The Universe's Energy Barrier

"As said since the time mankind first started on earth there has been interaction between man and so-called aliens. The so-called aliens have the ability to move in and out of galaxies and solar systems but not universes. No one from this universe may pass into another universe. There is a field of energy, per say, light energy to stop anyone. It simply cannot be done. When coming to the boundaries of your universe a craft would have to turn around. But, this area is so large, so expansive that one on your plane could not even imagine how large it is. "