Equation 7 · Part 1 · From Origins to Frontier: A History of Planetary Science and Exploration
Symbol r
What this part means
non-trivial), and a mantle viscosity low enough (i.
Its job in the formula
r is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.
Full expression→Symbol r→Article meaning
Where the article explains it
This is a first-order model, not a complete theory of core formation — real planetary interiors involve diapirism, iron rain, and turbulent entrainment rather than single isolated blobs — but it exposes the essential dependency: differentiation requires a large enough density contrast, a large enough body (so gravity g and blob size r are non-trivial), and a mantle viscosity low enough (i.
The passage around this formula
…iron rain, and turbulent entrainment rather than single isolated blobs — but it exposes the essential dependency: differentiation requires a large enough density contrast, a large enough body (so gravity g and blob size r are non-trivial), and a mantle viscosity low enough (i.e., hot enough) for sinking to complete within the age of the solar system. This is exactly why small, cold bodies — many asteroids among them — never fully differentiated and instead preserve primitive, unprocessed material from the…
Learn the underlying idea
A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.
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The article lists its research sources here.