From space, Earth is a blue planet with white cloud tops. It is 25,000 miles in circumference and 8000 miles in diameter. Earth revolves around the sun every 365 1/4 days, a period we call a year.
Earth's orbit varies over millions of years. It shrinks and stretches, causing ice ages.
Earth is tilted 23 1/2 degrees on its axis. This tilt causes the seasons. Northern and Southern Hemispheres alternately tilt toward and away from the sun. When it is summer in the United States, it is winter in Australia.
Earth's moderate distance from the sun is a factor in the evolution of life. Earth is neither too hot nor too cold. Liquid water can exist, and where there is water, there is life. It rained for millions of years to create the oceans.
Mountains are caused by stresses in the earth. Our atmosphere came from volcanoes and extends 300 miles. It provides protection from deadly rays.
Life began in the sea. 4 billion years ago, chemicals began showing signs of life. Viruses straddled the line between the living and nonliving. One-celled organisms evolved. Plants colonized the land. Plants produced oxygen by photosynthesis, making animal life possible. Invertebrates and vertebrates evolved. Fish evolved into amphibians, which evolved into reptiles. Dinosaurs lived in the Mesozoic Era between 65 million and 220 million years ago: tyrannosaurus, brontosaurus, triceratops, stegosaurus, ankylosaurus & duckbills. I wrote a paper called "The Other Sciences," which was dinosaur-based. A species is a group of animals whose members interbreed. There are 10 million species of animals.
The continents formed one land mass called Pangea. As continental drift occurred, reptiles evolved into birds and mammals. Most paleontologists believe that dinosaurs became birds. There was an age of giant mammals in the Cenozoic Era. Mammoths and mastodons became extinct at the end of the recent Ice Age. Man has existed in some form for 5 million years. He evolved from primates in southeast Africa and spread into Europe and Asia. From Asia, he populated the South Pacific islands and walked across the land bridge at the Bering Strait into the Americas. That was 50,000 years ago. Races as we know them came into existence 20,000 years ago at the end of the Ice Age. Civilization was born in Egypt and Mesopotamia. Recorded history spans 5,000 years. The colonization of the Americas by Europeans from the Renaissance forward is the most important human migration in history. World population is 7.6 billion with 326 million in the United States.
Natural history is explained in terms of the Geological Time Scale. Paleontologists study the fossil record. Fossils are found in sedimentary rocks, those laid down by water. Radio carbon dating can determine the age of a rock. Knowing the age of a rock is to know the age of its fossils.
I recall Al Gore's book about the environment. It was unreadable! George Bush 41 referred to Gore as "Ozone Man" because of his obsession with the ozone layer. Global warming is a big issue with Gore. It is the tendency for man-made carbon dioxide to trap heat in Earth's atmosphere. The fear is that the earth will be heated to the point that its polar caps will melt, flooding coastal cities. Paradoxically, geologists say we are between Ice Ages. If another Ice Age is inevitable, global warming might serve as a means for heating the planet. We are trying to figure out whether we will burn up or freeze to death. If global warming is taking place, it may not be so bad. It got pretty cold in Nashville this past winter. If it is a bad thing, man's ingenuity may find a remedy. We are rational beings. With the population of the earth almost 8 billion, we need to manage natural resources. The rain forest of South America cannot be destroyed without repercussions. We should be planting trees, one for each one cut down. Houses have traditionally been built with lumber, and books have been made of paper. That can change. New building materials can be developed, and libraries can become electronic. The large mammals of Africa need to be protected, otherwise they will become extinct in a few decades. It is up to the governments of African countries and their National Park systems. At the same time, it is a world problem. Man is one species despite his fragmentation into religions and nationalities. If man were to act as one species (I am not promoting a one-race concept) and stop warring, he could put his house in order. Energy and money spent by Muslims, Jews & Christians fighting each other could go a long way toward developing alternative fuels. Fossil fuels will eventually be depleted. It will take time, but the amount of coal, oil & gas in the ground is finite. If man does not prepare for a time when they are gone, civilization may collapse. For all the talk about renewable energy and hybrid cars, we are nowhere near a state of practical application.
JIM COLYER ALBUMS with PAM, KYMBERLY & ANNIE.
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