Galactic Barriers (Star Trek)

[Nutso]

The Barriers are two linked phenomena that mark the inner and outer limits of the milky way galaxy in the Star Trek mythos.
The Galactic Barrier is a turbulent storm of negative energy that bubbles the galaxy perhaps keeping ships in. Or something else out?
The Great Barrier sits around the galactic core and seems to have held back a mysterious entity.
The Enterprise and Kirk's crew are some of the only people to have visited both.