object from the viewer's perspective crosses just two surfaces. For such objects, the integral may be taken over the entire surface () by taking the absolute value of the integrand (so that the "top" and "bottom" of the object do not subtract away, as would be required by the Divergence Theorem applied to the constant vector field ) and dividing by two: In higher dimensions In analogy with the cross-section of a solid, the cross-section of an -dimensional body in an -dimensional space is the non-empty intersection of the body with a hyperplane (an -dimensional subspace). This concept has sometimes been used to help visualize aspects of higher dimensional spaces. For instance, if a four-dimensional object passed through our three-dimensional space, we would see a three-dimensional cross-section of the four-dimensional object. In particular, a 4-ball (hypersphere) passing through 3-space would appear as a 3-ball that increased to a maximum and then decreased in size during the transition. This dynamic object (from the point of view of 3-space) is a sequence of cross-sections of the 4-ball. Examples in science In geology, the structure of the interior of a planet is often illustrated using a diagram of a cross-section of the planet that passes through the planet's center, as in the cross-section of Earth at right. Cross-sections are often used in anatomy to illustrate the inner structure of an organ, as shown at the left. A cross-section of a tree trunk, as shown at left, reveals growth rings that can be used to find the age of the tree and the temporal properties of its environment. See also Descriptive geometry Exploded-view drawing Graphical projection Plans (drawings) Profile gauge Section lining; representation of materials Notes References Infographics Elementary geometry Technical drawing Methods of representation