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The logistics of it all were more than a little confusing, and there was a lot of science-y talk thrown around...mostly by Dr. Stein (Victor Garber). Basically, Barry needs to run at mach 2 inside the particle accelerator pipeline and collide with a hydrogen particle, opening up a stable wormhole. Once he's inside, he focuses on the moment he wants to go to, and using the speed force, he'll appear there. Once he saves his mother, he'll come back, and Eobard will get to go to his own time in the future, but Ronnie (Robbie Amell) needs to build a "time machine" for him to sit inside when he does since his powers are so unstable. Phew. Got that? Good, because here's where it gets really confusing.

If Barry does go back in time and save his mother, he might change literally everything he knows about his life today, creating an alternate timeline where no one remembers the life they all lead now. He'll lose Joe (Jesse L. Martin) as a father since his own dad will never go to prison for his mother's murder. That means he'll never live with Iris, losing his close friendship with her. He might never meet the S.T.A.R. Labs team.

And here's where it gets really tricky: if he doesn't run fast enough to collide with the hydrogen particle in the accelerator, he'll die. Or the explosion from colliding with the particle could create a singularity—aka a black hole, swallowing up Central City and possibly the whole world. Barry will only have 1:52 in the past before that happens. So many things could go wrong!