at the edge of universe it is a fog, in this fog it is the Universe Border

it is 3 types of Universe barrier

Strong Universe barrier

to pass the barrier, you need go at double the fastest speed in that universe & be bigger then 1 Kilometer

Normal Universe barrier

to pass the barrier, you need go at fastest speed in that universe & be bigger then 1 centimeter

Weak Universe barrier

to pass the barrier, you need go at half of fastest speed in that universe & be bigger then 1 Nanometer

a Universe System is a system of orbiting universes.

there's 2 types, Solar : like a planet orbits the sun & Chaotic : A Chaotic system of universes.

there's 4 Subtypes, Duo For 2 Universes, Stable For 3 - 6 Universes, Semistable For 7 - 12 Universes, Unstable For More Then 12 Universes, 

Two universes can get in orbit around each other spinning faster and faster into each other causing them to fuse into one.