Discussion:
Does this explanation from Clarke's "Earthlight" sound currently valid?
(too old to reply)
a425couple
2018-06-12 02:52:57 UTC
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Arthur Clarke wrote "Earthlight" in 1955. Humans have become
a multiplanetary species, but that also causes a problem!
Does this explanation of our important heavy metals currently
valid?

"The human race had been born on a world unique in the solar system,
loaded with a mineral wealth unmatched elsewhere. This accident of fate
had given a flying start to man's technology but when he reached the
other planets he found his surprise and disappointment that for many of
his most vital needs he must still depend on the Home world.

Earth is a densest of all the planets, only Venus approaching it in this
respect. But Venus has no satellite and the earth-moon system forms a
double world of a type found nowhere else among the planets. It's mode
of formation is a mystery still but it is known that when the Earth was
Molten the moon circled at only a fraction of its present distance and
raised gigantic tides in the plastic substance of its companion.

As a result of these internal tides the crust of the earth is rich in
heavy metals - far richer than that of any other of the planets: they
hoard their wealth far down within their unreachable cores, protected by
pressures and temperatures that guard them from man's depredations. So
as human civilization spread outward from Earth the drain on the mother
world dwindling resources steadily increased.

The Light Elements existed on the other planets in unlimited amounts but
such essential Metals as mercury, lead, uranium, Platinum, thorium and
tungsten were almost unobtainable. For many of them no substitutes
existed: their large-scale synthesis was Impractical despite two
centuries of effort and modern technology could not survive without them.

It was an unfortunate situation and a very galling one for the
independent republics of Mars, Venus, and larger satellites which had
now united to form the Federation. --"
Cryptoengineer
2018-06-12 03:43:05 UTC
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Post by a425couple
Arthur Clarke wrote "Earthlight" in 1955. Humans have become
a multiplanetary species, but that also causes a problem!
Does this explanation of our important heavy metals currently
valid?
"The human race had been born on a world unique in the solar system,
loaded with a mineral wealth unmatched elsewhere. This accident of
fate had given a flying start to man's technology but when he reached
the other planets he found his surprise and disappointment that for
many of his most vital needs he must still depend on the Home world.
Earth is a densest of all the planets, only Venus approaching it in
this respect. But Venus has no satellite and the earth-moon system
forms a double world of a type found nowhere else among the planets.
It's mode of formation is a mystery still but it is known that when
the Earth was Molten the moon circled at only a fraction of its
present distance and raised gigantic tides in the plastic substance of
its companion.
As a result of these internal tides the crust of the earth is rich in
heavy metals - far richer than that of any other of the planets: they
hoard their wealth far down within their unreachable cores, protected
by pressures and temperatures that guard them from man's depredations.
So as human civilization spread outward from Earth the drain on the
mother world dwindling resources steadily increased.
The Light Elements existed on the other planets in unlimited amounts
but such essential Metals as mercury, lead, uranium, Platinum, thorium
and tungsten were almost unobtainable. For many of them no substitutes
existed: their large-scale synthesis was Impractical despite two
centuries of effort and modern technology could not survive without them.
It was an unfortunate situation and a very galling one for the
independent republics of Mars, Venus, and larger satellites which had
now united to form the Federation. --"
Densities
Mercury 5.427
Venus 5.423
Earth 5.514
Mars 3.934
Moon 3.334

Mercury, Venus, and Earth are actually very similar in density.
In 1955, Clarke was writing well before we knew about plate tectonics,
which brings deep ores to the surface, and before the modern notion
of the moon being created after a Mars-sized planetesimal collided with
the proto-Earth. I could speculate that this event stripped a lot of
lighter outer material away from the planet.

pt
Robert Carnegie
2018-06-12 09:44:18 UTC
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Post by Cryptoengineer
Post by a425couple
Arthur Clarke wrote "Earthlight" in 1955. Humans have become
a multiplanetary species, but that also causes a problem!
Does this explanation of our important heavy metals currently
valid?
"The human race had been born on a world unique in the solar system,
loaded with a mineral wealth unmatched elsewhere. This accident of
fate had given a flying start to man's technology but when he reached
the other planets he found his surprise and disappointment that for
many of his most vital needs he must still depend on the Home world.
Earth is a densest of all the planets, only Venus approaching it in
this respect. But Venus has no satellite and the earth-moon system
forms a double world of a type found nowhere else among the planets.
It's mode of formation is a mystery still but it is known that when
the Earth was Molten the moon circled at only a fraction of its
present distance and raised gigantic tides in the plastic substance of
its companion.
As a result of these internal tides the crust of the earth is rich in
heavy metals - far richer than that of any other of the planets: they
hoard their wealth far down within their unreachable cores, protected
by pressures and temperatures that guard them from man's depredations.
So as human civilization spread outward from Earth the drain on the
mother world dwindling resources steadily increased.
The Light Elements existed on the other planets in unlimited amounts
but such essential Metals as mercury, lead, uranium, Platinum, thorium
and tungsten were almost unobtainable. For many of them no substitutes
existed: their large-scale synthesis was Impractical despite two
centuries of effort and modern technology could not survive without them.
It was an unfortunate situation and a very galling one for the
independent republics of Mars, Venus, and larger satellites which had
now united to form the Federation. --"
Densities
Mercury 5.427
Venus 5.423
Earth 5.514
Mars 3.934
Moon 3.334
Mercury, Venus, and Earth are actually very similar in density.
In 1955, Clarke was writing well before we knew about plate tectonics,
which brings deep ores to the surface, and before the modern notion
of the moon being created after a Mars-sized planetesimal collided with
the proto-Earth. I could speculate that this event stripped a lot of
lighter outer material away from the planet.
pt
I think the way that I heard it, Earth ended up keeping
most of the core matter of both bodies, but I wasn't
there myself. Ask James Nicoll. (Also what happened
where the fifth planet used to be. I'm not blaming...)
a425couple
2018-06-18 19:21:11 UTC
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Post by Cryptoengineer
Post by a425couple
Arthur Clarke wrote "Earthlight" in 1955. Humans have become
a multiplanetary species, but that also causes a problem!
Does this explanation of our important heavy metals currently
valid?
"The human race had been born on a world unique in the solar system,
loaded with a mineral wealth unmatched elsewhere. This accident of
fate had given a flying start to man's technology but when he reached
the other planets he found his surprise and disappointment that for
many of his most vital needs he must still depend on the Home world.
---
In 1955, Clarke was writing well before we knew about plate tectonics,
which brings deep ores to the surface, and before the modern notion
of the moon being created ---
Thank you.
But Clarke had read interesting things from a variety of disciplines
and times. Recall his quote about POTUS Jefferson and rocks falling
from the sky.

a few short excerpts from:
https://en.wikipedia.org/wiki/Plate_tectonics or
https://en.wikipedia.org/wiki/Timeline_of_the_development_of_tectonophysics_(before_1954)

Quote, Benjamin Franklin (1782): "The crust of the Earth must be
a shell floating on a fluid interior.... Thus the surface of the
globe would be capable of being broken and distorted by the
violent movements of the fluids on which it rested".

Antonio Snider-Pellegrini (Snider-Pellegrini 1858),[8] and others
had noted earlier that the shapes of continents on opposite sides
of the Atlantic Ocean (most notably, Africa and South America) seem
to fit together (see also Brusatte 2004,[9] and Kious & Tilling
1996[10]).
Note: Francis Bacon was thinking of western Africa and western
South America and Theodor Lilienthal was thinking about the
sunken island of Atlantis and changing sea levels.

Quote, Lyell: "Continents therefore, although permanent for whole
geological epochs, shift their positions entirely in the course of
ages." ((Lyell 1875, p. 258) cited in (Summerhayes 1990))

1912–1929: Alfred Wegener develops his continental drift hypothesis.
(Wegener 1912a, Wegener 1929)
In the 1920s Earth scientists refer to themselves as drifters
(or mobilists) or fixists (Frankel 1987, p. 206). Terms introduced
by the Swiss geologist Émile Argand in 1924 (Krill 2011).

Émile Argand (1916) speculated that the Alps were caused by the
North motion of the African shield, and finally accepted this
reason 1922, following Wegener's Continental drift theory (Argand
1922 as Staub 1924). Otto Ampferer in the mean time, at the
Geological Society Meeting in Vienna, held on 4 April 1919,
defended the link between the alpine faulting and Wegener's
continental drift.[2][24][25]

1948, Felix Andries Vening Meinesz, Dutch geophysicist who believes
in convection currents as a result of his work on oceanic gravity
anomalies.

J. Clarke
2018-06-12 03:53:38 UTC
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On Mon, 11 Jun 2018 19:52:57 -0700, a425couple
Post by a425couple
Arthur Clarke wrote "Earthlight" in 1955. Humans have become
a multiplanetary species, but that also causes a problem!
Does this explanation of our important heavy metals currently
valid?
"The human race had been born on a world unique in the solar system,
loaded with a mineral wealth unmatched elsewhere. This accident of fate
had given a flying start to man's technology but when he reached the
other planets he found his surprise and disappointment that for many of
his most vital needs he must still depend on the Home world.
Earth is a densest of all the planets, only Venus approaching it in this
respect. But Venus has no satellite and the earth-moon system forms a
double world of a type found nowhere else among the planets. It's mode
of formation is a mystery still but it is known that when the Earth was
Molten the moon circled at only a fraction of its present distance and
raised gigantic tides in the plastic substance of its companion.
As a result of these internal tides the crust of the earth is rich in
heavy metals - far richer than that of any other of the planets: they
hoard their wealth far down within their unreachable cores, protected by
pressures and temperatures that guard them from man's depredations. So
as human civilization spread outward from Earth the drain on the mother
world dwindling resources steadily increased.
The Light Elements existed on the other planets in unlimited amounts but
such essential Metals as mercury, lead, uranium, Platinum, thorium and
tungsten were almost unobtainable. For many of them no substitutes
existed: their large-scale synthesis was Impractical despite two
centuries of effort and modern technology could not survive without them.
It was an unfortunate situation and a very galling one for the
independent republics of Mars, Venus, and larger satellites which had
now united to form the Federation. --"
Given that there is at least one group planning to mine asteroids for
platinum, I think that his information is at least partially in error.

Then there's Mars, that red color is mostly iron oxide. Deserts full
of it.
nuny@bid.nes
2018-06-12 20:57:40 UTC
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Post by a425couple
Arthur Clarke wrote "Earthlight" in 1955. Humans have become
a multiplanetary species, but that also causes a problem!
Does this explanation of our important heavy metals currently
valid?
"The human race had been born on a world unique in the solar system,
loaded with a mineral wealth unmatched elsewhere. This accident of fate
had given a flying start to man's technology but when he reached the
other planets he found his surprise and disappointment that for many of
his most vital needs he must still depend on the Home world.
Earth is a densest of all the planets, only Venus approaching it in this
respect. But Venus has no satellite and the earth-moon system forms a
double world of a type found nowhere else among the planets. It's mode
of formation is a mystery still but it is known that when the Earth was
Molten the moon circled at only a fraction of its present distance and
raised gigantic tides in the plastic substance of its companion.
As a result of these internal tides the crust of the earth is rich in
heavy metals - far richer than that of any other of the planets: they
hoard their wealth far down within their unreachable cores, protected by
pressures and temperatures that guard them from man's depredations. So
as human civilization spread outward from Earth the drain on the mother
world dwindling resources steadily increased.
The Light Elements existed on the other planets in unlimited amounts but
such essential Metals as mercury, lead, uranium, Platinum, thorium and
tungsten were almost unobtainable. For many of them no substitutes
existed: their large-scale synthesis was Impractical despite two
centuries of effort and modern technology could not survive without them.
It was an unfortunate situation and a very galling one for the
independent republics of Mars, Venus, and larger satellites which had
now united to form the Federation. --"
I think he may actually have gotten it backwards. There's very little pure heavy metals in Earth's crust, most of it having sunk while the planet was still molten (pre- and post-Thera). What's available to us other than the nonreactive noble metals is mostly oxides, sulfides and so forth which float rather more easily along with granite on top of the generally denser stuff that makes up the mantle.

If lunar tides contribute that much to crustal flexing I'd think that would make denser stuff sift downwards through the cracks to fall into the mantle along with being melted out during subduction. Some may be recycled to the surface by vulcanism but I intuit the majority would sink. What happens afterwards due to currents in the mantle is anyone's guess but mine is that there aren't "Pineapple express" currents of relatively pure metals being wafted from the core to the crust.


Mark L. Fergerson
m***@gmail.com
2018-06-14 10:36:06 UTC
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Post by a425couple
Arthur Clarke wrote "Earthlight" in 1955. Humans have become
a multiplanetary species, but that also causes a problem!
Does this explanation of our important heavy metals currently
valid?
"The human race had been born on a world unique in the solar system,
loaded with a mineral wealth unmatched elsewhere. This accident of fate
had given a flying start to man's technology but when he reached the
other planets he found his surprise and disappointment that for many of
his most vital needs he must still depend on the Home world.
Earth is a densest of all the planets, only Venus approaching it in this
respect. But Venus has no satellite and the earth-moon system forms a
double world of a type found nowhere else among the planets. It's mode
of formation is a mystery still but it is known that when the Earth was
Molten the moon circled at only a fraction of its present distance and
raised gigantic tides in the plastic substance of its companion.
As a result of these internal tides the crust of the earth is rich in
heavy metals - far richer than that of any other of the planets: they
hoard their wealth far down within their unreachable cores, protected by
pressures and temperatures that guard them from man's depredations. So
as human civilization spread outward from Earth the drain on the mother
world dwindling resources steadily increased.
The Light Elements existed on the other planets in unlimited amounts but
such essential Metals as mercury, lead, uranium, Platinum, thorium and
tungsten were almost unobtainable. For many of them no substitutes
existed: their large-scale synthesis was Impractical despite two
centuries of effort and modern technology could not survive without them.
It was an unfortunate situation and a very galling one for the
independent republics of Mars, Venus, and larger satellites which had
now united to form the Federation. --"
No. It was doubtful even at the time of writing.

If earth's heavy metals were down in the core, tidal action would not bring them to the surface. The whole planet might be pulled into an oval shape, but the core would stay the core, the mantle the mantle, etc.

It is of course even less valid today, given all the catastrophic collisions that went into the formation of the planets. Made for a good story though.

Mike Stone, Peterborough, England.

Always drink upriver from the herd.
James Nicoll
2018-06-14 13:12:05 UTC
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Post by m***@gmail.com
Post by a425couple
Arthur Clarke wrote "Earthlight" in 1955. Humans have become
a multiplanetary species, but that also causes a problem!
Does this explanation of our important heavy metals currently
valid?
"The human race had been born on a world unique in the solar system,
loaded with a mineral wealth unmatched elsewhere. This accident of fate
had given a flying start to man's technology but when he reached the
other planets he found his surprise and disappointment that for many of
his most vital needs he must still depend on the Home world.
Earth is a densest of all the planets, only Venus approaching it in this
respect. But Venus has no satellite and the earth-moon system forms a
double world of a type found nowhere else among the planets. It's mode
of formation is a mystery still but it is known that when the Earth was
Molten the moon circled at only a fraction of its present distance and
raised gigantic tides in the plastic substance of its companion.
As a result of these internal tides the crust of the earth is rich in
heavy metals - far richer than that of any other of the planets: they
hoard their wealth far down within their unreachable cores, protected by
pressures and temperatures that guard them from man's depredations. So
as human civilization spread outward from Earth the drain on the mother
world dwindling resources steadily increased.
The Light Elements existed on the other planets in unlimited amounts but
such essential Metals as mercury, lead, uranium, Platinum, thorium and
tungsten were almost unobtainable. For many of them no substitutes
existed: their large-scale synthesis was Impractical despite two
centuries of effort and modern technology could not survive without them.
It was an unfortunate situation and a very galling one for the
independent republics of Mars, Venus, and larger satellites which had
now united to form the Federation. --"
No. It was doubtful even at the time of writing.
If earth's heavy metals were down in the core, tidal action would not bring them to the surface. The whole planet might be pulled into an oval shape, but the core would stay the core, the mantle the mantle, etc.
It is of course even less valid today, given all the catastrophic collisions that went into the formation of the planets. Made for a good story though.
Earth does have an abundance of water, though, which is quite useful
when it comes to forming ores.
--
My reviews can be found at http://jamesdavisnicoll.com/
My Dreamwidth at https://james-davis-nicoll.dreamwidth.org/
My patreon is at https://www.patreon.com/jamesdnicoll
Kevrob
2018-06-15 22:42:11 UTC
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Post by James Nicoll
Post by m***@gmail.com
Post by a425couple
Arthur Clarke wrote "Earthlight" in 1955. Humans have become
a multiplanetary species, but that also causes a problem!
Does this explanation of our important heavy metals currently
valid?
"The human race had been born on a world unique in the solar system,
loaded with a mineral wealth unmatched elsewhere. This accident of fate
had given a flying start to man's technology but when he reached the
other planets he found his surprise and disappointment that for many of
his most vital needs he must still depend on the Home world.
Earth is a densest of all the planets, only Venus approaching it in this
respect. But Venus has no satellite and the earth-moon system forms a
double world of a type found nowhere else among the planets. It's mode
of formation is a mystery still but it is known that when the Earth was
Molten the moon circled at only a fraction of its present distance and
raised gigantic tides in the plastic substance of its companion.
As a result of these internal tides the crust of the earth is rich in
heavy metals - far richer than that of any other of the planets: they
hoard their wealth far down within their unreachable cores, protected by
pressures and temperatures that guard them from man's depredations. So
as human civilization spread outward from Earth the drain on the mother
world dwindling resources steadily increased.
The Light Elements existed on the other planets in unlimited amounts but
such essential Metals as mercury, lead, uranium, Platinum, thorium and
tungsten were almost unobtainable. For many of them no substitutes
existed: their large-scale synthesis was Impractical despite two
centuries of effort and modern technology could not survive without them.
It was an unfortunate situation and a very galling one for the
independent republics of Mars, Venus, and larger satellites which had
now united to form the Federation. --"
No. It was doubtful even at the time of writing.
If earth's heavy metals were down in the core, tidal action would not bring them to the surface. The whole planet might be pulled into an oval shape, but the core would stay the core, the mantle the mantle, etc.
It is of course even less valid today, given all the catastrophic collisions that went into the formation of the planets. Made for a good story though.
Earth does have an abundance of water, though, which is quite useful
when it comes to forming ores.
--
...and using oars!

Kevin R
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