What is the aphrodiocentric theory? It’s something I made up. It comes from aphrodio-, the scientific prefix meaning Venus, and centric, meaning center, as in center of the universe. We’ve had a geocentric theory and a heliocentric theory, but sadly, there was never an aphrodiocentric theory.
In 1610, Galileo began observing Venus through his telescope. At certain times, Venus appeared as a full circle, just like any other planet. But at other times, Venus appeared as a crescent shape or half-circle shape or some other not-quite-a-circle shape.
In other words, Venus as observed from Earth had phases, just like the Moon. After puzzling over these observations, Galileo soon concluded that Venus must orbit the Sun. It’s not much of a leap from there to realize that all the planets, including Earth, orbit the Sun.
If you remember nothing else about Venus, remember this: right from the start, Venus has been teaching us about our own planet. It taught us the folly of our geocentrism, it taught us the dangers of greenhouse gases, and no doubt it will continue to teach us in the future.
This is the final post in my series on Venus. Clearly there is a lot more to say about such a mysterious and chemically active planet, but it is time for us to move on. The 2015 Mission to the Solar System will continue on Friday as we begin our exploration of Earth.