How well do we know people?

So I was talking with my mom and she was a little disturbed by my previous posts. She said she felt she was reading a blog of someone she didn't even know. I find that really interesting because she probably knows me better than anyone. But how well do we REALLY know people? I suppose everyone has a face or a side that they present to certain people. (For instance, since my MOM is reading this thing, you certainly won't get any really juicy gossip or...er...tidbits!!!! Ha ha. Just kidding mom, I love you!) I'm sure that there are things I'm interested in, books, movies, thoughts, ideas, that my mom and the others around me know nothing about. And it's not as if I'm trying to actively hide anything from those that I love. I suppose it's that I don't feel a huge need to share everything. This is different than hiding - some things I can enjoy, think about, stay up worrying about, laugh about, cry about, etc. all on my own. I don't need others to validate my enjoyment, thoughts, worries, laughter, tears, etc. I don't think this makes me cold or cut off from people - I think it makes me self-reliant and self-assured. How could you get through a day if you can't stand your own company? Do you have clutter up your world to get away from yourself? Is this what's behind crazy seeming behavior like drug addiction and such? I don't expect answers to these questions - just sending them out into the void, as it were.

Speaking of voids - just finished re-reading "Contact" by Carl Sagan. Such a thought provoking book. Are we alone in the universe? Is there intelligent life out there? There is so much about space and the universe that we'll never understand or never have more than hypotheses about. It's so maddening. What's out there? Who's out there? Are we completely alone? I hate to think so.