This movie celebrates inquiry -being curious about our world,, and following one's dream/beliefs/vision in spite of strongly opposing views and opinions to them. There is a casual sex scene (flash of breast) between the "man of faith" and the "scientist", which is inconsistent with messages I'd like my tween to have about sex. Unfortunately, info is revealled during the bed scene which is important to the plot later on....so skipping it would compromise understanding. Plenty of foul language. Also, Christians are portrayed as being on the "right" or extreme, which is a biased and atypical representation of Christians.
Although things seem to go wrong most of the time for the main character, it is all redeemed with the ending, which was fantastic. There really isn't any objectionable content in the movie either, except for a tame lying-in-the-same-bed-naked scene; but like I said, it's non-explicit.
I saw this with my father when it first came out, I was six, the sexual content went right over my head and I didn't find it scary. However I wouldn't recommend letting young kids watch it since they just won't understand it. I was asking my dad "what's happening?" every five minutes. Watched it again at age 14 and it became one of my favourite movies. Don't expect a typical sci-fi film though, it's much more grounded and realistic. Great themes to talk with teens about. The movie raises a lot of questions about religion, morality, what it is to be human etc. and if it doesn't give you a sense of awe and inspiration for the universe we live in, nothing will.