question: How are there different seasons on opposite sides of the earth?
comment: There was a man with big, round belly. On his belly button, which was right in the middle of his belly, all around the man was a line. The same like the equator on Earth. Up from the line was north and below the line of his belly button was the south. The man had a desk with candle that shined right on his belly button. The belly button was warm and happy thanks to the candle. Man leaned to the desk, to reach for the glass with water that was there. His belly button went down with his belly and now the candle shined to the up of his belly. That was the north. And top of the man belly was now in the light and warm and happy. This was the summer north. Below his belly now was darker. And there was colder. It was winter on the south. Which was below his belly button now in the dark. But then the man raised his glass and tipped back to drink. And it was different now on his belly. The bottom was full of light, warm thanks to candle. Dinner on the south And the top of his belly now was darker. Winter in the north.
passages: Section::::Non-calendar-based reckoning.:Indigenous ecological.
   Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. In June the Northern Hemisphere is tilted towards the sun, so at any given Northern Hemisphere latitude sunlight falls more directly on that spot than in December (see Effect of sun angle on climate). This effect causes seasons. Over thousands to hundreds of thousands of years, changes in Earth's orbital parameters affect the amount and distribution of solar energy received by the Earth and influence long-term climate. (See Milankovitch cycles).
   Six ecological seasons can be distinguished which do not have fixed calendar-based dates like the meteorological and astronomical seasons. Oceanic regions tend to experience the beginning of the hibernal season up to a month later than . Conversely, prevernal and vernal seasons begin up to a month earlier near oceanic and coastal areas. For example, prevernal crocus blooms typically appear as early as February in coastal areas of British Columbia, the British Isles, but generally don't appear until March or April in locations like the Midwest USA or parts of eastern Europe. The actual dates for each season vary by climate region and can shift from one year to the next. Average dates listed here are for mild and cool temperate climate zones in the Northern Hemisphere:
   Section::::Earth's movements.:Orbital shape (eccentricity).:Effect on lengths of seasons.
  
  The seasons are quadrants of the Earth's orbit, marked by the two solstices and the two equinoxes. Kepler's second law states that a body in orbit traces equal areas over equal times; its orbital velocity is highest around perihelion and lowest around aphelion. The Earth spends less time near perihelion and more time near aphelion. This means that the lengths of the seasons vary.
   Regardless of the time of year, the northern and southern hemispheres always experience opposite seasons. This is because during summer or winter, one part of the planet is more directly exposed to the rays of the Sun (see "Fig. 1") than the other, and this exposure alternates as the Earth revolves in its orbit. For approximately half of the year (from around March 20 to around September 22), the Northern Hemisphere tips toward the Sun, with the maximum amount occurring on about June 21. For the other half of the year, the same happens, but in the Southern Hemisphere instead of the Northern, with the maximum around December 21. The two instants when the Sun is directly overhead at the Equator are the equinoxes. Also at that moment, both the North Pole and the South Pole of the Earth are just on the terminator, and hence day and night are equally divided between the two hemispheres. Around the March equinox, the Northern Hemisphere will be experiencing spring as the hours of daylight increase, and the Southern Hemisphere is experiencing autumn as daylight hours shorten.
   Section::::Four-season calendar reckoning.:Astronomical.
  
  Astronomical timing as the basis for designating the temperate seasons dates back at least to the Julian calendar used by the ancient Romans. It continues to be used on many modern Gregorian calendars worldwide, although some countries like Australia, New Zealand, Pakistan and Russia prefer to use meteorological reckoning. The precise timing of the seasons is determined by the exact times of transit of the sun over the tropics of Cancer and Capricorn for the solstices and the times of the sun's transit over the equator for the equinoxes, or a traditional date close to these times.
   The Bengali Calendar is similar but differs in start and end times. It has the following seasons or ritu:
  
  The Tamil calendar follows a similar pattern of six seasons
  
  Section::::"Official" seasons.
   Compared to axial tilt, other factors contribute little to seasonal temperature changes. The seasons are not the result of the variation in Earth's distance to the Sun because of its elliptical orbit. In fact, Earth reaches perihelion (the point in its orbit closest to the Sun) in January, and it reaches aphelion (the point farthest from the Sun) in July, so the slight contribution of orbital eccentricity opposes the temperature trends of the seasons in the Northern Hemisphere. In general, the effect of orbital eccentricity on Earth's seasons is a 7% variation in sunlight received.
   As the orientation of Earth's orbit changes, each season will gradually start earlier in the year. Precession means the Earth's nonuniform motion (see above) will affect different seasons. Winter, for instance, will be in a different section of the orbit. When the Earth's apsides are aligned with the equinoxes, the length of spring and summer combined will equal that of autumn and winter. When they are aligned with the solstices, the difference in the length of these seasons will be greatest.
  
  Section::::Earth's movements.:Orbital inclination.
   The effect of axial tilt is observable as the change in day length and altitude of the Sun at solar noon (the Sun's culmination) during the year. The low angle of Sun during the winter months means that incoming rays of solar radiation are spread over a larger area of the Earth's surface, so the light received is more indirect and of lower intensity. Between this effect and the shorter daylight hours, the axial tilt of the Earth accounts for most of the seasonal variation in climate in both hemispheres.
  
  Section::::Causes and effects.:Elliptical Earth orbit.
   In some parts of the world, some other "seasons" capture the timing of important ecological events such as "hurricane season", "tornado season", and "wildfire season". The most historically important of these are the three seasons—"flood", "growth", and "low water"—which were previously defined by the former annual flooding of the Nile in Egypt.
  
  Section::::Causes and effects.
  
  Section::::Causes and effects.:Axial tilt.
  
  The seasons result from the Earth's axis of rotation being tilted with respect to its orbital plane by an angle of approximately 23.4 degrees. (This tilt is also known as "obliquity of the ecliptic".)
   Section::::Six-season calendar reckoning.
  
  Some calendars in south Asia use a six-season method where the number of seasons between summer and winter can number from one to three. The dates are fixed at even intervals of months.
  
  In the Hindu calendar of tropical and subtropical India, there are six seasons or Ritu that are calendar-based in the sense of having fixed dates: Vasanta (spring), Greeshma (summer), Varsha (monsoon), Sharad (autumn), Hemanta (early winter), and Shishira (prevernal or late winter). The six seasons are ascribed to two months each of the twelve months in the Hindu calendar. The rough correspondences are:
   Calendar-based reckoning defines the seasons in absolute rather than relative terms. Accordingly, if floral activity is regularly observed during the coolest quarter of the year in a particular area, it is still considered winter despite the traditional association of flowers with spring and summer. Additionally, the seasons are considered to change on the same dates everywhere that uses a particular calendar method regardless of variations in climate from one area to another. Most calendar-based methods use a four-season model to identify the warmest and coldest seasons, which are separated by two intermediate seasons.
  
  Section::::Four-season calendar reckoning.:Meteorological.
   Section::::See also.
  
  BULLET::::- Horae, Greek goddesses of seasons
  
  BULLET::::- Indian summer
  
  BULLET::::- Persephone, Greek mythological figure associated with the rebirth of vegetation in the spring
  
  BULLET::::- Sun path
  
  BULLET::::- Vertumnus, Roman god of the seasons
  
  Section::::References.
  
  BULLET::::- Maris, Mihaela, St. Luchian School, Bacau, Romania, "Seasonal Variations of the Bird Species", ref. ecological seasons pp. 195–196 incl. and pp. 207–209 incl.
  
  Section::::External links.
  
  BULLET::::- When do the Seasons Begin? (from the Bad Astronomer)
  
  BULLET::::- Why the Earth has seasons article on h2g2.
  
  BULLET::::- Aboriginal seasons of Kakadu
  
  BULLET::::- Indigenous seasons (Australian Bureau of Meteorology)
  
  BULLET::::- Mt Stirling Seasons
  
  BULLET::::- The Lost Seasons
   These "astronomical" seasons are not of equal length, because of the elliptical nature of the orbit of the Earth, as discovered by Johannes Kepler. From the March equinox it currently takes 92.75 days until the June solstice, then 93.65 days until the September equinox, 89.85 days until the December solstice and finally 88.99 days until the March equinox.
  
  Section::::Four-season calendar reckoning.:Astronomical.:Variation due to calendar misalignment.
   Section::::Reception.
   By astronomical convention, the four seasons are determined by the solstices (the two points in the Earth's orbit of the maximum tilt of the Earth's axis, toward the Sun or away from the Sun) and the equinoxes (the two points in the Earth's orbit where the Earth's tilted axis and an imaginary line drawn from the Earth to the Sun are exactly perpendicular to one another). The solstices and equinoxes divide the year up into four approximately equal parts. In the northern hemisphere winter solstice occurs on or about December 21; summer solstice is near June 21; spring equinox is around March 20; and autumnal equinox is about September 23. The effect of the Earth's axial tilt in the southern hemisphere is the opposite of that in the northern hemisphere, thus the seasons of the solstices and equinoxes in the southern hemisphere are the reverse of those in the northern hemisphere (e.g. the northern summer solstice is at the same time as the southern winter solstice).
   By astronomical convention, the four seasons can be determined by the solstices—the points in the orbit of maximum axial tilt toward or away from the Sun—and the equinoxes, when the direction of the tilt and the direction to the Sun are perpendicular. In the Northern Hemisphere, winter solstice currently occurs around 21 December; summer solstice is near 21 June, spring equinox is around 20 March and autumnal equinox is about 22 or 23 September. In the Southern Hemisphere, the situation is reversed, with the summer and winter solstices exchanged and the spring and autumnal equinox dates swapped.
   The Earth's orbit varies between nearly circular and mildly elliptical (its eccentricity varies). When the orbit is more elongated, there is more variation in the distance between the Earth and the Sun, and in the amount of solar radiation, at different times in the year. In addition, the rotational tilt of the Earth (its obliquity) changes slightly. A greater tilt makes the seasons more extreme. Finally, the direction in the fixed stars pointed to by the Earth's axis changes (axial precession), while the Earth's elliptical orbit around the Sun rotates (apsidal precession). The combined effect is that proximity to the Sun occurs during different astronomical seasons.
   Owing to the Earth's axial tilt, winter in the Northern Hemisphere lasts from the December solstice (typically December 21 UTC) to the March equinox (typically March 20 UTC), while summer lasts from the June solstice through to the September equinox (typically September 23 UTC). The dates vary each year due to the difference between the calendar year and the astronomical year.
  
  Its surface is 60.7% water, compared with 80.9% water in the case of the Southern Hemisphere, and it contains 67.3% of Earth's land.
  
  Section::::Geography and climate.
   Any point north of the Arctic Circle or south of the Antarctic Circle will have one period in the summer called 'polar day' when the sun does not set, and one period in the winter called 'polar night' when the sun does not rise. At progressively higher latitudes, the maximum periods of "midnight sun" and "polar night" are progressively longer.
   Seasonal weather fluctuations (changes) also depend on factors such as proximity to oceans or other large bodies of water, currents in those oceans, El Niño/ENSO and other oceanic cycles, and prevailing winds.
   Nepal and India observes six ecological seasons. Southern parts of India experiences the seasons on a different schedule than the one depicted here.
  
  Section::::East Indian Calendars.
  
  East Indian Hindu (Bengali and Mithila which too starts its new year from Mesh Sankranti, in fact, Nepali and Assamese and Odia Hindus too do the same, the season names are in all other in Sanskrit Vasanta, Grishma, Varsha, Sharada, Hemanta, Shishira) calendar.
   Section::::Precession of solstices and equinoxes.
  
  The precession of solstices and equinoxes is the third factor that plays a role in Earth climate change that deals directly with the earth itself. The basis of the precession of solstices and equinoxes is that it causes the seasons to occur at different times in Earth's revolution around the sun throughout a cycle recurring about every 23,000 years.
   Ecologically speaking, a season is a period of the year in which only certain types of floral and animal events happen (e.g.: flowers bloom—spring; hedgehogs hibernate—winter). So, if we can observe a change in daily floral/animal events, the season is changing. In this sense, ecological seasons are defined in absolute terms, unlike calendar-based methods in which the seasons are relative. If specific conditions associated with a particular ecological season don't normally occur in a particular region, then that area cannot be said to experience that season on a regular basis.
  
  Section::::Non-calendar-based reckoning.:Modern mid-latitude ecological.
  
raw_presuppositions: The Earth should all be in the same season at the same time. The Earth should all be in the same season at the same time.
raw_corrections: The Earth can have difference seasons due to it's orientation. The Earth can have difference seasons due to it's orientation.