> *From:* Carl Brown <catodon@...>

>

> New Scientist ran an article a few years back on orphan worlds. One idea

> was that the lower size limit for lone bodies could be quite low and

> that perhaps there were numerous gas giants even rocky world out there

> on thier own without a star. In my own future history I assume that

> these orphan worlds are quite common. They have thick atmospheres, even

> the rocky worlds retain amonia and hydrogen because there is no sunlight

> to give these light gasses the engergy for escape. The thick atmosphere

> can trap the heat of creation for billions of years so perhaps there is

> life. In my future history one such world spawn an alien civilisation

> for which what humans call visible light is an invisible and deadly

> radiation.



Sam McConnich wrote:



  > interesting there have been times I thought that as well, but the

  > science minded of the group always scoffed



Well, if the conditions really are as you describe, with an atmosphere

that's not frozen, and trapped heat keeping the planet from cooling too

far even after billions of years, then certainly life could evolve.

Clearly it wouldn't be based on sunlight, but then there are ecosystems

on the Earth that aren't, such as the ecosystems around the undersea

"smokers", or volcanic vents, which have at the bottom of the ecosystem

bacteria which metabolize high-energy sulfur compounds.



Now, it seems to me that over the course of billions of years, these

planets would be slowly cooling, so life may or may not have time to

evolve to a complexity sufficient for us to believe it could reach

intelligence.  But I can see a justification for having at least one

such civilization.  Heck, Niven made a space-traveling critter with a

metabolism run by a nuclear reaction-- the Starseeds!  Compared to that,

your "orphan world" civilization doesn't seem so unlikely.



Niven also has the Helium II critters on frozen, airless worlds, as

described in "The Coldest Place" and "Flatlander" (short story, not

collection).  But I wouldn't try to justify this sort of critter

developing a civilization; with the temperature so close to absolute

zero, there isn't any realistic energy source available to power their

industrial processes.



~~~~~~~~~~~~

Clear ether!

Lensman



Visit the Incompleat Known Space Concordance at:

http://www.freewebs.com/knownspace/

Sam McConnich wrote:



> depending on how the planet originally formed and from what,could

> radioactives within the planet contribute to maintaining heat



I think any sufficiently large terrestrial (rocky) planet will have

radioactives helping keep it warm.  Mars isn't large enough, it's cooled

off too much.  Earth is large enough; Venus may be.



The process by which *all* elements heavier than oxygen are formed, in

supernovae, will be the same everywhere.  The dust out of which planets

are formed all comes from supernovae explosions, which will all produce

the heavier elements.  I can think of no reason why the percentage of

radioactives in the dust should vary much from star to star, so we have

no good reason to believe the Earth is especially high in its percentage

of radioactives.



~~~~~~~~~~~~

Clear ether!

Lensman



Visit the Incompleat Known Space Concordance at:

http://www.freewebs.com/knownspace/