If a light beam were to travel from one end of the universe to another without encountering any obstructions or interactions along the way, it would continue moving in a straight line at the speed of light until it reached its destination.
In the absence of any intervening objects or gravitational fields that could affect its path, the light beam would propagate through the vacuum of space without any significant deviation. This is because light, as an electromagnetic wave, does not require a medium to travel through and can propagate through empty space.
However, it's important to note that the concept of "the end of the universe" is not well-defined, as our current understanding of the universe suggests that it is vast and possibly infinite. So, the scenario of a light beam traveling from one "end" to another would depend on the nature of the universe and its spatial curvature, which is still a topic of ongoing scientific investigation.
Nonetheless, if we consider a hypothetical scenario where a light beam traverses an extremely long distance across the universe, it would continue traveling in a straight line until it reaches its destination, maintaining its speed of light throughout the journey.