“Why has February sometimes 28 and sometimes 29 days?” asked Claire.
“I must tell you that the earth does not take exactly 365 days to turn around the sun. It takes nearly six hours more. To make up these six hours that were disregarded at first in order to have a round number of days in the year, they are reckoned in every four years, and the additional day they make all together is added to February, which then becomes 29 days long instead of 28.”
“So, for three years running, February has 28 days, and the fourth year it has 29.”
“Exactly. Remember, too, that the years when February has 29 days are called leap years.”
“And the seasons?” queried Jules.
“For reasons that would be a little too difficult for you to understand yet, the annual journey of the earth around the sun causes the seasons and the unequal length of days and nights.
“There are four seasons, of three months each: spring, summer, autumn, and winter. Spring is from about March 20th to June 21st; summer from June 21st to September 22d; autumn from September 22d to December 21st; winter from December 21st to March 20th.
“On March 20th and September 22d the sun is visible 12 hours and invisible 12 hours, from one end of the earth to the other. The 21st of June is for us the time of the longest days and shortest nights; the sun is visible sixteen hours and invisible eight hours. Farther north the length of the day increases and that of the night diminishes. There are countries where the sun, an earlier riser than here, rises at two o’clock in the morning and sets at ten o’clock at night; still others where the time of its rising and that of its setting are so close together that the sun has hardly sunk below the apparent edge of the sky before it appears again. Finally, at the very pole of the earth, that is to say at the point that remains stationary, like the end of the axle of a wheel, while all the rest turns, one could witness the wonderful spectacle of a sun that does not set, that turns around the spectator for six whole months, equally visible at midnight and midday. In those countries there is no longer any night.
“On the 21st of December we have a state of affairs just the reverse of that observed in June. With us the sun rises at 8 o’clock in the morning; at four in the afternoon it has already set. That is eight hours of day for sixteen of night. Farther north there are now nights of 18, 20, 22 hours, and corresponding days of six, four, and two hours. In the neighborhood of the pole, the sun does not even show itself, and there is no longer any daylight; for six months there is the same darkness in the middle of the day as at midnight.”
“And do people live in that country of the pole, where the year is composed of a day lasting six months and a night of six months?” asked Jules.