Callippus facts for kids

Callippus (pronounced Kah-LIP-pus) was an important ancient Greek astronomer and mathematician. He lived around 370 BC to 300 BC. He is known for improving how people understood the movements of planets and for creating a special calendar cycle.

A Smart Student and Teacher

Callippus was born in a place called Cyzicus. He studied with famous thinkers like Eudoxus of Cnidus and Plato at a school called the Academy. Later, he also worked with Aristotle at the Lyceum in Athens. This means he was active in Athens before 322 BC, when Aristotle passed away.

Understanding the Stars and Planets

Callippus spent a lot of time watching how the planets moved. He tried to use Eudoxus's idea of "connected spheres" to explain these movements. Imagine planets attached to invisible, clear spheres that spin around Earth.

Eudoxus thought 27 spheres were enough. But Callippus noticed this wasn't quite right. He found that 27 spheres could not fully explain how the planets moved. So, he added seven more spheres, making a total of 34. He added two spheres for the Sun, two for the Moon, and one each for Mercury, Venus, and Mars. This helped to better explain their paths in the sky.

Measuring Time and Seasons

Callippus also carefully measured the length of the seasons. He found that the seasons had slightly different lengths. Starting from the spring equinox (when day and night are equal), he measured them as:

• 94 days for spring
• 92 days for summer
• 89 days for autumn
• 90 days for winter

These different lengths showed that the Sun's apparent speed in the sky changes throughout the year. This change is sometimes called the "solar anomaly."

He also continued the work of Meton of Athens to measure the length of the year. This helped to create an accurate lunisolar calendar. A lunisolar calendar tries to keep track of both the Moon's phases and the Sun's position.

The Callippic Cycle

The Metonic cycle was a 19-year period. It had 19 tropical years (the time it takes for the Sun to return to the same position in the sky) and 235 synodic months (the time from one new moon to the next). This cycle lasted 6940 days.

Callippus improved this by creating the Callippic cycle. This cycle was 76 years long. It was equal to four Metonic cycles, but with one day removed. This made the calendar even more accurate over a longer period.

Callippus began his observation cycle on the summer solstice in 330 BC. This date was used by later astronomers to line up their own observations.

Lasting Legacy

The 76-year Callippic cycle appears to have been used in the Antikythera mechanism. This was an amazing ancient Greek device, like a complex mechanical computer, used to predict astronomical events. It was found in the sea off Greece. The mechanism even has a dial for the Callippic cycle.

Today, there is a crater on the Moon named Calippus in his honor.

See also

In Spanish: Calipo de Cícico para niños