[Q?]

Originally Posted by surfdude12

i dont think anyone can truly "explain" this film, except aranofsky.

but here goes my interpretation

[Show spoiler] only the present and future tom are real. the past tom is the conquisidor referenced in the book (who we see at beginning of the film). the past tom isn't real, just a character in the book.

as Q said, the present Tom was constantly trying to cure/fight/resist his wife's death, by trying to develop cures,etc. she died, hence he failed. at her funeral, he still says that "death is a disease", hence hasn't accepted death. he planted a tree at her grave. his wife talked about how (dont recall who) someone, after they died, became part of the plants/soil/etc.

at this point: how did present tom age 500 years to about the year 2600? i dont know if the movie spells this out, but i presume he just kept working in the lab and conjured up an anti-aging cure (the green mix he was eating in the spaceship). the tree thats in the spaceship supposedly represents his wife, and i think that is the tree he planted at her grave (and hence that she was absorbed into).

in the spaceship: we see future tom struggling to still finish the book. then it seems that he thinks back to changing a choice he made, and go for a walk with his wife, instead of going to the lab to fight death. this seems to be a cruicial realiziation for him in the future, as it shows he is starting to let go of the fighting/resisting of death. as he continues to do this, he was able to finish teh last chapter of the book (in his head, in the future), where he appeared to the mayan warrior in the buddha-posture, and not fighting/resisting any violence against him. hence, he was identified as the one and permitted to teh tree of life (i guess b/c he didnt resist any attempts to kill/strike him), and at the tree of life he fed off, he didnt die but was merely redistributed/reborn (as his wife said) through death. all of this "past tom" realization is mental writing of the last chapter by the future tom, who then completes "the book" and his soul is free to shoot through the mayan star (as i guess his wife said: this is where souls go to be reborn?!)

Wow.. I have to see this again in the near future...
I'll have to consider everybody's intrepretations
Try reading Jhiggy's take.