oh btw small thing - I belieeeve james ortiz mentioned on Some podcast Somewhere that they did film material with grace's ex but ultimately cut it, and if I were to guess I'd say this is probably her in the first flashback montage. she's standing right up next to grace as he watches the news report with the first footage of astrophage, and he's staring down at his phone with his earbuds in instead of playing it out loud and holding the phone between them for them both to watch this massive news event at the same time, which would line up with the two (2) lines we have about the relationship in the movie. there doesn't appear to be anyone else around in this space, the physical environment isn't forcing them to be so close, this looks like two people who are standing together for the purpose of deliberate socializing, and he's completely tuning her / the rest of the world out. if this is part of a pattern of behavior then I can totally see it being a "screw it, you're not even present for this conversation, let alone this relationship" last straw, but also imagine learning aliens exist then taking out your earbuds and immediately getting dumped, lol.