### Titius-Bode law

**(Titius-Bode rule, Bode's law)**
(relationship between the distances between solar system planets)

The **Titius-Bode law** (or **Titius-Bode rule** or **Bode's law**)
is an observed relationship between the semi-major axes
of the solar system planets. As a formula:

a = 2^{n} × 3 + 4

- a - semi-major axis.
- n - number counting planets outward: -∞ (Mercury), 0 (Venus), 1 (Earth), 2, 3, ... (i.e., 2
^{n} would be 0, 1, 2, 4, 8, ...)

The relationship was conceived at a time when all the known planets,
i.e., through Saturn, fit the pattern (within perhaps 5%)
excepting one gap between Mars and Jupiter,
and the subsequent discovery of **Ceres** (once considered a planet,
currently considered the one asteroid that qualifies as a
dwarf planet) filled the gap. Uranus also fit the pattern,
and in fact, a planet with Uranus's orbit was predicted on the basis
of the relation. But Neptune's orbit did not fit.

It is now considered a coincidence and curiosity, though it is occasionally
contemplated when new planets or planet systems are uncovered. Perhaps
the closest it comes to relevance is that stable orbits of significant
bodies in a system must be spaced out to some degree.

(*astronomy,planets*)
http://en.wikipedia.org/wiki/Titius-Bode_law

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