Tracking the ancient origins of time from early mankind up to our modern understanding of the concept, Eoin Murphy tells the story of how time came to be.
Discovered in the Lebombo Mountains between South Africa and Eswatini and shown by radiocarbon dating methods to be ~44,000 years old, the Lebombo Bone is the oldest known mathematical artefact. The fibula bone from a baboon contains 29 distinctive notches, strongly believed to have been used as a counting device or a rudimental calendar used to track the phases of the moon.
The Lebombo Bone. Image: Robert Hart, The McGregor Museum, Kimberley, South Africa
By ~12,000 years ago sites had been built containing markings and structures suggesting their use as early calendars. Gobekli Tepe, located in modern Turkey is believed to be the oldest permanent human settlement in the world. V-shaped carvings have been discovered at this site, which some archaeologists believe could represent a solar calendar.
Locations such as Newgrange and Stonehenge dating back to around 5,000 years ago demonstrate the understanding people had developed in order to align with the solstices. As incredible as this was, what was going on further east was even more astonishing.
The Egyptians and Sumerians had both derived 12-month lunar calendars. The calendars weren’t perfect, but they were pretty close. The Sumerians had developed a 360-day year, with the Egyptians getting even closer with their 365-day year.
Calendars fall out of sync
The Romans had also been using a 12-month calendar. However, in their version there was only 355 days. Despite the addition of an extra month known as Mercedonius every two or three years, by 46 BC it is estimated that the Roman calendar had drifted by 90 days.
To rectify the situation, Julius Caesar turned to his adviser, Sosigenes. The Greek philosopher and astronomer devised a plan to bring the civic calendar back into line with the sun. By adding in two additional months, as well as a Mercedonius month, 46 BC would have 445 days spread across 15 months. The longest year in history would become known as ‘The Year of Confusion’.
Despite future calendar years being made up of 365 days and a leap year in every four, by the 15th century the calendar had once again drifted by 10 days.
Recognising that the Julian Calendar was working off the premise that the Earth rotated around the sun every 365.25 days, Aloysius Lilius derived a system whereby the calendar would be based off a 365.24219-day year. Instead of a leap year every four years (100 in every 400 years), there would now be 97.
He also proposed skipping the leap year for the next 40 years, to gain back the 10 days.
Lunario Novo by Aloysius Lilius. Image: Biblioteca del Vaticano
Pope Gregory XIII implemented the changes regarding the reduction in leap years, however he chose to gain back the 10 days by simply deleting 10 days from the calendar. Thursday 4 October 1582 was followed by Friday 15 October 1582 and to this day our calendar is known as the Gregorian Calendar.
Advancements in timekeeping
As far back as the sixth century, it is believed that incense clocks were being used in China. Hourglass or sandglass clocks may go back even further, with some believing they may date back as far as the fourth century.
Another timekeeping device known as a water clock had been used in one form or another since the 16th century BC. But in 1088 AD, Su Song, the Chinese engineer would take the concept to a whole new level. He built a 12-metre high hydro-mechanical astronomical clock tower, using gears and automation in a manner which would not be seen in Europe for hundreds of years.
Throughout the 14th century, the rate of advancements in the field of timekeeping exploded in Europe. In 1336, the first clock believed to strike on the hour using a verge and foliot escapement mechanism was recorded in Milan.
Then in 1371, Henri de Vic constructed and installed a clock in the tower of Charles V’s palace in France. The oldest public clock in Paris, still present today, would set the basis for all advances in timekeeping over the next 300 years.
The 24-hour system and division into 60 minutes had been established by the Babylonians and Egyptians long ago. But through the introduction of modern mechanical clocks, time was now becoming a part of everyone’s lives.
The scientific revolution
In the late 15th century Leonardo da Vinci is believed to have produced the earliest known drawing of a pendulum.
Then, almost a century later Galileo discovered that the regular swing of a pendulum was only dependent on length and not weight. This discovery would lead to the creation of the pulsilogium, a device capable of accurately measuring a person’s pulse. In time Galileo would realise that regular motion could be used to measure time accurately, ultimately paving the way for the scientific measurement of time.
Although Galileo did start to build a pendulum clock, it would never be completed. Inspired by Galileo’s work, Christiaan Huygens, the Dutch physicist would in 1656 patent the first pendulum clock. His invention improved the accuracy of timekeeping devices from 15 minutes per day to within 10-15 seconds per day, making it possible to now include minute and second hands on domestic clocks.
Horologium Oscillatorium by Christian Huygens (1673). Image: Smithsonian Libraries
Great minds change time
In 1687 when Isaac Newton published ‘The Principals of Natural Philosophy’, he changed how we defined time by developing the Theory of Absolute Time. Newton thought of time as something which passes regardless of what is happening in the world. This was in contrast to the previously held view where time could not pass without change occurring somewhere.
However, when Einstein introduced the Special Theory of Relativity in 1905 it would challenge the view that time was absolute. Instead he proposed that the closer an object gets to travelling at the speed of light, the more time slows down and the shorter an object becomes. By 1915, Einstein would advance his theory to include gravity in general relativity.
The theory of relativity changed the world, allowing for modern technology such as GPS navigation. It has also given a theoretical basis for which time travel may be possible, although not as it would appear in science fiction movies.
Stephen Hawking’s Time Travellers Invitation. Image: Science and Industry Museum, Manchester
Although Einstein’s theories have to date stood up to all scrutiny, physicists have been unable to satisfy both general relativity and quantum mechanics (behaviour of atoms and subatomic particles) in one theory. This has led to some physicists asking whether time is real or simply an illusion?
But for now, the next time you look down at your wristwatch or check your phone, take a moment and consider that the first steps on this incredible journey may have started with our ancestors looking up to the sky and asking: “Why?”
By Eoin Murphy
Eoin Murphy is a teacher and science communicator. He is on the board of the Mary Mulvihill Association, which is hosting its annual awards ceremony and Science@Culture talk on Wednesday, 20 May. Tickets are free but extremely limited.
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