I just want to reiterate for those who are having trouble finding the cache: NO CLIMBING NEEDED. It's placed in a spot that's just barely reachable without climbing. The second-to-last person who climbed to get this cache, didn't quite put it back where it came from, and I had to pull a Spider-Man myself to get it back where it belongs. Normally, I'm all over climbing things, but you could really hurt yourself badly with a fall from here (not to mention draw a lot of unwanted attention) as the ground beneath you is pure concrete. I don't recommend climbing around here.
It's hard to reach, and you need to find just the right angle for it, but even with short arms like mine, the cache is reachable. (And if your arms are even shorter than mine, then that climb is going to have a really tough spot in the middle of it, so it ain't going to be easier.)
If you DO choose to climb (and really, I don't recommend it), please try to be discreet, and be absolutely certain to put Mercury back exactly where you found it. I don't want to have to go back up there. Once was terrifying enough.
This cache is part of a 1:133,700,000 scale model of the solar system. The dome on the Monroe County Courthouse in downtown Bloomington serves as a model of the sun. Mercury is about 4,880 kilometers in diameter, so this model is roughly 1.44 inches wide. At the low point of its orbit, Mercury is only 4.60 million kilometers from the sun, but its orbit will take it as far as 6.98 million kilometers away. If that seems like a lot of distance to cover, you're right; Mercury has the most eccentric orbit of all the planets (that means it's a squashed ellipse, not a round circle). The cache is about 0.32 miles from the dome, right at that furthest distance.
Since Mercury is closer to the sun than the Earth, it can only be seen in the sky right after sunset or right before sunrise. It took the ancient Greeks awhile to realize that the planet they saw in the morning (which they called "Apollo", after the sun god) was the same as the one they saw in the evening (which they called "Hermes", after the fleet-footed messenger of the gods). Eventually they figured out they were the same and they stuck with "Hermes", and today it's still named after that same god (which the Romans called Mercury).
If you want to get a good idea just how close to the sun Mercury is, head up to the roof of the parking garage and take a look at the Courthouse dome. Imagine the sun was hanging in the sky at that huge size.
When you look at the surface of Mercury, you may notice that some of the larger craters have radiating lines streaking out from their centers, as if the impact had thrown out thin streams of debris in several different directions. Well, they look that way because that's exactly what happened!
The orbit of Mercury wobbles a little bit in a way that is unexpected, even after you take into account the gravitational pull of all the other planets in the solar system. This made the astronomers of the late 19th century think that there might be another planet even closer to the sun. At the time, this seemed like a pretty good bet considering that this was the same kind of reasoning that astronomers had used to guess that there was another planet out past Uranus (Neptune!). They named this hypothetical planet "Vulcan", but it turns out that the real explanation for the wobble was even weirder than Spock's home world: general relativity!
Congratulations to dsuperfan23 on the first-to-find!