Humans have been predicting eclipses for thousands of years, but it's harder than you might think

• But it turns out calculating exactly when and where we can watch an eclipse in its full glory can be surprisingly hard.
• Read more:
  Since the late 19th century, adventurous female 'eclipse chasers' have contributed to science in Australia

Watching the Sun and the Moon

• Being so dominant in the sky, the Sun and the Moon were the most captivating celestial bodies for ancient cultures to observe.
• While the Sun’s movement is quite simple, the Moon moves across the sky with much more complexity.
• During a lunar eclipse, where Earth blocks sunlight that would otherwise illuminate a full moon, the dimmed Moon takes on a bloody hue.

The not-so-mythical Saros cycle

• This 18-year cycle, which can persist as a sequence for over a thousand years, is now known as a Saros cycle.
• The Saros cycle represents how long it takes for the Sun-Earth-Moon system to return to almost exactly the same triangular configuration.
• This is much more frequent than an 18-year Saros cycle, and is possible because multiple repeating Saros sequences overlap at once (roughly a dozen), each offset by at least six months.
• After about a thousand years, when one long-term Saros sequence ends, another will begin with slightly different timing.

From antiquity to modern day

• Yes, if we are talking about lunar eclipses, and perhaps even partial solar eclipses.
• That is, they wouldn’t have predicted that 18 years later (567 BCE) a total solar eclipse was visible in what is now the United States.
• But significantly, it could not predict total solar eclipses at a precise place on Earth – just their timing.
• Entering the modern era of science, the first true prediction of a total solar eclipse (both in time and location) occurred in 1715.