The sundial, one of the oldest known timekeeping devices, is believed to have been invented by the ancient Egyptians around 1500 BC. However, the concept of using a shadow to indicate time was independently developed by various cultures over the centuries.
In its early form, the sundial comprised a stick, known as a gnomon, that cast a shadow on a flat surface marked with lines denoting hours of the day. The position of the shadow would change as the sun moved across the sky, allowing people to tell the time based on the length and angle of the shadow.
While the Egyptians were pioneers in sundial technology, the Greeks and Romans further refined and popularized the device. Notably, the Greek philosopher Anaxagoras (c. 500–428 BC) made significant contributions to the understanding of sundials and their functioning. Thus, while the sundial has a rich history with many contributors, its origins can primarily be traced back to ancient Egypt.