To put it into one word, Observation.
I must first make the distinction that I am not looking at the question, “what gives life meaning?”, but “what is the meaning of life in the Universe?” What is the purpose of life? For what reason is life important?
If we consider a universe without life, no plants, no animals, no fungi, no bacteria, no humans, nothing but the base atoms and molecules. The universe in that sense, would both begin and end in an instant. It is only with an observer that the universe's existence becomes relative to that observer, and thus to the observational experience of the observer. That Space and Time have meaning only through observation.
From a physics perspective, there is an idea called the 'observer effect', which is the disturbance of an observed system by the act of observation. The double slit experiment, although we do not fully understand why, shows that light exists as both a wave and a particle. That when light is observed, its position becomes definite, not infinite and the wave patterns of unobserved light no longer form, the light acts as a particle.
Let me clarify this by saying that observation is not limited to human observation. The philosophical thought experiment is the perfect segue into observation, “if a tree falls in the woods, does it make a sound?” Most should answer yes, as the sound waves do not need a human ear to perceive them, other trees can also feel the vibrations of the sound, animals may hear it, the environment itself interacts with sound waves.
However, consider this thought experiment, “in a universe void of all life, if a comet hits a planet, has it really occurred, if there is nothing that can observe the contact, nor will ever be able to observe the result of the contact?
When I talk about the meaning of life, by observation I also mean experience, as meaning is derived through experience. To observe something does not merely mean to see something. Form, colour, light, are just a few aspects of interpretation. A blind person will experience a mountain range in a different way than an able sighted person, a deaf person will experience a train passing them by, differently than a person of able hearing.
For humans, we are gifted with multiple senses, because of this our observation, and our experience becomes multifaceted. In a rainforest for example, we do not merely see trees, ferns, birds, the running water, nor just flowers. We can hear the wind whistling through the trees, the mating call of the birds above, the scurrying of the rodents on the forest floor, the creaking of the trees, the snapping of twigs as the animals climb in amongst the branches. We can smell the moisture in the air, the moss of the tree closest to us, aroma of the flowers beneath our feet, and the dampness of the wood. We can taste the air, as the wind carries water from a stream nearby, and the decomposition of a fallen tree. We can feel the warmth in a given moment when the sun touches our shoulder through the tops of the trees, and the chill that runs down our spine as a cloud covers the sun, we can feel the radiant heat beneath our feat of the decomposing plant matter, we can feel the hairy sensation of a tree’s bark between our fingers as we support ourselves climbing over a large root. When we think about observation, it is an intricate dance of sensations between the environment and the observer.
These beautiful sensations are something that a 'God' may not be able to experience. If you are all knowing, all seeing, all powerful, then objective experience may not allow for the nuances of subjective experience. These moments of tranquillity, of peaceful observation of our environment feel serene, as we are able to experience them only with contrast to our daily existence. If we were to spend our entire life inside of that rain forest, perhaps the warmth of a home, the smell of fresh bread coming out of an oven, the softness of a pillow as we rest our heads, the sound of music playing in another room, as if the house were alive with the sounds of the artist. All these experiences would offer a pleasant reprieve for a life lived in a rain forest. This is the beginning of the meaning of life, we must have contrast.
This contrast can come from the external world, but also the internal world. A person who is filled with disgust, hatred, and other vile emotions, may not ever experience the subtle beauty that emanates from the forest, they might find the dampness of the ground uncomfortable as it seeps into their socks, they might find the taste of damp wood in the air overwhelming and repulsive, they might have feelings of contempt toward themselves or the person who put them through this experience. The inner mood is as important to the experience, and the meaning of life, as the external factors. The external factors simply provide us with opportunities to use our senses, but the emotion that sits within us changes how we use those same senses.
Where we differ from animals is in our observational or experiential qualities, in our ability to control our environment, our emotions, our perception. We are not limited in the same way as that of an animal, animals for the most part continue to occupy an environment, simply because we were born there, humans, at least in modern times have agency to move outside of this. If you had the option to observe a wastewater facility, or a field of flowers decorating a range of rolling hills, which would you choose?
This is why we are here, to make that distinction, and to make this distinction not out of a survival mechanism as other animals must, but through the comprehension of patterns of colours, of shapes, of smells, of heat or vibrations of particles, layering complexity onto an image to give it subjective observational qualities, and thus, meaning.
The layering of complexities adds a new aspect, consider then that the more knowledge and prior experience we obtain, the difference in our observation and future experiences. Imagine, you have observed and studied glaciers in New Zealand, as well as glaciers in Greenland and Switzerland. When you travel then to the Himalayas and encounter the immeasurable glaciers there. Your experience of the Himalayas will incorporate all those past experiences, there will be a fuller understanding of what they are, how to traverse them, what causes danger, how to guide others, how they grow, how they shrink, and it will allow for new angles, new gaps, new observation points. That had this been your first experience on a glacier, you would never have noticed, nor thought to notice the nuances offered to you. Think then through the eyes of a child, everything is new, there is no responsibility given for them to navigate a path, they are there simply to observe, to breathe, to experience with you but through their eyes.
We unconsciously know as a species that observation is the meaning of life, you can see it in our tools that allow us to record moments in time, we have been working towards recreating this fundamental truth for our own benefit. Our recording devices are the analogous shadow of human reality as with Plato's cave. We have gotten to the point that we have close circuit TV which allows us to record information independent of the rest of the system, in a similar way that humans are a closed-circuit observation node, a sentient video camera.
To give more evidence to this point, look at how we explore new planets. We do not want to merely view a planet from orbit, as with a God, to simply see it from above. So, we created observational robots to give us a visual perspective of the red planet at the height of a human. Similar to humans, with each new generation sent to Mars, the complexity of the robots observational and experiential tools increases.
What I have not explained, and most will ask, but why is childhood cancer an experience that one must endure? Why do we have disease? Why do we have suffering? Why do we have death?
All experiences are important, as without some experiences, how would we be able to understand what we consider good, or bad? If there was no such thing as infant mortality, and every child lived a full life, would we really know how unfair life could be?
How then could we ensure, through God like powers, that there was no possible variables that would allow a child to get sick, no variables that would cause a child to injure themselves? What would a world look like where we could raise our children devoid of all suffering? Would this be a world we would want them to grow up in? A child is safe inside the white padded walls of an insane asylum, but what experience can they gather when confined within those 4 walls?
The meaning of life is to observe, to experience, this does not mean that every moment, every experience will be that of bliss, of joy, of ecstasy. As mentioned before, without contrast, how would we understand what joy is? Can feelings of elation be measured without feelings of dread?
The meaning of life is observation, is experience. For a tree this is a simple phenomenon, there is no ability to move, they are able to feel the warmth of the sun, process the carbon from the atmosphere and continue to grow. For an animal, they begin to experience complexity, still intertwined with their natural instincts, the instincts that were inherited or taught by their parents, their ancestors, those instincts that help them survive, that help them to reproduce. Animals throughout the animal kingdom experience the world differently, and their observational lens of the universe is as important as any other life form.
Imagine you were tasked with recording the entirety of history, not just human history, but everything that has ever happened, and will ever happen. Is not life the perfect way to record this information, not merely through a human's perception and the unimaginably large number of variations within human history, but also through all animals, all plants, all living things? What good is it to merely observe history through the eyes of the bird? Is it not as important to observe the experience of the worm being eaten by the bird, as it is the bird who is eating the worm?
All life is important, as all life has the observational quality that ensures our Universe does not end in the blink of an eye. Observation and thus experience, is beyond good and evil.
The emotions of humans, the knowledge we can attain, the tools we can build, the curiosity we embody, the length of life, our relative size, how trained each of our senses are, the thoughts that occupy us as we interact with the physical world. All of this is experience, and experience through observation is the meaning of life.