Due to the staggering immensity of the universe, it is virtually guaranteed that other intelligent life is out there, and for the same reason (and because FTL travel may prove impossible) it's virtually guaranteed thst we will never, ever encounter them.
∆(𝐩 + −𝐩) = (𝐩ₙ + −𝐩ₙ) − (𝐩ₙ₋ₘ + −𝐩ₙ₋ₘ) = (𝐩ₙ − 𝐩ₙ) − (𝐩ₙ₋ₘ − 𝐩ₙ₋ₘ) = 𝟢 − 𝟢 = 𝟢
Under acceleration, the (net) momentum of a physical, [mass] balanced object remains zero (i.e., constant).