March 24, 2009

What's In A Name?

The other night Pete and I watched a wonderfully entertaining program on CSpan. It featured a talk by Neil deGrasse Tyson who was talking about his newest book, The Pluto Files. The auditorium at the American Museum of Natural History was packed with people of all ages. The questions at the end of the talk were terrific and it made me feel good to see so many people enamored with the Cosmos. I have been thinking about what I learned from watching the program ever since.

Tonight, Mike called me while driving home from work. I love it that he calls me. After catching up, I mentioned something regarding the talk given by Tyson and how much I loved it. Mike replied that I was speaking about his nemesis. I was surprised to learn that he was still sticking to his stance on the whether Pluto is a Planet controversy.

All this time, I thought that the great video he made while wearing a Sandwich Board sign saying “Pluto Is A Planet” was made as an adventure in humor, not an actual protest. It looks like I didn't understand after all. He is sticking to the position that Pluto is a Planet. If we stuck with the old definition, the number of planets that orbit our Sun would be considerably larger than we thought it was when we counted Pluto as the planet furthest from our sun. Apparently there are lots and lots of 'dwarf planets' in the Kuiper Belt where Pluto resides. Maybe that isn't a bad thing. The more the merrier.

The old definition of what makes a planet a planet was: a planet is anything that orbits a star, doesn’t fuse elements in its core and has enough internal gravity to be nearly round.

The new definiton accepted by the IAU is: "A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet, and (c) has "cleared the neighborhood" around its orbit.."

Tyson argues that we need to define more terms to distinguish between the differing heavenly bodies. For instance, Pluto and its moon, Charon, orbit one another; and interestingly, the axis of their orbit is in the space in between them. He suggests that this double planet group should have it’s own classification. I guess what he is saying is that we shouldn't be comparing chalk to cheese. I guess I am satisfied with Tyson's explanation, and at least for now, I'm OK with the new definition.

Everything is changing all the time. The speed of change seems to be increasing at an astonishing pace. There is always more to learn. We truly live in an amazing age.

Posted by Judi at March 24, 2009 10:01 PM | TrackBack
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