It's innate in human nature to contemplate on our long-term objectives in life: "What career path do I wish to follow?" "Do I want kids?" "What house do I want to live in?" For some, these objectives are within the cusp of their fingertips, while others still have a long road ahead to accomplish them. What we all share is a sense of fate, of the inevitability of the trajectory to which we ceaselessly travel.

Each path we take as humans indubitably leads to an inevitable demise: death. Just as we contemplate what happens when we die, scientists hope to ascertain an understanding of the fate of the vast universe long after we have acquiesced to the void. The uncertainty of if the soul transcends to another realm to meet judgment, or if the soul even exists, science has served as an outlet to theorize the fate of this heavenly realm.

The first modern humans appeared in Africa at approximately 200,000 BCE, but the fact of the matter is our existence is a mere grain of sand to the dune formed at the bottom of the universe's hourglass; the three theories regarding what happens once that final granule falls to the bottom are The Big Rip, Crunch, and Freeze.

The Big Bang is believed to have occurred about 13.7 billion years ago, where the entire mass of the universe began to disperse from an astronomical explosion. The Big Rip is theorized to occur 22 billion years from today and developed by Marcelo Disconzi, assistant professor of mathematics in Vanderbilt University. Collaborating with Thomas Kephart and Robert Scherrer, they discuss the nature of cosmic viscosity and current beliefs of an elusive substance composing the observable universe: dark energy.

Although it was once believed that the universe was infinite, observations have been made of it expanding at an accelerating rate! The vector driving the acceleration of the universe's expansion is coined the term dark energy, yet it is unknown what physical state this is believed to exist in. However, this undetectable substance is believed to comprise 70 percent of the entire universe. Cosmological viscosity—the tendency for the universe to resist contraction and expansion—revolved around Disconzi's as he studied fluid mechanics in neutron stars and supernovae. This led to evidence that the expansion of the universe will be infinite and that cosmic viscosity and dark energy will drive the splicing of all atoms, ripping the universe apart.

Another theory pertaining more towards our understanding of thermodynamics is the Big Freeze, also known as the "Heat Death." Believed to be the most probable and sound in modern physics, it is believed that the entropy or disorder of the universe will continue to increase until it reaches a certain value. This is in concordance with the Second Law of Thermodynamics, stating that the entropy of a system increases with spontaneous processes. The maximum entropy would result in an equal distribution of heat across the universe, making it impossible for viable energy to exist. Matter would be spread so thin the universe would simply become a desolate void.

The most optimistic theory is The Big Crunch, involving the overcoming of gravity in its strife with dark energy. As dark energy has a tendency to accelerate expansion, gravity has a tendency to pull things closer based on mass. Eventually, the force dark energy applies to expand will be overpowered by gravity, resulting in the reversal of the Big Bang as the mass of the entire universe will return to one singularity. In theory, the Big Bang and our universe can simply be one of many iterations of expansion and contraction.

These ideas are of such an incomprehensible scale that it may feel as though your personal goals are at an arbitrary scale. In comparison to the universe, they may seem to play a small role in the gears that grind the cosmos. However, while we're granted the conscious mind, we should make the most of that one grain of sand and feel liberated to raise the stakes in accomplishing our aspirations.