membrane exactly two molecules thick (Gorter and Grendel 1925:439). [added 02/01/03]
In 1924, John Burdon Sanderson Haldane began a series of papers in which gene
frequency substitutions in a population were treated systematically.
In 1924, Alfred Lotka, in Elements of Physical Biology, compared the global eco-system
to "a great world engine" in which "plants and animals act as coupled transformers of
energy" in "the mill-wheel" that is driven by "solar energy" (Lotka 1924:331-335). Lotka
gave analytical substance to the vision intuitively adopted by field biologists. Population
ecologists took the 'logistical equation' for population growth, which is in fact based on an
analogy with autocatalytic chemical reactions, from his book.
In 1924, Satyendranath Bose derived Planck's black box radiation law from photon
statistics, that is, independent of classical electrodynamics. Instead of photons being
statistically independent, he assigned them to cells and wrote of the cell's statistical
independence.
In 1924, Bohr, Hendric Anton Kramers, and John C. Slater tried and failed to solve the
apparent contradiction between waves and particles by the concept of the 'probability
wave.' This probability is different from chance: "It meant a tendency for something. It
was a version of the old concept of potentia in Aristotelian philosophy. It introduced...a
strange kind of physical reality just in the middle between possibility and reality"
(Heisenberg 1958:41; Bohr et al. 1924:785-812).
In 1924, Bose, in "Wärmegleichgewicht im Strahlungenfeld bei Anwesenheit von
Materie," and Einstein, in an appendix to Bose's paper, predicted the existence of the
statistical phenomena, now known as 'Bose-Einstein condensation,' whereby a significant
fraction of particles at a sufficiently low temperature could occupy the same quantum
state of lowest energy. In other words, in this state, the atoms--later recognized as
particles of integer spin and still later called 'bosons,' in Bose's honor--would lose their
individual properties and would act collectively as a single entity. Integer spin is either
zero or an even number of multiples of the basic unit of spin.
In 1924, Eddington, in "On the Relation between the Masses and Luminosities of the
Stars," correctly derived the various mass-luminosity relations of stars; e.g., for stars like
the Sun, the absolute luminosity is proportional to the fourth power of the mass, but for
more massive stars the absolute luminosity is proportional to the cube of the mass.
In 1924, Carl Wirtz suggested that the smaller a galaxy appeared the larger its change in
color toward the red end of the spectrum. This is called 'cosmological redshift.' But Wirtz
lacked the direct evidence to conclude that these smaller, redder galaxies were farther
away.
In 1924, Hubble, using the 100-inch telescope on Mount Wilson and the same scale
which Shapley had used to map the Milky Way, measured the distance to the nearer
spiral galaxies, which was two million light years. So vast was this distance that "the
whole Galaxy in which we live was suddenly shrunken, in the astronomical imagination,
into a tiny mote floating in a vast, dark sea of emptiness" (Gribbin 1998a:65).
In 1925, Raymond Arthur Dart published his discovery of a skull of a new species,
Australopithecus africanus, a missing link in the human fossil record. He speculated that
"Australopithecus had been a bloodthirsty carnivore, [giving birth to] the killer ape myth...,
including a connection between warfare and hunting and the concept that aggressiveness
drives cultural progress" (de Waal 2001:45).
In 1925, Gilbert Adair published his determination of the correct size of the hemoglobin
molecule and subsequently wrote the equation for hemoglobin's cooperativity.
In 1925, George Richard Minot and William Parry Murphy noticed that feeding raw liver
aids in the treatment of 'pernicious anemia.' Their discovery led to the isolation of vitamin
B12.
In 1925, Theodor Svedberg designed the ultracentrifuge.
In 1925, Samuel A. Goudsmit and George Eugene Uhlenbeck assigned angular
momentum to electrons and established that they have the quantum mechanical property
of spin.
In 1925, Heisenberg, in "Über quantentheoretische Umdeutung kinematischer und
mechanischer Beziehungen," in order to avoid giving definite numbers to changing
positions of quanta, changed the relationship between physical concepts and
mathematical symbols through his use of symbols as imaginary quantities with arrays of
numbers, called matrices. The rules for calculating these symbols often depends on the
order they are written down. This became known as 'matrix mechanics.'
In 1925, Wolfgang Pauli perceived the principle that no two electrons in the atom can be
in the same quantum state; in other words, two electrons must have opposite spin, thus
cancelling each other, and there can be no more than two in the same orbital. This is