Quick Answer
A second Moon would make Earth’s sky and tidal system more complex. If it were small and distant, the effects could be modest; a Moon-sized companion could produce substantial additional tides and gravitational interactions. Stable orbits would be possible in some configurations, but not every two-moon arrangement would remain stable.
There is nothing in basic physics that forbids a planet from having two moons. The difficult part is arranging their masses and orbits so the system remains stable.
The night sky
Two large moons would produce multiple cycles of moonlight and more frequent opportunities for eclipses and conjunctions. Their phases would not necessarily line up.
Tides become more complicated
Each moon would raise its own tidal bulges. Depending on their orbital periods, the tides could sometimes reinforce one another and sometimes partially cancel.
Orbital stability matters
Two moons that approach one another closely could exchange orbital energy or become unstable. A carefully separated system could remain stable for long periods.
Life could notice
Nocturnal animals, coastal organisms and species that use lunar cycles could respond to the new light and tidal patterns.
SpeculativeThere is no single “two Moon” outcome. Mass, distance, inclination and orbital resonance would determine almost everything.
The bottom line
Two moons could produce a stable and spectacular sky, but the most dramatic differences would come from the combined gravitational and tidal system.
A note on our approach: Every article on WhatIfLab separates what current science establishes from what remains genuinely speculative. Where we cite a figure or finding, it reflects published, mainstream research at the time of writing — not a prediction dressed up as fact.