The maximum duration of a total solar eclipse is about ______ minutes.

The maximum duration of a total solar eclipse is about ______ minutes.

• A. 3
• B. 5
• C. 7
• D. 9

Answer: (C)

During a total solar eclipse, the total phase lasts only as long as the Moon completely covers the Sun. The Sun’s apparent size is about half a degree, and the Moon’s size as seen from Earth varies only a little, even at its largest. The Moon also moves relative to Earth quickly, and the Earth's rotation changes the geometry as the shadow (the umbra) sweeps across the surface. These factors cap how long totality can last. Even in the best possible arrangement—Moon near its closest point to Earth and a central crossing—the total phase can endure only about seven and a half minutes at most. In practice, totalities are shorter, so seven minutes is the closest common figure. Nine minutes would require conditions beyond what’s physically possible, while three or five minutes are simply shorter than the maximum achievable.

During a total solar eclipse, the total phase lasts only as long as the Moon completely covers the Sun. The Sun’s apparent size is about half a degree, and the Moon’s size as seen from Earth varies only a little, even at its largest. The Moon also moves relative to Earth quickly, and the Earth's rotation changes the geometry as the shadow (the umbra) sweeps across the surface. These factors cap how long totality can last. Even in the best possible arrangement—Moon near its closest point to Earth and a central crossing—the total phase can endure only about seven and a half minutes at most. In practice, totalities are shorter, so seven minutes is the closest common figure. Nine minutes would require conditions beyond what’s physically possible, while three or five minutes are simply shorter than the maximum achievable.