Sunday, November 30, 2014

Universe teeming with life? Not so fast, say physicists

This NASA Hubble Telescope photo shows 10,000 galaxies.
Of them, 9,000 are dead and lifeless, say research astrophysicists.

New study: gamma ray bursts make life impossible in 90% of galaxies
This is a peer-reviewed article from Science, one of the most prestigious peer-reviewed journals. It speaks to the fine-tuning of the galaxy for life.
The article says:
Of the estimated 100 billion galaxies in the observable universe, only one in 10 can support complex life like that on Earth, a pair of astrophysicists argues. Everywhere else, stellar explosions known as gamma ray bursts would regularly wipe out any life forms more elaborate than microbes. The detonations also kept the universe lifeless for billions of years after the big bang, the researchers say.
Another relevant discovery: "Invisible shield above the Earth protects us from electron threat."
A team led by the University of Colorado Boulder has discovered an invisible shield some 7,200 miles above Earth that blocks so-called “killer electrons,” which whip around the planet at near-light speed and have been known to threaten astronauts, fry satellites and degrade space systems during intense solar storms.
The "shield" is related to the Van Allen Belt, an electromagnetic ring around the earth that was discovered in the mid-1950s. The VAB is the product of the fact that earth's core is made up mostly of iron, the outer layer of which is liquid. The Earth's rotation produces convection about the core that in turn creates a magnetic field around the entire planet. The convection is itself produced by loss of heat from the core, and this heat loss comes from plate tectonics that, over enormous periods of time, churn the earth from the outer core to the near-surface and back again. Without plate tectonics, says Joseph Kirschvink of Cal Tech, there would be no convective "cells" to generate the magnetic field.

"Without our magnetic field," write paleontologist Peter Ward and astronomer Donald Brownlee in Rare Earth: Why Complex Life is Uncommon in the Universe,
Earth and its cargo of life would be bombarded by a potentially lethal influx of cosmic radiation, and solar wind "sputtering" (in which particles from the sun hit the upper atmosphere with high energy) might slowly eat away at thew atmosphere, as it has on Mars.
Even in the 10 percent of galaxies that  "can support complex life like that on Earth," the radiation problem remains at the planetary level: does an otherwise-suitable planet have the necessary shields against lethal, non-gamma radiation? Unless the planet is highly ferrous, it won't. Unless is is highly ferrous and rotating fairly rapidly, it won't. Unless it is highly ferrous and rotating fairly rapidly and features plate tectonics, it won't. And none of these features have been found on any extra-solar planet.

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