OK i have a question about goosebumps…my girlfriend says she remembers a biology test question that said when your cold you get goosebumps because you retain the most heat when your hair stands stright up that way…my thinking is that makes no sence by a physics standpoint…i mean what will keep you warmer a blanket laid flat over you or the thin edge side covering you?? Thoughts anyone??
The reason hair, or fur, helps retain heat isn’t only that it impedes conduction like a blanket does. It also prevents convection. The hair creates a thermal boundary layer near the skin’s surface. This boundary layer slows down convection, which is the major form of heat loss you usually experience. I’m not sure how much effect the measley abount of body hair humans would have, but I imagine animals with fur can stay warm pretty easily by fluffing up.
Hmmm…it seems to me that when “fluffing up” your actually releasing heat ie the trapped and already heated air pockets…also along the same lines as when people run thier fingers thru thier hair to cool off. the best way to indeed form the thermal pocket of air is for the hair to be paralell to the skin and not perpendicular…and another side point…if goosebumps are a reaction to cold…doesnt the bumps in fact increase surface area of the skin and allow MORE heat to be lost?
I’ll approach this from a different angle. The primary way that you usually lose heat is through convection. Air is a pretty bad thermal conductor and unless you are lying down on the ground or something, that is where most of your heat is going(to the air). If the air is still around you, then conduction is the only means of heat transfer, but if the air is moving, convection comes into play(it even comes into play if the air isn’t moving, but that’s a different story). Convection depends on how much the air is moving, that’s why it seems so much colder(windchill) when it’s windy. So, the purpose of fur isn’t so much to insulate from conduction of heat, but to create a layer of stationary air near the skin to slow down convection. When you run your fingers through your hair you are disturbing that boundary layer. If the layer remains stationary, then your head will retain the heat and stay hot. As I said before, I’m not sure that our amount of body hair is doing any real good and you might be right about the fact that it increases the surface area of our skin slightly.
You retain heat better because your body is reducing blood flow to the outer layers of skin, shunting it inward toward the muscles. Vasoconstriction. It’s also related to the fight-or-flight response which gets your muscles pumped up and ready to do their job.
Goosebumps are kinda a throwback to earlier humans. The idea is to standup the hair on our bodies to make a convection dead zone of air our body can warm and keep trapped near ourselves. Along with vasoconstriction to keep the warmer blood away from the cooler skin, we try to stay warm…
now only if we had enough hair to make it work…
not enough hair to make it work??? your OBVIOUSLY not italian like me hehehehe
Hea, I’m still a young’n here, give me another decade or so… 