According to Professor Lupin, even Muggles can feel the dementors' presence, even if they can't see them. The Patronus in this is more metaphorical, symbolizing hope. Even a little goes a long way.
From:
magically me
(Sun Feb 13 07:44:02 2005)
Very powerful...
From:
lunna
(Sun Jul 30 21:25:50 2006)
powerfull and touchiing
From:
gwynnblack
(Wed Nov 15 15:37:29 2006)
i agree with everyone else. incredible. i can feel it...