Curvature was not known. Aristotle denied the earth to be a plane and the authorities didn’t accept of a theory other than that which placed the earth in the centre of the universe for they stated that the universe revolved around the earth forgetting the major fact that the stars that revolved appeared bigger and smaller at their apogee and perigee relatively, which was brought to evidence during the 16th century after the death of Copernicus through a student of his.
Nicolas Copernicus denied the fact that the earth was flat, not just merely perceiving for a circular orbit with a spherical shape to it but sculptured to naturally occurring references amongst nature.
He reasoned with evidence of the moon having the shadow of a circular nature upon it, the ship that moves away from the shore seems to disappear in the far away vicinity with the hull of the ship disappearing first; confirming to the spherical shape the earth inhabits.
However less fortunate was he that he withheld it from publishing but shared it amongst his circle of friends and got the first published version of the book on his deathbed in 1543. Thus it was Nicolas Copernicus who asserted with evidence unlike the people of his time who asserted to geometry concerning the centre of the earth is the centre of the universe itself, for it was considered anti-divine to place the earth elsewhere from the centre. Nicolas reasoned with the distant stars relative to the earth that the earth revolved around its on the elliptical circle. To demystify the mysteries of the world above and below one has to start from within it and thus came into creation Des révolutions des orbes célestes (On the Revolution of the Celestial Spheres). Thus was laid the foundation to elliptical cycles and the revolutionary evidence that the earth was one of the planets and it like all other planets revolved around the Sun, which was fixed in the centre and the revolution of it gave us a year and the moons’ revolution a month.
Copernicus gave attention to what the container was rather than what is contained in it to understand fully the mysteries of the universe.
Black holes were an unknown phenomenon and so was the galaxies. Theories leapt forward, forgetting the great grandeur of the ancient theories [Plato (427-347 B.C.) visited Italy after the execution of his friend Socrates (470 – 399 B.C. to see Philolaus the Pythagorean who lived in Italy, who had that the earth was perfectly spherical and was amongst one of the planets] that were in place. One became unaware of the foundation and “built the house on sand” to see it die in years to come. As time proceeds one learns that the foundation has to be deciphered in order to build the theory with great efficacy.
Black holes became the theme for movies and universe photography a mere abrupt form of showing the exactitude of the mystery. It is of great help are these sources for it helps in aiding the progress towards the subtlest and highest form of arts as Nicolas Copernicus put it; Astronomy (αστρονομία).