Honestly I'm surprised birdie, I thought you'd be less willing to rule it out. I wasn't going to post in this because, although I believe time travel in the sense it's usually meant is and always will be impossible, I didn't really think it was a decidable question, scientifically. Eg one plausible means of travelling through time (and space) would be a wormhole, which is kind of theoretically sort of possible, maybe, in Relativity? Or locally near rotating black holes there is an effect which is similar enough to count as time travel.
If another regular AB commentator hadn't exiled herself from AB's science board then Naomi would have been along to say something along the lines of her not knowing and nor does anybody else, and I wouldn't really be able to disagree with that. We've made a lot of progress in understanding the nature of time in the last century or so, but not enough, I would suggest, to make any kind of definitive statement that time travel must be impossible. Implausible and unlikely, certainly.