A night of unrelenting physics questions

[se7entse7en]

I had some coffee yesterday and just couldn't shut by brain off all night. Couldn't fall asleep until after 6:00am. Kept asking myself physics questions all night long. One of them was: Would wearing a black cycling jersey in the summer:
a) cause me to be hotter while biking than a lighter colored jersey
b) cause me to be cooler while biking than a lighter colored jersey
c) have no noticeable difference in cooling compared to a lighter colored jersey.
d) depends

If 'd', then what factors would come into play, and at which point does the cross-over occur.

Many of you wore green jerseys when you played hockey in... Genesis(?). Did you feel at an advantage or a disadvantage?

I guess what I'm wondering is if it's worth the 65% discount on getting a black jersey or not.

[geForce]

It depends on the lighting out right? Darker colours absorb a broader UV spectrum than lighter colours.

But then, if you're sweating, then wearing a darker colour would cause your sweat to evaporate faster. Faster evaporation would equal more cooling. If you're wearing black and it makes you hotter, then you'd sweat more. More sweat, more cooling.

I guess the factors that come into play would be:

- how much idle time are you expecting during your trip (idle time = no wind to help with evaporation)
- how much sun is out on that day, but I guess this is unpredictable and non-constant
- how much you tend to sweat

[geForce]

I've mostly only ever wore the green jersey, and the white jersey I did wear the few times was thicker material so it doesn't make a good comparable.

[joel]

just my opinion, but:

d) depends if it was a sunny day or not.

the color black absorbs the most (or reflects the least amount) of light of any color. the absorbed light will be converted to thermal energy released by the jersey. so on a sunny day i would say the answer is a. on a day with less sunlight, probably c.


as for the newlife jerseys, i don't think they particularly gave us a disadvantage playing, but those rinks were saunas regardless and we also weren't playing under direct sunlight either.

[se7entse7en]

I was thinking along the lines of a full-on midday summer sun.

Here was my train of thought:
Clearly standing there waiting at lights would be torture, but other than that... ... dunno.

Black absorbs light/heat. White reflects light/heat. Originally I started to wonder, am I generating heat quicker than the sun would be heating me? If that was the case, then wouldn't it be better to wear black as it would absorb MY heat and radiate it out quicker? Same reasoning as to why car radiators are black and not chrome or white or whatever. If I wore white, it would reflect my own body heat back towards myself. In the case of working out indoors, it almost makes sense to me that wearing dark clothing would cool you off quicker.

In the case of working out outdoors with a full-on midday sun, though...

I then started to wonder, evaporation aside (and there's a reason why I'm keeping it aside), can wind cool anything off... and can it cool anything off cooler than the wind itself.

I think it's pretty obvious that wind can cool something off, even without evaporation involved, but it cannot cool it off any cooler than itself.

My next train of thought was, how fast would the wind have to be to cool me off, evaporation aside, quicker than the sun can heat me.

My reasoning for all of this thinking is the idea that if the wind I face while biking cools me off quicker than the sun alone can heat me, then perhaps having a black shirt would help cool me quicker than a white one as it would more easily absorb my body heat and radiate it out.

Anyway, I think there are just too many variables for my tiny little mind to sort through.

[nature boy]

i was under the impression that dark colours absorb light, not heat. and the light energy from the sun is converted into heat energy, which makes you feel warm, but it doesn't absorb the heat away from the body as you seem to be suggesting.

but then, i studied theology.

[se7entse7en]

Our bodies glow. They're just below the spectrum our eyes can perceive.

[nature boy]

do they glow more when we're hot?

[se7entse7en]

yes. Ever see a thermal scan?

I still think black absorbs the heat radiated from objects. It certainly radiates it better.
...

Or am I just having a brain fart due to only getting 2 hours of sleep last night?

[nature boy]

i have seen a thermal scan, but from what i understand it's not a light or spectral scan, as it detects heat intensities and colour codes it for our eyes to understand.
for example:

i don't think farts emit light.

[geForce]

[se7entse7en]

Also, Isn't Jupiter just a big ball of gas?

[geForce]

[se7entse7en]

Yeah, I thought about that too.
Quick, do an experiment. Get two frozen chicken breasts. Put one on a black pan, the other on a white one and see if either of them defrosts quicker than the other. Make sure both pans are made of the same material though.

[nature boy]