Also, it doesn’t take too much acceleration to make that trip. Comfortable earthlike 1g (~ 10m/s/s) is enough to build up a decent speed in a very reasonable time. Energy is the issue though.
Unless we invent a reactionless drive the idea of traveling between solar systems remains a pipe dream.
Oh, and all light from the universe is now gamma radiation focused intensely ahead of the spacecraft cooking the whole thing.
An atomic nucleus sitting in deep space becomes an apocalyptic collision at 99.99% light speed.