For a long time scientists have been arguing over the possibility of something( non-hypothetical) being infinite, I will allow usage of hypothetical theories to support existence of infinity non-hypothecatally.
This will be our definition of infinite-
Description of something meaning that what the term infinite is describing has no end, and every possible outcome happens.
Infinity must exist because no wall or barrier can prevent it from existing. When you construct a limit to the universe, then, there is always an area outside of that limit which has not been taken into consideration. Also, just because you can't see infinity doesn't mean that it doesn't exist. Infinity goes forever outwards and forever inwards. You can stop infinity or put any limitations on how far or how small it may be. It is only the limitations of the human mind to comprehend infinity that is the major problem. Human ego doesn't allow the universe to be infinite. This is too intimidating a concept for humans to contemplate. Thus, they construct artificial barriers to contain the universe into an acceptable size that is not too intimidating for their egos to accept. Currently scientists believe that the universe is 93 billion light years wide because that's as far as their instruments can reach.
if something was infinite, lets say the universe, everything that can exist exists including theese to things: 1.A wall or barrier that's stops it, and behind the barrier is nothing, since this can possibly, while improbably exist, according to our definition this is a possible outcome therefore, it must exist, and therefore it is not infiltrate, which means the wall or barrier may not exist. This creates a paradox, and if it creates a paradox, it must not be correct. 2. If all possible outcomes exist than why has nothing destroyed everything. In an infinite universe something capable of destroying all of it must exist, and therefore it can't exist for any amount of time. Unless you want to argue that it is not possible for an object to destroy an infinite universe, in that case let's make the same argument about earth. A possible thing at can exist, and thus exists in an infinite universe. Is a comet destined to hit earth 5 seconds from when you read this. So if a comet hits earth in he next 5 seconds the universe is infinite, if not its finite.
Simplified version- if the universe is infinitie than all things that can exist must exist, including a barrier. This creates a paradox. Also since all things exist a comet about to hit earth is a possibility, and therefore if the universe is infinite we will be wiped out by a comet in the next 5 seconds