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ashone17 (Chapter 17 ** )

Chapter Seventeen — Into The Troposphere

A Short History of Nearly Everything – by Bill Bryson

Chapter 17 — Into the Troposphere

  • Without the Earth’s atmosphere, the Earth would be a lifeless ball of ice with an average temperature of minus 60 degrees Fahrenheit.  Also, the atmosphere absorbs or deflects incoming swarms of cosmic rays, charged particles, and ultraviolet rays.  Our atmosphere is equivalent to a fifteen-foot thickness of protective concrete, and without it, these invisible visitors from space would slice through us like tiny daggers.  Even raindrops would pound us senseless if it weren’t for the atmosphere’s slowing drag.
  • The atmosphere extends upward for about 120 miles.  If you shrank the Earth to the size of an average desktop globe, the atmosphere would only be about the thickness of a couple of coats of varnish on the globe.
  • The troposphere (or ‘turning sphere’) is about 10 miles thick at the equator and no more than 6 or 7 miles high in the temperate latitudes where most of us live.  Eighty percent of the atmosphere’s mass, virtually all the water, and thus virtually all the weather are contained in this thin and wispy layer.
  • When you see the top of a storm cloud flattening out into the classic anvil shape, you are looking at the boundary between the troposphere and the stratosphere.
  • The temperature just 6 miles up into the atmosphere is -70 degrees Fahrenheit.
  • After you have left the troposphere and moved upward, the temperature warms up to about 40 degrees Fahrenheit.  This is due to the absorptive effects of ozone.  The temperature then plunges again to as low as -130 degrees in the mesosphere before skyrocketing to 2,700 degrees in the aptly named thermosphere.
  • At the height of the thermosphere, at 50 miles or more, the air is so thin that any two molecules will be miles apart.
  • Altogether there are about 5,200 million million tons of air around us (25 million tons for every square mile of the planet).
  • A typical weather front may consist of 750 million tons of cold air pinned beneath a billion tons of warmer air.
  • One thunderstorm, it has been calculated, can contain an amount of energy equivalent to four days’ use of electricity for the entire United States.  A bolt of lightning travels at 270,000 miles an hour and can heat the air around it to 50,000 degrees Fahrenheit, several times hotter than the surface of the Sun.  At any one moment, 1,800 thunderstorms are in progress around the globe.  There are approximately 40,000 thunderstorms per day here on Earth.  Day and night across the planet, about 100 lightning bolts hit the ground every second.
  • The Earth revolves at 1,041 miles an hour at the equator, though as you move toward the poles the rate slopes off considerably, to about 600 miles an hour in London or Paris, for instance.  If you are on the equator, the spinning Earth has to carry you quite a distance (26,000 miles) to get you back to the same spot.  If you stand beside the North Pole, however, you many need to travel only a few feet to complete a revolution.  Both journeys take a full 24 hours.
  • Oceans are the real powerhouses of Earth’s surface behavior.  Water is marvelous at holding and transporting heat.  Every day, the Gulf Stream carries an amount of heat to Europe equivalent to the world’s out from coal for 10 years, which is why Britain and Ireland have mild winters compared to Canada and Russia.  Water also warms slowly, which is why lakes and swimming pools are cold even on the hottest days.
  • The Atlantic Ocean is saltier than the Pacific Ocean.  The more salt contained in water, the denser it is, and dense water sinks.  Without its extra burden of salt, the Atlantic currents would proceed up to the Arctic, warming the North Pole but depriving Europe of all that kindly warmth.
  • The main agent of heat transfer on Earth is known as the thermohaline circulation.  It originates in slow, deep currents far below the surface of the oceans.  Surface waters, as they get to the vicinity of Europe, grow dense and sink to great depths and begin a slow trip back to the southern hemisphere.  When they reach Antarctica, they are caught up in the Antarctic Circumpolar Current, where they are driven onward into the Pacific.  It can take over 1,500 years for water to travel from the North Atlantic to the mid-Pacific.
  • Our seas and oceans do another great favor for us.  They soak up tremendous volumes of carbon and provide a means for it to be safely locked away.
  • What keeps our world stable and cool?  Life does.  Trillions upon trillions of tiny marine organisms capture atmospheric carbon, in the form of carbon dioxide, and they use it to make their tiny shells.  By locking up the carbon in their shells, they keep it from being re-evaporated into the atmosphere, where it would build up dangerously as a greenhouse gas.
  • Altogether there is about 20 thousand times as much carbon locked away in the Earth’s rocks as in the atmosphere.  Eventually much of that limestone will end up feeding volcanoes, and the carbon will return to the atmosphere and fall to the Earth in rain.  This is the long-term carbon cycle.  The entire process takes about 500,000 years for a typical carbon atom.

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