What governed the initial growth from micron-sized dust grains to centimeter-sized objects?
Answer
Soft, non-gravitational forces like coagulation.
The very early stages of accretion, involving particles starting as small as micron-sized dust grains and growing into centimeter-sized objects, relied on non-gravitational interactions. This initial process is described as coagulation, where particles gently collide and stick together, similar to static cling. These forces are sufficient for small aggregates to build mass, but this gentle mechanism proves inadequate once objects become larger, typically around the meter scale, where drag forces become insurmountable barriers to further slow accumulation.
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