is the comprehensive genus that embraces every one of the earths. Allah hints at their number in Surah At-Talaq: “Allah is the One who created seven heavens, and of the earth the like of them” (At-Talaq: 12). That is, they resemble the heavens only in count, not in nature or magnitude—for the heavens vastly surpass the earth—yet they match them numerically. The Sunnah states this plainly, as in the Prophet’s ﷺ words: “Whoever unlawfully appropriates even a handspan of land, Allah will collar him with it on the Day of Resurrection from the seven earths.”

“—and in the alternation of night and day” manifests itself in several respects:

1. Night is dark while day is radiant, as Allah says: “We have made the night and the day two signs; We erased the sign of the night and made the sign of the day enlightening” (Al-Israʾ: 12).

2. They vary in length: sometimes the night is long, sometimes the day is long, and at times they are equal, as Allah says: “He causes the night to enter into the day and He causes the day to enter into the night” (Al-Hajj: 61), meaning He lets each encroach upon the other, taking part of its span—this too is an aspect of their alternation.

3. They differ in temperature: at times the air is cold, at other times hot.

4. They also alternate between fertility and barrenness; at times the world is