This morning, after being woken at 4am by the garbage trucks emptying bins in the street outside, I walked to the back of the apartment and saw a wonderful sight. The clouds had mostly cleared, and in the eastern sky three planets in close conjunction blazed over the city: Venus, Jupiter, and Mars.
The snapshot, taken with a handheld camera, doesn’t in any way capture the scene (indeed, it doesn’t capture Mars, the faintest of the three, at all).
This led me to think. In the ages of geocentric, Ptolemeian astronomy, did no clever person ever wonder about the huge difference between Mercury and Venus (which stay close to the sun) and the other planets (which wander over the whole zodiac)? Of course this can be (and was) explained with epicycles, but conceptually it is so much simpler to have a heliocentric model, with the orbits of Mercury and Venus inside that of the earth.
Also, was there no pre-telescopic astronomer sharp-eyed enough to observe the phases of Venus (a crucial piece of evidence for the heliocentric theory for Galileo, when he saw them through his telescope)?