Anaxagoras was a thinker and philosopher who lived in Greece around 400 BC. Being interested in finding out as much as he could about the natural world, he came up with a few theories about the relationship of the Sun and the Earth.
He appreciated that the Sun must be at some distance from the Earth, and he reckoned that it was probably a fiery metal ball. However, when it came to estimating its size he was slightly out when he wrote that it must be a bit bigger than the Peloponnese peninsula of southern Greece. This would give it a diameter of around 150 miles!
Even though we know that Anaxagoras was hopelessly wrong in his estimate (Planet Earth would fit into the Sun’s diameter 109 times!), at least he made the attempt to describe a physical phenomenon based on observations rather than relying on myth.
However, this did not do him any good, because his views ran counter to those of the religious authorities who maintained that the sun was a god (Helios) who drove a fiery chariot across the sky during the day and then cut through the ocean under the Earth at night so as to be in position to do the same the next day. For stating his heretical views Anaxagoras received death threats and was eventually driven out of Athens.