[D66] Lunar Real

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https://www.smithsonianmag.com/science-nature/ancient-greek-philosopher-was-exiled-claiming-moon-was-rock-not-god-180972447/

An Ancient Greek Philosopher Was Exiled for Claiming the Moon Was a
Rock, Not a God
By
David Warmflash
smithsonianmag.com
5 min
View Original

2,500 years ago, Anaxagoras correctly determined that the rocky moon
reflects light from the sun, allowing him to explain lunar phases and
eclipses

Close to the north pole of the moon lies the crater Anaxagoras, named
for a Greek philosopher who lived in the fifth century B.C. The eponym
is fitting, as Anaxagoras the man was one of the first people in history
to suggest the moon was a rocky body, not all too dissimilar from Earth.
Streaks of material thrown out during the impact that formed the crater
extend 560 miles southward to the rim of another crater, this one named
for Plato.

Like Plato, Anaxagoras the scholar did most of his work in Athens, but
the similarities between the two men stop there. Influenced strongly by
the Pythagoreans, Plato posited a mystical universe based on sacred
geometric forms, including perfectly circular orbits. Plato eschewed
observation and experimentation, preferring to pursue a pure knowledge
he believed was innate in all humans. But Anaxagoras, who died around
the time Plato was born, had a knack for astronomy, an area of study
that requires careful observational and calculation to unlock the
mysteries of the universe.

During his time in Athens, Anaxagoras made several fundamental
discoveries about the moon. He reiterated and expended upon an idea that
likely emerged among his predecessors but was not widely accepted in
antiquity: that the moon and sun were not gods, but rather objects. This
seemingly innocuous belief would ultimately result in Anaxagoras’ arrest
and exile.

Piecing together the lives of early philosophers such as Anaxagoras, who
is thought to have written just one book, lost to us today, can be a
major challenge for historians. Modern scholars have only “fragments” to
describe the life of Anaxagoras—brief quotes from his teachings and
short summaries of his ideas, cited within the works of scholars from
later generations, such as Plato and Aristotle.

Through persistent observation, Anaxagoras came to believe that the moon
was a rock, not totally unlike the Earth, and he even described
mountains on the lunar surface. The sun, he thought, was a burning rock.
In fragment 18, Anaxagoras says, “It is the sun that puts brightness
into the moon.” While Anaxagoras was not the first to realize that
moonlight is reflected light from the sun, he was able to use this
concept to correctly explain additional natural phenomena, such as
eclipses and lunar phases.

Hailing from Clazomenae in the Ionian lands east of the Greek mainland,
Anaxagoras grew up during the Ionian Enlightenment, an intellectual
revolution that began around 600 B.C. As a young man, he saw Athens and
Sparta align to drive the Persian Empire out of Ionia. When he relocated
to Athens, Anaxagoras and his contemporaries brought philosophy to the
budding Athenian democracy. Although many Greek philosophers of the
sixth and fifth centuries B.C. believed in one or a few fundamental
elements—such as water, air, fire and earth—Anaxagoras thought there
must be an infinite number of elements. This idea was his way of
resolving an intellectual dispute concerning the nature of existence
that had emerged between the naturalistic-minded philosophers of Ionia
to the east and the mystical-minded philosophers to the west, in
Greek-colonized Italy, such as Pythagoras and his followers.

Daniel Graham, a professor of philosophy at Brigham Young University and
one of the few Anaxagoras experts in the world, says that of the
Italian-based philosophers, Parmenides in particular influenced
Anaxagoras and his ideas about astronomy.

“Anaxagoras turns the problem of lunar light into a problem of
geometry,” Graham says. He noted that when the moon is on the opposite
side of the Earth than the sun, the full face is illuminated,
“[producing] a model of the heavens that predicts not only phases of the
moon, but how eclipses are possible.”

The moon’s phases, Anaxagoras realized, were the result of different
portions of the celestial object being illuminated by the sun from
Earth’s perspective. The philosopher also realized that the occasional
darkening of the moon must result from the moon, sun and Earth lining up
such that the moon passes into the Earth’s shadow—a lunar eclipse. When
the moon passes directly in front of the sun, the skies darken during
the day, a phenomenon Anaxagoras also described and we now call a solar
eclipse.

Anaxagoras also wrestled with the origins and formation of the moon, a
mystery that still challenges scientists today. The philosopher proposed
that the moon was a big rock which the early Earth had flung into space.
This concept anticipated a scenario for the moon’s origin that physicist
George Darwin, son of Charles Darwin, would propose 23 centuries later.
Known as the fission hypothesis, Darwin’s idea was that the moon began
as a chunk of Earth and was hurled into space by the Earth’s rapid
rotation, leaving behind the Pacific basin. (Today, many astronomers
believe that a Mars-sized body slammed into the early Earth, expelling
material that then coalesced into the moon, though other theories exist
for the origin of our natural satellite.)

By describing the moon as a rock of terrestrial origin, and the sun as a
burning rock, Anaxagoras moved beyond earlier thinkers, even those who
realized the moon was a kind of reflector. This forward thinking got
Anaxagoras labeled as a chief denier of the idea that the moon and sun
were deities.

Such an idea should have been welcome in democratic Athens, but
Anaxagoras was a teacher and friend of the influential statesman
Pericles, and political factions would soon conspire against him. In
power for over 30 years, Pericles would lead Athens into the
Peloponnesian wars against Sparta. While the exact causes of these
conflicts are a matter of debate, Pericles’ political opponents in the
years leading to the wars blamed him for excessive aggression and
arrogance. Unable to hurt the Athenian leader directly, Pericles’
enemies went after his friends. Anaxagoras was arrested, tried and
sentenced to death, ostensibly for breaking impiety laws while promoting
his ideas about the moon and sun.

“In the Athenian democracy, with its ‘democratic’ trials before large
juries on criminal charges being brought by private citizens—there was
no district attorney—all trials were basically political trials,” Graham
says. “They were often disguised as being about religion or morality,
but they aimed at embarrassing some public figure by going after him
directly if he was vulnerable, or a member of his circle if he was not.
If you wanted to attack Pericles, but he was too popular to attack
directly, you found the weakest link in his group. As a foreigner and
intellectual with unorthodox new ideas, Pericles’ friend and ‘science
advisor’ Anaxagoras was an obvious target.”

Still holding some political sway, Pericles was able to free Anaxagoras
and prevent his execution. Though his life was spared, the philosopher
who questioned the divinity of the moon found himself in exile in
Lampsacus at the edge of the Hellespont. But his ideas regarding
eclipses and lunar phases would live on to this day, and for his
recognition of the true nature of the moon, a lunar crater, visited by
orbiting spacecraft some 2,400 years later, bears the name Anaxagoras.