Under the Microscope: I have put together what I hope are some interesting questions and answers, plus a couple of brain-teasers, writes Prof William Reville.
There is much at www.sciquiz.com/trivia/explain/index.asp to amuse you.
Why is it that tickling yourself isn't ticklish?
When you tickle yourself you are in control: our brains screen out stimulation from our intentional actions. You are not normally conscious of your tongue moving when you chew food, for example, or of the vibrations of your vocal cords when you speak. When someone tickles you, however, they are in control: they usually do it unexpectedly, and you panic. The symptom of your panic is hysterical laughter rather than terror, because you quickly realise your tickler means no harm.
What is a fart and why does it smell?
Come now, admit it: you always wanted to know the answer to this one. A fart is a mixture of nitrogen, oxygen, carbon dioxide, methane, hydrogen and hydrogen sulphide, gases generated in the gastrointestinal tract. They leave your body through your anus. When you swallow too much air or eat food your digestive system cannot easily handle, gas becomes trapped in your stomach or is generated in the intestine by bacteria digesting the food that passes undigested through your stomach and small intestine. We all fart - about 16 times a day. We fart most in our sleep. Women fart as much as men. Animals also fart, elephants the most. Farts that contain significant amounts of hydrogen and methane are inflammable. Farts smell because of hydrogen sulphide. The more sulphur you eat - in the form of beans, cheese, cabbage and eggs, for example - the smellier your emissions.
Why do we have eyebrows?
Eyebrows keep rain or sweat from flowing into our eyes, their arched shape directing it away. Sweat is salty and irritating to the eye. The eyebrow is also an expressive facial feature. Frowning eyebrows usually indicate upset or preoccupation. We also correlate eyebrow size and shape with notions of beauty. Big, thick and hairy eyebrows are normally considered unattractive.
Why does hair go grey?
We usually start to go grey around the age of 30, but this varies from person to person. It happens because cells in the roots of our hair stop making pigment. Greying is more noticeable in dark-haired people but occurs at about the same time in everybody.
What makes your stomach growl?
Your stomach growls when its walls squeeze together to mix and digest food that turns out not to be there. The growling is the sound of gases and digestive juices swirling around. A "hunger centre" in your brain scans your blood for certain nutrients. When these are absent the centre triggers your stomach and intestine into action, causing growling if no food is present.
Why do parts of the body "fall asleep"?
It is due to pressure on your nerves. Your arm may fall asleep after you have slept on it, for example: the pressure your sleeping body put on the nerves inhibited them from carrying messages to your brain and to the rest of your body. If you also squeezed blood vessels you probably also stopped the passage of oxygen through these vessels to the nerves. Nerves are bundles of very long, thin cells called nerve fibres. The thicker the fibre, the more sensitive it is to pressure and to oxygen deprivation. When pressure is released on a limb that has fallen asleep, the thinner nerve fibres awaken first and the thicker ones later. The first sensation in the awakening limb is a tingling, followed by a burning, correlating with the awakening of the fibres that control pain and temperature. Numbness disappears later, as the thicker fibres that control touch and position awaken. Finally, the motor neurons that control movement awaken, allowing normal movement again.
Does a camel store water in its humps?
Camels are the only animals with humps, mounds of fat and flesh that weigh up to 36 kilograms. The humps store not water but food, to allow the camel to survive for weeks in the desert without food or water. Metabolising the fat in its humps produces the essential water it needs under these conditions.
Brain-teaser 1: General Custer's choice
General George Custer stood on the battleground, surrounded by Indians. All of his men were dead, and the Indians were about to attack again. He saw a jar on the ground and picked it up. Out popped a genie, who offered to grant Custer a wish. There was a catch, however: whatever Custer wished for the Indians would each get two of. What did Custer ask for?
Brain-teaser 2: matchstick maths
Consider this mathematical equation, written in Roman numerals: VII-VI=VII. This equation is, of course, incorrect. Think of each stroke in the equation as a matchstick and make the equation correct by moving one match.
Brain-teaser answers next week