#horizons

2 public notes

The observable universe is not necessarily the whole universe

The observable universe is the region from which signals have had time to reach us during cosmic history. Its boundary is a limit on available information, not a known physical wall. Space may continue beyond it, and observers elsewhere would have observable regions centred on their own locations.

Space♡ 0🔖 0

blackholes

What makes a black hole's event horizon a boundary

An event horizon marks a boundary beyond which signals cannot escape to distant observers. It is not a solid surface surrounding a black hole. Outside it, gravity can still allow ordinary orbits, so a black hole does not automatically pull in every nearby object like a cosmic vacuum cleaner.

Space♡ 0🔖 0