Seriously? Why do we need a new reference Earth model?

Unlike fashion models, who have stylists and artists crafting their appearance, geophysicists construct structural models of the Earth by using mathematical tools, observations and simulations of seismic waves propagating through the Earth's interior, from its surface to the core. In these one-dimensional (1D) models, the Earth (or, as a matter of fact, any other planet) is divided into kilometres thick spherical layers, just like an onion on a much smaller scale. In these layers, the quantities such as density, gravity, or the speed of seismic waves, are given in terms of their spherical averages, i.e. they do not vary laterally, and we refer to such models as spherically symmetric. Geophysicists and astronomers have been using them as the points of reference for physical properties along planetary radii. But, seriously, do we need new reference Earth models?

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