SUEZ, Egypt—To get the giant container ship blocking the Suez Canal unstuck, engineers needed the stars to align. Actually, the sun, Earth and moon.
After several days trying to dislodge the Ever Given cargo ship, which had veered off course and embedded itself in the side of the canal, the salvage team pinned their hopes on this week’s full moon, when, beginning Sunday, water levels were set to rise a foot-and-a-half higher than normal high tides. That would make it easier to pull the 1,300-foot vessel out from the side of the canal without unloading a large number of the 18,000 or so containers it was carrying.
The engineers would have to work fast to make the most of this narrow window. The effect would only last a few days. But it would be their best shot at freeing up the canal—and with it, billions of dollars’ worth of global trade flows in the process.
Tides are higher whenever there is a full or new moon, which occurs when the…