What to say when somebody asks about the big bang

[Whateverist]

You mean if the things we think we know have always been true, then ...


I don't think that premise will hunt.

I suppose what I think you're suggesting is the safest place: "We can only speak of the predictability of the universe right now, it may not have been so in the past and might not be in the future." Feel free to trash or refine that statement.

It's doesn't bode well for science though.

I don't see why.  Science isn't concerned with finding all the objective, unvarying and eternal truths, just empirical ones. You know, in the here and now.