The universe is 13.8 billion years old, yet the observable universe is about 93 billion light-years across. That isn’t because light broke its own speed limit: while the oldest light travelled toward us, the space separating us from its source continued to expand, leaving that source’s present-day location roughly 46.5 billion light-years away.

The 93-billion-light-year observable diameter is a present comoving distance, not the length travelled by ancient photons. Distinguishing four cosmic horizons resolves the paradox. The post The universe is 13.8 billion years old, yet the observable universe i…