I think time travel in both directions is at least theoretically possible, but they're very different challenges.
Going forward in time seems much more realistic since we already know that time can be affected by speed and gravity. If someone could travel close to the speed of light, or spend time near an extremely strong gravitational source like a black hole, less time would pass for them compared to people on Earth. In a sense, they'd be traveling into the future. We already observe tiny versions of this effect with satellites and astronauts, so the science behind it is pretty solid.
Going back in time is where things get much more speculative. I've read about ideas involving quantum entanglement and black holes, but as far as I know, there's still no evidence that any of them can actually send information or matter into the past. The math behind some theories suggests it might be possible, but there are so many unanswered questions, especially when it comes to paradoxes and causality.
Personally, I think traveling forward in time is something humanity could potentially achieve on a larger scale someday. Traveling backward in time feels like it would require us to discover entirely new physics, or at least understand parts of the universe that we're still completely missing. Either way, it's one of the most fascinating concepts in science because the more we learn about time, the less straightforward it seems to be.
