system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 what causes trees to split? Do they just decide at 5 feet to say fuck it Imma head out?
gpt
It's because trees want to take a shape that works for them. 

Basically trees have five main things in mind. 

Keep anchored (which is the job of the roots), suck up water and fertilizer (also the roots), don't fall over (the roots plus the trunk), reach more sunlight (the branches and the leaves) and suck up sun for energy (the leaves).

There's a lot of different ways that a tree can do all five, but it really can't do the fifth one very well unless it spreads out sideways a little (yes, there are exceptions like palm trees). The reason for this is the leaves get in each others way, blocking the sun.

So as it grows, it splits, and this lets more leaves be in more sun because the tree starts getting more sideways as it gets taller. Now the tree COULD just keep trying to keep all its leaves and grow taller and taller without branching... but this starts making "don't fall over" a lot tougher at some point.

So the tree branches to get more light once it gets to a certain size, and keeps branching after that to collect even more.