Answer: (1) The solar terms shown at points A and D in the figure are: A _ _ _ _ D _ _ _ _ (2) The revolution speed of the earth when it revolves from A to C in the figure.

(1) As can be seen from the schematic diagram of the earth's revolution, when the earth is in position A, the sun shines directly on the Tropic of Cancer, which is the summer solstice in the northern hemisphere, and when the earth is in position D, the latitude of direct sunlight is the equator, which is the vernal equinox in the northern hemisphere;

(2) From the beginning of 1 month to the beginning of July, the revolution speed of the earth becomes slower and slower, and from the beginning of July to the beginning of the following year1month, the revolution speed of the earth becomes faster and faster. When the revolution is from A (summer solstice and early July) to C (winter solstice and 1 early July), the revolution speed of the earth is faster and faster;

(3) When the earth revolves from point B (autumnal equinox) to point C (winter solstice), the days in the northern hemisphere get shorter and the nights get longer, while from point C to point D, the days in Beijing get shorter and then longer, and the nights get longer and then shorter.

(4) When the earth is at point A, the law of global day and night changes with latitude is: from north to south, the day becomes shorter, the night becomes longer, and extreme days and nights appear in the Arctic and Antarctic regions;

(5) When the earth is at point C, the global midday sun height angle changes with latitude: it decreases from the tropic of Capricorn to the north and south poles;

(6) When the earth is at position C, the latitude of direct sunlight is tropic of Capricorn, which is the winter solstice in the northern hemisphere, with the shortest day and the longest night in the northern hemisphere, and the highest sun height in the area south of tropic of Capricorn at noon.

Therefore, the answer is: (1) summer solstice; Vernal equinox; (2) faster and faster; (3) The day first becomes shorter and then longer, and the night first becomes longer and then shorter; (4) From north to south, the days become shorter and the nights become longer, and extreme days and nights appear in the Arctic and Antarctic regions; (5) decreasing from the tropic of Capricorn to the north and south poles; (6)C； C.