In the vastness of space, light can travel incredible distances before encountering any significant obstacles. In the absence of any intervening objects, light can continue traveling indefinitely. However, space is not entirely empty and contains various particles and objects that can scatter or absorb light.
Interstellar space, the region between stars in a galaxy, is generally extremely sparse, with an average density of about one atom per cubic meter. In such an environment, light can travel immense distances before interacting with any matter. It is estimated that light from distant stars can travel thousands of light-years through interstellar space without colliding with anything substantial.
On larger scales, the universe contains galaxies, clusters of galaxies, and vast cosmic voids. These structures are separated by enormous distances, and light can traverse these voids without obstruction.
However, on smaller scales, there are objects such as planets, moons, asteroids, comets, and interstellar clouds that can intercept and scatter light. These objects are more likely to cause light to hit something if they are in the path of the beam. Additionally, the presence of cosmic dust and gas clouds within galaxies can also obstruct light to some extent.
To summarize, the distance a beam of light can travel before hitting something depends on the specific environment it passes through. In the mostly empty regions of interstellar and intergalactic space, light can travel vast distances. However, when encountering denser regions with objects or interstellar material, the light may be absorbed, scattered, or blocked by these obstacles.