To Hunt a Star - Four Revolutions in the Earth Sciences - page 147

As one encyclopedia sums him up: “He is renowned for a career dogged by pla-
giarism, being fired from two observatory staffs, grand egotistical claims, being
'exiled' to an isolated outpost, and his vitriolic attacks on relativity.” 2 Named for
two heroes of the Confederacy, Jefferson Davis and Stonewall Jackson, standing
six feet, four inches tall and dressed in the uniform of a U.S. naval commander, T.
J. J. See was impossible to ignore.
See is generally credited with the theory that Frank Taylor also espoused: that
the Moon had been captured by the Earth's gravity. Like most cosmologists of his
day, See had begun to doubt the nebular model for the origin of the planets and
their moons. In 1900, Moulton, who had been See's student at the University of
Chicago and later Chamberlin's collaborator on the planetesimal hypothesis, de-
livered LaPlace's model a mortal blow by showing that it could not explain the an-
gular momentum of the solar system. The concept of angular momentum is crucial
to evaluating the theories for the origin of the Moon, so a brief explanation is in
order.
Newtonian mechanics defines linear momentum as the product of the mass of a
moving object times its velocity. The larger the object, or the faster it moves, the
greater its momentum. Like energy, momentum is a conserved quantity. When you
shoot a cue ball head-on into a stationary billiard ball, the cue ball stops dead, and
the other ball moves away with all (assuming zero friction) the momentum the cue
ball had before the collision. That momentum can be transferred but not destroyed
is a universal law of nature and one of the most important.
An object rotating on its axis, like a spinning top or rotating planet, also has mo-
mentum, but instead of being linear it is “angular.” Newton showed that angular
momentum is also conserved. One of the most fundamental facts of cosmology is
thatalthoughtheSunholds99.9percent ofthemassofthesolarsystem, ithasonly
1 percent of the angular momentum. This lopsided ratio could not have resulted
had the Sun flung off blobs that became the planets. Moulton concluded that the
“numerical discrepancies aresogreatthatitseems torenderthenebularhypothesis
absolutely untenable.” 3 These discrepancies led Chamberlin and Moulton to their
planetesimal hypothesis, which they believed was consistent with the distribution
of angular momentum in the solar system.
See's idea was that the planets, instead of being hurled from the Sun, had ori-
ginated elsewhere in the solar nebula and been captured by the Sun's gravity. Like-
wise, the moons had originally circled the Sun but been trapped by the gravity of
the planets. Thus our Moon had grown up somewhere else but been inexorably at-
tracted by the Earth's gravity, never the twain to part: the “spouse” theory.