By now you’ve no doubt heard that Alfonso Cuaron’s “Gravity” is terrific, and indeed it is; I wrote about it after seeing it at the Toronto International Film Festival last month, and will review it this week for its Friday opening. But it got me thinking about how movies can make us anxious about things we’ll likely never experience: After watching “Gravity,” I was stressed out about the possibility of being untethered and free-floating in space — something that seems unlikely to ever happen to a very ground-level writer who doesn’t even climb ladders if she can avoid it. Other things that haunted my nightmares after movies this year: being attacked by a killer whale (“Blackfish”), having all my money taken away by Alec Baldwin (“Blue Jasmine”), encountering the undead in a pub bathroom (“The World’s End”), the possibility that I might be kidnapped by Somali pirates (“Captain Phillips”), and that in the future, Jodie Foster might try to prevent me from getting medical treatment (“Elysium”). Movies are meant to affect us on some level that we can’t entirely control, and it’s to the credit of all of these movies that, though the likelihood of encountering Somali pirates or killer whales in my Seattle neighborhood is miniscule, they made me put myself into a place where it could happen. Then again, I do routinely go down to my basement — the place that countless movies have taught us that we should never go (most recently “The Conjuring,” which also taught us not to buy an old house, or to get attached to a dog). But I always turn the lights on.