Re: _Echoes of an Alien Sky_ by James P. Hogan -- wretched garbage

David DeLaney <dbd@xxxxxxxxxxxxxxxxxx> wrote:
And the traces of what happened are there in his fiction all the
way back to Inherit the Stars and The Genesis Machine (1977 &
1978 respectively), though at that point they're just "actual
scientists/engineers get all vocally grumpy at length about how
people aren't keeping their minds open enough to do REAL Science
because you have to be able to question everything you know no
matter what, if data turns up to contradict it".

The smell of a skunk several miles away isn't particularly unpleasant.

There was a faint whiff of Velikovsky-like ideas in _Inherit the
Stars_. It was tolerable, especially after he retconned it away in
the sequels. (In the sequels, the cause of the solar system having
been redecorated was explained away as a side effect of the Giants
using their starship's main drive inside the solar system.)

But when the skunk moves into my bedroom, that's quite another thing.
Especially when every page or two contains a rant insisting that the
malodorous mammal is actually a sweet little kitten.

This didn't evolve into "and hey, what if the data really DOES
support $quackery_N, despite there being no surviving reliable data
that point that way?" for quite a while ...

Exactly. There's an enormous difference between being open to
discarding accepted ideas if the data point that way, and being
open to discarding data if sufficiently cool and weird ideas would
require it.

Ironically, the accepted ideas are actually much cooler and more
bizarre than anything Velikovsky ever dreamed up. If only Hogan
truly understood the fundamental weirdness of quantum mechanics or
of general relativity. Playing dice with the whole universe is
much cooler than playing billiards with a few planets and moons.

"Keith F. Lynch" <kfl@xxxxxxxxxxxxxx> wrote:
I'd be very curious how Hogan thinks Venus's rotation period could
change that quickly, other than in a tremendous collision which
would of course make the planet even *less* hospitable to life than
it is today.

That I can possibly see as a relic of however it managed to pick up
the moon in the first place.

There are two known ways for a planet to get a moon: A collision,
as apparently happened with Earth, and a three-body interaction,
as apparently happened with Mars. The latter cannot significantly
change the planet's rotation rate.

Rotation rates can change through tremendous collisions or through
eons of slow tidal drag. The latter is a very slow process, as it
depends on the interaction of a moon (or the sun) with the *lag* in
the planet's tidal bulge. A perfectly rigid planet would have no
tidal bulge. A perfectly fluid planet would have a tidal bulge that
would always be aligned with its moon. A planet that's somewhere in
between would have a lag in its tidal bulge. Its moon pulls half
of the lag in the bulge in one direction, and the other half in the
other, but the two pulls don't quite cancel out, since the near half
is slightly closer. It's a small effect, but over eons it adds up.
Earth's day has gained about an hour in the past hundred million years.

This effect can speed up rather than slow down a rotation rate, but
only if the moon circles the planet in less than a day, and does so
in the same direction the planet rotates. But it's still a very
slow process.

These same slow processes cause orbits to become more nearly circular,
and moons to always show the same face to their planet. Note that
Venus's orbit is even more nearly circular than Earth's, implying that
it's been there for a very, very long time.

Hogan did say it was an electromagentic effect, not a gravitational
one. But I don't see how that helps. If a planet somehow gained a
strong electrostatic charge, it would promptly lose it by expelling
either ions or electrons until it was electrically neutral. Planets
are "grounded" to space. The sun has a weak positive charge, but it's
only sufficient to make it just as easy for the sun to lose a proton
as an electron, given that the former is heavier.

How about magnetism? That's even less useful over interplanetary
distances, as it falls off with the inverse *cube*, rather than the
inverse square. Some planets have fields strong enough to deflect
ions near the planet, but not to deflect anything much heavier than a
single atom, not even right next to the planet. And magnetic fields
have almost no tendency at all to deflect anything that isn't
electrically charged. It can cause another magnetic field to line up
with it. But the attraction of two magnets for each other falls off
with the inverse *fourth* power, making them undetectably weak over
interplanetary distances. When's the last time you felt your compass
being actually dragged toward to the north pole? If you were ten
thousand times further away (i.e. as close as two planets ever get),
that undetectably weak tug would become ten thousand million million
times weaker, which I don't think is quite enough to pull a planet out
of its orbit.

Could magnetism change a planet's rotation period? If the field is
very strong and not aligned with the planet's poles, then yes, there
would be a weak effect, much weaker than tidal drag. But this effect
could only slow the planet down, not speed it up. And even then, this
effect would align the field with the poles or vice versa long before
it would slow the rotation much, just as an attempt to levitate one
magnet with another will probably only result in one magnet promptly
flipping over.

What about electromagnetic fields? The strongest such field in the
solar system is ordinary sunlight. That can push things around, but
over billions of years it has a negligible effect on the orbit of
anything much larger than a brick. There could have been a stronger
field in the past, but not without melting down all the planets into
so much slag.

I'm actually thinking his Velikovsky universes are in a giant
computer simulation, run by a bored 25-year-old deity who's taking
a break from his college research, ...

I've been trying to think of any consistent set of physical laws that
could be programmed into such a simulation to get the desired effect,
and I'm drawing a complete blank. The programmer would have to cheat,
simply poking a new value of position and momentum for each planet
into memory at the appropriate times.
--
Keith F. Lynch - http://keithlynch.net/
Please see http://keithlynch.net/email.html before emailing me.
.

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