Earth is our only example of a habitable planet, and, as a result, often serves as a "stand-in" for how we think a habitable exoplanet would appear to a telescope capable of observing such worlds. My dissertation focused on the construction and validation of a tool that can simulate the appearance of the distant Earth to astronomical instrumentation. This model --- the Virtual Planetary Laboratory (VPL) 3-D spectral Earth model --- can accurately predict the time-dependent spectrum of the Pale Blue Dot over a wide range of wavelengths and viewing geometries. The model is a tool that is available to the exoplanetary science community, and it has already been used in a number of studies. For example, the VPL 3-D spectral Earth model has been used to better understand how we might detect oceans on the surfaces of exoplanets, and it has been used to verify techniques for constructing crude maps of exoplanets from spatially-unresolved observations.