If it were not for the planets, where would civilization be today? For one, I doubt I would have this computer, and the electricity to power it. The people of this alternative 21st century would be waiting at least several hundred years more for those amenities.
The classical planets of the Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn are the exceptions in the sky. (And did you just notice that there are seven of them? Think of the days of the week.) There are clouds too, but for our ancestors those were easy to explain as both the chores and whims of the gods. The stars are fixed, as far as the unaided can see. But those crazy planets break the rules, making the geocentric universe difficult to explain.
(Uranus was out there too, but likely went unnoticed until Sir William Herschel came along as nothing but an insignificant, dim star, moving too slowly for anyone to appreciate.)
The Sun and Moon are fairly easy as well. Though they wobble in the sky throughout the year, nothing is perfect, right? The point being their motions are very easy to predict, day after day, month after month, and year after year.
Then there are the visible planets, the real planets of Mercury, Venus, Mars, Jupiter, and Saturn. If not for these, there may never have been any questioning of the order of our solar system, or our place in it. Scientific advancements took off, in the context of the arc of history, once people accepted that the Earth revolved around the Sun. For if we did not have these planetary exceptions in the sky, would there ever have been the intellectual curiosity to question?
The planets, unlike the “fixed” stars, offer these problems to explaining the geocentric model (i.e. Earth being at the center of the universe):
- There is a difference in behaviors between the two inner planets and the three outer planets. Whereas Mars, Jupiter, and Saturn at least appear follow the elliptic path of the Sun, Venus and Mercury are constantly zigging and zagging in proximity to the Sun. Mercury quickly bounces from dusk to dawn. Venus sometimes climbs really high in the sky, yet also falls back into Mercury-like behavior.
- The planets speed up and slow down.
- Sometimes, the planets start moving in the opposite direction of everything else (retrograde motion).
- Mars is a very curious case by itself, since at times it will shine as brightly as Venus and at others be dimmer than Saturn.
Copernicus was the first to publish the notion that the planets revolve around the Sun. Later, Kepler devised his laws of planetary motion, which explain all of the conditions listed above. Still later, Newton came long, basing his general laws of gravity and motion on Kepler’s earlier work (and Kepler’s laws turned out to be a special case of Newton’s general gravitational laws). Newton’s work in this and related areas was the genesis of our modern scientific knowledge.
If there were no planets, there would have been no questioning of the Earth’s status relative to the Sun. If that questioning never happened, we would have never had a true reference as to our place in the universe, making fundamental questions on physics difficult to comprehend. I don’t doubt that eventually we would have come around to figuring these things out, only that it would have taken far longer if not for the guidance of the planets.
So here’s to you, Mercury, for your quickness.
Here’s to you, Venus, for your brightness.
Here’s to you, Sun, for keeping the lights on when we need them.
Here’s to you, Moon, for all of your cool phases.
Here’s to you, Mars, for being the most famous red beacon in the sky.
Here’s to you, Jupiter, for your steadfastness.
And here’s to you, Saturn, for the delight you reveal through our telescopes.