អ្នកប្រើប្រាស់:ទួន សាម៉ន/ប្រអប់ខ្សាច់/សមភាពរាត្រី
 | March equinox និង September equinox ត្រូវបានណែនាំឲ្យដាក់បញ្ចូលគ្នាជាមួយទំព័រ ឬផ្នែកនេះ។ (ពិភាក្សា) បានដាក់ស្នើតាំងពី December 2012. |
សមភាពរាត្រី កើតឡើងពីរដងក្នុងមួយឆ្នាំប្រហែល ថ្ងៃទី 20 ខែមីនា និងថ្ងៃទី 22 ខែកញ្ញា។ ពាក្យដោយខ្លួនវាមាននិយមន័យពាក់ព័ន្ធមួយចំនួន។ អត្ថន័យ ចាស់ជាងគេគឺថ្ងៃនៅពេលដែល ពេលថ្ងៃ និង ពេលយប់ គឺមានរយៈពេលប្រមាណស្មើគ្នា ។ [១] សមភាពរាត្រី ពាក្យនេះបានមកពីនិយមន័យនេះចេញមកពី ឡាតាំង aequus (ស្មើ) និង nox (យប់) ។ សមភាពរាត្រី គឺមិនត្រឹមត្រូវដូចថ្ងៃដែលរយៈពេលនៃការពេលថ្ងៃនិងពេលយប់គឺ មានប្រវែងស្មើគ្នាសម្រាប់ហេតុផលពីរ។ ដំបូង, ថ្ងៃរះ ដែលចាប់ផ្តើមថ្ងៃ, កើតឡើងនៅពេលកំពូលនៃ ផ្ទៃ របស់ព្រះអាទិត្យកើនឡើងខាងលើភាគខាងកើត ផ្តេក ។ នៅថាការ បន្ទាន់ , កណ្តាលថាសនេះគឺនៅតែមាននៅខាងក្រោមផ្តេកនោះទេ។ ទីពីរ បរិយាកាសផែនដី refracts ពន្លឺព្រះអាទិត្យ ។ ជាលទ្ធផលអ្នកសង្កេតការណ៍បានមើលឃើញពន្លឺថ្ងៃមុនពេលឃើញដំបូងនៃ ថាសរបស់ស៊ុនខាងលើផ្តេកនោះទេ។ ដើម្បីជៀសវាងភាពមានន័យមិន ច្បាស់លាស់នេះពាក្យ សមភាពរាត្រី ជួនកាលត្រូវបានប្រើដើម្បីមានន័យថាថ្ងៃដែលពេលនៃការពន្លឺថ្ងៃនិងយប់នេះគឺស្មើគ្នា។ [២][note ១] ពេលវេលានៃការ ថ្ងៃលិច និងថ្ងៃរះខុសគ្នាជាមួយនឹងទីតាំងសង្កេតការណ៍របស់ ( តមនងចា និង latitude ) ដូច្នេះ កាលបរិច្ឆេទពេលថ្ងៃនិងពេលយប់គឺមានប្រវែងស្មើគ្នាយ៉ាងពិត ប្រាកដក៏អាស្រ័យលើទីតាំង។
ការនិយមន័យផ្សេងទៀតត្រូវបានផ្អែកលើការជាច្រើនដែលពាក់ព័ន្ធ ជាបន្តបន្ទាប់ តារាសាស្រ្ត ព្រឹត្តិការណ៍និងយោងទាំងទៅព្រឹត្តិការណ៍ខ្លួនឯងឬទៅថ្ងៃដែលពួក គេបានកើតមានឡើង។ ព្រឹត្តិការណ៍ទាំងនេះគឺជាមូលហេតុដែលថារយៈពេល នៃការពេលថ្ងៃនិងពេលយប់គឺមានចំនួនប្រហែលស្មើគ្នានៅថ្ងៃនៃ សមភាពរាត្រី មួយនេះ។
សមភាពរាត្រី កើតឡើងនៅពេលដែល ដំណើគោចរ របស់ផែនដី តំបន់អេក្វាទ័ ឆ្លងកាត់កណ្តាលនៃព្រះអាទិត្យ។ នៅថាការ បន្ទាន់ ដែលជា ភាពលំអៀងនៃអ័ក្សផែនដី មិន inclines ឆ្ងាយពីក៏មិនមែនជាការឆ្ពោះទៅរកព្រះអាទិត្យ។ សមភាពរាត្រី ប្រចាំឆ្នាំពីរដងគឺមានតែនៅពេលដែល ចំណុច subsolar -កន្លែងនៅលើផ្ទៃផែនដីជាកន្លែងដែលកណ្តាលនៃព្រះអាទិត្យនេះគឺ ពិតជាចំណាយគឺនៅលើតំបន់អេក្វាទ័ហើយទន្ទឹមគ្នានេះព្រះអាទិត្យ គឺនៅ មកដល់ចំនុចកំពូល នៅលើខ្សែអេក្វាទ័រ។ ចំណុច subsolar នេះហូរកាត់សមីការនេះបានផ្លាស់ប្តូរទៅខាងជើងនៅ សមភាពរាត្រី ខែមីនានិងនៅភាគខាងត្បូងនៅ សមភាពរាត្រី ខែកញ្ញា។ ក្នុងអំឡុងពេល សមភាពរាត្រី នោះ ផែនដី បង្គោលខាងជើងនិងខាងត្បូងរបស់មិនត្រូវបាន tilted ឆ្ពោះទៅរកឬនៅឆ្ងាយពី ព្រះអាទិត្យ និងរយៈពេលនៃការពន្លឺថ្ងៃគឺទ្រឹស្តីដូចគ្នានៅគ្រប់ចំណុចនៅលើ ផ្ទៃផែនដី។
នៅ សមភាពរាត្រី
មួយព្រះអាទិត្យគឺនៅមួយក្នុងចំណោមចំណុចពីរផ្ទុយគ្នានៅលើ ដែនសេឡេស្ទាល ដែលជាកន្លែង សមីការសេឡេស្ទាល (ពោលគឺ ធ្លាក់ចុះ 0) និង ecliptic ចំនុចប្រសព្វ ។ ចំណុចប្រសព្វទាំងនេះត្រូវបានគេហៅថាចំណុច equinoctial: Classic ចំណុច vernal នេះ ( RA = 00 ម៉ោង 00 ម៉ែត្រ 00 s និងតមនងចា = 0 លេខ) និងចំណុចរដូវស្លឹកឈើជ្រុះ (RA = 12 ម៉ោង 00 ម៉ែត្រ 00 s និងតមនងចា = 180 លេខ) ។
សមភាពរាត្រី នេះគឺជាដងតែប៉ុណ្ណោះនៅពេលដែល Terminator ព្រះអាទិត្យ គឺជាការកាត់កែងទៅតំបន់អេក្វាទ័រ។ ជាលទ្ធផលនៅភាគខាងជើងនិង ភាគខាងត្បូង អឌ្ឍគោល ត្រូវបានបំភ្លឺស្មើភាពគ្នា។
សមភាពរាត្រី នៅលើផែនដី កែប្រែ
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Diagram of the Earth's seasons as seen from the north. Far right: December solstice. -
Diagram of the Earth's seasons as seen from the south. Far left: June solstice.
កាលបរិច្ឆេទ កែប្រែ
ពេលដែល Julius Caesar បានបង្កើតឡើង ប្រតិទិនរបស់គាត់ នៅក្នុង 45 ម.គ. លោកបានកំណត់ជា សមភាពរាត្រី និទាឃរដូវ 25 ខែមីនា។ ដោយសារតែក្នុងមួយឆ្នាំលោក Julian (365.25 ថ្ងៃ) គឺយូរជាងមួយឆ្នាំពិតប្រាកដប្រតិទិនឃ្លាតឆ្ងាយដោយគោរពតាម សមភាពរាត្រី នេះបន្តិចដូចថា សមភាពរាត្រី នេះត្រូវបានកើតឡើងនៅប្រហែល 21 ខែមីនាក្នុង 300 គ.ស. និងដោយ 1500 គ.ស. វាបានកើនឡើងដល់ 11 ខែមីនា។
ដោយសារកត្ដានេះប្រាស់ចាកពី ប្រកាន់ទោសលោក Gregory XIII ដើម្បីបង្កើតសម័យទំនើប ប្រតិទិនគ្រីកូរី ។ ប្រកាន់ទោសចង់ស្ដាររាជបញ្ជាដែលទាក់ទងនឹង កាលបរិច្ឆេទនៃបុណ្យ Easter នៃ ក្រុមប្រឹក្សានៃ Nicaea នៃ 325 គ.ស. ។ (ដោយចៃដន្យកាលបរិច្ឆេទនៃបុណ្យ Easter ខ្លួនវាត្រូវបានជួសជុលដោយប្រហាក់ប្រហែលនៃវដ្ត Lunar បានប្រើនៅក្នុងប្រតិទិន Hebraic មួយនោះទេប៉ុន្តែបើយោងតាមអ្នកប្រវត្តិសាស្រ្ត Bede ឈ្មោះជាភាសាអង់គ្លេស "បុណ្យ Easter" មកពីការប្រារព្ធពិធីជឿទៅលើព្រះគ្រីស្ទដោយកុលសម្ព័ន្ធអាល្លឺម៉ង់ vernal (និទាឃរដូវ) សមភាពរាត្រី នេះ ) ។ ដូច្នេះការផ្លាស់ប្តូរនៅក្នុងកាលបរិច្ឆេទនៃការ សមភាពរាត្រី ដែលបានកើតឡើងរវាងទី 4 និងសតវត្សទី 16 ដែលត្រូវបានទុកជាមោឃៈជាមួយនឹងប្រតិទិនគ្រីកូរីប៉ុន្តែគ្មាន អ្វីដែលត្រូវបានធ្វើសម្រាប់ដំបូងបួនសតវត្សនៃប្រតិទិនលោក Julian ។ ថ្ងៃ 29 ខែកុម្ភៈឆ្នាំនៃ គ.ស. 100 គ.ស. 200, 300 គ.ស. ហើយថ្ងៃដែលបង្កើតដោយកម្មវិធីមិនទៀងទាត់នៃ ឆ្នាំបង្គ្រប់ រវាងធ្វើឃាតរបស់ Caesar និងក្រឹត្យរបស់ Augustus ឡើងវិញរៀបចំប្រតិទិននៅក្នុង 8 គ.ស. នៅតែមានប្រសិទ្ធិភាព ។ នេះបានផ្លាស់ប្តូរ សមភាពរាត្រី បួនថ្ងៃមុនជាងនៅក្នុងពេលវេលារបស់ Caesar ។
ឈ្មោះ កែប្រែ
- Vernal equinox and autumnal equinox: these classical names are direct derivatives of Latin (ver = spring and autumnus = autumn). These names are based on the seasons, and can be ambiguous since seasons of the northern hemisphere and southern hemisphere are opposites, and the vernal equinox of one hemisphere is the autumnal equinox of the other.
- Spring equinox and fall equinox or autumn equinox: these are more colloquial names based on the seasons, and are also therefore ambiguous across hemispheres.
- March equinox and September equinox: names referring to the times of the year when such equinoxes occur. These are without the ambiguity as to which hemisphere is the context, but are still not universal as not all people use a solar-based calendar where the equinoxes occur every year in the same month (as they do not in the Islamic calendar and Hebrew calendar, for example), and the names are not useful for other planets (Mars, for example), even though these planets do have seasons.
- Northward equinox and southward equinox: names referring to the apparent motion of the Sun at the times of the equinox. The least culturally biased terms.
- Vernal point and autumnal point are the points on the celestial sphere where the Sun is located on the vernal equinox and autumnal equinox respectively. Usually this terminology is fixed for the Northern hemisphere.
- First point (or cusp) of Aries and first point of Libra are names formerly used by astronomers and now used by navigators and astrologers. Navigational ephemeris tables record the geographic position of the First Point of Aries as the reference for position of navigational stars. Due to the precession of the equinoxes, the astrological signs of the tropical zodiac where these equinoxes are located no longer correspond with the actual constellations once ascribed to them. The equinoxes are currently in the constellations of Pisces and Virgo. In sidereal astrology (notably Hindu astrology), by contrast, the first point of Aries remains aligned with Ras Hammel "the head of the ram", i.e. the Aries constellation.
ប្រវែងនៃថ្ងៃនិងយប់ សមភាពរាត្រី កែប្រែ
On the day of the equinox, the center of the Sun spends a roughly equal amount of time above and below the horizon at every location on the Earth, so night and day are about the same length. The word equinox derives from the Latin words aequus (equal) and nox (night). In reality, the day is longer than the night at an equinox. Day is usually defined as the period when sunlight reaches the ground in the absence of local obstacles. From the Earth, the Sun appears as a disc rather than a point of light, so when the center of the Sun is below the horizon, its upper edge is visible. Furthermore, the atmosphere refracts light, so even when the upper limb of the Sun is 0.4 degrees below the horizon, its rays curve over the horizon to the ground. In sunrise/sunset tables, the assumed semidiameter (apparent radius) of the Sun is 16 minutes of arc and the atmospheric refraction is assumed to be 34 minutes of arc. Their combination means that when the upper limb of Sun is on the visible horizon, its center is 50 minutes of arc below the geometric horizon, which is the intersection with the celestial sphere of a horizontal plane through the eye of the observer. These effects make the day about 14 minutes longer than the night at the Equator and longer still towards the Poles. The real equality of day and night only happens in places far enough from the Equator to have a seasonal difference in day length of at least 7 minutes, actually occurring a few days towards the winter side of each equinox.
ទិដ្ឋភាព ដែលវាស់ពីផ្ចិតផែនដី នៃរដូវកាលតារាសាស្ត្រ កែប្រែ
 | ផ្នែកនេះមិនបានបញ្ជាក់អំពីប្រភព ឬឯកសារយោងទេ។ សូមចូលរួមជួយក្នុងអត្ថបទនេះ ដោយរក-បញ្ជាក់អំពីប្រភព-ឯកសារយោងដែលគួរទុកចិត្តបាន។ ខ្លឹមសារគ្មានប្រភពអាចនឹងត្រូវ ជជែក ហើយនិងដកចេញ ។ (December 2011) |
In the half-year centered on the June solstice, the Sun rises north of east and sets north of west, which means longer days with shorter nights for the Northern Hemisphere and shorter days with longer nights for the Southern Hemisphere. In the half-year centered on the December solstice, the Sun rises south of east and sets south of west and the durations of day and night are reversed.
Also on the day of an equinox, the Sun rises everywhere on Earth (except at the Poles) at about 06:00 and sets at about 18:00 (local time). These times are not exact for several reasons:
- The Sun is much larger in diameter than the Earth, so that more than half of the Earth could be in sunlight at any one time (due to unparallel rays creating tangent points beyond an equal-day-night line).
- Most places on Earth use a time zone which differs from the local solar time by minutes or even hours. For example, if the Sun rises at 07:00 on the equinox, it will set 12 hours later at 19:00.
- Even people whose time zone is equal to local solar time will not see sunrise and sunset at 06:00 and 18:00. This is due to the variable speed of the Earth in its orbit, and is described as the equation of time. It has different values for the March and September equinoxes (+8 and −8 minutes respectively).
- Sunrise and sunset are commonly defined for the upper limb of the solar disk, rather than its center. The upper limb is already up for at least a minute before the center appears, and the upper limb likewise sets later than the center of the solar disk. Also, when the Sun is near the horizon, atmospheric refraction shifts its apparent position above its true position by a little more than its own diameter. This makes sunrise more than two minutes earlier and sunset an equal amount later. These two effects combine to make the equinox day 12 h 7 min long and the night only 11 h 53 min. Note, however, that these numbers are only true for the tropics. For moderate latitudes, the discrepancy increases (e.g., 12 minutes in London); and closer to the Poles it becomes very much larger (in terms of time). Up to about 100 km from either Pole, the Sun is up for a full 24 hours on an equinox day.
- Night includes twilight. If dawn and dusk are instead considered daytime, the day would be almost 13 hours near the equator, and longer at higher latitudes.
- Height of the horizon changes the day's length. For an observer atop a mountain the day is longer, while standing in a valley will shorten the day.
Day arcs of the Sun កែប្រែ
Some of the statements above can be made clearer by picturing the day arc (i.e., the path the Sun tracks along the celestial dome in its diurnal movement). The pictures show this for every hour on equinox day. In addition, some 'ghost' suns are also indicated below the horizon, up to 18° below it; the Sun in such areas still causes twilight. The depictions presented below can be used for both the Northern Hemisphere and the Southern Hemisphere. The observer is understood to be sitting near the tree on the island depicted in the middle of the ocean; the green arrows give cardinal directions.
- In the Northern Hemisphere, north is to the left, the Sun rises in the east (far arrow), culminates in the south (right arrow), while moving to the right and setting in the west (near arrow).
- In the Southern Hemisphere, south is to the left, the Sun rises in the east (near arrow), culminates in the north (right arrow), while moving to the left and setting in the west (far arrow).
The following special cases are depicted:
-
Day arc at 0° latitude (Equator)
The arc passes through the zenith, resulting in almost no shadows at high noon. -
Day arc at 20° latitude
The Sun culminates at 70° altitude and its path at sunrise and sunset occurs at a steep 70° angle to the horizon. Twilight still lasts about one hour. -
Day arc at 50° latitude
Twilight lasts almost two hours. -
Day arc at 70° latitude
The Sun culminates at no more than 20° altitude and its daily path at sunrise and sunset is at a shallow 20° angle to the horizon. Twilight lasts for more than four hours; in fact, there is barely any night. -
Day arc at 90° latitude (Pole)
If it were not for atmospheric refraction, the Sun would be on the horizon all the time.
សេឡេស្ទាលសំរបសំរួលប្រព័ន្ធ កែប្រែ
The vernal equinox occurs in March, about when the Sun crosses the celestial equator south to north.[៣] The term "vernal point" is used for the time of this occurrence and for the direction in space where the Sun is seen at that time, which is the origin of some celestial coordinate systems:
- in the ecliptic coordinate system, the vernal point is the origin of the ecliptic longitude;
- in the equatorial coordinate system, the vernal point is the origin of the right ascension.
Because of the precession of the Earth's axis, the position of the vernal point on the celestial sphere changes over time, and the equatorial and the ecliptic coordinate systems change accordingly. Thus when specifying celestial coordinates for an object, one has to specify at what time the vernal point and the celestial equator are taken. That reference time is called the equinox of date.[៤]
The autumnal equinox is at ecliptic longitude 180° and at right ascension 12h.
The upper culmination of the vernal point is considered the start of the sidereal day for the observer. The hour angle of the vernal point is, by definition, the observer's sidereal time.
The same is true in western tropical astrology: the vernal equinox is the first point (i.e. the start) of the sign of Aries. In this system, it is of no significance that the equinoxes shift over time with respect to the fixed stars.
Using the current official IAU constellation boundaries – and taking into account the variable precession speed and the rotation of the ecliptic – the equinoxes shift through the constellations as follows[៥] (expressed in astronomical year numbering in which the year 0 = 1 BC, −1 = 2 BC, etc.):
- The March equinox passed from Taurus into Aries in year −1865, passed into Pisces in year −67, will pass into Aquarius in year 2597, will pass into Capricornus in year 4312. It passed along (but not into) a 'corner' of Cetus on 0°10' distance in year 1489.
- The September equinox passed from Libra into Virgo in year −729, will pass into Leo in year 2439.
ទិដ្ឋភាពវប្បធម៌ កែប្រែ
A number of traditional spring and autumn (harvest) festivals are celebrated on the date of the equinoxes.
សមភាពរាត្រី របស់ភពផ្សេងទៀត កែប្រែ
| | ផ្នែកនេះមិនបានបញ្ជាក់អំពីប្រភព ឬឯកសារយោងទេ។ សូមចូលរួមជួយក្នុងអត្ថបទនេះ ដោយរក-បញ្ជាក់អំពីប្រភព-ឯកសារយោងដែលគួរទុកចិត្តបាន។ ខ្លឹមសារគ្មានប្រភពអាចនឹងត្រូវ ជជែក ហើយនិងដកចេញ ។ (September 2012) |
Equinox is a phenomenon that can occur on any planet with a significant tilt to its rotational axis. Most dramatic of these is Saturn, where the equinox places its normally majestic ring system edge-on facing the Sun. As a result, they are visible only as a thin line when seen from Earth. When seen from above – a view seen by humans during an equinox for the first time from the Cassini space probe in 2009 – they receive very little sunshine, indeed more planetshine than light from the Sun. [៦]
This lack of sunshine occurs once every 14.7 years. It can last a few weeks before and after the exact equinox. The most recent exact equinox for Saturn was on 11 August 2009. Its next equinox will take place on 30 April 2024.[ត្រូវការអំណះអំណាង]
One effect of equinoctial periods is the temporary disruption of communications satellites. For all geostationary satellites, there are a few days around the equinox when the sun goes directly behind the satellite relative to Earth (i.e. within the beam-width of the ground-station antenna) for a short period each day. The Sun's immense power and broad radiation spectrum overload the Earth station's reception circuits with noise and, depending on antenna size and other factors, temporarily disrupt or degrade the circuit. The duration of those effects varies but can range from a few minutes to an hour. (For a given frequency band, a larger antenna has a narrower beam-width and hence experiences shorter duration "Sun outage" windows.)[ត្រូវការអំណះអំណាង]
សូមមើល កែប្រែ
កំណត់សំគាល់ កែប្រែ
- ↑ This meaning of "equilux" is rather modern (c. 2006) and unusual; technical references since the beginning of the 20th century (c. 1910) use the terms "equilux" and "isophot" to mean "of equal illumination", in the context of curves showing how intensely lighting equipment will illuminate a surface. See for instance John William Tudor Walsh, Textbook of Illuminating Engineering (Intermediate Grade), I. Pitman, 1947.
ឯកសារយោង កែប្រែ
- ↑ "equinox" at Oxford Dictionaries
- ↑ Owens, Steve (20 ខែមីនា 2010). "Equinox, Equilux, and Twilight Times". Dark Sky Diary (blog). Retrieved 31 ខែធ្នូ 2010.
- ↑ Strictly speaking, at the equinox the sun's ecliptic longitude is zero. Its latitude won't be exactly zero since the earth isn't exactly in the plane of the ecliptic. (The ecliptic is defined by the center of mass of the earth and moon combined.)
- ↑ Montenbruck, Oliver; Pfleger, Thomas. Astronomy on the Personal Computer. Springer-Verlag. p. 17. ល.ស.ប.អ. 0-387-57700-9.
- ↑ J. Meeus; Mathematical Astronomical Morsels; ISBN 0-943396-51-4
- ↑ "PIA11667: The Rite of Spring". Jet Propulsion Laboratory, California Institute of Technology. Retrieved 21 ខែមីនា 2014.
តំណភ្ជាប់ខាងក្រៅ កែប្រែ
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វិគីមេឌាទូទៅមានមេឌាដែលទាក់ទងទៅនឹង: ទួន សាម៉ន/ប្រអប់ខ្សាច់/សមភាពរាត្រី |
- Details about the Length of Day and Night at the Equinoxes. U.S. Naval Observatory. Naval Meteorology and Oceanography Command
- Calculation of Length of Day (Formulas and Graphs)
- Equinoctial Points – The Nuttall Encyclopædia
- Table of times for Equinoxes, Solstices, Perihelion and Aphelion in 2000–2020
- Table of times of Spring Equinox for a thousand years: 1452–2547
- Gray, Meghan. "Solstice and Equinox". Sixty Symbols. Brady Haran for the University of Nottingham.
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