MELISSA BLOCK, host:

The wildfire has endangered a historic observatory. For more than 100 years, the Mount Wilson Observatory has been a hub for astronomers and astrophysicists. The site has been evacuated and shut down because of the fire. Images broadcast from a camera attached to a 150 foot tower over the observatory show a thick yellowish grey smoke enveloping the mountain. But according to an observatory blog, things are looking more promising than they have in the last few days. Hal McAlister has been updating that blog. He's director of the Mount Wilson Observatory. He's also professor of astronomy at Georgia State University and he joins us from Atlanta. Professor McAlister, welcome to the program.

Professor HAL MCALISTER (Director, Mount Wilson Observatory): Thank you very much. Pleased to be here.

BLOCK: And it must be a tough thing for you. You go back and forth, but right now you're there in Atlanta. It's got to be hard to be following this from across the country. What are you hearing?

Prof. MCALISTER: Well, it is hard. Although with the Internet and telephone and so forth, I'm really as well poised to hear things here as I would be in LA since I can't be on the mountain.

BLOCK: Mm-hmm.

Prof. MCALISTER: But this - as the blog has shown, it's been kind of a roller coaster ride. The latest news is actually quite encouraging. Yesterday morning, about sunrise, the firefighters were pulled off Mount Wilson because of the danger of their being trapped back on the observatory grounds. But then this morning, they were redeployed about 9:40. We learned that the firefighters were once again back on the ground and that's terrific news. They've been working very hard for the last 48 hours, further reducing brush and fuel for the fire and we have, for the last few years, been working hard mitigate fire danger from trees and oaks clusters and things like that. So we think the place is in good shape.

BLOCK: What are the water resources up there?

Prof. MCALISTER: We have a firefighting system up there that includes a half million gallon of water tank. That's also can be supplemented by our potable water tank, that's another quarter million gallons. And that's fed into a high pressure fire hose system that feeds hydrants around the observatory grounds.

BLOCK: Has the Mount Wilson Observatory have been threatened by fire before?

Prof. MCALISTER: You know, every year we go through white-knuckle time with the fire season in southern California and we've been lucky until this year. There was an episode back in the '70s where fire reached within a mile of the observatory, but that was beaten back by firefighters.

BLOCK: Well, the observatory goes all the way back to 1904. Why don't you tell us about some of the breakthrough discoveries that have been made there?

Prof. MCALISTER: Certainly. Mount Wilson was founded by a remarkable man named George Ellery Hale who was responsible for, successively, the world's four largest telescopes culminating with the Mount Palomar 200 inch telescope that opened in 1949. The telescopes and facilities he built on Mount Wilson were for 40 years, the most powerful, most sophisticated in the world, the largest. And he assembled an extraordinary talented staff including luminaries such as Edwin Hubble whose name is known to most people, the namesake of the Hubble space telescope.

BLOCK: Sure.

Prof. MCALISTER: Hubble of course found that the universe was vaster than we had ever imagined before, that it's expanding. And his work inspired the big bang theory for the origin of the universe.

BLOCK: And that all stems from Mount Wilson.

Prof. MCALISTER: That stems from work that originally which started at the Lowell Observatory but Mount Wilson's larger telescopes were able to take it to four fruition to really define how fast the universe is expanding and really how old it is.

BLOCK: You know, I would think with the lights of LA County all around you that that would be a pretty tough spot to try to be doing astronomical work there.

Prof. MCALISTER: Well, it is. If you're interested in looking at the faintest objects in the universe, you've got to go elsewhere. But Mount Wilson remains a superb site for astronomy because of its proximity to the Pacific Ocean. You can imagine the Pacific can cool down air coming across it. It stabilizes and flows very smoothly over the mountains and the San Gabriels are the first mountains to encounter it. And it produces really steady star images, and its among the best in the world in fact in that regard.

BLOCK: And right now, at least as far as you can tell, the observatory seems at least safer than it did maybe a day or two ago.

Prof. MCALISTER: I feel a lot better now than I did yesterday at this time. That's for sure.

BLOCK: Well, Hal McAlister, thanks for talking to us.

Prof. MCALISTER: Glad to. Thank you for your interest.

BLOCK Hal McAlister is the director of the Mount Wilson Observatory. He joined us from Atlanta. And you can find a link to his blog at the NPR blog The Two-Way. Transcript provided by NPR, Copyright NPR.

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