In geometry, a solid angle (symbol: Ω) is the two-dimensional angle in three-dimensional space that an object subtends at a point. It is a measure of how large the object appears to an observer looking from that point. In the International System of Units (SI), a solid angle is a dimensionless unit of measurement called a steradian (symbol: sr).
A small object nearby may subtend the same solid angle as a larger object farther away. For example, although the Moon is much smaller than the Sun, it is also much closer to Earth. Therefore, as viewed from any point on Earth, both objects have approximately the same solid angle as well as apparent size. This is most easily observed during a solar eclipse.
Read more about Solid Angle: Definition and Properties, Practical Applications, Solid Angles in Arbitrary Dimensions
Famous quotes containing the words solid and/or angle:
“Manuel showed her his open hand: “Look at this finger, how meager it seems, and this one even weaker, and this other one no stronger, and this one all by himself and on his own.”
Then he made a fist: “But now, is it strong enough, big enough, solid enough? It seems so doesn’t it?””
—Jacques Roumain (1907–1945)
“So much symmetry!
Like the pale angle of time
And eternity.
The great shape labored and fell.”
—N. Scott Momaday (b. 1934)