One of my responsibilities at the Science Museum is to collect the paper questions visitors submit to our featured Scientists on the Spot. Sometimes the questions don’t quite mesh with the featured scientist’s background, but are good questions anyway, or are entertaining, or fun, and I thought this would be a good forum to answer some of the questions that would otherwise go unanswered. So, here we go!

Q: How many people are there in the world?

A: According to the World Population Clock from the United States Census Bureau, as of 3:30pm on June 2, 2006 there are approximately 6,519,746,485 people in the world. This number is constantly increasing, so for the most current number, you should visit the link above.

Q: How many bones are there in the human body?

A: The adult human skeleton has 206 bones, but they don't all start out as single bones. Even long bones (like your femur) start out with the epiphyses separate from the main shaft, and these unify with time. There are 800 centers of ossification in the skeleton that unite with age, and as such, the number of bony elements in a subadult can vary greatly.

Q: What is a spider monkey?

A: From the Wikipedia entry on spider monkeys:

Spider monkeys are New World monkeys of the family Atelidae, subfamily Atelinae. Found in tropical forests from southern Mexico to Brazil, spider monkeys belong to the genus Ateles; the closely related woolly spider monkeys, are in the genus Brachyteles.

Here’s a picture of one kind of spider monkey.
Spider Monkey: Image courtesy dgphilli.

Q: How long does it take to digest gum?

A: My parents always told me not to swallow my gum because it would take seven years for it to be digested. That’s just not true. Chewing gum has five basic ingredients - sweeteners, corn syrup, softeners, flavors and gum base. The first four ingredients are soluble, meaning they dissolve in your mouth as you chew or in your stomach when you swallow. Gum base doesn't dissolve – it just passes through us with the rest of our waste a day or two after you swallow it.

Q: How old do you have to be to donate blood or anything else? Can you be under 18?

A: Well, if you are deceased and a minor the decision to donate you organs is made by your parents or legal guardians. Licensed drivers can make a personal commitment to organ and tissue donation by indicating their wish to donate on their driver's license application. This lets families and emergency personnel know your wishes. Donation information is available in all driver's license bureaus in Minnesota, North Dakota and South Dakota. In these states, if you indicate your wish to become a donor on your driver's license, it is legally binding. Parental authorization is required for individuals under the age of 18.

To give blood for the Red Cross, you must be at least 17 years old. For more information visit the American Red Cross blood donation site.

Q: What are nails made of?

A: I am going to assume the question is regarding finger or toe nails. Fingernails and toenails are made of a protein called keratin. Keratin is the major protein component of hair, wool, nails, horns, hoofs, and the quills of feathers.

Q: Do you like bubble gum?

A: Not really. My favorite gum when I was a kid was Big League Chew. Now I prefer Swedish Fish.

That’s all for now. Do you have any odds and ends questions you’d like us to try to answer? Leave them for us – we’ll try our best to answer them for you.