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Alan Alda in Scientific American Frontiers


Photo Latham

Dr. David Latham of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA writes:

"I am an observational astronomer. I like telescopes and tall mountains and staying up all night and seeing the sun rise just before I go to bed. When I was younger I built instruments, but now I am happy to let others do that job. I have worked on observational cosmology, mapping out the distances to nearby galaxies, and I have studied the structure and evolution of our own Milky Way galaxy. Most of my recent work has focussed on stars and their companions, especially low-mass companions such as planets and brown dwarfs. I have participated in some of the exciting discoveries involving extrasolar planets: the first planet candidate (orbiting HD 114762) found with Doppler shifts in 1988, and the first planet to transit its parent star (orbiting HD 209458) found in 2000. Astronomy has been very, very good to me."


For links to this scientist's home page and other related infomation please see our resources page.

Latham responds :

1.03.01 Miguel asked:
I have a very simple question. Aren't we thinking like people thought in the past? After all, we used to think that Europe was the only place in the Galaxy, then we found America. So now we think that there is life in this world only. Aren't we making the same mistake?

Latham's response:
We do not yet have any convincing scientific evidence that there is (or was) life elsewhere in the universe. But, like you, I would be amazed if it turns out that we are alone. This is one of the really big questions, and we are now in an era where we are beginning to have the technological capability to look for some answers.

1.03.01 Juwon Kwon asked:
I wanted to know if do you think that the planets and their civilizations are far more advanced than we are?

Latham's response:
We have no evidence that there is life in any of the planetary systems found so far. If intelligent life has arisen often, then inevitably one of two things must be true: there are many technical civilizations out there now, and the vast majority must have attained our level of technology a long time ago, or else there are very few out there now because technical civilizations destroy themselves before or soon after they reach our level.

1.03.01 Bob Cicalo asked:
Can black holes be detected with the same wobble measurement techniques mentioned in the show? If so, is there a mathematical formula for this?

Latham's response:
Yes, black holes may not radiate any light that we can detect, but they still have gravitational pull. In fact, this is one of the main ways for detecting black holes, by seeing how hard they pull on nearby stars or gas. Newton's theory of gravitation is good enough for describing the motions that result. One formula that is especially useful is Newton's revised version of Kepler's third law, which gives the relationship between the period of the orbit, the size of the orbit, and the masses involved. You should be able to find this formula in an astronomy text book.

1.03.01 Russell M Mott asked:
Could the Earth's magnetic field be generated from salt water -a conductor in motion. Could that be why Earth has a magnetic field and Mars does not?

Latham's response:
I'm not a geologist, but my understanding is that convective motions in the molten inner regions of the earth generate the magnetic field. Mars does not have a molten interior, and thus can not generate a significant magnetic field. The oceans may seem deep, but compared to the radius of the earth they are a very thin layer. I bet it would be hard to generate a large-scale magnetic field with such a thin surface layer.

1.03.01 Fred Metterhausen asked:
On the show they said that the planet found orbiting HD 209458 was much larger, therefore less dense then what was originally calculated. I was just wondering if it was considered that the gravitational field of the planet might make the planet divert more of HD 209458 light then the planet alone, therefor making the planet much smaller?

Latham's response:
The giant planet orbiting HD 209458 is indeed larger and less dense than Jupiter. Astronomers who make theoretical models for giant planets say they have an explanation for this. The planet is so much closer to its parent star that it has not had a chance to cool off, so it has stayed puffed up. In fact, if the planet formed out in the distant icy regions around its star, like Jupiter, and then migrated into its present orbit, it had to do so in the first few million year after it formed, otherwise it would have cooled off too much.


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