If we had one single time zone for Earth, noon would be the middle of the day in some places, but it would be morning, evening, and the middle of the night in others.
Since different parts of Earth enter and exit daylight at different times, we need different time zones. In theory time zones are based on the division of the world into twenty four time zones of 15 degrees longitude each. The Royal Observatory in Greenwich, England, is the key location for timekeeping worldwide.
It is also located at the internationally recognized prime meridian, which is 0 degrees longitude, where each day begins at midnight. Naturally, India decided to be 30 minutes between the two time zones , which is why the country is only 30 minutes ahead of nearby Pakistan, for example. This hour time standard is kept using highly precise atomic clocks combined with the Earth's rotation. The Greenwich Meridian in London, England. American railroads maintained many different time zones during the late s.
Operators of the new railroad lines needed a new time plan that would offer a uniform train schedule for departures and arrivals. Four standard time zones for the continental United States were introduced on November 18, The United States is spread across six time zones.
Crossing time zones can throw off your body's internal clock also known as your circadian rhythm and interfere with your ability to sleep well. The more time zones you traverse, the more challenging it can be for your body to adjust to the new local time. Because the Earth is not flat and it rotates. This creates light and dark at different relative times around the world. Timezones are how we adjust our relative time to our internal time sense. The planet itself didn't care about timezones , as they are a human invention.
But because the Earth is generally known to be spherical, that means all humans are scattered across it without a uniform method of keeping everyone in sync, which would wreak havoc on international shipping and travel. As described above, in theory, each fifteen degrees of longitude moved toward the east corresponds to moving the clock an hour forward. In practice, however, this is a rather simplistic explanation, and things are not always as they seem. Time zone regions today, although roughly corresponding to fifteen degrees of longitude, conform more to national and international boundaries than to the rigid fifteen degrees longitude rule.
The irregularity of the time zone borders is necessary politically and for the convenience of the local populace. This is pretty easy to work out with simple mathematics. There are 24 hours in a day, and degrees of longitude encompassing the globe — dividing by 24 gives you the 15 degrees of longitude that equates to a one-hour difference in each time zone. Based on this, you can then deduce that there are 24 time zones around the world.
Believe it or not, time zones are historically linked to pendulum clocks. A bunch of astronomers declared the Greenwich Observatory to be the prime meridian at an conference. What's funny is that the observatory moved to Sussex in the s, but the original site remains the prime meridian. Sign up for our Newsletter! Mobile Newsletter banner close.
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