A Brief History of Time

A Brief History of Time. . Children's Science and Nature Area , Niagara Region , A Brief History of Time , Since the beginning of time, humans have been searching for a better way to answer the age-old question: What time is it? , , The earliest humans used the position of the sun to approximate the time. If the sun was on the horizon, the day was beginning or ending. If the sun was high in the sky, it was mid-day. But what if clouds were covering the sun? Or you wanted to know the time at night? These limitations made finding a better method important. , , The First Timepieces: Around 3500 B.C., the Egyptians constructed "obelisks", or huge stone pillars to serve as primitive sundials. The pillars cast shadows on the ground that changed positions depending on the time of day. This method became popular because it was much easier to look at shadows on the ground than looking at the sun itself. , , Sundials: Several hundred years later, sundials similar to the one on display here were developed. You can see that the huge stone pillars have been replaced with a smaller and more functional structure. , , Hourglasses: The next great advance was the development of the hourglass in 3450 B.C. This device was basically a bowl with a hole in the bottom. Water dripped slowly as the day wore on and grooves (cut into the side of the bowl) measured the passage of time. The hourglass worked on cloudy or sunny days, so it provided some advantage over the sundial. But of course, this primitive hourglass had its limitations too. For example, it wouldn't work in freezing temperatures because the water inside the hourglass turned to ice. , , More than 2,000 years later, water in the hourglass began to be replaced with sand. The sand didn't freeze, which made it a better year-round option. But sand is heavy, so the sand hourglasses could really only be used to measure small passages of time. , , Modern Timepieces: It took until the 1300's for a mechanical clock to be properly developed. The first models had no hour or minute hands, and no faces! A lever (or "escapement") that pivoted and meshed with a toothed wheel was controlled by weights and springs to strike a bell every hour. This method of timekeeping was fairly effective and tended to be off by only about a minute per day. , , By 1852, the clock as we know it today was almost fully realized. These clocks functioned using a combination of weights and a swinging pendulum. However, it took until 1999 for the most effective version to appear with the invention of the cesium clock. This clock has an error ratio of 1 second every 20 million years. It is hard to imagine a clock that could possibly be more accurate than this one.