Conversations on the topic of summer, winter, standard, local, astronomical time prompted me to this post. I will tell and show you how to calculate the local time. You will find out what it is standard time... There will be a bit of theory and history. And there will be no medicine and physiology, and I will also leave aside the political and economic views on this issue. I am not a physician, not an economist, and certainly not a politician, I am a navigator.
Therefore, one of the sciences necessary for navigation even in our time - nautical astronomy is well known to me.
Nautical astronomy allows you to control the position of the ship by observing celestial bodies. The heavenly bodies are constantly moving and, in order to determine their place in this moment, it is necessary to know the laws of their motion, studied in astronomy. The same applies to artificial satellites Earth. In addition, nautical astronomy provides information about the service of time and various phenomena occurring on Earth (sunrises / sunsets, illumination, eclipses, etc.) and in the Universe.
The main tasks solved by nautical astronomy are:
- determination of a place in the sea according to observations of luminaries;
- determination of corrections for directional devices (compasses);
- providing time service.
Auxiliary tasks:
- determination of illumination;
- the culmination of the luminaries, etc.
Russia wants it to be smaller. No, he's not going to spill any territory, but President Dmitry Medvedev has suggested Russia reduce its number of time zones from 11 to 4, arguing that the extreme time difference in which Western Russia wakes up for breakfast is the same as eastern Russia climbs into bed, "divides" the country and "makes it difficult to effectively govern." Could Russia just change those time zones? How are time zones determined?
Prior to the adoption of standard zones, cities set their local time. But with the advent railways and their accompanying travel schedules in the 19th century, people suddenly needed to know exact time so they don't miss their trains. S. and Canada adopted the standard time system. The following year, delegates from 22 countries met in Washington DC to agree on times between the countries. They have chosen a longitudinal line that runs through Greenwich, England as the standard from which they will be measured.
Now we come to the topic of time. It is clear that humanity has taken one day as a unit of time - during this time the Earth makes one revolution around its axis, or the time interval from sunrise to sunrise. Then this period of time was divided by 24 and received - 1 hour. Since one revolution is 360 degrees, we get that 1 hour is 15 degrees of the Earth's rotation around its axis (the apparent motion of the Sun), and one degree of the Sun's motion (Earth's rotation) is 4 minutes of the time accepted by earthlings.
And let's not complicate the task with the knowledge that:
- the Earth's rotation slows down by 0.00023 seconds per century;
- random jump-like changes in the speed of rotation of the Earth (several were noted, one - in 1920 by 0.000000045 s);
- the value of true solar days during the year changes by an average of 59.14 s;
- a year is not 365 days, but 365.2422 days.
Every 15 longitudinal degrees, the time changed by an hour, thus creating 24 time zones around the world. Over the years, governments have adopted, changed, or ignored Greenwich Mean Time as they see fit. Congress passes the Unified Time Act to provide summer savings national practice but the one that asserts can decide whether to watch. In the first year in summer time only 19 states participated. Over the years, more states have agreed to a timetable summer timetable the federal government, which was created for energy-saving purposes, with the idea that an extra hour of daylight in the winter will force people to use less oil.
Therefore, to discuss the topic of sleep-rest-work and the translation of hours, we will not talk about true solar and sidereal times (astronomical). We will only operate with the mean solar time, taken for time reckoning on Earth. When the length of the day is calculated not from one day, but an average of 1 year.
Local time
- the time of the observer on the given meridian, and since meridians are countless, and local times are countless. But all observers on the same meridian have the same local time.
Greenwich time is the local time of an observer standing on the Greenwich meridian.
Because The Greenwich meridian is taken as the origin of longitude on the globe, then the local time differs from Greenwich exactly by the longitude of the place, converted from an angular measure to a time one at the rate of 360 degrees = 24 hours.
There is a saying:
"Longitude west, Greenwich time best.
Longitude east, Greenwich time least ".
Which in any translation means, with east longitude you have more time than Greenwich, and with west longitude - less than Greenwich.
Arizona never adopted a new timing plan on the grounds that it was too hot in the summer for the "spring ahead" hour. Daytime hours don't change much in Hawaii, and a tropical state never needs a timing plan. The Americans noticed summer time, but they didn't like it. The result left part of Indiana in Central Time, part in Eastern Time, part observing summer day and partly observing standard time during a year.
If Indiana can have two time zones, there is no reason that Russia, 180 times the size and with many millions of people, cannot change its clocks to please its eastern citizens. S. saved energy by starting Daylight Saving Time three weeks ago. Nepal is 15 minutes ahead of India and an hour and 15 minutes behind China. Iran cannot decide what to do with the summer day, its parliament wants to abide by it, and President Mahmoud Ahmadinejad says no. After all, time is really relative.
Now we know that Greenwich time is taken as a reference point, but local time is inconvenient for everyday life.
Therefore, for a whole region or country, a single time was taken (local observatory, ruler's palace, etc.). But...
With this approach, inconveniences arise - the difference with the time of another region or country could contain fractional parts of hours and even minutes. The development of civilization, communication of peoples demanded the streamlining of time counting.
Important parallels of latitudes
In this post: Latitude and Longitude - Latitudinal Thermal Zones of Earth - Longitude and Time - Standard Time and Time Zones - International Date Line - Indian Standard Time - Taibagaan Time. Latitude and longitude are imaginary lines used to determine the location of a place on earth. Latitude is the angular distance of a point on earth surface measured in degrees from the center of the earth. Since the earth is slightly flattened at the poles, the linear distance of the degree of latitude at the pole is slightly greater than at the equator. For example, at the equator it is 704 miles, at 45 ° it is 054 miles, and at the poles it is 407 miles. Besides the equator, north pole and south pole, there are four important latitude parallels - the Tropic of Cancer in the northern hemisphere.
Latitudinal thermal zones of the earth
The midday sun is definitely overlapped at least once a year at all latitudes between the Tropic of Cancer and the Tropic of Capricorn. Thus, this area receives maximum warmth and is called the hot zone. The midday sun never shines overhead at any latitude outside the Tropic of Cancer and Tropic of Capricorn. Thus, the areas bounded by the Tropic of Cancer and the Arctic Circle in the northern hemisphere, as well as the Tropic of Capricorn and the Antarctic Circle in southern hemisphere have moderate temperatures. Therefore they are called temperate zones... The areas lying between the Arctic Circle and the North Pole in the Northern Hemisphere, and the Antarctic Circle and the South Pole in the Southern Hemisphere, are very cold. This is because the sun does not rise much above the horizon here. Therefore, its rays are always inclined. Therefore, they are called frigid zones. Longitude is the angular distance measured in degrees along the equator east or west of the Prime Meridian. On the globe, longitude is shown as a series of semicircles that run from pole to pole, passing through the equator. Such lines are also called. Unlike the equator, which is located in the center between the poles, any meridian could be taken to begin the numbering of longitude. As the Earth commits one full turn 360 ° in one day or 24 hours, it goes through 15 ° in one hour or 1 ° in 4 minutes. The earth rotates from west to east, so every 15 ° we go east, local time advances by 1 hour. Thus, we can conclude that places east of Greenwich see the sun earlier and gain time, while places west of Greenwich see the sun later and waste time. If each city were to keep the time of its own meridian, there would be a lot of local time difference between one city and another. Travelers traveling from one end of the country to the other will have to change their hours if they wish to maintain their destinations. To avoid all these difficulties, the standard time system is followed by all countries. Most countries take their standard time from the central meridian of their countries. P, it would be inconvenient to have a single time zone. Thus, these countries have multiple time zones. And there are five time zones - Atlantic, Eastern, Central, Mountain and Pacific time zones. The difference between the local time of the Atlantic and Pacific coasts is almost five hours. There are now nine time zones in Russia. Thus, there is a total difference of 24 hours or a whole day between the two sides of the 180-degree meridian. This is the International Date Line, where the date changes by exactly one day when it intersects. A traveler crossing the date line from east to west loses the day; and, crossing the dating from west to east, he gets a day. International dating line in the middle The Pacific curve from the normal meridian at 180 ° in the Bering Strait, Fiji, Tonga and other islands to prevent confusion of day and date in some island groups cut by the meridian. Some of these follow Asian or New Zealand standard time, while others follow US date and time.Why is the international reference line zigzag
Therefore, if the data line was straight, then two regions of the same island country or island group fall under different zones dates. Thus, to avoid confusion with the date, this line goes through where the sea lies, not land. The Indian government has adopted a meridian of 5 ° East for standard time, which is 5 hours 30 minutes, ahead of Greenwich Mean Time. The area that lies between the Tropic of Cancer and the Tropic of Capricorn is called the Torrid Zone.- The shape of the earth is "Geoid".
- And the location of a place on earth can be referred to in terms of latitudes and longitudes.
- The average premium is 69 miles. 1 mile = 607 km.
- Tropic of Capricorn in the southern hemisphere.
- Arctic Circle 66½ ° north of the equator.
- The Antarctic Circle is 66 ½ south of the equator.
- The angle of the sun's rays continues to decrease along the poles.
- T. or Greenwich Mean Time, which is sometimes called World Time.
- Conversely, if we go west, local time slows down by 1 hour.
- This is impractical and very inconvenient.
- The international date line runs across the Pacific Ocean.
- It is an imaginary line like longitude and latitude.
- The time difference on either side of this line is 24 hours.
- So the date changes as soon as it crosses that line.
- Some groups of islands fall on one of the dates.
- The shape of the Earth is a Geoid.
- Due to the shape of the earth, the temperature decreases from the equator to the poles.
- North Poles - Latitude.
At the astronomical congress in 1884, a system of standard times was proposed and gradually adopted in almost all countries of the world. In the system of standard times, time is counted at 24 central meridians of the Earth, separated from each other by 15 degrees of longitude, so that in neighboring zones the time differs by 1 hour. Zone time extends to 7.5 degrees of longitude on either side of the central meridians.
Zone time
Zone time is the average local time of the central meridian of a given time zone, taken throughout the zone.
Which of the following statements is false?
Which of the above statements are false? Timing has historically been closely related to astronomy. A day is defined as the apparent orbit of the sun around the Earth, a month above the lunar phase, and a year later in the Earth's orbit around the Sun. The more accurate the time was, the more significant the deviations from these definitions were, and corrections became necessary. These events have led to numerous definitions of time intervals, times and calendars.
If you want to describe the corresponding time in one day, then it is obvious for the state of the sun. But since this differs from place to place on earth, some legend... First, you enter the true solar time... To start the day at 0 o'clock, add another 12 hours. The same true solar time exists everywhere in longitude. Due to the Earth's elliptical orbit and ecliptic, but it doesn't work evenly. Therefore, the average Sun is determined, which moves with a constant angular velocity around the equator and needs the same time as the true sun for the ecliptic.
But there is a small focus - on the 12th central meridian longitude is 180 degrees, and one part of its belt is in the eastern hemisphere, and the other is in the western. The time on the clock of the inhabitants of this zone is the same, but the number on the calendar for the inhabitants of the eastern and western hemispheres is different and differs by 1 day. The inhabitants of the western hemisphere still had yesterday, in comparison with us - the inhabitants of the eastern part of the Earth. And the meridian is called the date line.
Then the hour angle of the mean sun determines the mean solar time and it is applied. However, this average solar time is different for each meridian. Therefore, starting from the prime meridian, you have created 15-degree intervals, in which the same time prevails, time zones. Thus, there are 24 time zones. However, the equation of time is not constant, but changes throughout the year and has four extremes.
Date and calendar To determine the day, the rotation of the earth around its own axis or the apparent migration of the sun around the earth was used. Likewise, the Earth's orbit around the Sun is used to determine the year. And here, too, there are different definitions. A tropical year is defined as the time interval during which the sun once moves from spring to spring. At the vernal equinox, the sun crosses the equator from south to north. But since only whole days make sense as a calendar definition, an additional leap day is introduced every four years.
With such a structure of belts, standard time cannot differ from local time by more than 30 minutes. However, the theoretical boundaries of the belts are observed only in the seas, oceans and sparsely populated areas. In fact, the boundaries of the belts are determined by the governments of the countries, taking into account the administrative, geographic and economic characteristics.
Daylight saving time. In order to save electricity in the evening lighting, the clock on the territory of the USSR was set 1 hour ahead of standard time. Initially, this time was introduced only in summer (summer time), but by decree in 1931 it was permanently left. Ie daylight saving time is standard time 1 hour.
Summer time.
In a number of countries, the clock is set forward 1 hour (sometimes 2 hours) only for the summer. In the USSR, daylight saving time (1 hour to daylight saving time or 2 hours to standard time) was introduced in 1980. I will not describe the further game with time and time zones in our country - everyone knows.
Today our country is divided into time zones in this way.
The resulting longitude (so as not to waste time on trifles, we take only an integer number of degrees) is converted into hours and minutes at the rate of 15 degrees - 1 hour, 1 degree - 4 minutes. We make a small assumption that the Sun passes its upper climax (noon) at about 12.00 local time (in fact - 12.00 plus or minus about 15 minutes).
Now we subtract from 12:00 pm (for the eastern hemisphere, and for the western hemisphere we add) the obtained value of longitude in hours and minutes. We get the Greenwich time of half a day at the given meridian (longitude). Next, we add the difference on your watch to Greenwich Mean Time (UTC, universal) for the Eastern Hemisphere (and subtract it if we count the Western Hemisphere).
Ask: "Where can I find Greenwich time?" I will answer - this is today's Moscow minus 4 hours (today is February 3, 2013, otherwise we don't know what will happen tomorrow).
Example: east longitude 33 degrees, Moscow time, i.e. Greenwich 4 h.
We translate the longitude into hours:
- 33/15 = 2.2 means 2 hours
- 2,2-2=0,2
- 0.2 * 60 = 12 means 12 minutes
- longitude 33 degrees expressed in hours - 2 h 12 m.
Determine the time of our local noon GMT:
12h00m - 2h12m = 9h48m
Add the difference of hours (what is on the hand or near) with Greenwich:
9h48m + 4h = 13h 48m.
This is the time of half a day according to our clock (which is on the hand or nearby) in a place with a longitude of 33 degrees of the eastern hemisphere (remember - with an accuracy of 30 minutes, since the Sun is not always at the upper climax at 12.00). For accurate counting, boatmasters use astronomical tables.
Now is standard time. It is necessary to translate the longitude of the place into hours and round up to the nearest hour.
For example: longitude 142.9 degrees East.
142,9/15=9,526
This means the 10th eastern time zone. Those. 10 hours ahead of Greenwich.
A few words about the rising of the sun. At the Equator, the Sun always rises around 6 a.m. local time, respectively, sets around 6 p.m. Further to the North or South, the time of sunrise and sunset depends on the latitude of the place and the time of year. But on the days of the vernal and autumnal equinox at all latitudes, the Sun rises and sets, as in the Equator - about 6 and 18 hours local time.
On the example of St. Petersburg and all places at a latitude of 60 degrees north latitude. Local time:
March 20, sunrise at 6:00, sunset at 18.15
June 21, sunrise at 2 h 36 m, sunset at 21.28
September 22, sunrise at 05:45 pm, sunset at 18:00
December 21, sunrise at 8h 5m, sunset at 14.55
Used by: "Naval Astronomy" by B.I. Krasavtsev (Moscow "Transport" 1986), MAY 2012.
How to determine the local time. As you already know from the 7th grade geography course, at the same moment in different parts of the planet, lying on different meridians, there will be different local (Those. solar )time ... You know that this is due to the rotation of the Earth on its axis. The time will be the same only at all points lying on the same meridian. So, on the western and eastern outskirts of even one settlement local time will differ. This difference will grow with increasing distance between the meridians. So, on neighboring meridians drawn through 15 °, the difference in local time is 1 hour, Carried out after 1 - 4 minutes, Carried out after 1 "(one minute, one degree is divided by 60 minutes) - 4 s (it is at such angular distances that the points rotate one meridian for the indicated time intervals).
In this case, the local time on the meridian, located to the east of which point, is ahead of the time in it, and on the more western meridian - to lag behind. For example, if local time in Kiev afternoon tea (12 h), then in Donetsk already 12 h 29 h, A in Lvov at this moment - only 11 hours 33 hours 56 seconds. Therefore, in order to establish the exact time at different points, knowing it at one of them, you need to carry out such calculations.
a) Kiev - 30 ° 34 "E;
b) Donetsk - 37 ° 49 "east longitude;
c) Lviv - 24 ° 03 "east.
2. Set the difference in longitudes between points (in degrees and minutes):
a) between Donetsk and Kiev - 37 ° 49 "- 30 ° 34" = 7 ° 15 "E;
b) between Kiev and Lvov - 30 ° 34 "- 24 ° 03" = 6 ° 31 "east.
3. Convert the difference in longitudes (from degrees and minutes) to the difference in time (in hours, minutes and seconds):
a) 7 ° 15 "= 7 x 4 хв15 х 4 с = 29 хв;
b) 6 ° 31 "= 6 x 4 x 31 x 4 s = 26 x 4 s.
the found values show the difference in local time on the meridians drawn through Kiev, Lvov and Donetsk.
4. Until the known time in Kiev (12 hours Add (in the case of Donetsk, which lies to the east of Kiev) or subtract from it (in the case of Lvov, which is to the west of Kiev) the obtained value:
a) if it is 12 o'clock in Kiev, then the local time in Donetsk will be
12 hours + 29 hours = 12 hours 29 hours;
b) if it is 12 o'clock in Kiev, then the local time in Lviv will be
12 h - 26 x 4 s = 11 h 33 x 56 s.
Time zones and standard time. It is almost impossible to use the local time, which is different at every point, in everyday life. For convenience all over the world use zone time . For this, as you know, the globe was conventionally divided by meridians into 24 bands (according to the number of hours in a day) - into Time Zones(15 ° longitude each). At all points of one belt, it was agreed that the time should be considered the same. By standard time, the local time of the meridian is taken, passing through the middle of this belt (middle meridian).
Time zones are numbered from 0 to 23 eastward: the middle meridian of the 0th zone is Greenwich(Initial) meridian, 1st belt - meridian 15 ° east. d., 12th zone - 180th meridian, 23rd zone - meridian 15 ° W. etc.
The time of the 0th zone is called Western European , 1st - Central European , another - Eastern European ... The zone number indicates the standard time at the moment when the north is on the Greenwich meridian. The time difference between two adjacent zones is 1 hour. Moving around the globe from west to east, we must move the clock hand one hour forward when crossing the borders of each next zone, and moving to westward- one hour ago.
The location of Ukraine relative to time zones is convenient: 95% of its territory lies in the second zone, only Luhansk and parts Donetsk and Kharkiv regions- In the 3rd belt, and an insignificant part Transcarpathian region - in the first belt. However, in practice, for convenience, the boundaries of time zones on land are drawn not strictly along the meridians, but taking into account state boundaries. Therefore, the entire territory of Ukraine is assigned to the second time zone. Standard time in our country is the average time for the second zone of the meridian (30, which passes almost through Kiev... Therefore, in Ukraine, the belt is also called Kiev .
Amazing Ukraine
By the time of the second zone, in addition to Ukraine, Belarus, Latvia, Lithuania, Estonia, Finland, Moldova, Romania, Turkey also live in Europe. All western neighbors of Ukraine, Central countries and most countries Western Europe use Central European time, while Great Britain, Ireland, Iceland and Portugal use Western European time. On the adjacent to the borders of Ukraine Russian territories the so-called Moscow time operates, which is 1 hour ahead of Moscow time
Ri c ... Time zones of the world
Summer time. Annually in Ukraine is introduced summer time : on the night of the last Sunday in March hour hand translate one hour forward. This makes it possible to make fuller use of the light part of the day and save energy. On the night of the last Sunday in October, the clock is returned one hour back, restoring the standard time.
The introduction and cancellation of daylight saving time is carried out synchronously by most European
