to say that, in general, water is one of the substances that is hotter than the average of the temperature of all substances in the universe.

Could that be true? Is water generally more likely to be warmed up than a random given substance?

What is the average temperature of the universe? How different is the average when measured as an average over space (say, measure the temperate in each cubic centimetre then find the average temperature of a cubic centimetre in the universe) as opposed to an average over substance (measure the temperature of each molecule in the universe then find an average temperature per molecule)?

I wanted to say that the former average will be close to the temperature of the cosmic microwave background (i.e. about 3 K) while the latter would be somewhere around five or six digits K (on account of all the stars being very hot and very heavy).
Then I found out about the warm-hot intergalactic medium. So apparently even the former average will still have 5-7 digits (at least as long as we ignore all the cubic centimeters that don't have any non-dark matter - if we instead count them by the background radiation, the average comes down to somewhere around double digits K; it's hard to estimate more precisely without knowing a lot of astronomical stuff, but it's probably less than 273).
On the other hand, for the latter average, if we don't count all the various types of plasma as "molecules", the remainder will be likely dominated by cosmic dust (the temperature of which varies a bit, but tends to stay in single digits K).

That said, it's probably hard to estimate whether interstellar H₂O is typically any warmer than interstellar dust in general (which mainly consists of hydrogen); I'd suspect that it is because of its typical way of formation, but, again, it's likely hard to say.

[JeffR23]

What about the related question about the average temperature of all water that is part of Earth? Just how much water content is there in the mantle and core, anyhow? Enough to not be dominated by the oceans?

[gmalivuk]

I remember reading something last year or so about there being three times as much water in the mantle as on/near the surface.

[krabcat]

in the march issue of scientific american, one article mentions that we are not quite sure how much water is in the mantle but estimates at least another oceans worth and potentially more than that in the core in the form of hydrogen that would otherwise bond outside of the extreme conditions

[Andries]

Well, I think the sign means that usually the water is around 33 °

[xkcddar]

When I first saw this comic there was significantly more content that has subsequently been removed.

Randall references the paper "Climate change inferred from borehole temperatures" by Henry N. Pollack (available on umich.edu), and talks about it. Any idea why it was removed?

[january1may]

When I first saw this comic there was significantly more content that has subsequently been removed.

Randall references the paper "Climate change inferred from borehole temperatures" by Henry N. Pollack (available on umich.edu), and talks about it. Any idea why it was removed?

I don't think this was removed. It's all right there (in footnote 2).

Maybe it originally was in the main text (perhaps even longer) and then moved to a footnote due to being an aside.
However, I suspect it's much more likely that you just read it in the footnote originally, then forgot it was a footnote, and didn't notice it this time (so couldn't read the text in it).

[Keybounce]

Sign one has a reference for sign 2
Sign 2 fails to finish the sentence.

Sign 2 did make me think of "Sunless Sea"...