Not necessarily true. It depends on the object's optical properties.

I well remember working on my parents' car in Phoenix summers. The chromed wrenches on our driveway surface got to instant-blister temperatures. Tools with black surfaces were uncomfortable to pick up, but were usable.

The chromed tools had a lower absorption of sunlight than the black tools, but their IR radiation coefficient was even lower. So equilibrium temperature (at which radiated energy = incident energy) was much higher for the chromed tools.

I was always careful to put my tools in the shade under the car :-)

(Used to live in Glendale.)

No need to be an asshole about it. Some folks probably don't know the relative darkness of asphalt and tarmac.

But according to GP's numbers, tarmac is less dark than asphalt so should get less hot than asphalt. But those numbers are suspect and probably only refer to very fresh asphalt/tarmac; the albedo aka "lightness" of worn asphalt is something like 0.3.

Snow can have an albedo lower than 50% - and non-white sand can have an albedo higher than that.

It's not as simple as color.

In particular, there are dark things that have an albedo higher than asphalt's 0.05...

Dark will get hotter in sunlight but can be cooler at night if the sky is unobstructed.

> Dark will get hotter in sunlight but can be cooler at night if the sky is unobstructed.

What would the sky be obstructed by? Clouds? How could that affect how cool tarmac on the ground gets at night?

Yes, clouds.

With a clear sky, you're radiating (based on your own temperature) out to the blackness of space, which is radiating back at 4 Kelvin. Which is to say, it's contributing basically nothing. You're just giving up heat to the cosmos.

With a cloudy sky, you're radiating (based on your own temperature) out to the bottoms of the clouds, which are reflecting your radiation back to someone else on the ground, and their own heat is reflecting back to you. And such. The cloud looks white in the daytime because it's very reflective, so it acts like a mylar blanket to hold the heat in.

Physics is strange:

> At night, when cloud coverage increases, downwelling infrared radiation also increases. So, clouds act like space heaters, emitting energy towards the ground. Blankets only limit the transfer of heat energy away from your skin(convection).

Huh, that's very interesting and non-intuitive for a non-physicists like me. Thanks for the explanation!

This is what the greenhouse effect is, literally. At "thermal IR" wavelengths the sky is a blanket. Cloudy sky is even more of a blanket.

I live near a grape growing are, and they have wind turbines to blow air on cool nights slightly above freezing because the radiation from the ground to to sky can be enough to frost-damage their crops.

So they turn them on the blow the stagnant warmer ambient air around and mitigate that.

I was told that light reflects heat, and heats more quickly, but also radiates badly (cools more slowly).

This is why heatsinks are often painted black.

It is also the reason for all the strange white/black colors on rockets.

> heats more quickly

Errata: “heats less quickly”.

The difference between "not surprised" and "understand why" is vast. For example we (humanity) still don't understand _why_ gravity works despite not being surprised by its existence.

And don't forget the 10,000 rule: https://xkcd.com/1053/

Yes, but GP's quote was not an explanation, it was literally saying that "light objects reflect more light". Albedo literally means "whiteness" ie. how light something is.

From GP:

> Traditional asphalt has a low albedo, which means it reflects radiation poorly and instead absorbs it

Seems like a pretty good high level explanation of why that matters. Darker objects absorb energy instead of reflecting it. I'm sure there's more to it than that when you get into details.

If you're lucky there's a course you can overpay for.