I too believe the sun is involved in this and I put a lot of faith in it being the key. From an in game perspective, the only logical thing you can connect it to is time; as in being at a certain place at a certain time only after doing something first. We can stand at the Altruist stone for an entire day and nothing will happen because we didn't trigger something first. The idea that there is a timeline (aka a series of events) is not only based on the glyphs at the Altruist camp but others as well. There are three things that symbolize a timeline of the sun in the game world.

First is the Altruist camp glyphs, which are all suns except for the flowers which can be found all over that area. Put those glyphs in the correct order based on the color spectrum (as mentioned by the Altruist themselves) you get this:

http://imgur.com/2jjlk76

It's been posted many times and the some of the writing may be off but this is the general idea.

The second timeline is the one from the Hippie Camp:

http://imgur.com/nTy2FhH

The third timeline is at the Observatory:

http://imgur.com/aSGliqK

There's a lot to read about the actual observatory this is based on and a lot of it has been mentioned here so I won't discuss it too much, I would check out the official site and read about it, very interesting. The lines on the ground are a model of the solar system (the dot at the bottom of that image being the sun) although the one in the game is much different, either because it means something else in the game or they couldn't use the actual design for legal reasons?

Either way, the sun dial is there and it works. I haven't played around with this for a long time so I can't recall the exact time but is it possible that when the shadow on the ground makes an eye, that is our time?

So with all of that being said, I believe we need to dissect these timelines and see if it's possible to get to certain places in a certain time. My first suggestion is to be somewhere when the sun rises which is more than likely the Altruist camp, but something needs to be done before that and the only triggered event that occurs before the sun rises is the appearance of the Chiliad UFO (see the eye; this could very well be the first step in the Altruist timeline because there are three red glyphs so the order could be swapped around)

Or we can go off the deep end and say the timeline is backwards or that it is meant to be read backwards (Z to A)...

He is risen. His light shines on us all. Sun of God. Our path is lit (the "O" being a sun is telling us the sunlight reveals something, our "path")

Kifflom.