Time travel into the past would be extremely dangerous. Your mere presence there could, and would, set off a chain reaction of events that, though seemingly unnoticeable, would change the course of history. After all, history is a web of billions of interactions stacked upon each other like dominoes. Remove, or even nudge, one domino, and an entire series of events will unfold differently. What might feel like a harmless gesture could completely erase the world you came from and replace it with something unrecognizable.
That being said, if I had been able to see in 1955 what life would be like seventy years later in 2025, I would have been shocked at the large number of homeless and mentally ill people wandering the streets of my hometown. However, I would not have been surprised to see cell phones or artificial intelligence, since both were already depicted in 1950s science-fiction comic books.
