When the Sun exhausts its nuclear fuel and enters the later stages of its life, it will undergo several significant changes. One of these changes is the expansion into a red giant star. The expansion of the Sun will cause its outer layers to extend outward, engulfing the inner planets, including Earth. However, it's important to note that the red giant phase of the Sun is estimated to occur in approximately 5 billion years, so this is a very long-term scenario.
Once the Sun becomes a red giant, it will continue to burn its remaining fuel for a relatively short period, roughly a few hundred million years. During this time, the conditions on Earth will become increasingly inhospitable. The increased heat and radiation from the expanding Sun will likely cause the oceans to evaporate, and the Earth's atmosphere will be stripped away by the intense solar wind.
Ultimately, the fate of life on Earth when the Sun becomes a red giant is uncertain. The intense changes and conditions will make it extremely challenging for complex life forms, including humans, to survive. However, it's worth noting that life is resilient and adaptable, and it's difficult to predict the exact outcome. There's a possibility that life may find a way to persist in some form, perhaps in extreme environments or deep underground.
It's important to keep in mind that the timescales involved in the red giant phase of the Sun are vast, and there are numerous other factors that could affect the long-term survival of life on Earth, such as geological events or cosmic events. However, in the specific scenario of the Sun becoming a red giant, the conditions would become increasingly hostile for life as we know it within a few hundred million years.