What Alien Worlds Are Like

There are alien worlds with liquid water and rivers. There are waterfalls. There are definitely trees unless they've all been cut down or died off somehow. In the centers of the areas there is some sort of great growing tree-form. 

There are collections of related animals that are growing in number. The most intelligent species probably has various inventions that are ultimately things on the ends of sticks. 

There could be a dominant stationary life-form and a dominant mobile life-form that have a common heritage. 

The mobile life-form evolved through orbiting around the stationary life-form. 

Although we are uncertain exactly how the Universe began, or if it did at all, it's possible that it began with a big tree-shaped Boom. 

First, there was likely a Big Bang... 

Then a Galaxy formed within the shadow of the Big Bang likely orbiting around inside it...

Then a Star developed in the shadow or field of the Galaxy as it orbited around it...

Then a Planet developed in the shadow or the field of the Star as it orbited around it...

Then a River Delta developed on the Planet which moved around on the Planet over time...

Then one or more stationary Tree-shaped life-forms developed in the area of the River Delta and stated reproducing and moving around within the area of it...

Then, perhaps, one of the Tree-shaped life-forms developed into a mobile life-form and lived in the shadow or field of one of the Tree-shaped life-forms... 

This life-form was shaped like the Trees it evolved from and it mimicked the Universe... it developed things on the ends of sticks in it's area of domain...

The mobile life-form orbiting the stationary Tree-form became more and more conscious slowly over time... it began to spontaneously understand the Universe... which led to the creation of its first "thing on a stick" and perhaps over time... it became aware that it had the ability to think... 

The mobile life-form used it's processing unit to study the world around... it likely invented some concept of god... and possibly created things that reminded it of what it thought god to be... 

Eventually... the beings noticed the other Stars in the sky and studied them intimately... they discovered Planets like their own and considered other beings like them were out there... he felt an affinity to them as he thought of them.. and he tried to apply his whole understanding of the Universe to take a guess at what they might be like... 

Then the beings advanced their technology... attempted to spread life to the other planets... overcame the challenges of space... and perhaps traveled to nearby Planets or Stars... always careful to disguise themselves as they did so...

Mimicking the Universe as they know it... they would look for tree-forms to orbit... and by doing so advance themselves further and inch closer to becoming immortal and all-knowing...