While we’re growing up various hormones control growth (getting bigger) until we’re fully grown. Bones get longer, you get taller and other changes like puberty hit. At some point we stop growing. Ageing causes a lot of changes in the body – we get grey hair, our bones might get more brittle, and we become more likely to get some disease. Everyone ages at a different rate and scientists believe that this is controlled by molecules at the end of chromosomes called telomeres. Telomeres seem to control how often a cell can divide. We need our cells to divide to replace ones that die. Scientists think that Telomeres might provide information on how to make people live longer.
In the olden days people told time by looking at where the sun was in the sky. So it’s highest at midday, and you could try to work it out from that. Sundials were also quite useful in working out time. We have had calendars for many thousands of years, often by counting the number of days between things like the equinoxes (when day and night are closest to equal length, in March and September) or the solstices (shortest day in December and longest day in June). I think people worried less about being late as well!