Equation 1 · Part 3 · How We Know What Is Inside a Planet
Symbol M
What this part means
M occurs below the fraction bar. The quantity above the bar is divided by this expression; zero is excluded as a denominator.
Its job in the formula
M occurs below the fraction bar. The quantity above the bar is divided by this expression; zero is excluded as a denominator.
Full expression→Symbol M→Article meaning
The passage around this formula
The fourth quantity is the one that does real work. The polar moment of inertia, normalised by mass and radius, is . and it measures how mass is distributed radially rather than how much there is. A uniform sphere has = 0.4 . Anything smaller means mass concentrated toward the centre; anything approaching 0.4 means a body that is close to uniform in density, which for a rocky planet means undifferentiated.
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.
Open the illustrated variables: a letter stands for a value guide →
See this notation across published equations →
Sources cited in the article section
- [7] Gravity field and internal structure of Mercury from MESSENGER ↗
- [9] Geodetic evidence that Mercury has a solid inner core ↗
These citations provide research context; check each source for the exact claim it supports.