etsiot ® 14-Apr-2019 21:39

Time and Navigation


Year: 2015
Language: english
Author: A. Johnston, R.D. Connor, C. E. Stephens, P.E. Ceruzzi
Genre: Handbook
Publisher: Smithsonian Books
Edition: 1
ISBN: 978-1-58834-492-2
Format: EPUB
Quality: eBook
Pages count: 220
Description: We are all navigators. To find our way from here to there, we often look for landmarks or use maps. Today, we use smartphones and GPS to get around. But navigating has not always been effortless. Across the centuries, as people crafted new methods by which to navigate, they faced technical complexities, harsh environments, and personal peril. Voyagers often became lost, never to be found. Having a reliable way to navigate could mean the difference between life and death. The human need to travel and make connections across the world has inspired, among many other things, the art and science of navigation.
Getting from one place to another involves more than just knowing where. We also need to know when. If we want to know where we are, we need a reliable clock.
This surprising connection between time and place has been crucial for centuries. About 250 years ago, mariners first used mechanical clocks to navigate the oceans. Today we locate ourselves on the globe with synchronized atomic clocks in orbiting satellites. Among the many challenges facing navigation from then to now, one stands out: keeping accurate time. Time and place are connected in ways that most people do not realize in their daily lives, and this connection has been an essential element in the development of global commerce and modern society.
There is no better place on Earth for understanding the connections between time and place than the courtyard of the Royal Observatory in Greenwich, England. On this spot overlooking the city of London, those connections, first established generations ago, endure to this day on a global scale. Visitors can straddle a brass line in the courtyard corresponding to zero degrees longitude. This is the line from which all the other lines of longitude are based, reaching all the way around the globe. Greenwich reminds us that the oldest clock is Earth itself, and the oldest means of keeping time came from observing changes in the sky. Some of the earliest forms of navigation were based on the same principles. Prominent clocks at Greenwich and other observatories count the hours, minutes, and seconds—once determined with an astronomer’s eye on a telescope in a nearby dome, now transmitted from a physicist’s atomic clock in a laboratory.

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