What physical principle explains why the majority of solar system bodies orbit in a narrow, single plane?

Answer

The law of conservation of angular momentum acting during the nebula's collapse.

As the initial spinning cloud of gas and dust collapsed under gravity, conservation of angular momentum caused the material to flatten into a spinning disk, confining subsequent planetary orbits to that plane.

What physical principle explains why the majority of solar system bodies orbit in a narrow, single plane?

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The Solar System - What Holds It All Together? - YouTube

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