The Changing Phases of Venus

sky, of course.

One of the other celestial sights Galileo can now be seen low in the western sky shortly after sunset. You’ve almost certainly noticed it there glistening in the waning light of dusk -- the brightest of all planets -- Venus.

Venus shines so brilliantly because it’s a world the size of Earth that now lies less than 70 million miles away. In addition, the planet is shrouded by thick white clouds that reflect into space more than two-thirds of all sunlight that falls on them.

What makes Venus particularly interesting right now is exactly what Galileo found four centuries ago. The planet appears through a telescope not as a round disk but in a quarter phase -- not unlike our moon every few weeks. By July 8, Venus will have approached to about 41 million miles and will appear through a telescope as a thick crescent. And by the end of July, it will lie less than 30 million miles from us and appear as a thin crescent that you might even see in binoculars!

While this may not seem like an epic discovery in today’s fast-paced, hightech world, it was this simple observation that led Galileo to conclude that the phases of Venus could not happen if the planet were orbiting the Earth as both the great Aristotle and the Catholic Church had long taught. No, the only way its phases could appear as they did was if Venus circled the sun!

In other words, our world was not the center of the universe as had long been believed. And this ultimately helped to change forever how we view ourselves and our place in the universe.

If you don’t have a telescope of your own, go online and search for an amateur astronomy club in your area.