I concur w/the others; I think that on some level that they know we're there in spirit. I've also read and I've come to believe that sometimes people hang on because they know that their loved ones want them to stay and whenever those loved ones leave to attend to something else or to get a bite to eat or whatever, that's when the person who is ill makes his/her transition. Whatever the case, it will take some time to get used to the idea of not having Dad around. Myself, I became angry for a bit because the world didn't stop and life for everyone else went on as usual when my Dad died. Right now you're still in shock. Gather your loved ones close and lean on them to help you through and you'll find that you'll do the same for them, too. (((HUGS)))