If we can neglect the off-diagonal elements the equations will uncouple and simplify drastically.

With this convention the metric equation of Minkowski space-time simplifies to.

First let us establish how the geodesic equation simplifies when the motion can be described approximately by classical mechanics.

For this reason, CO is generally the test gas used to measure the diffusing capacity and the equation simplifies to:

The equation for can simplify since a variety of quantities will now equal zero, for example:

With no relaxation (that is both T and T ) the above equations simplify to:

In this case, equation (1) above simplifies to:

Thus, the first term can be eliminated and the equation simplified once more to:

If the distance is doubled, the equation simplifies to which equals 6.02 (or approx.

However, for an observer at infinite distance from the star, the above equation simplifies to: