ផែនដី

ដោយវិគីភីឌា
(ត្រូវបានបញ្ជូនបន្តពី ភពផែនដី)
ផែនដី
Earth
  Earth symbol.svg
The Earth seen from Apollo 17.jpg
Designations
Alternate name(s) Blue Planet, Terra, Planet Earth
Epoch J2000.0
Aphelion 152,097,701 km
1.0167103335 AU[១]
Perihelion 147,098,074 km
0.9832898912 AU[១]
Semi-major axis 149,597,887.5 km
1.0000001124 AU[១]
Eccentricity 0.016710219[២]
Orbital period 365.256366 days
1.0000175 yr[១]
Average orbital speed 29.783 km/s
107,218 km/h[១]
Inclination 1°34'43.3"
to Invariable plane[៣]

ផែនដី (អង់គ្លេសEarth) គឺ​ជា​ភពទី​៣ ពី​ព្រះអាទិត្យ​ ហើយ​ក៏​ជា​ភព​ណែន​បំផុត និង ធំបំផុត​ទី៥ ក្នុង​ប្រព័ន្ធព្រះអាទិត្យ។ វា​ក៏​ជា​ភព​ដី​មួយ​ ក្នុង​ចំណោម​ភព​ដី​ទាំង៤ របស់​ប្រព័ន្ធ​ព្រះអាទិត្យ។ This means most of its mass is solid. The other three are Mercury, Venus and Mars.

ផែនដី​ គឺ​ជាទី​តាំង របស់​វត្ថុ​មាន​ជីវិត​ជា​ច្រើន​អំបូរ​ផង​ដែរ ដោយ​រាប់​ទាំង​មនុស្ស​ផង។ វា​ជា​អង្គ​តារាសាស្រ្ត​​តែ​មួយគត់ ដែល​គេ​រក​ឃើញ​មាន​ជីវិត​ស្ថិត​នៅ។​​ [៤] ផែន​ដី​បាន​កើត​ឡើង​ ៤,៥៧ ពាន់លាន​ឆ្នាំ​មុន ហើយ​ជីវិត​បាន​កកើត​ឡើង ក្នុង​កំឡុង​ប៉ុន្មាន​ពាន់លានឆ្នាំ​មក​នេះ។ [៥] ស្រទាប់​​ជីវិត​របស់​ផែនដី(Biosphere) បាន​កែប្រែ​បរិយាកាស​ និង លក្ខខណ្ឌ​អជីវិត​ផ្សេងទៀត របស់​ភព​នេះ អោយ​ទៅមាន​ការ​សាយ​កូន នៃ​សរីរាង្គ​រស់​នៅ​ត្រូវ​ការ​ខ្យល់ ក៏​ដូច​ជា​ការ​បង្កើត​នូវ​ស្រទាប់​អូសូន ដែល​រួម​គ្នា​ក្លាយ​ជា​ ដែន​ម៉ាញ៉េទិច​ផែនដី សំរាប់​ទប់​នូវ​ចំណាំង​ព្រះអាទិត្យ​គ្រោះថ្នាក់ ហើយ​អនុញ្ញាត​អោយ​មាន​ការ​កកើត​ជីវិត​នៅ​លើដី។[៦] លក្ខណៈ​មុខងារធម្មតា​របស់ផែន​ដី ក៏ដូច​ជា​ប្រវត្តិ​ភូមិសាស្រ្ត និង គន្លង​របស់​វា បាន​ផ្ដល់​អោយ​ជីវិត​ស្ថិត​ស្ថេរ​បាន​នៅ​ក្នុង​កំឡុង​ពេល​នេះ។ ភពផែន​ដី​ ត្រូវ​បាន​គេ​ប៉ាន់​ប្រមាណ​ថា​ នឹងទ្រទ្រង់​ជីវិត​ យ៉ាង​តិច​ណាស់​ក៏​សំរាប់​រយះពេល ៥០០ លាន​ឆ្នាំ​ទៀត​ដែរ។[៧][៨]

គេ​ចែក ស្រទាប់​ខាង​ក្រៅ​របស់​ផែន​ដី​ ជា​ ចំណែក​រឹង​ជា​ច្រើន,​ រឺ​ក៏​ហៅ​ថា ស្រទាប់​តិចតូនិច(Tectonic Plate) ដែល​ធ្វើ​ចលនាឆ្លង​កាត់​ផ្ទៃ​ផែនដី អស់រយះ​កាល​រាប់​លាន​ឆ្នាំ​មក​ហើយ។ ប្រហែល​ ៧១%​ របស់​ផ្ទៃ​ផែន​ដី ត្រូវ​គ្របដណ្ដប់​ដោយ​ ទឹក​សមុទ្រ​ប្រៃ ហើយ​ក្រៅ​ពីនេះ​គឺជា ទ្វីប​ និង​ កោះ ដែល​វា​ទាំង​ពីរ​មាន បឹង និង ធនធានទឹក​ផ្សេង​ទៀត ក្នុង​ការ​ចូលរួម​បង្កើត​ជា​ ស្រទាប់​ទឹក(Hydrosphere)។ ទឹក​រាវ ដែល​មាន​សារៈសំខាន់​សំរាប់​គ្រប់​ជីវិត​ដែល​គេ​ដឹង​ទាំង​អស់ គឺ​មិន​ត្រូវ​បាន​គេ​រក​ឃើញ​ ក្នុង​ចំនួន​សមតា ណាមួយ​ទេ​ នៅ​លើ​ផ្ទៃ​ភព​ដទៃ​ទៀត។[៩] ប៉ូល​របស់ផែនដី សឹង​តែ​ត្រូវ​បាន​គ្រប​ដណ្ដប់​ទាំង​ស្រុង​ដោយ​ទឹកកករឹង (ផ្ទាំង​ទឹក​កក​ អង់តាកទិច) រឺ ទឹកសមុទ្រ​កក (គំរបទឹកកក អាចទិច)។ ផ្ទៃ​ខាង​ក្នុង​ផែនដី នៅ​តែមានសកម្មភាព ដែល​មានសំបក​រឹង​មធ្យម, ស្នូល​ខាង​ក្រៅ​រាវ ដែល​បង្កើត​ជា​ដែន​ម៉ាញ៉េទិច​ផែនដី និង ស្នូល​ដែក​ខាង​ក្នុង​រឹង។

ផែនដីគឺជាភពដំបូងបំផុតដែលត្រូវបានគេស្គាល់ថាមានទឹករាវនៅលើផ្ទៃរបស់វា ហើយក៏ជាទីកន្លែងតែមួយគត់នៅក្នុងចក្រវាឡដែលត្រូវបានគេស្គាល់ថាជាទីសំចតនៃជីវិត។ ផែនដីមានដែនម៉ាញេទិក​​​, រួមនឹងបឋមស្រទាប់ខ្យល់នីត្រូ-អុកស៊ីហ្សែន, ការពារផ្ទៃផុតពីចំនះថាមពល(ការជះថាមពលដែលបង្ថឡើងក្រោមរូបភាពរលកឬបំណែកតូចៗ ក្នុងលំហ)ដែលមានគ្រោះថ្នាក់ដល់ជីវិតរស់នៅ។ ស្រទាប់ខ្យល់ ក៏បំរើជាខែលមួយបង្កនូវអាកាសភូត(meteors)តូចៗវិញ ដើម្បីដុតកំទេចមុននឹងចំនះថាមពលទាំងនោះសំរុកទៅលើផ្ទៃផែនដី។

ផែនដីបានកកើតកន្លងមកខ្ទង់ 4.57 [ពាន់កោដិ]ឆ្នាំ ហើយរណបភព​(ចក្រវាឡរណប=satellite)​របស់វាគឺព្រះច័ន្ទបានវិលជុំវិញផែនដីកន្លងមកប្រមាណ 4.53 ពាន់កោដិឆ្នាំ។ បច្ចុប្បន្ន ផែនដីវិលជុំវិញ ព្រះអាទិត្យមួយដងក្នុងរាល់366.26ដងវិលជុំវិញអាក្សខ្លួនឯង(ស្មើនឹង 365.26 ទិវាសុរិយៈ), ដំណាក់កាលមួយត្រូវបានស្គាល់ថាជាទំព័រពិតនៃឆ្នាំ។ ទំរេត 23.4° នៃអ័ក្សធ្វើអោយមានបំរែបំរួល រដូវនានាលើផ្ទៃនៃផែនដី។

ប្រវត្តិ[កែប្រែ]

សូមមើល: Historical geology បន្ថែម, Age of the Earth, និង Giant impact hypothesis

ផែនដី និងភពដទៃទៀតបានកកើតឡើងតាំងពីជាង 4.6 - 4.8 billion ឆ្នាំមុនមកម៉្លេះ ។[១០] They were made of the leftover gas from the nebula that made the Sun. The Moon may have been formed after a collision between Earth and a smaller planet (sometimes called Theia). Scientists believe that parts of both planets broke off — becoming (by gravity) the Moon.[១១]

Condensing water vapour, comets and asteroids hitting the Earth made the oceans. Within a billion years (that is at about 3.8 billion years ago) the first life evolved, in the Archaean era.[១២] Some bacteria developed photosynthesis, which lets plants make food from the Sun's light and water. This released a lot of oxygen into the atmosphere or air, making the Earth's surface suitable for life. This oxygen also formed the ozone layer which protects the Earth from bad ultraviolet radiation from the Sun. This protection made it possible for things to move from the deep ocean to the surface. Long ago almost all land was in one place. This is called a supercontinent. The earliest known supercontinent was called Rodina. Scientists think that soon after this there was a time (the Cryogenian) when the Earth was almost entirely covered by thick ice sheets (glaciers).[១៣] This is called the Snowball Earth theory.[១៣]

What it is made of[កែប្រែ]

A rough size comparison of Earth and the other three terrestrial planets, Mercury, Venus and Mars.

Earth is a terrestrial planet. This means it is made up of solid rock unlike a gas giant such as Jupiter. It is the largest out of the four terrestrial planets in mass and diameter.

ទម្រង់រូបរាង[កែប្រែ]

The Earth's shape is an oblate spheroid. This means it is basically a sphere but it bulges around the middle. The circumference of the Earth is about 40,000 kilometers; the average width of the Earth is about 12,700 km. The highest point on Earth is the peak of Mount Everest at 8,848 m above sea level. The lowest natural point is the bottom of the Mariana Trench at 10,911 meters below sea level. Because of the bulge at the middle or the equator, the farthest point from the Earth's center is the top of Mount Chimborazo in Ecuador.[១៤][១៥][១៦]

A diagram of the inside of the Earth, showing the different layers.

Internal structure[កែប្រែ]

Inside, the Earth is similar to the other terrestrial planets. It has an outer, solid rock layer called the crust. Everything that lives on Earth is on top of the crust. Below that is a layer of thick, semi-liquid rock called the mantle. Under that is a thin liquid layer called the outer core and then the solid iron inner core. The thickness of the crust changes. On land the average is between 30–50 kilometers thick. Under the oceans in some places it is only 6 kilometers thick.[១៧] The inside of the Earth is very hot, the temperature of the outer core may be as high as ៧០០០ °C (១២៦៣០ °F).[១៨]

ផ្លាកទិចតូនិក (Tectonic plates)[កែប្រែ]

A map showing the Earth's major tectonic plates.

The Earth is the only terrestrial planet with active plate tectonics.[១៩] Due to plate tectonics the Earth's crust basically floats on the thick liquid rock of the mantle below.[២០] The crust is split up into parts called plates. These plates interact as they move about causing earthquakes and creating volcanoes and mountain ranges. The place where plates meet are called plate boundaries. There are three types of plate boundary: constructive, destructive and transform.[១៩][២១][២២]

  • At a transform plate boundary, two plates move parallel to each other. As they move the grind against each other. This kind of plate boundary causes earthquakes. Example:San Andreas Fault.[២២]

ផ្ទៃដីខាងក្រៅ[កែប្រែ]

The Earth changes greatly from place to place. Over 70% of the Earth surface is covered by water.[២៥] The underwater surface has many of the same features as the above sea with volcanos, mountains and trenches or canyons. The 30% not covered by water is mostly forests, deserts, plains, mountains and plateaux. Human civilisation has led to increasing urbanisation — the growth of cities.

Many things can change the surface of the Earth. Plate tectonics is main cause of change but there are others such as erosion from wind and rain, erosion by the oceans or meteorite impacts. There are three main types of rock that make up the Earth's surface:

  • Igneous rock is made when magma or lava from the mantle reaches the surface and cools. As it gets colder it turns into rock or solidifies.
  • Sedimentary rock is made from sediment, like sand or small bits of other rock, that has been crushed and packed tightly together.

Hydrosphere[កែប្រែ]

All the water on Earth, on land or in the atmosphere, is part of the hydrosphere. About 97.5% of all water is salt water. About half the fresh water is currently ice.[២៦] The oceans absorb or soak up carbon dioxide, a gas that adds to the greenhouse effect and global warming.

បរិយាកាស[កែប្រែ]

A planet's atmosphere is a layer of different gases surrounding it. It is kept there by gravity. The Earth's atmosphere is made of about 78% nitrogen, 21% oxygen and small amounts of other gases.[២៧] This mixture is often called air. Further up there is a layer of ozone gas called the Ozone layer. Ozone absorbs ultraviolet radiation from the Sun. Ultraviolet radiation is dangerous to people, so without the Ozone layer life would not be possible. The atmosphere also protects the earth from crashes with meteors and small asteroids. This is because they burn up due to all the friction as they fly through it. It also helps to keep Earth warm. Some gases including carbon dioxide and methane act like a blanket around the Earth, they trap heat under them, keeping the Earth warm. This is called the natural greenhouse effect.[២៨] When humans build factories and power plants to make electricity, combustion is involved. Combustion lets out a lot of carbon dioxide. This carbon dioxide goes up into the atmosphere and traps more heat. This is called global warming.

អាកាសធាតុ និងវដ្តនៃទឹក[កែប្រែ]

Hot air rises. As it rises it gets colder again and falls. This is called convection currents.[២៩] When hot air meets cold air different weather effects happen. Convection currents are the cause of almost all weather on Earth. When it gets hot on the surface water evaporates and becomes steam or water vapour. This hot water vapour rises. As it rises it gets colder. When it gets cold enough it turns back into water again. This causes the clouds and rain. It is called the water cycle.[២៩]

Orbit and rotation[កែប្រែ]

Earth's axial tilt (or obliquity) and its relation to the rotation axis and plane of orbit.

The Earth takes about 24 hours to complete one day and about 365 days to complete a year. Actually, the Earth takes 365.24 days to revolve around the sun.[៣០] To make up this quarter day every year, an extra day is added every four years making the year 366 days. This is a leap year. The Earth is, on average, 150 million kilometers away from the Sun, and moving at a speed of 30 kilometers a second or 108,000 miles an hour.[៣១]

The Moon orbits the Earth at an average distance of 250,000 miles. It is tidally locked to Earth, which means it always has the same side facing the Earth. It takes roughly one month to complete one orbit.

The Earth is part of the Solar System and orbits the sun along with thousands of small objects and eight planets. The Sun, and therefore the Solar System, are currently traveling through the Orion Arm of the Milky Way Galaxy and will be for approximately the next 10,000 years.[៣២]

កំណត់ចំណាំ[កែប្រែ]


មើលផងដែរ[កែប្រែ]

ឯកសារយោង[កែប្រែ]

  1. ១,០ ១,១ ១,២ ១,៣ ១,៤ Williams, Dr. David R.។ "Earth Fact Sheet"។ NASAhttp://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html។ បានយកមក 2011-02-03 
  2. Standish, E. Myles; Williams, James C។ "Orbital Ephemerides of the Sun, Moon, and Planets" (PDF)។ International Astronomical Union Commission 4: (Ephemerides)http://iau-comm4.jpl.nasa.gov/XSChap8.pdf។ បានយកមក 2010-04-03  See table 8.10.2. Calculation based upon 1 AU = 149,597,870,700(3) m.
  3. Allen, Clabon Walter; Cox, Arthur N. (2000)។ Allen's Astrophysical Quantities។ Springer។ ទំ. 294។ ល.ស.ប.អ. 0387987460http://books.google.com/?id=w8PK2XFLLH8C&pg=PA294 
  4. http://en.wikipedia.org/wiki/Earth#cite_note-science_241_4872_1441-25
  5. http://en.wikipedia.org/wiki/Earth#cite_note-age_earth1-26
  6. http://en.wikipedia.org/wiki/Earth#cite_note-Harrison_2002-27
  7. http://en.wikipedia.org/wiki/Earth#cite_note-britt2000-28
  8. http://en.wikipedia.org/wiki/Earth#cite_note-carrington-29
  9. http://en.wikipedia.org/wiki/Earth#cite_note-water_vapor-30
  10. Cite error: Invalid <ref> tag; no text was provided for refs named age_earth
  11. "Origin of the Moon in a giant impact near the end of the Earth's formation"។ Nature.comhttp://www.nature.com/nature/journal/v412/n6848/abs/412708a0.html។ បានយកមក 2009-07-28 
  12. "Earth life appeared on land 1.5 billion years earlier than previously thought"។ SpaceRef.comhttp://www.spaceref.com/news/viewnews.html?id=258។ បានយកមក 2009-07-03 
  13. ១៣,០ ១៣,១ "The Snowball Earth"Paul F. Hoffman and Daniel P. Schrag។ Harvard Universityhttp://www.eps.harvard.edu/people/faculty/hoffman/snowball_paper.html។ បានយកមក 2009-07-28 
  14. Senne, Joseph H. (2000)។ "Did Edmund Hillary climb the wrong mountain?"។ Professional Surveyor 20 (5): 16–21។ 
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