[Ians Daddy]

How long does the "evolution" take to adapt to the amount of sun? ie.. transplanted people from different regions. I know that a tan would fade, but how does and how long for the melocytes to alter?

Why do freckles fade with age in some people? ie... kids with freckles on their noses.[)]

Why do I turn deep red [!](not a burn)[V] as opposed to brown when I'm in the sun alot?

Just some thoughts.

[cuso4]

May be you don't have enough melocytes to produce a tan. Instead, the capillaries near the surface of your skin expand allowing more blood flow, you therefore lose heat through radiation and convection. This is vasodilation.

Angel

[Qing]

why do people get headache [xx(] after being exposed to bright sunlight for a long time perticularly if you skin colour is light?

Qing

[cuso4]

Don't people get overheated and the enzymes in the body start malfunctioning?

Angel

[Donnah]

Ronnie, maybe you turn red due to your Indian heritage.  

As for the geographic effect of the sun over the course of generations, why are Eskimo and Inuit people, who live in the far north, dark skinned?

[Ians Daddy]

Maybe the elevation. Or, the reflective affect of the snow and sun. Actually, maybe the evolutionary adaptation period is very slow and these people are decendants from a southern race. It's fascinating to see that Eskimo, Somoan, Polinesian, Mexican, Native American Indian and Asian people have very present similarities in skin tone and features. So, maybe our "family tree" is more narrow than we thought.

[Quantumcat]

Snow reflects more light than soil, a lot more. Either that or they haven't lived in the far north for very long.

Am I dead? Am I alive? I'm both!

[Donnah]

There's also the issue of constant daylight in northern summers, and constant dark in winter.

[bezoar]

I seem to remember, way back in high school, being taught that it isn't the number of melanocytes, but the size of the granules of melanin that makes for the differences in skin color.  Any feedback on that?

Bezoar

[Quantumcat]

Oh, yes!! That's it. In summer their nights would be like one hour long. But, their days in winter would be like one hour long too, so it doesn't work. Bugger.

Am I dead? Am I alive? I'm both!

[NakedScientist (OP)]

ANSWER TO "WHY DO PEOPLE HAVE DIFFERENT COLOURED SKINS ?"
 
It’s all down to a substance called melanin, the stuff that suntans are made of. The body produces melanin, which is a dark brown colour, to protect us from the sun because melanin stops harmful ultraviolet rays that can cause sunburn and skin cancer. People with dark skins naturally make much more melanin than fair-skinned people and that’s why their skin is browner. Most of these people have ancestors from hot countries where there is a lot of strong sun and so they have their own natural sun-block. Scientists think that our ancient ancestors came from Africa and all had dark skins to protect them from the sun. But, over thousands of years as they migrated out of Africa to inhabit colder countries, it was no longer an advantage to have a dark skin because there was less sunlight, so people lost their natural sun-protection and became fair skinned.

[NakedScientist (OP)]

This week's question of the week was suggested by Tom (Nilmot)

WHY CAN YOU SOMETIMES SEE THE SUN AND MOON IN THE SKY TOGETHER ?

Have a go below...answer next week.

TNS

[Donnah]

Why wouldn't you be able to see them both?  The sun emits light and the moon reflects that light.  It just depends on where they are relative to the observer's field of vision.

[chris]

Quick comment to Bezoar in relation to her remark about melanocytes - yes you are definitely right. The melanocyte density is equivalent in black and white people. However, the expression of melanin and the cellular environment differs to make black people produce more melanin overall.

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[Qing]

usually,when we see the sun and the moon appear in the sky together will either be break or dawn except when there is a solar or lunar eclipse,so what I am thinking is that it depends on the angle the earth "lays"and the orbital it is "running" aroud the sun and also how the moon orbiting around the earth.besides this,I guess there must be something to do with at which latitude you are standing and observing from. I vaguely remember when I was in school I was taught that the orbital of the earth travelling around the sun is not horizontal,it's kind of oblique,a few degrees to the horizontal.
These just pure guesses,and don't know how to explain it clearly[]hope you can all understand me.

Qing

[NakedScientist (OP)]

HERE'S THE ANSWER TO LAST WEEK'S "QUESTION OF THE WEEK", SUBMITTED BY NILMOT (Tom Lin)

The appearence of the moon in the sky depends upon the position of its orbit. There is no reason why the moon and sun should not appear together in the sky since they are totally independent of each other. The moon orbits the earth and the earth orbits the sun. Therefore sometimes the moon coincide on its orbit with the rising of he sun and hence the two will appear in the sky together.

This is precisely how an eclipse occurs, only on this occcasion the path of the moon crosses the path of the sun. But the two bodies are still in the sky at the same time.

I think most people seemed to get that one right. Good question though. By an amazing co-incidence a lady phoned the radio show a few weeks ago with the same question !

[NakedScientist (OP)]

THIS WEEK'S QUESTION OF THE WEEK

"HOW DO WE KNOW HOW HOT THE SUN IS SINCE WE CAN'T GO AND MEASURE IT ?"

TNS

[Ians Daddy]

Guessing....will take a better stab at it later after some thought.
Guess: Temp. x Distance

I know that's probably wrong, but I'll build on it.

[Quantumcat]

colours - the material of anything burns at different colours depending on the temperature and what the materials are

we know what the materials are from the spectrum

Am I dead? Am I alive? I'm both!

[cuso4]

Is this called the BLACK BODY RADIATION? Never mind me if I'm talking rubbish.

Angel