JamesCronen.com

I’ve been wrapping up some selected bits of gravitation with some students. I do gravitation right before Christmas break, and any student that was out of class for significant time before the holiday needs to work on this material now.

I got into a discussion about the solar system with a student and a fellow faculty member yesterday, and I used Pluto as an example of a planet with a large orbital period (time to go around the Sun).

At the mere mention of Pluto I was greeted with two sad faces. “Poor Pluto,” they said.

I replied, “But nothing’s different! Pluto is still there! We just know more about it now!”

Pluto is still there. It’s still going around the Sun. Its orbit didn’t change, its characteristics didn’t change, its three moons didn’t change, nothing changed. Scientists sitting in a meeting can’t modify the objects in the solar system on a whim.

For the entire first half of the nineteenth century, astronomers classified four asteroids (1 Ceres, 2 Pallas, 3 Juno, and 4 Vesta) as planets too. Discovered between 1801 and 1807, they became visible to us as our observational tools (i.e., telescopes) improved. If we had lived in the early nineteenth century, Many Very Educated Men Could Prove Just Visible Junk Shines Uniformly.

But all this changed on December 8, 1845, when K. L. Hencke discovered 5 Astraea. A fifth asteroid? Who would have thought! By the end of 1850, a total of 13 asteroids were known. By the end of 1860, there were 62 known. By the end of 1870, 112. Currently there are more than 173,000 identified asteroids, most within the designated asteroid belt. There are also more out there — as our tools allow us to see more clearly, we learn more about what is around us.

The anatomy teacher listening to our exchange replied, “But I want to know everything. I can’t stand it when we don’t know something.”

What makes science great is that we don’t know.

Our classifications and groupings of things and ideas needs to change as we continue to observe. This makes many people uncomfortable, students and teachers.

Science is a process, not a body of knowledge. We discover new things by looking at everything we can see, and finding the connections between new observations and old. Sometimes we need to change our classifications as a result of new information. It happened to Pluto and Ceres and will happen to other objects.

I want to know everything, but the moment we know everything, science will be over. What’s more exciting, watching an exciting game or the game’s highlight reel two weeks later?

Never one to be shy of surreal performance art projects, I was intrigued to hear about the Geostationary Banana Over Texas project. From the site:

“[The] Geostationary Banana Over Texas is an art intervention that involves placing a gigantic banana over the Texas sky. This object will float between the high atmosphere and Earth’s low orbit, being visible only from the state of Texas and its surroundings… [I]t will stay up for approximately one month.”

Geostationary? Between high atmosphere and Earth’s low orbit? Interesting. But it can’t be.

Don’t be misled by “stationary”; an object in geostationary orbit is not at rest. The satellite still revolves around the Earth, but the altitude of the orbit is calculated so as to make the duration of the orbit the exact same as the time it takes the Earth to rotate once. From our point of view, the satellite appears to stay in the same place in the sky; in actuality, it’s just rotating at the same speed we are.

The math for calculating the altitude of a geostationary orbit really isn’t that hard; use Kepler’s third law to find the orbital radius of the satellite. Geostationary satellites should be at an altitude of about 35,786 kilometers (22,240 miles) in order to maintain their orbits. Additionally, they need to be located over the equator.

Communications satellites are a perfect application of satellites with geostationary orbits. Your television satellite dish needs to be able to find the satellite in the sky. If the satellite appeared to move with respect to your point of view (as the Sun moves through the sky, for example) you’d need to constantly move your satellite dish to maintain a line-of-sight between it and the satellite. Additionally, your television would be useless for that half of the time in which the satellite was on the other side of the Earth!

Doing a little more research uncovers that the giant floating tropical fruit is indeed not a geostationary one, but will be a giant airship that flies around the state of Texas.

Airships, no matter what their shape, aren’t at all new. The golden age of the dirigible (what we would today call a blimp) ran from about 1900 until the high-profile Hindenburg disaster in 1937. By that time travel by airplane was ready for prime time, and since planes were much faster than dirigibles, there was little reason to continue using the lighter-than-air flying crafts for travel.

Geostationary or not, if this project happens to become the top banana, I’d love to see it in action. Perhaps the project could seek sponsorship from Chiquita?