Equinox, I and my shadow. In how many there comes midday?
the Majority without reflecting will answer this question: “ At twelve o`clock, of course “. Also will cruelly be mistaken. Let`s remember what is midday, and what distinctive features of this moment of days. Let`s use at the same time only simple common sense and we will not listen to the astronomers claiming that there are some solar days, star days, various on duration for several minutes (or even seconds).
Midday is a half of the day understood as daylight. In other words, a half of a period from rising to a sunset.
Many will remember also that:
1. In midday of a shadow the shortest, and on the equator in general hide under legs. This property of half a day is remembered if not from school, then, at least, from the name of once popular movie “ Shadows disappear at midday “.
2. At midday the sun is precisely in the south that allows to orient in the unfamiliar district, having hours (or monitoring shortening of a shadow).
It is necessary to tell that if we lived not in the concrete state with its government, laws and decrees and where - nibud on the desert island, it is desirable without communication with world around, then midday for us really would come at twelve o`clock in the afternoon.
From what it appears? In day of a vernal or autumn equinox day length is equal to duration of night. In days 24 hours from which 12 hours light-, and 12 - are dark. The sun rises at 6 in the morning and sets at 18 in the evening. 18 - 6 = 12. Here it is midday!
For the day following after an equinox the sun will rise several minutes later (go earlier, depending on a season) and will be gone on as much minutes earlier (or later), but the middle all the same is necessary on 12 o`clock in the afternoon. And so all the year round. On the desert island.
The simple common sense is good the fact that it gives in to simple check. Here we will also check when there is a midday in our corner of the world. Let`s use for this purpose properties of half a day 1 and 2.
In 11. 45 we will hammer into the table standing on rather plain surface, a long nail, and far away from nailing we will put an exact compass. In 11. 50 we will mark with a pencil on a table surface the provision of a shadow from a hat nailing. And after that we will draw the line indicating the South on a table. In 12. 00 we will mark the provision of a shadow again nailing, the shadow became a little shorter. And here sun still not in the south! Suspiciously. 12. 10 - the shadow becomes even shorter! 12. 20 - even well, 12. 30 - still. It becomes clear that: or we not on the desert island, or properties of half a day “ wrong “ or midday did not come yet. The common sense inclines to the last assumption (without speaking about the first).
Inquisitive and patient will continue measurements of a shadow, and patience it is required to it much because the shadow will become the smallest only in one or one and a half hours, then and the sun will crawl, at last, to the South. In what business?
In - the first, we did not consider summertime. In the spring all amicably threw hands for the hour ahead and right there forgot about it. Now midday began to come (on summertime) at one o`clock in the afternoon. But also at one o`clock in the afternoon our improvised observatory did not record approach of half a day.
In - the second, we forgot that we live in the country where the standard time works. What is it?
“ The Standard time is entered by the resolution of Council of People`s Commissars of the USSR of June 16, 1930 for the purpose of more rational use of light part of days and the corresponding economy of the electric power. The standard time is more zone for 1 hour “ - the quote from the encyclopedia.
It turns out that midday comes in the summer only at two o`clock in the afternoon.
During reorganization, on a crest of changes, the standard time was cancelled (in March, 1991). I perfectly remember this year, it was one of the happiest years in my life. I remember how began to darken not at four o`clock in the afternoon in the fall, as usual, and in three, and it was pleasant to nobody. Therefore the standard time the same year on - silent was returned, in turmoil of that time very few people noticed it. You remember, somehow time clock was put not for an hour, and on two?
What show data of our observatory? In 14. The 00th shadow is really close to the smallest size, and the sun is close to the southern direction, but again not quite precisely. In what put this time?
In time zones. Within one time zone, for convenience of inhabitants, time is considered identical. For example, 14 hours of Moscow time at the same time happen in Vyatka and in Pskov, and between them more than 1000 km on width.
How many it will be required to the sun that “ to creep “ one thousand kilometers? About an hour. Everyone who flew from the Far East to Moscow or St. Petersburg, knows that “ time “ for flight it is not spent: both took off at ten in the morning local time, and arrived at ten in the morning, but already Moscow time though stayed in the plane of 7 hours. And the plane flies with a speed of 900 - 1000 km/h. Therefore, and the sun moves with the same speed.
In days of the Prohibition when the alcohol was sold only from two o`clock in the afternoon, it was known “ the bridge through the river Psou “. This river separates Abkhazia from Russia (then still the uniform state of USSR). In Abkhazia already two, shops trade, and in Sochi even hour, here and run eager on the bridge through the river Psou. It is an example of how movement of several hundreds of meters, changes time for hour
And indications of your observatory which measures an apparent time in your district, can strongly not coincide with zone time of your region.
I took similar measurements on the longitude of Moscow, and it turned out that midday comes in an interval between 13. 35 and 13. 45 (to obtain more exact data, very long nail and graph paper is necessary). Subsequently I found the data validating my measurements (exact time of midday in Moscow - 13. 40).
And if you have a device of satellite navigation of GPS, then he without effort will prompt you exact approach of the moment of midday in your district.
Here also decide, to spend what is more interesting time for verification of laws of the nature by means of common sense or to spend this time to earn money for the very expensive device. And whether often it is necessary to know in how many there will be a midday?