Night is also called night or night. It refers to the period when the sun is lower than the horizon. During this time, the human eye cannot observe the sun. Because it is in the second half of the direct sunlight, the sunlight cannot be illuminated, so the light is dark. There are different lengths in different heights, time zones, seasons and latitudes. Usually in the summer, the night is shorter than winter. In areas with lower latitudes, the difference between summer and winter nights is smaller. The length of day and night on the equator is fixed at 12 hours, and there will be a night of extremes at the north and south poles. People usually eat dinner in the evening, and traditionally they usually have two meals in the morning and afternoon. This is because they have to work hard all day to replenish their energy. However, some people think that dinner should be eaten less than two meals in the morning, so as not to interfere with digestion because the food does not fall into full sleep.