By the time the Wright brothers took to the air, standard time was used in most of the civilized world. Twenty years later, however, two Army Douglas World Cruisers circled the Earth, and global aviation was in business. The value of the standard time system became apparent. As aviation shrank the globe, accurate navigation became even more vital. Over land, pilots could follow highways and railroad tracks; by the mids, they even had a system of lighted airways and radio beacons.
However, flying in bad weather and over water was quite another story. It hired Harold Gatty, a navigator just back from a worldwide flight, as an advisor.
Most of the needed tools were at hand. The Germans had developed an aerial sextant. Accurate drift meters had appeared soon afterward, along with slide rules for solving course and distance problems. The Army had watches as accurate as the big shipboard chronometers. The trick was to teach flyers to use the stuff. The Air Corps set up a navigation training program for pilots and later expanded it into a full five-month course for navigators.
At the heart of the new air training was a centuries- old technique. From that, the navigator could figure his heading, ground speed, and time of arrival. The process involved taking repeated position readings using everything from maps to celestial observation. Celestial fixes were made using star charts based on Greenwich Mean Time. The Army Air Forces adopted it not only for navigation but also for timing its worldwide operations. World War II navigators lived by it.
Army Air Forces navigators from Italy to the Far East could tell you to the second what time it was in that little town near London. Since the war, technology has taken much of the drudgery out of navigation, and in many aircraft, black boxes have replaced human navigators altogether. Time systems themselves have gone through a series of changes.
That practice confused other people, but it was not until the s that the schedule was revised. The stargazers still kept their system but renamed it Greenwich Mean Astronomical Time. The rest of us went on a midnight-to-midnight routine. As is typical of the military, it coined its own term. They still correct their observations to show the time at the Greenwich meridian, but the old building there has been converted to a museum. Nor are the time zones still the neat parallel lines we envision.
They wiggle around international borders and state boundaries and are redrawn every now and then. When US time lines were changed in , they moved several west Texas towns into the Central Time Zone, where they are an hour ahead of parts of New Mexico that are farther east.
In some countries, the time zones are based on half-hour differences from GMT. A few nations have not adopted standard time. Some scientists and chronologists would like to dump the old, Mesopotamian system of keeping time and come out with metric clocks. Some firebrands proposed that change during the French Revolution, when the populace was trying to get rid of everything aristocratic, including the timepieces.
Some sociologists think we already may have gone too far just by introducing digital clocks. If they take over completely, whole generations could grow up without ever seeing an analog clock face. For centuries, for example, the second was the smallest division of the solar day. Then scientists discovered that electrical currents make quartz crystals oscillate at regular rates.
As I understand it, in aviation and some armed forces, the term Zulu time denoted by the letter Z is used to refer to GMT. What is the origin of this? It's all explained in this Wikipedia article. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams?
Learn more. What is the origin of Zulu time? Conversion Table. The combination of the Bravo and Zulu nautical signal flags, i. Bravo Foxtrot. Bravo Zulu. Due to various scientific reasons and increased accuracy in measuring the earth's rotation, a new timescale, called Universal Time Coordinated or Coordinated Universal Time UTC , has been adopted and replaced the term GMT. Greenwich mean time was based upon the time at the zero degree meridian that crossed through Greenwich, England.
The time one minute after is pronounced "thirteen hundred". This continues until One minute later is "zero hundred" , and the start of a new UTC day. Definition of Universal Time. Based on the rotation of the Earth, time can be measured by observing celestial bodies crossing the meridian every day. Astronomers found that it was more accurate to establish time by observing stars as they crossed a meridian rather than by observing the position of the Sun in the sky.
More Than 24 Time Zones. The Alpha time zone is primarily used in aviation and military operations.
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