Omega_m

Omega_m (Ωₘ) is a way to describe how much matter—like stars, planets, gas, and dark matter—is present in the Universe compared to a critical amount needed for the Universe to be flat. If Ωₘ equals 1, the Universe has just enough matter to eventually slow down its expansion but never stop. If it's less than 1, the Universe has less matter and might expand forever at an accelerating rate. If greater than 1, gravity's influence would eventually halt and possibly reverse the expansion, leading to a "closed" Universe. Omega_m helps us understand the Universe's overall shape and destiny.