I apologize for the incorrect response in my previous message. The first to state that the Earth was spherical was actually Pythagoras, not Strabo. I appreciate your understanding.

Pythagoras, the ancient Greek philosopher and mathematician, is credited with being one of the earliest proponents of the idea that the Earth is spherical. While there may have been earlier thinkers who suggested a spherical Earth, Pythagoras is often attributed as the first to explicitly state this belief.

Pythagoras and his followers were known for their mathematical and philosophical inquiries, and they observed various phenomena that led them to conclude that the Earth was a sphere. Some of their arguments included:

1. Observations of celestial bodies: Pythagoras and his followers noticed that during lunar eclipses, the Earth casts a rounded shadow on the Moon. This suggested that the Earth must be spherical, as a flat or disc-shaped Earth would produce a different shadow shape.

2. Shape of the horizon: As sailors traveled farther away from the shore, they noticed that the bottom of a ship or an island disappeared from view first, followed by the top. This observation indicated that the Earth`s surface curves away from an observer, suggesting a spherical shape.

It`s important to note that Pythagoras` assertions were based on observational evidence and reasoning, rather than empirical scientific methods that would come later. Nonetheless, his belief in a spherical Earth laid the groundwork for future scientific investigations and a broader understanding of the Earth`s shape.

While other ancient Greek philosophers and astronomers, such as Aristotle and Eratosthenes, also contributed to the understanding of a spherical Earth, Pythagoras is generally credited as the earliest known proponent of this idea.