Big Bang to Civilization: 10 Amazing Origin Events ~ Roger Briggs, LIVE SCIENCE.
One of the unheralded achievements of modern science is that it can now provide a coherent origin story for humanity, something that was not possible just a
Big Bang to Civilization: 10 Amazing Origin Events ~ Roger Briggs, LIVE SCIENCE.
One of the unheralded achievements of modern science is that it can now provide a coherent origin story for humanity, something that was not possible just a few decades ago. With new discoveries in astrophysics, evolutionary biology, molecular genetics, geology and paleoanthropology, a continuous story has emerged starting from the Big Bang. This is both a new cosmology that humanity is embedded in, and a grand tour of science. Here is one science-lover’s top 10 list of the coolest science underlying the human origin story, in chronological order.
There is so much I left out — for more, see “Journey to Civilization: The Science of How We Got Here” (Collins Foundation Press, 2013) and As Myth Marries Science, the Origin Story Matters(Op-Ed).
The Big Flash: Origin of the Cosmic Background Radiation
When the universe was about 380,000 years old it had cooled to about 3000 K, cool enough for electrons to attach to nuclei and form atomic matter in highly excited states. This produced a massive flux of photons near the visible range (typical of excited atoms) that filled the early universe. As the universe and space itself expanded, the wavelength of this light was stretched into the microwave range to become the Cosmic Microwave Background (CMB) that Penzias and Wilson inadvertently discovered in 1964.
George Gamow had predicted that a Big Bang should produce just such a background radiation, and the CMB became one of the first pieces of evidence supporting the Big Bang Theory. Since then, the study of the CMB with space-based instruments like COBE, WMAP, and now the Planck Spacecraft continues to be a rich source of information about the early universe and it’s deepest structure.
End of the Dark Age: The First Stars are Born
After about 400 million years of expansion following the Big Bang the universe was cool enough for gravity to begin coalescing clouds of hydrogen into stars, igniting nuclear fusion for the first time. The prodigious outpouring of radiation from the first stars marked the end of the Dark Age, and ionized nearby clouds of hydrogen. This re-ionization is the fingerprint of the first stars and can be seen in the spectral signatures of quasars, in the polarization of the CMB, and in the 21-centimeter emission line of hydrogen.
The birth of the first stars marked a turning point in the life of the universe: from here on the universe took on the features we see today, with galaxies full of stars surrounded by planetary systems. Stars perform some of the most important work in the cosmos: they manufacture the elements heavier than hydrogen, they create planets as part of their own formation, and they provide energy for those planets, as our own Sun does for us. We love stars!
The Solar System Forms: Unusual or Not?
Yellow, G-class stars like the sun are a dime a dozen throughout the universe, but only a fraction of them exist as single stars and contain all 92 naturally occurring elements like our sun. Astronomers now have strong evidence from exoplanet research that virtually all stars form planetary systems as a natural part of their own formation, and this agrees with current theories of star formation. But most of the planetary systems observed so far seem weird and inhospitable for life — for example, with planets the size of Jupiter orbiting much closer than Mercury orbits the sun, or five planets packed into a space smaller than Mercury’s orbit. Astronomers have yet to see a solar system that is neatly ordered like our own with a nice rocky planet located in the sweet spot for liquid water and life.
Just how special is Earth’s situation?
The media was recently abuzz when researchers estimated (PNAS, Nov. 26, 2013) that there could be 8 billion or 9 billion stars in our galaxy with Earth-like planets — about 5 percent of stars — making the odds very high for intelligent life elsewhere. Yet no life, or evidence of it, has ever been found beyond Earth, so the jury is still very much out on the questions of how rare or common the Earth is, and how unique humanity may or may not be.
The presence of Carbon-12 in ancient rocks suggests that life began on Earth about 3.8 billion years ago. This means that DNA or some precursor molecule had assembled and could begin its relentless self-replication that drove the evolution of life. But how did such a fragile and complex molecule assemble?
Organic molecules have now been seen throughout the universe. They can be found in the spectral signatures of stars and gas clouds, and the Murchison meteorite that fell to Earth in 1969 contained 92 different amino acids, most never seen on Earth. However it’s a giant leap from amino acids to a living organism with a metabolic system that provides energy, and a genetic system that stores information, directs the construction of proteins, regulates every function of the organism, and replicates itself, all enclosed within a membrane.
Could life have been seeded from elsewhere? Or maybe it was just the chance sloshing together of molecules that was bound to happen somewhere. Or could there be some fundamen