The poem "Fire and Ice" by Robert Frost explores the idea of the world ending either in fire or ice as a metaphor for the human emotions of desire and hatred.  One possibility for the Earth's demise is the expansion of the sun. In about 5 billion years, the sun will exhaust its hydrogen fuel and expand into a red giant, engulfing the inner planets, including Earth. This scenario is in line with the "fire" mentioned in the poem. Another possibility, though less likely, is that the sun could undergo a process that would cause it to cool down, making the Earth uninhabitable. This scenario could be associated with the "ice" mentioned in the poem. However, it is worth noting that the sun cooling down to such an extent is not considered a probable outcome based on our current understanding of stellar evolution. There are other potential threats to the Earth's existence, such as asteroid impacts, gamma-ray bursts, or even human-induced catastrophes. While it is impossible to predict the exact course of events, it is important for humanity to continue to study and understand the universe to better prepare for potential challenges.