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Chapter Thirteen — Bang!

A Short History of Nearly Everything – by Bill Bryson

Chapter 13 — Bang!

  • Sometime in the very ancient past, when Manson, Iowa stood on the edge of a shallow sea, a rock about a mile and 1/2 across, weighing ten billion tons and traveling at perhaps 200 times the speed of sound ripped through the atmosphere and punched into the Earth with a violence and suddenness that we can scarcely imagine.  Where Manson now stands became, in an instant, a hole 3 miles deep and more than 20 miles across.
  • 2.5 million years of passing ice sheets filled the Manson crater right to the top of the rich glacial till, then graded it smooth, so that today the landscape at Manson, and for miles around is as flat as a tabletop.
  • Meteor Crater in Arizona is the most famous asteroid impact site on Earth and a popular tourist attraction.
  • Asteroids are rocky objects orbiting in loose formation in a belt between Mars and Jupiter.  Since the solar system is quite a roomy place, the average asteroid is about 1 million miles from its nearest neighbor.  No one knows precisely how many asteroids there are tumbling through space, but the number is thought to be probably not less than one billion.  They are presumed to be planets that never quite made it, owing to the unsettling gravitational pull of Jupiter, which kept — and keeps — them from coalescing.
  • William Herschel calculated that asteroids are no where near planet sized but are much smaller.  He called them asteroids (Latin for ‘star-like’) which was unfortunate as they are not like stars at all.  Sometimes now they are more accurately called planetoids.
  • As of July 2001, 26,000 asteroids had been named and identified (half of those in the two years before 2001).  With up to a billion to identify, the count obviously has barely begun.
  • Steven Ostro has said, “Suppose that there was a button you could push to light up all the Earth-crossing asteroids larger than about 10 meters.  There would be over 100 million of these objects in the sky.  Millions upon millions of the nearer, randomly moving objects exist, all of which are capable of colliding with the Earth and all of which are moving on slightly different courses through the sky at different rates.  It would be deeply unnerving.”
  • It is estimated that approximately 2000 asteroids big enough to imperil Earth’s civilized existence regularly cross Earth’s orbital path.  But even a small asteroid (the size of a house) could destroy a city.
  • The first small asteroid wasn’t spotted until 1991, and that was after it had already crossed our orbital path.  Named 1991-BA, it was noticed as it sailed past us at a distance of 106,000 miles.  That distance, in cosmic terms, is the equivalent of a bullet passing through one’s sleeve without touching the arm.  Two years later, another, somewhat larger asteroid missed us by just 90,000 miles – the closest pass yet recorded.  It, too, was not seen until it had passed and would have arrived without warning.  Such near misses probably happen two or three times a week, going completely unnoticed.
  • Each year the Earth accumulates some 30,000 metric tons of “cosmic spherules” (space dust) which would be quite a pile if it were swept into one pile, but it is infinitesimal when spread across the globe.
  • Alvarez, Alvarez, and other scientists, toward the end of the 20th century, convincingly showed that the extinction of dinosaurs happened in a short period of time, and was probably due to the after-effects of a cataclysmic asteroid impact on Earth.  The scientific world was slow to accept their theory.
  • In 1994, a series of asteroids slammed into Jupiter.  The impacts began on July 16, 1994 and went on for a week.  The impact was bigger by far than anyone expected.  One fragment, known as Nucleus G, struck with the force of about 6 million megatons, 75 times more than all the nuclear weaponry in existence.  Nucleus G was about the size of a small mountain, but it created wounds in the Jovian surface equal to the size of Earth.  Watching the impact  of these collisions convinced all of the correctness of the Alvarez theory.
  • When asked how much warning the inhabitants of Earth would have if an asteroid was heading for the Earth today, a space scientist name Anderson responded, “Probably none.  The asteroid would not be visible to the naked eye until it warmed up, and that wouldn’t happen until it hit our atmosphere, which would be about 1 second before it hit the Earth.  You’re talking about something moving many tens of times faster than the fastest bullet.  It is likely it would take us completely by surprise.”
  • An asteroid or comet traveling at cosmic velocities would enter the Earth’s atmosphere at such a speed that the  air beneath it would be unable to get out of the way and would be compressed, as in a bicycle tire pump.  Compressed air grows hot swiftly, and the temperature below the asteroid would rise to 60,000 degrees Kelvin, or 10 times the surface temperature of the Sun.  In this instant of the asteroid’s arrival, everything in its path (people, houses, factories, cars, etc.) would crinkle and vanish like cellophane in a flame.  One second after entering our atmosphere, the meteorite would slam into the Earth’s surface.  The meteorite itself would vaporize instantly, but the blast would blow out a thousand cubic kilometers of rock, earth, and super-heated gases.  Every living thing within 150 miles that hadn’t already been killed by the heat of entry would now be incinerated in the blast.  Radiating outward at the speed of light would be the initial shock wave, sweeping everything before it.  For those outside the zone of immediate devastation, the first inkling of catastrophe would be a flash of blinding light – the brightest ever seen by human eyes – followed shortly by an apocalyptic sight of  unimaginable grandeur: a roiling wall of darkness reaching high into the heavens,filling an entire field of  view and traveling at 1000 mph.  Its approach would be eerily silent as it would be moving faster than the speed of sound.  People up to 1000 miles away would be knocked off their feet and sliced or clobbered by a blizzard of flying projectiles.  The impact would set off a chain of devastating earthquakes.  Volcanoes across the globe would begin to rumble and spew.  Tsunamis would rise up and head for distant shores.  Within an hour, a cloud of darkness would blanket the planet.  It is estimated that a billion and a half people would be dead by the end of the first day.  The amount of soot and ash from the impact and the subsequent fires would blot out the Sun, certainly for months, possibly for years.  It is likely that the impact would affect Earth’s climate for about 10,000 years.  Again, in all likelihood, this event would come without warning, out of a clear sky.

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