The Earth, with an infinite realm of biological animals, life, and plants, along with history dating back centuries, could all be lost at any second…or will be preserved for many centuries to come. There have been many theories developed exploring the fate of the universe, as well as multiple calculated outcomes that would ultimately result in the demise of our planet. Many of these scenarios listed below are forecasted for several billions of years in advance, yet this natural life cycle of the universe is still quite unsettling and difficult to comprehend.
One of the many theories of how the universe could end is known as The Big Rip Theory, a mathematical and astronomical explanation that was concocted by scientists Marcelo Disconzi, Thomas Kephart, and Robert Scherrer. If possible and realistic, the scenario is projected to occur in around 22 billion years. The entire theory stems from the current expansion of the universe, where the influence of dark energy helps accelerate and expand in this process. The theory essentially describes a potential scenario where the expansion rate becomes faster than the speed of light and the forces holding everything in space together would fall apart. Astronomical objects would start to move farther away at increasing speeds during this process, while dark energy will continue to grow producing more “space that fills space”, ripping apart the said forces that are necessary to keep galaxy clusters and the universe stable. Galaxies, planets, and moons would then be stretched apart because of this, and atoms would be torn apart until only astronomical objects the size of a Planck length would be left. The theory states that the process will continue until everything in the observable universe is filled with relatively the same components that had originated during or even before the Big Bang. A timeline of this event would consist of the start of the Big Bang, which introduces the growth and formation of atoms, stars, galaxies, solar systems and our own planet. From here, expansion only grows faster, which is where the Big Rip theory is believed to occur: the destruction of galaxies, planets, and eventually atoms.
Another possibility of how the universe will end is much more realistic: the Sun expands into a red giant. Although the Sun is currently withstanding the forces of gravity by burning hydrogen fuel, it will eventually run out in over 5 billion years, which is when the core will be crushed, increasing pressure and expanding the star into a red giant. During the red giant phase, the chances of Earth’s demise are much greater than its survival. For instance, the Sun would lose much of its mass during the stage, causing orbits to fall into chaos. Additionally, the Sun could completely engulf the inner planets during the expansion, or kill everything with increased radiation. If Earth survived this intense scenario, it would find itself orbiting a small white dwarf star, and then finally a black dwarf star as the solar system goes dark.
A galaxy collision, although unlikely, could also destroy Earth. A neighboring spiral galaxy called Andromeda is only slightly larger than the Milky Way galaxy and is on course to merge. Projected to occur within 5 billion years, the red giant phase will have already occurred in our solar system, here Earth will probably have been engulfed. Although the galaxy would be expanding during this time, the Milky Way and Andromeda are linked by gravitational forces, similar to the entire Local Group. The Local Group itself may also collide with the Virgo Cluster in the future.
These three events are extremely unlikely to occur during the presence of humans, including the rise and fall of interplanetary exploration. However, the likelihood of outside astronomical scenarios wiping out the planet is significantly lower than the chances of human extinction due to climate change, nuclear war, a pandemic, or the rise of AI.