Nicolaus Copernicus’s On the Revolutions of Heavenly Spheres marked the beginning of a major shift in Western thought. Concepts of perfection and heaven at that time were deeply rooted in the religious political structure that prevailed throughout the Middle Ages and were tied to ideas about the ultimate fate and purpose of human life. The existence of planets alone was no threat to the dogma of the Catholic Church; the Greek origin of “planet” translates literally into “wandering star,” and Earth could still be viewed as the heart of the cosmos through a complicated mathematical scheme for the paths of Mercury, Venus, Mars, Jupiter, and Saturn. But as Copernicus knew, to categorize our own home, Earth, as merely another planet was dangerous, and he cleverly dodged a certain fate by waiting for a posthumous publication of his monumental work. This fate was passed on five years after his death in 1543 to a talented Italian born Filippo Bruno. Bruno’s insistence that the Sun was a star just like all the others, and that there existed other worlds and other intelligent life throughout the universe, caused quite the controversy.
|Bruno lives on as a statue in Rome, at the site of his death.|
So why was the Church so against this idea, given their acceptance of the five other known planets? The idea of a planet as a world is something unique among astronomical objects. Galaxies, black holes, stars; these are all things, but none, except planets, are actually places. The word "world" connotes humanness, or the affairs of life, such that the existence of other worlds would imply that we are not alone. Though this may have been heretical in the eyes of the Church, it is the root of a philosophical fascination with planets. Our ability to comprehend other worlds and to have a glimpse at understanding our place within an immense vastness—our cosmic context—invokes inspiration, connectedness and awe. The flip side of this is that our new perspective puts us in no particularly special place and our individual scope is considerably diminished. We are not the center of the universe. We're not even the center of the solar system! What a blow to the ego of humanity!
We know Bruno was correct in one regard—that there are countless numbers of other planets out in the vastness, circling their respective stars just as we are. But his second principle has not yet been verified: are we the lone settlers of the cosmos? Carl Sagan famously referred to Earth as a "lonely speck," and as such, finding life elsewhere in the universe would be a monumental breakthrough, arguably one of the greatest in human history, wholly redefining our ideas on the meaning of life itself! This discovery would draw the attention of every soul on this planet skyward, and while looking upwards, each would also be compelled to look inwards at himself. "Life as we know it" is a limiting statement in itself; who knows what foreigners may lie beyond our solar system? We are on the hunt to find planets which are more than just objects; we are searching for those that are homes. Twenty years ago, when the first extrasolar planet was confirmed, the door of discovery was flung open wide. Twenty years ago, Bruno rolled over in his grave—figuratively, as his final state was merely a pile of ashes—and triumphantly proclaimed "I told you so!" Now here lies the search for other worlds, stemming back to the 1500's. It is an ongoing investigation, with a colorful history of progressive, and sometimes absurd ideas, but as we pick up steam into the 21st century we press onward, making compelling discoveries into the nature of planets, and by extension, discoveries about ourselves and our own home.