CHRISTMAS LECTURES 1998: Nancy Rothwell - Times of our lives

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How do our bodies know what time it is?

Many of us wake up in the morning to the sound of an alarm clock. But our bodies each have a unique clock of their own. This natural body clock is set in rhythm every morning by the Sun, and tells us when it’s time to wake up and when it's time to go to sleep.

In her fourth lecture, Nancy Rothwell explores how our bodies and those of animals are trained by sunlight. From summer to winter, and land to ocean, Nancy explores nature's most unique examples of timing, including why Cicadas emerge from the nest after exactly 17 years, and how the Iguana can tell whether it’s daytime even with its eyes shut. 

The changes in season have a particular effect on animals, and the time an animal is born will determine how likely it is to survive. In winter, food is scarce and the freezing conditions can be tough. Find out how many animals collect and store food in preparation for hibernation and why they do it.

Nancy ends her lecture with a look at life span which varies greatly across the animal kingdom. A mayfly will only live for one day after it hatches, whereas an elephant can expect to live for 70-80 years, and giant turtles for several hundred years.

Small animals normally have shorter life spans than big animals. So why do little creatures like bats or lobsters often see their 50th birthday? As Nancy reveals, cells have a pre-programmed time of death that tells them exactly when their time is up.