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Chapter Sixteen — The Lonely Planet

A Short History of Nearly Everything – by Bill Bryson

Chapter 16 — The Lonely Planet

  • From the bottom of the deepest ocean trench to the top of the highest mountain, the zone that covers nearly the whole of known life, is only something over a dozen miles — not much when set against the roominess of the cosmos at large.
  • For humans it is even worse because we happen to belong to the portion of living things that made the rash but venturesome decision 400 million years ago to crawl out of the seas and become land-based and oxygen-breathing.  As a consequence, no less than 99.5% of the world’s habitable space by volume is fundamentally off-limits to us.
  • In the Mariana Trench in the Pacific Ocean, about 7 miles in depth, the water pressure rises to over 16,000 pounds per square inch.
  • Most oceans are must more shallow, but even at the average ocean depth of 2.5 miles, the pressure is equivalent to being squashed beneath a stack of 14 loaded cement trucks.
  • The zone on this remote planet that sustains life is only 12 miles wide (from ocean floor to mountain top).
  • If you ascend to a height of about 500 feet (e.g. the Washington Monument), the change in pressure would be indiscernible. But if you descended in water a similar distance, your veins would collapse and your lungs would compress to the size of a Coke can.
  • The deepest any human has descended in water (without breathing apparatus and without being killed) is 236 feet, somewhat less than the length of a football field.  This feat was performed by Umberto Pelizzari in 1992.
  • The air we breathe is 80% nitrogen.  Put the human body under pressure, and that nitrogen is transformed into tiny bubbles that migrate into the blood and tissues.  If the pressure is lessened too rapidly (as with a quick ascent of a diver), the bubbles trapped within the body will begin to fizz in exactly the same manner as a freshly-opened bottle of champagne.  This bubbling clogs tiny blood vessels, deprives the cells of oxygen, and causes pain so excruciating that sufferers are prone to bend double in agony (hence, the bends).
  • For reasons that are still poorly understood, beneath depths of about a hundred feet nitrogen becomes a powerful intoxicant.  Under its influence, divers have been known to offer their air hoses to passing fish or decide to have a smoke break.
  • Even in quite mild weather, half the calories we burn go to keep our bodies warm.  We can counter our human frailties by employing clothing or shelter, but the portions of earth on which we are prepared or able to live are modest indeed:  just 12% of the total land area, and only 4% of the whole surface if you include the oceans and seas.
  • There are many helpful breaks that we have receive that make life on Earth possible.  Perhaps the principal four are:
    • Excellent location — we are near the right type of star at the best distance from this star.  It is calculated that the Earth would have been uninhabitable if if had been just 1% farther from or 5% closer to the Sun.  For example, the surface temperature of Venus is a roasting 470 degrees Centigrade (roughly 900 degrees Fahrenheit).  This is hot enough to melt lead.
    • The right kind of planet — without the magma swirling beneath us, life would not be possible on Earth.
    • We’re a twin planet — the Moon can be considered a companion planet, and it is the right size of companion.  Without the Moon’s steadying influence, Earth would wobble like a dying top, with very unpleasant consequences on our climate and weather.  The Moon is slipping away from Earth at the rate of about 1.5 inches per year.  In another 2 billion years, it will have receded so far that it will no longer keep the Earth steady.
    • Timing —  we are at the proper end of a very long chain of outcomes involving reasonable periods of stability interspersed with just the right amount of stress and challenge.
  • Of all the elements found here on Earth, the most elusive appears to be francium, which is so rare that it is thought that our entire planet may contain, at any given moment, fewer than twenty francium atoms.  Altogether only about 30 of the naturally occurring elements are widespread on Earth, and barely six are of central importance to life.
  • Oxygen is our most abundant element, accounting for just under 50 of the Earth’s crust.  Who would guess that silicon is the 2nd most common element on earth, or that titanium is tenth?
  • Many of the more obscure elements are actually more common than the better-known ones.  There is more cerium on Earth than copper, more neodymium and lanthanum than cobalt or nitrogen.
  • Abundance of an element doesn’t necessarily relate to importance.  Carbon is only the 15th most common element, accounting for a very modest 0.048 percent of the Earth’s crust, but we would be lost without it.  Carbon is not all that plentiful even in humans, who so vitally depend on it.  Of every 200 atoms in your body, 126 are hydrogen, 51 are oxygen, and just 19 are carbon.
  • The degree to which organisms require or tolerate certain elements is a relic of their evolution.  Modern cattle need quite a lot of copper because they evolved in parts of Europe and Africa where copper was abundant.

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