When one moves from a point \( 16 \, \text{km} \) below the earth's surface to a point \( 16 \, \text{km} \) above the earth's surface. The change in \( g \) is approximately \( \alpha\% \). The value of \( \alpha \) is ______.
\( 0.12 \)
\( 0.25 \)
\( 0.50 \)
\( 0.75 \)