Re: YASID

On Mar 4, 12:57�am, "Otto York" <gophe...@xxxxxxxxxxxxx> wrote:
On Mar 3, 4:05 pm, "Mike Stone" <mwst...@xxxxxxx> wrote:





"Keith F. Lynch" <k...@xxxxxxxxxxxxxx> wrote
in messagenews:esclp7$f35$1@xxxxxxxxxxxxxxxxxxx> Otto York <gophe...@xxxxxxxxxxxxx> wrote:
djhe...@xxxxxxxxxxx (Dorothy J Heydt)
wrote:
As I recall, the orbit is eccentric,

and the colonists find it hot> >> at perihelion, cold at aphelion, but
not unbearably so.

In positing that "the orbit is

eccentric," AWC's authors making but> > a token gesture towards reality..  Even

an orbit that ranges from> > Venus-distance to the sun to

Mars-distance would kill life on planet> > Beta well before Beta reached either

orbital extreme, especially at> > the Venus end.

How do you figure?  It takes time to heat

up or cool down.  Anyhow, a> planet where Mars is would be warm enough

to support a life if it had> Earth's mass, hence more air pressure.

And a planet where Venus is> would be cool enough to support life if

not for the runaway greenhouse> effect.  It's not obvious whether that

runaway greenhouse effect was> inevitable, if, say, Venus was less

massive.  Even if it was, it would

probably take many centuries.

I doubt if it would happen at all.

Due to its lower orbital velocity at greater
distances form the Sun, a planet in an
eccentric orbit spends more time near
aphelion than near perihelion, and in
general more time in the "outer" half of its
orbit than in the "inner", So a planet with
a perihelion near Venus and an aphelion near
Mars, will be warmer than Mars, but probably
somewhat cooler than _Earth_, never mind
Venus.
Ronald Knox

Your point is excellent, but it relates only to the average
temperature of the planet in moderately elliptical orbit (moving
between Venus distance and Mars distance from the sun).  By the time
the inward bound planet reaches earth distance, it will have warmed up
considerably from its cold Mars temperature.  And by the time it gets
close to Venus distance and begins it's roughly 150-degree turn around
the sun, the planet should already be considerably warmer than earth
(if earth were still in orbit).  Even 100 days going around the sun
would be plenty of time to fry and, probably, fatally radiate the
colonists.


Assuming the planet's atmosphere and magnetic field are similar to
Earth's, I don't see why anyone should be fatally irradiated. No doubt
the background radiation will be higher (for part of the orbit) than
on Earth, but for the greater part of its year the planet is further
from the Sun than Earth, hence solar radiation is _less_. Compared
with all the other problems there'll be, that one is likely to be
pretty trivial - at worst a few extra cancer cases over the course of
decades, and maybe not even that.

As for temperature, perihelion may indeed be uncomfortably warm, but I
don't see anyone getting fried. After all, the planet is in the orbit
of Venus only momentarily, and at the point where its orbital velocity
is highest. Even for most of the period when it is within Earth's
orbit, it is still closer to that than to Venus'. Also, in the longer
period when it is beyond Earth's orbit, quite a bit of snow is likely
to fall, so that its albedo is higher than Earth's, hence less solar
radiation is absorbed.

I'm not suggesting that it will be paradise, or that I'd much fancy
living there. In particular, the weather is likely to be awful. All
that water vapour in the atmosphere after perihelion, condensing again
as the temperature drops, will produce the mother of all rainy
seasons, and violent storms will be the rule rather than the
exception. But uncomfortable |= uninhabitable.


--
Mike Stone - Peterborough, England


"It is so stupid of modern civilisation to
have given up believing in the Devil, when
he is its only explanation."


Ronald Knox



.

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