Flag day balloon

(1) The direction of the earth's revolution is from west to east; When the earth rotates to point A, it is the summer solstice in the northern hemisphere, and when the earth rotates to point B, it is the winter solstice in the northern hemisphere.

(2) When the earth revolves to point A, the date is around June 22nd every year, which is called the summer solstice in the northern hemisphere. The direct point of the sun is on the tropic of cancer, and the Arctic Circle has extreme days. This day is the earliest day to raise the national flag in front of Tiananmen Square and the shortest day for the shadow of the flagpole at noon.

(3) When the earth turns to D, the season in the northern hemisphere is autumn, and the sun shines directly on the equator twice a year (vernal equinox and autumnal equinox);

(4) We are now taking the final exam (about 65438+ 10 month). At this time, the earth is moving from the winter solstice B (65438+February 22nd) to the vernal equinox C (March 2nd1day), and the direct point of the sun is also moving northward, but the days are still short and the nights are long in the northern hemisphere.

So the answer is: (1); Summer solstice; Solstice of winter; (2) Tropic of Cancer; Extreme day; The earliest; Shortest; (3) autumn; Second; (4) winter solstice; C vernal equinox; The days are short and the nights are long.