Jane Brindle, of Nga Tawa School, asks :-

What makes our bones white?

Alex Davies, a veterinarian with Massey University's Department of Physiology and Anatomy, responded.

Your bones will be white if you die in the desert and your skeleton remains there, bleached of life. The mineral (calcium phosphate) in your bones absorbs none of the colours of the light that falls on them, so that no colours are created in the reflected light. The carbon and nitrogen containing substances, well over half of bone volume, are slowly burnt away (oxidised), and bones become bleached in the sunlight.

Your bones will also look white if you have to be X-rayed. The atoms of calcium in your bones absorb X-rays more than the light atoms (carbon, hydrogen and oxygen) which predominate in your flesh so that your bones make a shadow on a photographic plate and protect it from the blackening effects of the X-rays.

But living bones aren't really white at all. Although the collagen fibres that hold the calcium phosphate crystals together and keep your bones elastic are white like the mineral crystals themselves, healthy bones contain many of the pigmented chemicals essential to your body, especially the red hemoglobin that must pass through fine vessels in all bones. Without blood, your bones would die and fail to support you in all your activities.

So, sorry, the skeleton that grew with you and keeps you company day and night isn't as smooth, clean and white as you thought. But feed them, exercise them and protect them well from injury, your bones will be good friends for as long as you need them.