= Centrifugation
{wiki}
<Centrifugation> separates suspended material by its motion relative to a rotating liquid. A <centrifuge rotor> creates an outward <centrifugal acceleration> in the <rotating reference frame>; material denser than its surroundings tends to move outward, opposed by <drag force>. Collected material can form a <centrifugation pellet>, leaving a <supernatant>, or remain in separated zones within a <density gradient>. The useful question is which physical difference the separation exploits: a difference in <sedimentation coefficient> or a difference in <buoyant density>.
\Image[/centrifuge-rotor-and-separated-fractions.png]
{title=<Centrifuge rotor> geometry and the <centrifugation pellet>–<supernatant> distinction}
{description=Original schematic of one swung-out tube during rotation and a conceptual pelleting comparison. <Rotor radius> increases toward the tube's outer end. Colors and particle counts illustrate incomplete separation and trapping; they are not measured recovery fractions. The tube remains horizontal in this depiction of the rotating geometry.}
<Centrifugation> makes otherwise slow settling useful for studying <biological cells>, <organelles>, <proteins> and <DNA>. Separation and identification are different steps: a <centrifugation pellet> is a collected fraction, not proof that it contains only one kind of <organelle>. The <lysozyme wall-removal experiment> illustrates a complementary readout: testing material released into the separated liquid can be more informative than inspecting the retained solids.
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