Aristarchos of Samos calculated the Earth's circumference very well, and realized that the Earth must revolve around the Sun. Nobody liked this, so we had to wait 1700 years for Nicolaus Copernicus (1473–1543) to once more put forth the idea in the public sphere.

It has been said that Cleanthes (a Stoic) considered Aristarchos a dangerous enemy, (perhaps due to the 'providence or atoms' issue?)

One of the earliest recorded woman mathematicians, working in philosophy and astronomy. Renowned in her own lifetime as a great teacher and counselor.

She wrote a commentary on Diophantus's thirteen-volume Arithmetica, which may survive in part, having been interpolated into Diophantus's original text, and another commentary on Apollonius of Perga's treatise on conic sections, which has not survived. Many modern scholars also believe that Hypatia may have edited the surviving text of Ptolemy's Almagest, based on the title of her father Theon's commentary on Book III of the Almagest.

Hypatia's murder [by a Christian mob] shocked the Eastern Roman Empire and transformed her into a "martyr for philosophy" […] During the Age of Enlightenment, she became a symbol of opposition to Catholicism.

Lived in a barrel in the Athens marketplace. Famous for stunts such as carrying an oil lamp in daylight, saying "I'm looking for an honest man". Once, Alexander the Great, the king that had conquered the known world, visited Diogenes and asked if there was anything he could do for him. To which Diogenes replied "For the present, that you stand a little out of my sun".

Took lots of precise stellar measurements in a purpose-built observatory – by eye, before telescopes were invented!

Tycho wanted to combine what he saw as the geometrical benefits of Copernican heliocentrism with the philosophical benefits of the old Ptolemaic system into his own model of the universe.

His precise measurements indicated that "new stars" (stellae novae, now called supernovae), in particular that of 1572 (SN 1572), lacked the parallax expected in sublunar phenomena and were therefore not tail-less comets in the atmosphere, as previously believed, but were above the atmosphere and beyond the Moon. Using similar measurements, he showed that comets were also not atmospheric phenomena, as previously thought, and must pass through the supposedly immutable celestial spheres.