The Primary Universe is fraught with great peril. War, plague, famine and natural disaster are common. Death comes to us all.
The Fourth Dimension of Time is a stable construct, though it is not impenetrable.
Incidents when the fabric of the fourth dimension becomes corrupted are incredibly rare.
If a Tangent Universe occurs, it will be highly unstable, sustaining itself for no longer than several weeks.
Eventually it will collapse upon itself, forming a black hole within the Primary Universe capable of destroying all existence.
/ and if it never collapses upon itself? /