Future Space War

In article ,
Ian Stirling wrote:
Not enough to form a viable population, let alone a civilization.

Biologically viable population is one woman and a freezer full of sperm.

Not in the long run -- not enough genetic variety (mitochondrial DNA in
particular comes only from the mother). Also not enough kids in the first
generation for a stable and capable society, quite aside from practical
problems of taking care of them and educating them.

A few hundred is probably minimal. A few thousand would be safer.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

In article ,
Master and Owner, Beryl J. Turner III wrote:
One to consider that a common tactical axiom is that whomever has the high
ground, has the advantage...

Yes and no and kind of. Consider that there has been little interest in
military occupation of Mount Everest.

You put a mass-driver on the moon, calculate the ballistics and wham!

Calculate the energetics instead of the ballistics. Lunar catapults (they
are generally not mass drivers -- that's a specific type of catapult) are
massively overrated as weapons. I'm sorry to shatter illusions, but
Heinlein blew this one badly. Their power supplies have to be too big and
the waste heat would be too hard to hide.

You get missiles in orbit, wait for the right moment, launch and bam!

The "bam" is the sound of your missiles being hit by ground-launched
antisatellite weapons. Orbit is a *lousy* place to put missiles, unless
you can armor them very heavily. They're too easy to spot and too hard
to protect. Silos dug into hard rock are a far superior location.

You build a gigantic magnifying glass in orbit, aim it just right and
sizzle!

Try computing just how large such a "magnifying glass" (in practice you'd
use mirrors) has to be, bearing in mind that the Sun is not a point source
and hence there is a limit to how tightly you can focus sunlight over long
distances.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

In article ,
(Henry Spencer) writes:
| In article ,
| Ian Stirling wrote:
| Not enough to form a viable population, let alone a civilization.
|
| Biologically viable population is one woman and a freezer full of sperm.
|
| Not in the long run -- not enough genetic variety (mitochondrial DNA in
| particular comes only from the mother). Also not enough kids in the first
| generation for a stable and capable society, quite aside from practical
| problems of taking care of them and educating them.
|
| A few hundred is probably minimal. A few thousand would be safer.

Yes, with the probable exception of your remark about mitochondrial
DNA. Were it inherited solely from the mother, then all that is
needed is one woman with sound mitochondrial DNA - the genetic
issues are the same as for bacteria and yeast, after all. It isn't
quite that simple, but one source is probably enough and the one
woman and lots of sperm solution isn't as infeasible as it seems,
because even X chromosomes would be well mixed in the second
generation.

If you selected humans from many different races (and heavily from
Africa) and were ruthless about removing exposed genetic defects,
then a few dozen would be enough for the genetic aspect, ignoring
the freezer. Even less has been for many other mammals, after all,
but the ruthlessness is key.

I can't even guess what the minimum number for a viable society
would be, but my guess is that even a few thousand would work only
with STRONG selection for effectiveness. Current social structures
would just not cut the ice.


Regards,
Nick Maclaren.

In article ,
Nick Maclaren wrote:
| Not in the long run -- not enough genetic variety (mitochondrial DNA in
| particular comes only from the mother)...

Yes, with the probable exception of your remark about mitochondrial
DNA. Were it inherited solely from the mother...

It is. Mitochondria have their own genetic material -- they are almost
certainly the distant descendants of symbiotic bacteria -- and there are
none in a sperm cell. Check any textbook on the subject if you don't
believe me. (In fact, there's active research in tracing back the details
of mankind's origins using genetic comparisons of mitochondrial DNA, which
is hugely easier because that DNA doesn't get *mixed* every generation.)

then all that is
needed is one woman with sound mitochondrial DNA ...

Note that I said "variety". You assume that there is one optimal (or just
permanently adequate) choice of the genes involved, but that's a huge
assumption and quite unjustified. You want *diversity* in this, as in
other genetic material, to cover against the possibility that different
combinations will be needed for different future challenges.

If you selected humans from many different races (and heavily from
Africa) and were ruthless about removing exposed genetic defects,
then a few dozen would be enough for the genetic aspect, ignoring
the freezer. Even less has been for many other mammals, after all...

Kind of, sort of, loosely speaking. Many of the species that have gone
through major population crunches show serious signs of inbreeding, and
are very vulnerable to things like new diseases because of lack of genetic
variety. Variety is key, and even major genetic defects aren't necessarily
known and obvious.

| A few hundred is probably minimal. A few thousand would be safer.

I can't even guess what the minimum number for a viable society
would be, but my guess is that even a few thousand would work only
with STRONG selection for effectiveness. Current social structures
would just not cut the ice.

There is plenty of past experience with isolated human populations in that
size range, although more people would certainly be better. Social
structure is certainly an issue, but not an unsolvable one.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

(Henry Spencer) wrote:
[...]
massively overrated as weapons. I'm sorry to shatter illusions, but
Heinlein blew this one badly. Their power supplies have to be too big and
the waste heat would be too hard to hide.


He wasn't positing a secret catapult designed to be used as a
weapon...just a "targeting error" with a load of freight (okay, he
replaced the wheat with rock so it wouldn't be mistaken for Postum).
He didn't have to hide the power supply or the waste heat.

Now whether UPS would ever agree that having one in brown paint was
worth while....

/dps

On Mon, 29 Mar 2004 01:27:33 GMT, (Henry Spencer)
carved upon a tablet of ether:

It is. Mitochondria have their own genetic material -- they are almost
certainly the distant descendants of symbiotic bacteria -- and there are
none in a sperm cell. Check any textbook on the subject if you don't
believe me. (In fact, there's active research in tracing back the details
of mankind's origins using genetic comparisons of mitochondrial DNA, which
is hugely easier because that DNA doesn't get *mixed* every generation.)

That's just plain wrong. Sperm cells have a _lot_ of mitochondria -
they're what provide a cell with energy, and sperm use a lot of energy
wriggling around. However, for some reason (possibly that they're
'worn out', last I heard no-one really really knows) the sperm's
mitochondria are flagged with a marker that says to a cell's clean-up
machinery 'for disposal'. Once the sperm merges with the ovum its
mitochondria get taken apart as things get underway. Mitochondria,
like many bacteria exchange DNA between themselves, BTW.

Now, according to some research I've seen (on the web, so I can't
vouch for its quality), this cleaning up takes several hours, and
sometimes the sperm's mitchondria will exchange DNA with the egg's
mitochondria before they are destroyed.

A basic rule for biology - nothing's a clean as you'd like it to be,
and nothing's as clear-cut as text books like to pretend.

--
Rupert Boleyn
"Just because the truth will set you free doesn't mean the truth itself
should be free."

Henry Spencer wrote:
In article ,
Nick Maclaren wrote:

| Not in the long run -- not enough genetic variety (mitochondrial DNA in
| particular comes only from the mother)...

Yes, with the probable exception of your remark about mitochondrial
DNA. Were it inherited solely from the mother...


It is. Mitochondria have their own genetic material -- they are almost
certainly the distant descendants of symbiotic bacteria -- and there are
none in a sperm cell. Check any textbook on the subject if you don't
believe me.

Actually, there is evidence that paternal (sperm) mitochondrial DNA can
be inherited. See for example:

http://www.biomedcentral.com/news/20020822/03/

and references therein. Also, from this article, you can infer that
sperm cells contain mitochondria -- but I won't check a textbook

Note that this observation complicates molecular clocks based on
mitochondrial DNA.

Rob Wheatley

"Juergen Nieveler" wrote ...
However,
they also found out that the same Y chromosome was present in males
from other family trees - looks like some men weren't exactly faithfull
over the milennia and did have some illegitimate offspring ;-)

Next up in Science News - "Fire - it's hot!"

(dave schneider) writes:

(Henry Spencer) wrote:
[...]
massively overrated as weapons. I'm sorry to shatter illusions, but
Heinlein blew this one badly. Their power supplies have to be too big
and the waste heat would be too hard to hide.

He wasn't positing a secret catapult designed to be used as a
weapon...just a "targeting error" with a load of freight (okay, he
replaced the wheat with rock so it wouldn't be mistaken for Postum).
He didn't have to hide the power supply or the waste heat.

Uh, you are forgetting about the "secret" catapult he had the Loonies build
under Mare Undarum, which was the one used for the majority of the bombardment.

I would note, however, that the Undarum catapult was not used until the F.N.
took out the main catapult, so until then, the waste heat production would
presumably have been relatively low. Also, Heinlein went to some pains
to point out that such a major construction job could =NOT= be _completely_
hidden, so the Loonies had to disguise it as an HKL mining operation sited
at a relatively inaccessible location where surveillance would be difficult,
that they had to come up with a plausible excuse for why it had to be powered
by a reactor rather than Douglas-Martin Sunpower Screens (tm), etc., etc....


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

In article ,
dave schneider wrote:
(Henry Spencer) wrote:
[...]
massively overrated as weapons. I'm sorry to shatter illusions, but
Heinlein blew this one badly. Their power supplies have to be too big and
the waste heat would be too hard to hide.


He wasn't positing a secret catapult designed to be used as a
weapon...just a "targeting error" with a load of freight (okay, he
replaced the wheat with rock so it wouldn't be mistaken for Postum).
He didn't have to hide the power supply or the waste heat.

He seriously overestimated the impact the incoming objects
would have on their targets. The off-shore UK impact should have only
raised a ripple a inch or so deep by the time it got to London, and
by my estimate it should have taken hundreds of thousands of shots
to dismantle Cheyenne Mt.
--
"Thousands of people will be exposed to Shakespeare who normally wouldn't. Now
everyone will be able to enjoy 'Hamlet'. That's the way it should be." "But
don't you see? Don't you understand what you are doing?" "Oh, yeah. I'm
destroying Shakespeare's snob appeal." "You _fiend_." [Lenny and Cowboy Wally]