Download A brief history of a glorious universe

Art Hobson, [email protected]
NWA Times, 16 June 2013
A brief history of a glorious universe
A contradiction stalks the modern age. If we applied our excellent brains to
the humane use of modern technology, all humans could be living like kings and
queens. But our culture remains mired in medieval beliefs harking back to an era
when life was nasty, brutish, and short. The crying need of modern times is for our
culture to get over the middle ages. Magical thinking is serving us miserably. In
particular, our ignorance of planetary history is an anachronism.
The universe started from a high-energy sub-microscopic quantum physics
event 14 billion years ago (Bya). We have direct evidence of this big bang all
around us in microwave radiation that bears its details.
The first stars and galaxies formed during the first billion years. Our
knowledge of how stars age informs us that our Milky Way galaxy's earliest stars
developed 13 Bya.
Eight billion years later, the sun and Earth were born. Here's how: A gas
cloud in the Milky Way collapsed into many tens of stars, including massive stars
that soon exploded and contributed their heavy chemical elements to the stillforming smaller stars. Some gases gravitated together to become our sun. Heated
by infalling material, the sun eventually warmed sufficiently to ignite nuclear
reactions, providing energy that then radiated through the solar system. A disk of
left-over material coalesced, under gravity, into the planets. We know all this from
other star-forming regions, meteorites, and computer simulations.
Dating of ancient meteorites show that Earth emerged 4.6 Bya. Life was
impossible in the turbulent early solar system. It is striking that, as soon as things
quieted down sufficiently, life began as shown by the earliest chemical evidence
3.8 Bya and the earliest fossil evidence 3.3 Bya. Radioactive dating gives us these
ages.
All life on Earth is related chemically, and probably originated from a single
source 3.8 Bya. The details are lost in deep time. Numerous origin-of-life
experiments, beginning from such early-Earth ingredients as steam, water, carbon,
and nitrogen, show that a wide variety of plausible energy sources generate amino
acids and nucleic acids--the building blocks of life. Numerous scenarios show how
these can form into simple biological cells.
Single-cell microorganisms multiplied in the oceans for 3 billion
years. Photosynthesizing bacteria evolved, supplying oxygen (a byproduct of
photosynthesis) to the atmosphere. Complex "eukaryotic" cells appeared 2 Bya,
making sexual reproduction possible. This increased the evolution rate, resulting
in the first multicellular organisms.
Atmospheric oxygen accumulation allowed formation of the ozone layer
(ozone is a form of oxygen), which shielded the planet from the sun's high-energy
radiation, allowing complex life to survive on land. Organisms proliferated in a
creative burst called the Cambrian explosion during 580-500 million years ago
(Mya). The rate of evolution increased by a factor of ten, the diversity of life
began to resemble that of today, and life moved onto land. Higher oxygen levels
permitted large, active animals. Animals with vertebrae evolved.
Dinosaurs and mammals appeared at about the same time, 225 Mya. A
comet or asteroid impact in the Gulf of Mexico 66 Mya made nearly all dinosaurs
extinct. Only a few bird dinosaur bird species, the source of all of today's birds,
survived. Mammals suffered losses, but many survived and then diversified.
The first primates, tree-living animals including lemurs and monkeys,
evolved 75 Mya. Apes diverged (formed a separate evolutionary line) from the
monkeys 25 Mya. 6 Mya, a new type of ape evolved, one that came down from
the trees to stand erect on two feet. These are called "hominids," meaning any
species on our side of the ape-human divergence. There have been over 20
separate hominid species. All stood on two feet. These include
genus Sahelanthropus evolving 6 Mya, genus Ardipithecus 4.4 Mya, 8 species of
genus Australopithecus during 4.2-2.1 Mya, and at least 9 species of the
genus Homo, including Homo habilis 2.4 Mya, Homo erectus 1.8 Mya,
archaic Homo sapiens 0.5 Mya, Homo sapiens neanderthalensis 0.23 Mya, and
modern Homo sapiens evolving 0.20 Mya (200,000 years ago)--the only hominid
left standing today. Nine of these hominid species survived far longer than we
have so far.
This history has an unmatched grandeur. It's time to bring education into the
modern age, and to begin to understand who we are. We have a far deeper natural
inheritance, and inhabit a far more majestic universe, than we could possibly have
imagined. Standard history courses extend to the ten thousand years since the
agricultural revolution; this represents only an instant of our true heritage.