May 07, 2012

The changing solar system

I read a minor rant one time by Larry Niven, that went something like this: "How the hell are we supposed to write SF about the Solar System when you astronomers keep changing everything?"

I think it was a comment about his story "The Coldest Place", which assumed that Mercury was tide locked, and its dark side was eternally dark and very cold. It actually turns out that Mercury is tide-locked, but it's in a 3:2 resonance. Basically, a Mercury day is 1.5 Mercury years long. But it means that all parts of the surface are exposed to the sun about half the time.

I'm rereading Heinlein's novel "Space Cadet", which is subject to a bit of that. I just encountered a scene where Pete, from Ganymede, mentions that the surface gravity there is 32% of Earth. And it occurred to me that this might have been subject to revision.

I was right. The current estimate is that the surface gravity is 14.6%. The earlier estimate was based on guesses about the moon's internal composition, which assumed it was about like Earth: rock and metal. We now know that there's a hundreds-of-miles-thick layer of ice, which is a lot less dense.

The mass of Ganymede was calculated based on how it affected Galileo's flybys, so it's very accurate. The earlier number was little better than an educated guess.

The last third or so of this book is where things really changed the most, though. It was written back when the orthodoxy (at least in SF) was that the surface of Venus was a jungle. Of course we now know it ain't so. The surface of Venus is the closest approximation in the Solar System of traditional Hell. There is no life on Venus and there never will be. The temperature on the surface of Venus is hot enough to melt lead.

None of which takes away from enjoying the story, of course. But it's interesting to think about just how much the Solar System has changed during my lifetime -- or at least, how much our conception of it has changed.

When I was a kid, there were nine planets. Now there are only eight.

UPDATE: They changed things on me again. Now the orthodoxy is that Mercury's day is two Mercury years.

Posted by: Steven Den Beste in Weird World at 05:59 PM | Comments (9) | Add Comment
Post contains 387 words, total size 2 kb.

1 I write science fiction.   I have a pretty elaborate "universe" set up, too.

...I'm just waiting for Kepler to discover planets in the "wrong" places around nearby stars....

Posted by: atomic_fungus at May 07, 2012 06:23 PM (E1y9u)

2 What would you consider to be wrong? The planetary search so far has found planets in all kinds of strange orbits, like planets larger than Jupiter in orbits closer than Mercury.

Posted by: Steven Den Beste at May 07, 2012 07:22 PM (+rSRq)

3 So clearly the inhabitants of Mercury are nomadic, taking two years to migrate around the planet.

Posted by: Mauser at May 08, 2012 12:01 AM (cZPoz)

4 Including gas giants in the blue zone, IIRC, one of the more friendly configurations for sci-fi writing.

As for Venus, writers haven't totally written it off.  There's still the potential for extremophiles and/or high altitude microorganisms.  Certainly you aren't going to find jungles and natives, though.

Posted by: metaphysician at May 08, 2012 05:26 AM (3GCAl)

5 Apparently, at about 50 km above Venus' surface, the environment is the "most Earthlike in the solar system" (whatever that means).  And because the atmosphere is very dense, breathable air will rise, giving rise to lots of absurd speculation about floating cities on Venus.  There's even an article on wikipedia: http://en.wikipedia.org/wiki/Floating_city_%28science_fiction%29#Venus

The notion of living there would still be pretty terrifying. 

Posted by: Mark at May 08, 2012 06:26 AM (aUPJJ)

6 "Wrong" would be anything that invalidates my setting.  Meaning, "wrong for me".

Okay, if I say--in my story--that Gliese 691 has an Earthlike planet just close enough that it gives it kind of a cool and drizzly climate, and Kepler finds one of those superhot superjovian planets less than 50,000,000 miles from the star and nothing else:  that's an example of finding a planet in the "wrong" place.

And it'd be an example of astronomers invalidating SF with an ugly reality....

Worse, if they go ahead and discover that none of the close-by (within 60 light years) G- and F-class stars have Earthlike planets?  Then I'm really screwed,  because I either have to totally change the colonial expansion of Man into the stars, or else ignore the latest science and say, "I don't care!  There's an Earthlike world orbiting Pollux!"

(I do admit that I lean towards the latter.  "Never let the facts get in the way of good fiction!")

Posted by: atomic_fungus at May 08, 2012 06:42 AM (E1y9u)

7 So things like "Tau Ceti seems to have a large disc of dust and rocks, but there is no evidence yet that there are any planets." Right?

Posted by: Steven Den Beste at May 08, 2012 07:37 AM (+rSRq)

8

I think it is time for the MST3K mantra or variation thereof, to be applied to science-fiction.  Or a load of handwavium.  Though even those two are not enough to fix Joss Whedon's efforts.

C.T.

Posted by: cxt217 at May 08, 2012 12:05 PM (QzVZ+)

9 Yes, exactly like that.  *sigh*  There isn't supposed to be a "large disk of dust and rocks" there until after about 2130 AD....

Posted by: atomic_fungus at May 08, 2012 01:09 PM (E1y9u)

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