Death
Death is a rather contradictory affair, one of great loss and unending wonder for those left living. It is a constant pull, a tendril which ceases to retreat from our struggles against it.
Death, though, is not experienced only by people. For the smallest of virus and bacteria to the largest of aquatic creatures struggle to perpetuate their existence. If we are willing to be just the smallest bit more imaginative, we can expand our thinking further.
To some of the smallest of things, such as photons, to the largest of things, like super massive black holes, all things eventually are reduced to nothing.
Throughout the universe and in all organized systems we see there is Death. A physicist may well tell you this is what we call Entropy, the eventual decay of all things to Disorder. Some may even smugly tell you that no such process exists to reverse Entropy.
What is perhaps removed, or more likely unknowingly left out, it is this Entropy that our Universe exists at all. Without it, our Universe would have remained as it did during the Big Bang, which is to say as an incredibly hot, dense, and boring point in space-time. No Stars would have been created, they wouldn’t have spectacularly exploded under their own gravitational/thermodynamic disequilibrium. Those same Stars wouldn’t have jettisoned and fused together heavier elements such as Carbon and Oxygen and Iron and Uranium. Clumps of material from these stars wouldn’t have reformed into newer, smaller stars, with large celestial objects like planets to orbit them.
And it is in this Entropy, or Death, that we see complex systems of Consciousness form and ponder the loss of loved ones. It is this unstoppable force of Disorder which spontaneously creates the tiniest bubbles of Order, which we call Earth, for us to inhabit and question our very existence.
For we are all created by Death, and so shall be reclaimed by it. This bubble is here for not but a moment, and to lose it is forever.