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一、晨昏线的特点1．晨昏线实际上是一个球面上的大圆。2．晨昏线所在的平面总是与太阳光线垂直,且过地心。3．晨昏线总是把地球分成相等的两个半球,即昼半球和夜半球。4．赤道总被晨昏线等分成两部分,所以赤道上总是昼夜等分。5．春分和秋分时晨昏线过南北极点,且平分所有纬线,全球昼夜等分。6．夏至和冬至晨昏线与南北极圈相切,夏至北极圈以内为极昼,冬至南极圈以内为极昼。7．在一天当中,随着地球的自转,晨昏线的视运动方向与地球的自转方向相反,由东向西扫过地球。8．一年当中,随着地球的公转,晨昏线所在平面与地轴之间保持0°—23°26′的夹角来回摆动。其中夏至和冬至,晨昏线所在平面与经线圈平面之间夹角最大,达23°26′。春分和秋分晨昏线所在平面与地轴之间的夹角为0°。
First, the characteristics of the morning light line The twilight line is actually a big circle on a sphere. 2. The plane where the twilight line is located is always perpendicular to the sun’s rays and passes through the center of the earth. 3. The twilight line always divides the earth into two equal hemispheres, namely hemispheres and night hemispheres. 4. The equator is always divided into two parts by the twilight line, so the equator always divides day and night. 5. When the equinox and the equinox sundown line crosses the north and south poles, and evenly divides all the wefts, the world divides day and night. 6. The summer solstice and the winter solstice dimmer line are tangential to the North and South Pole Circles. The summer solstice in the Arctic Circle is extremely slim, and the winter solstice in the Antarctic Circle is extremely ambiguous. 7. In the course of the day, with the rotation of the earth, the direction of the twilight line’s apparent movement is opposite to that of the earth’s rotation, sweeping the earth from east to west. 8. During the year, with the Earth’s revolution, the angle between the plane of the twilight line and the earth’s axis maintained an angle of 0°–23°26′ back and forth. In the summer solstice and winter solstice, the angle between the plane of the twilight line and the plane of the coil is the largest, reaching 23°26′. The angle between the plane of the vernal equinox and the equinox line and the axis is 0°.