Monday, March 05, 2007

Even astronomers can make a mistake

I think most scientists would agree that we are not infallible. Every scientist makes mistakes, sometimes big, sometimes small. Today I want to point out a small mistake, mainly because it shows how science (and astronomy) can change and because it highlights new avenues of research.

The mis-statement was made by Robert Massey, a British astronomer and member of Britain's Royal Astronomical Society. In an article on, Massey says, "It's not an event that has any scientific value, but it's something everybody can enjoy."

Until the past few years, this statement was mostly true. Total lunar eclipses had very little scientific value, beyond trying to study how much dust was in Earth's atmosphere (based on how faint the moon became). But as astronomers are beginning to study planets around other stars, we are learning that total lunar eclipses do have some scientific value.

One way we can study planets around is to look at planets that pass in front of their parent stars as seen from the Earth. The planet will block out some of the star's light, and, if the planet has an atmosphere, some of the star's light will make it to Earth after passing through the planet's atmosphere. I talked about this science a week ago.

Now, suppose we want to learn about these planets -- what gases are in their atmospheres, and if they may harbor life. Can we tell this from the light passing through their atmospheres?

During a total lunar eclipse, the only light reaching the moon is sunlight that is refracted through Earth's atmosphere. This is almost exactly the same situation that we have when studying planets around other stars! We know what the sunlight looks like before it goes through Earth's atmosphere, so if we compare the spectrum of the light reflected by the moon during a total lunar eclipse, we know that the differences are caused by Earth's atmosphere. Even more, we know what the composition of Earth's atmosphere is, and we even know the weather (clouds) at the edges of the Earth during the eclipse. If we can manage to back out what we know about the Earth from the eclipsed moonlight, then we can use similar techniques on other worlds around other stars.

I do not know if any such research was done during this total lunar eclipse. The western hemisphere observatories didn't get a good look at the eclipse, though several world-class observatories in the eastern hemisphere could have.

So, you see, what used to be a non-scientific event now has scientific value again. This is the way science goes -- things that are interesting become boring, and things that are boring become interesting again. It all depends on what types of research people are focusing on, and what questions can be answered by a certain experiment.

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