# North-facing rocks that soak up polar sunlight [duplicate]

Chapter 155 in the book '365 Surprising Scientific Facts, Breakthroughs, and Discoveries' of Sharon Bertsch McGrayne (Wiley, 1994) states that:

North-facing rocks that soak up polar sunlight can be 15°C (60°F) warmer than the surrounding air.

• Simply that polar sunlight is not really a thing? Or is it? – fffred May 22 '16 at 12:25

It is strange because

The formula to convert Celsius to Fahrenheit is: $ºC = \frac{ºF - 32}{ 1.8}$ so a difference a difference of $1°C$ corresponds to a difference of $1.8 °F$ so a difference of $15°C$ is a difference of $27°F$

This book is confusing the conversion $15°C$ = $60°F$ with the conversion of $\Delta ºC$ to $\Delta ºF$.

• I always tried to distinguish in my teaching between 5 Celsius degrees, and 5 degrees Celsius. Similar to 5 miles on Interstate 94, and Mile 5 on Interstate 94 – DJohnM May 22 '16 at 18:26

Celsius and Fahrenheit have different starting points, so converting between absolute temperatures is not the same as converting between relative temperatures (i.e. differences). This book converted an absolute temperature of 15 degrees Celsius rather than a relative temperature difference: the correct value would be only about 27 degrees.

Hmmm...where should I start?

"north facing rocks". how can rocks have a face?

But let's say they do.
It is kind of strange to ...

receive sunlight when you are facing north. But this can still happen if you are at the south poll. Then it's north in every direction

• But the question does not ask whether it could be true. It simply asks what is strange. Which is strange btw – fffred May 22 '16 at 12:30
• @fffred. I explained what I think is strange. I also added my personal thoughts that this can still happen. Is it strange that I did that? – Marius May 22 '16 at 12:32
• Your answer is fine. But your reason why it could be true sounds like a puzzle solution, not real science, and the question cites something real it seems. Well, I guess this could still be the right answer – fffred May 22 '16 at 12:36
• Rocks that are close enough to the north-pole can receive sunlight on the north-facing side, since earths axial tilt is currently ~23.4°. Inside the arctic circle there's a season, when the sun doesn't set for a few days to month, depending on how far north the position is and thus as well shines, when it's north from the viewer. And we can define "north facing" as "the largest side of the rock is on the north-side of the rock" – Paul May 22 '16 at 15:03

If we take the direction absolute:

The sun is never in the North. It comes up in the East, travels over South to the West. North-facing rocks will not soak up any (direct) light because the sun is never there.

• @Lordofdark is probably right though, that's the biggest flaw. – Mast May 23 '16 at 10:20
• The north pole is ice, and under the ice is sea. there are no rocks at the north pole. so clearly the rocks are at the south pole. – Jasen May 24 '16 at 8:49
• @Jasen Is polar light something only happening at the exact poles? I'd assume Greenland and Svalbard would be possible locations as well. – Mast May 24 '16 at 8:57

It is strange because

rocks that are 15 degrees Celsius warmer will be above freezing, thereby eliminating permafrost and melting ice multiple months out of the year.