Seleucus of Seleucia

Seleucus of Seleucia was an astronomer and thinker who lived long ago, around 190 BC. He came from a place called Seleucia, which was in a region known as Mesopotamia. Some people think he might have also been from another town with a similar name near the Erythraean Sea.

Seleucus is most famous for supporting the idea that the Sun, not the Earth, was at the center of our solar system. This was a new and exciting idea at the time. He also tried to explain why the oceans have tides, which are the rising and falling of sea levels. His work helped other scientists understand space and Earth better.

Heliocentric theory

Seleucus supported the idea that the Sun was at the center of the universe. This idea was first suggested by Aristarchus of Samos. He was the first to show this idea could work using logic, but we do not know exactly how he did it. Some think he used math to figure out where planets would be, similar to what Nicolaus Copernicus did much later.

People before Seleucus sometimes called Mercury and Venus "solar planets" because they stay close to the Sun. Seleucus also believed the universe was endless. We do not have any of his original writings, but a small piece of his work exists in an Arabic translation.

Tides

Seleucus believed that tides were caused by the Moon. He thought the Moon's pull changed the tides. He also noticed that tides were different in different parts of the world.

Seleucus in Strabo

Seleucus was known by writers like Plutarch, Aetius, and Strabo, who were Greeks, and also by the Persian Muhammad ibn Zakariya al-Razi. Strabo listed Seleucus among the four most important astronomers called "Chaldaeans." In his book Geographia, Strabo said, "Seleukios of Seleukia was a Chaldaean too." The word "Chaldaean" was used for Babylonian astrologers and astronomers. Their work was later translated into Greek and used by other writers, such as Geminos. The other astronomers Strabo mentioned were Kidenas, Naburianos, Sudines, and Seleukos.