Can a physical object escape the universe?

Question

Can a particle, like an electronic or photon, leave the universe? If the photon for instance travels out toward the edges of the universe, assuming it is flat, will it encounter an invisible wall, or will it leave the universe?

Answer 1

To the best of our knowledge the universe does not have a boundary or an edge.

Answer 2

As another way of looking at it, under the current thinking in quantum field theory, the universe is made up of quantum fields. A quantum particle, like an electron or a quark, is simply an excitation (or a vibration or a wave) of the electromagnetic or the quark field. So it would not be possible for a particle to exist where there is no field.