Why do we hear the sound of the sea when we hold a shell to our ear? It is not the sound of sea you hear when you hold a shell to your ear. Rather what you hear is the sound of your blood rushing through the blood vessels in your ear. The shape of the shell provides a simple sort of echo chamber, and the opening in the shell allows other sounds to be almost shut out when we hold the shell to our ear. It is not just sea-shells that have this effect. Hollow animal horns and tin cups also achieve the same effect. Do you know who was the original 'Nosy Parker'? It is believed the original Parker in the saying 'Nosy Parker' was Matthew Parker, who was Archbishop of Canterbury (1559-75). Historians credit Matthew Parker, who supervised Elizabeth I's religious settlement, with a reputation for prying into the affairs of others, thereby acquiring the nickname 'Nosy Parker'. Why is the sea salty? The erosion of minerals from the earth's surface releases many ions which are washed into the seas. The main ones are iron, magnesium, potassium, calcium carbonate, sulphate, chlorine and sodium. All except chlorine and sodium are readily involved in organic and chemical reactions, yielding new sedimentary rocks. Sodium and chlorine therefore built up in the seas throughout geological time. The saltiness of the sea can be used as a basis of measuring the age of the ocean. In leap years why is an extra day added to the end of February instead of the end of December? When Julius Caesar adopted the Egyptian calendar of 365 days (which became known as the Julian calendar), an extra day was added every four years to stop the calendar drifting away from the seasons. Since February was the end of the Roman year, it made sense to add the extra day then, a practice which continues to this day. The modern months of September, October, November and December take their names from the Latin for seven, eight, nine and 10, their respective positions in the calendar of ancient Rome. Why do colds cause runny noses? The virus triggers the release of inflammatory chemicals that make your nose congested. Then the fluid is used as a transportation mechanism, so when you blow your nose, the virus can infect others. But most of the virus remains se curely fixed inside the cells of your nose and is difficult to get rid of, no matter how often you use your handkerchief.