SOLAR TIME, TIME LEGAL. - II - SOLAR TIME, TIME LEGAL. - II -
Sundial vs Mechanical Watch
Trying to understand time.
The intention of the previous post is to show a more explicit, rational or justified, by the sundial hours usually vary with time in the watch and not just say simply that the difference is observed is due to the mechanical watch is the movement of an imaginary sun gear and the sun regularly makes true variable-speed ahead at times and falling behind in others. How curious is the engine of our intelligence wanted to go for the more anxious a possible route that took us to unravel the mystery of the mean sun, from where he and his close relationship with the real sun.
Also, we know that this imaginary Sun called "Sun Media" is conveniently placed Ecuador on the other blue and that his commuting from west to east is performed at a constant rate throughout the year. As your speed is the average value of true solar day length throughout the year, while the real sun, which directly controls our lives moves over the sky at variable speed and makes bending over Ecuador blue, for this two cases, at some time during the real Sun is ahead of the mean sun, otherwise you fall behind and in another match. Because these oscillations Sun's true that is placed on one side or the other of the mean sun, our watch does not indicate the time recorded by the sundial but was compensated for the time difference between the meridian of reference to establish the Legal Time and longitude on which is the sun clock
Something else we learned in the last post is that the time difference between the sundial and the wrist is due to two causes conjugate of geographic origin and other astronomical. The cause is geographically the angular difference between the reference meridian and the Time Zone adopted by the country and the meridian where the sundial taken hours. The cause is due to astronomical annual movement Sun in the sky.
Again, comparing the mean solar day about Sidereal day, this is late with respect to the sidereal time in 3 minutes 56.5554 seconds each day. Hence if we consider the sidereal day of 24 hours, the mean solar day has 24 hours 3 minutes 56.5 seconds and if the basis is a 24-hour solar day, sidereal day have 23 hours 56 minutes 3.4 seconds long.
The reason that the mean solar day is delayed with respect to the sidereal day is due to the displacement of the earth around the sun
Being the center "O" land "T1" line and a star turn with the center of the sun and those with the meridian of the place (OS line in Figure 6), in the course of a sidereal day the Earth changes from "T1" to "T2" to travel on its orbit, leaving the star "E "again aligned with the meridian (O'-E), but due to displacement, the sun," S "is not completed yet and need additional time to elapse so that the angle" SO'-E "is fulfilled and the sun reaches the meridian.
The phenomenon occurs because the stars are extremely far from Earth and translational movement of the world practically does not alter the position of the star in the sky, while the Sun is very close and their position in the sky is strongly affected by the translation.
The reason is not used Sidereal time despite constant for the adjustment of mechanical watches is due to the delay of the mean sun (and thus the true sun is always close to the average Sun) day by day so that after 6 months, the watch indicate almost noon when the sun is as true midnight would have moved across the world as a tour along the ecliptic.
The sidereal time is used in astronomy to indicate hours of celestial phenomena and ease of monitoring of the stars with telescopes.
After this torturous journey from where you know the average time is regulating the progress of our watches.
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from 09 December in the year 2007 the National Executive declares a time zone change, from UTC -4:00 to UTC -4:30, implying Watch our nationwide were delayed 30 minutes. Although information about what meridian is taking the official time is confusing, some say it is the meridian passing through Rio Chico (-66 °) and others that passes near Villa de Cura (-67 °: 30 '). Regardless of the meridian in question, time is fixed to the spindle -4:30, which means that in one case an additional adjustment is necessary to obtain the value of -4:30 and the other does not.
For demonstration purposes, we will take as a reference meridian passing through Chico River which corresponds to -66 ° and the longitude of Puerto Ordaz where the sundial corresponds to -62 °: 27 ' . Measurements were taken on 2 September 2009 as shown in the picture below.
The time difference between the meridian of Puerto Ordaz and the Rio Chico is 3 °: 33 '(-62 °: 27'-[-66 °]), corresponding in time: 14 minutes 12 seconds ahead.
taken as the time zone to regulate the legal time in Venezuela is the -4:30 'UTC, the meridian that corresponds to the Time Zone is -67 °: 30' (15 ° x -4:30 ') the Chico River Meridian disagrees in 1 °: 30 '(-66 ° - [-67 ° 30']) which led in time is 6 minutes fast (1 °: 30 'x 4 minutes), which implies that time difference between the Meridian of Time Zone and Puerto Ordaz is 20 '12 "ahead.
For September 2, Equation of Time is to +3 seconds, which added to the time between meridian gives the total of 20 ': 15. "
However, due to poor resolution in the graduation of our quadrant azimuthal orientation error sundial with respect to the meridian of Puerto Ordaz and omitting the second, we can clearly see that the discrepancies in the photograph is 20 minutes ahead of the sundial with respect to the mechanical clock (synchronized by the Cajigal Observatory) is for all practical purposes identical to the 20 minutes calculated.
By 20 September, the equation of time is +6 minutes rounding, which according to the above, the advancement of the clock Sun should be 26 minutes, 20 minutes corresponding to the time difference between meridians and 6 minutes of the Equation of Time. The next picture shows time and time Solar Legal.
can clearly see that the shadow of the gnomon is very close to 3 pm while the cellular clock indicates 2:34 PM, so that the time difference is (3h: 0m- 2h: 34m) for 26 minutes, as expected value.
The photograph below shows the time Solar and Legal for October 1, 2009.
The difference in date is approximately one month compared with the first record, yet We can easily see that the discrepancy between the sundial and the bracelet is 30 minutes and we can see that the difference of 20 'we had in the first record of the previous month but not maintained the sundial and the mechanic are exactly in the same place.
What has changed between a date and the other is the true position of the Sun to the Sun means and the time difference between the two suns is 10 minutes 4 seconds according to the tables that determine the equation of time for the first October. Again, if the time difference product of the separation between the meridian (20 ') we add the value of the Equation of Time for the day in question we obtain that the time difference between the sundial and the mechanical clock is 30 minutes which is noted in the photograph.
With these examples, it is clear that the time difference normally seen between the sundial and the mechanic has two sources, first to the angular distance between the meridian of the place where is located the sundial and the Meridian Country reference to establish the Legal Time and second, by the separation that currently exists for the measurement of time between the hour circle of the sun mean sun and the true, the so-called equation of time.
In our case at this latitude and location, the best time for both clocks den "same time" would be for the February 15, when the equation of time is -14:09 minutes so that the difference between the clocks would be 5 minutes.
Obviously the time difference of the clocks directly read is not accurate to the calculations due to various errors in the sundial (manufacturing details, orientation, resolution, width of the gnomon, etc), besides the digital clock employee only shows the minutes. Considering that only employ minutes and round values, our "uncertainty" between the measured with digital clock and the calculated cell should be around 2 minutes in the best. However, within minutes the results are excellent.
I tried to be worn in a very tangled subject, with the hope that this report has not confused over what they were and that allows the reader to understand better what the measurement of time, that when one is facing these strange and beautiful instruments Solares know the reason why they differ from the hours between his watch and clock Sun ... ... In my opinion, I think the graphics displayed cases accurate enough to leave no doubt about the origin of the discrepancy between the sundial and clock time gives us Legal.
