Yes: If Time Machine gets invented then past can be changed but time travel involves a number of problems. For that read Time Travel Paradoxes. But let's be hopeful that it happens in our lifetimes.

I really want to see two things happening in my lifetime. One is the invention of time machine and the other Elixir of life, if that's possible, there must be some aging gene, we gotta locate it and tamper with it for constant renewal of youth and elimination of natural death. We will become immortals then- how cool is that?