Near-light travel isn't possible yet, at least for humans, but it is mathematically possible. The void between the stars means there aren't a lot of obstructions a starship would encounter (space is named space for a reason). But at super fast speeds, they'll encounter obstacles that slower vehicles don't have to contend with. Near the speed of light, one of those obstacles would be photons. Other particles may also harm such a ship, but authors Ulvi Yurtsever and Steven Wilkinson hand wave those away, saying they expect those particles to be much easier to tackle. What will be harder to mitigate is the way light plays with super fast vehicles. Those photons will cause a drag, the authors say.