Here's why:

* Umbra: The umbra is the darkest part of a shadow, where the light source is completely blocked. In a solar eclipse, the Moon's umbra is the area on Earth where the Sun is completely obscured by the Moon.

* Total Solar Eclipse: A total solar eclipse happens when the Moon completely covers the Sun, casting its umbra on a specific region of Earth.

* Visibility: Only those within the Moon's umbra will experience a total solar eclipse. People outside the umbra will see a partial eclipse (where the Moon covers only part of the Sun) or no eclipse at all.

Therefore, only people within the Moon's umbra can see a total solar eclipse.