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Thermodynamics!

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NutmegCT said:
One of the mysteries in all this: there are several references to "the shiny side should be down", due to its lower emissivity. See PC's reference:

https://www.dulley.com/docs/f411.htm

But the windshield shades have the shiny side up toward the sun.

hmmm
Click to expand...

Actually, mine are shiny on both sides.

Different situation, different solution. In the attic, the paper is getting hot by both radiation in the IR region and by conduction; the foil side blocks the radiation of that heat towards the remainder of the attic. No visible light is present. It's more or less coincidence that the foil appears shiny in visible light (looks shiny to our eyes since we only see in visible light).
 
Randall, so let me see if I understand this

If it's in a dark forest and there is none around to see it
I doesn't look shinny?
 
NutmegCT said:
One of the mysteries in all this: there are several references to "the shiny side should be down", due to its lower emissivity. See PC's reference:

https://www.dulley.com/docs/f411.htm

But the windshield shades have the shiny side up toward the sun.

hmmm
Click to expand...

Depends on what you’re reflecting. In case of windshields, it is the visible light that should be reflected right back through the windshield, in its visible form, so it leaves the car without changing to infrared (which would heat the car).

Edit: Just saw Randall’s post after posting mine. He’s right; I think we’re saying the same thing, more or less, with different words.


If a tree falls onto a piece of tinfoil in the forest, it simply bounces back up as if nothing ever happened.
 
Re: those outboards. Years ago, I had a 16'7" Boston Whaler with a 40 horse Evinrude. Pushed me along at almost 30 mph. How much faster do you want to go? I can see two motors for safety in salt water, but 3 or 4, especially on a smaller boat? That's crazy. And those big motors aren't cheap; maybe $12-$15 K each new.
 
"That would work real fine in our New Mexico winds!"

I was thinking the same thing about the wind in Oklahoma Bas.
 
That would sure save on gas - but nothing's new under the sun.

640px-Hendrik_Gerritsz._Pot_001.jpg
 
Trying to tack while following a road would be interesting, to say the least ...
 
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