WhyAre There Seasonal Changes? 为什么会有四季的变化？

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There are two reasons for seasonal changes.First，theearthmovesaroundthe sun.Second，theearth hasa tilted axis of rotation.

Theearth spins around an axis.This imaginary line extends from the South Poletothe North Pole.Theearth'saxisis notvertical. It's actually tilted at an angle of 23.5∘ .Theplanetisalways tiltedin the same directionasitmovesaroundthesun.

Whatdoestheearth'stiltedaxishave todowith seasons？ Itmeansthatdifferent partsoftheplanetaretiltedtowardthesun atdifferenttimesofthe year. It'salsowhythe seasonsaredifferentindifferentpartsofthe world.

Notallpartsoftheearthhavefourdistinct seasons.Butthey all experience seasonal variation.ClosertotheNorthPoleandthe SouthPole，daylightandtemperatureschange with the seasons.Near the Equator， daysare alwaysabout12hours long.Buttheseareas usuallyhaveawetseasonandadryseason.

引起季节变化的原因有两个。（剩余1631字）