Or Why Effective Theories are so … Effective

Solids, liquids, gases.  What do these words really mean?  How about cell, organ, or human?  At a fundamental level, these things are complex assemblages of interacting subatomic particles.  But you probably have an easy time recognizing a human without knowing about their electron configurations; you might instead identify key characteristics like physical appearance or behavior.  These various abstractions help us understand the macro-world, but a seemingly naive philosophical question is “why can we do that?” Continue reading →