About what is beyond the universe, the scientific community has given three relatively acceptable theories. Strictly speaking, the vast universe is full of unknowns and mysteries for human beings, and many people should have various doubts about it.
About the mysterious universe
Fortunately, researchers have never given up on the exploration of the universe. On the contrary, they are constantly developing their own abilities and want to speed up the pace of exploration of the universe. During this period, after humans gradually realized the vagaries of the universe, they even became more and more confused, and realized how small humans really are in the vast universe.
Some researchers believe that because human beings cannot reach the speed of light because of their scientific and technological strength, it is difficult to move quickly in the universe, which makes it impossible to reach the edge of the universe. Regarding the existence of the edge of the universe, we can only conduct a rough analysis based on the existing observation data.

Reasoning with the status quo
All guesses are based on analysis based on a certain basis. Although the results may not be 100% accurate, all conclusions are obtained through reasoning and have a certain degree of credibility.
Regarding the universe, researchers have sorted out three reasonable analyses. First, there is no substance in the periphery of the universe, and it is nothingness. The universe currently observed by human beings is not the whole picture of the universe. Second, people must have heard of the theory of parallel universes. It is very likely that there is another parallel world outside the universe. Thirdly, human beings on earth have always lived under the control of advanced civilizations, and human beings are like their test products.

In-depth investigation is still needed
The above three conjectures are based on the analysis made by scientific researchers based on the existing situation, what is there in the depths of the universe, where is the edge of the universe, and whether there are other more advanced intelligent civilizations in outer space.
The above-mentioned questions are still unable to get definite answers. The real answers behind them still need to wait for further investigation and exploration by scientific researchers. I believe that time will reveal all the mysteries.