A book by Dava Sobel
This book attempts to explain Earth, the solar system, our galaxy and our universe, in clear and easy-to-understand language.
For thousands of years, humans had made quite detailed observations about the heavens. It wasn’t until the 14th century, when humanity emerged from the Dark Ages, that people started to test their theories about why the heavens were the way they were. Stars, like the Sun, emit energy in wavelengths shorter and longer than visible light, ranging from gamma rays to radio waves to ultraviolet light. Detecting those waves can tell a lot more about objects in the sky than just what we see.
Billions of years ago, matter, time and energy existed as what is known as the initial singularity, smaller than an atom and with nothing else outside of it. Then the Big Bang happened. If the expansion had happened just a little faster than it did happen, then gravity could not have drawn matter together to form stars and planets. Of the four forces that affect various kinds of matter (strong nuclear force, electromagnetic force, weak interaction and gravity), gravity is the weakest, but it has an unlimited range, working over hundreds of millions of miles.
The book explores the Solar System, giving a short profile of all of its inhabitants, from the Sun to Pluto (no longer considered a planet). Also explored is the search for life on other planets; as of now, there is no actual evidence of life anywhere except on Earth.
The axis of Earth is tilted by approximately 23 degrees, which helps to explain Earth’s seasons. At the summer solstice, the North Pole is tilted toward the Sun, so its rays beat down most strongly on the Northern Hemisphere. At the winter solstice, the North Pole is tilted away from the Sun, so its rays beat down on the Southern Hemisphere. During the spring and autumn equinoxes, the tilt is sideways to the Sun, so both hemispheres get an equal amount of light.
The author does a very good job at presenting the material in language accessible to anyone. For those who want to learn more about the heavens, but consider themselves scientifically illiterate, this is an excellent place to start.
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A book by Dava Sobel
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