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Earth – The LIVING Planet! Where is life found? Between 5 - 30 Million species (who knows?!), located in 867 distinctly different “life zones” WHY is each zone so different from the others?! Life is extremely DIVERSE – can you categorize or classify any of these animals? • How is this Greyhound different from a regular Greyhound? • What caused this “change”? – Clue 1: it’s not from working out… – Clue 2: it was born this way… Earth is “just right” for life • Earth is located in the “habitable zone” around a star, and travels in its orbit around the Sun (a distance of 600 million miles!). It’s size and gravitational force causes it to veer from a straight line only one-ninth of an inch every eighteen miles. If it veered by one-tenth of an inch away, the orbit would become so large that life on the Earth would be impossible due to drastically-reduced temperatures; if it veered by one-eighth of an inch toward, life on the Earth would be impossible due to drastically-increased temperatures. One-ninth of an inch – just right! • The Earth completes its orbit in about 365 days—which represents what we call one year. This, together with the fact that the Earth is tilted on its axis, allows for what we call "seasons." The rotation of the Earth on its axis, (stabilized by our Moon – which also causes the vital tides of the ocean), provides periods of light and darkness, which is necessary to sustain life as we know it. Without the tilt, most of our planet would either bake or freeze. If the Earth rotated much faster, fierce hurricanes would stir over the Earth like a kitchen food mixer. If the Earth turned significantly slower, the days and nights would be impossibly hot or cold. Venus, for example, turns only once every 243 days, which accounts in part for the fact that daytime temperatures can reach as high as 500 degrees Celsius (water boils at 100 degrees). 365 days, with a moon and a tilted axis – just right! • Wrapped around the Earth, and about 90 miles deep, is a protective blanket of gasses we know as the atmosphere. The proper balance of these gases is essential to life on the Earth. The atmosphere of Venus is too thick to sustain life; that of Mars is too thin. But the Earth’s atmosphere does several things. Without water vapor and certain gases, the heat would escape as soon as the Sun set each day, & we would freeze every night. Were it not for the fact that most meteors burn up (from friction) when they strike the thick atmosphere, the Earth would be pounded almost daily by these unwelcome visitors. Between 6-30 miles above the Earth, the ozone layer filters out most of the ultraviolet rays from the Sun that would be harmful to life’s DNA, and fatal in larger amounts. Earth is also one of the few planets that has plentiful liquid water – essential to all living things. 90 miles of uniquely composed atmosphere, with liquid water – just right! • “The laws of science, as we know them at present, contain many fundamental numbers, like the size of the electric charge of the electron and the ratio of the masses of the proton and the electron …. The remarkable fact is that the values of these numbers seem to have been finely adjusted to make possible the development of life.” – Stephen Hawking • “The more I examine the universe and the details of its architecture, the more evidence I find that the universe in some sense must have known we were coming…” – Freeman Dyson Disturbing the Universe New York: Harper & Row, 1979, p. 250