【简答题】[名词解释] 春分

【简答题】某颗地球同步卫星正下方的地球表面上有一观察者，他用天文望远镜观察被太阳光照射的此卫星，试问，春分那天（太阳光直射赤道）在日落12小时内有多长时间该观察者看不见此卫星？已知地球半径为R，地球表面处的为g，地球自转周期为T，不考虑大气对光的折射。

【单选题】春分时，太阳直射在：（）

【简答题】Nowroz: Iranian New Year or Nowroz is celebrated on the first day of spring sometime in March. People sing, dance and parade as in a carnival through the streets with drums and trumpets to spread the ...

【单选题】I was born on the last day of February. I’ve always felt sorry for February, squeezed between the big months of January (named for the Roman god Janus, keeper of gateways) and March (after Mars, the g...

【判断题】春分日,太阳与赤道垂直。

【简答题】Nowroz: Iranian New Year or Nowroz is celebrated on the first day of spring sometime in March. People sing, dance and parade as in a carnival through the streets with drums and trumpets to spread the ...

【单选题】北半球的春分日 [     ]

【简答题】贾府的“四春”分别是：

【简答题】某颗地球同步卫星正下方的地球表面上有一观察者，他用天文望远镜观察被太阳光照射的此卫星，试问，春分那天（太阳光直射赤道）在日落12小时内有多长时间该观察者看不见此卫星？已知地球半径为R，地球表面处的为g，地球自转周期为T，不考虑大气对光的折射．