Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: dentstudent on 06/06/2007 11:48:42
-
I understand the reasons as to why we go brown in the sun, but I don't understand why it should be this way round. White things are cooler as they reflect more of the energy, and so if melanin were to be white (for arguments sake), wouldn't this make more sense? Or perhaps "white" skin is a misnomer, and it's actually "clear", which would mean that the sun's energy penetrates further into the epidermal layer, which may cause internal harm?
-
I've often wondered that myself. I started thinking about that when I lived in Uganda & wondered why people from such a hot country are black which, as you rightly state, absorbs more heat than white. [???]
-
White skin is pretty much clear- that's why you can see the veins etc under it.
Unless you use a metal (which would be interesting, but biologically tricky) you can't get very good reflection easily. The reflection depends on the difference in refractive index and most of the materials that biology makes (proteins, fats etc) have pretty similar refractive indexes. To get good reflection isn't inpossible; Scarab beetles do it beautifully and they recently got a write up in one of the physics journals for doing so. On the other hand, making things that absorb light is relatively easy - you just need a messy collection of double bonds.
This page gives a selection of scarabs; if you don't like beetles don't look.
http://www.iamanangelchaser.com/products/tears_of_the_rain_forest/tears_of_the_rain_forest.html
-
Scarab beetles do it beautifully
Yes, and birds' feathers and butterflies wings and some flowers(?) too.
We could have lustrous skins instead of just boring pink / brown.
However, the physics is much more critical for an interference filter then for a simple absorption system. The degree of reflection in such a filter is a lot harder to vary than the amount of absorption by a pigment.
-
All those rely on structures containing air to produce the different refractive index needed for good reflection. That's fine for a fairly rigid structure but It would be really tricky to get a flexible skin that could do it. A reptile's scales might be able to.