As the Sun ages, it is expected to transform into a red giant — a phase where it expands massively, consuming nearby planets in the process. While this event is billions of years away, the scenario of the Sun turning into a red giant in present times raises intriguing questions. What would happen to Earth and its inhabitants if this cosmic shift occurred now?
Immediate effects on the human body
Gajendra Pal Singh, retired professor, Theoretical Physics, Firozabad, tells indianexpress.com, “If the Sun were to begin its gradual expansion into a red giant, the most immediate physical effects on the human body would stem from drastically increasing temperatures and heightened levels of radiation. As the Sun grows in size, its outer layers would expand and its surface temperature would decrease slightly, but the overall energy output and radiation levels reaching Earth would dramatically increase.”
Extreme Heat: The Earth’s temperature would soar well beyond habitable levels as the Sun’s expansion progresses. Humans would face hyperthermia (a condition where the body’s core temperature rises uncontrollably) almost immediately. With surface temperatures likely exceeding 100°C (212°F), the body would be unable to regulate heat, leading to symptoms such as intense dehydration, organ failure, heatstroke, and eventual death. The skin, as the body’s first line of defense, would blister and burn due to direct exposure to such extreme heat.
Increased Radiation Exposure: The Sun’s radiation output would also increase, including ultraviolet (UV), X-ray, and gamma radiation. Even with some protective atmosphere remaining, the intensity of solar radiation would lead to severe radiation burns, DNA damage, and a much higher risk of skin cancer. The human body’s cells would experience oxidative stress, and the immune system would weaken due to the damage caused by prolonged exposure to radiation. Additionally, the eyes, being highly sensitive to radiation, would likely suffer from irreversible damage, potentially leading to blindness.
Immediate Environmental Effects: Along with the heat and radiation, the surrounding environment would become increasingly inhospitable. Food supplies would diminish as crops fail due to the rising temperatures, and the lack of water would make survival increasingly difficult.
Even with some protective atmosphere remaining, the intensity of solar radiation would lead to severe radiation burns, DNA damage, and a much higher risk of skin cancer. (Source: Freepik)
Change in the Earth’s atmosphere and gravitational forces
As the Sun expands into a red giant, Singh informs that Earth’s atmosphere and gravitational forces would dramatically change, causing catastrophic effects on human life.
“Increased solar radiation would strip away Earth’s atmosphere, including the protective ozone layer, making breathing impossible and exposing the surface to deadly Ultraviolet (UV) radiation. Without atmospheric pressure, humans would suffer from oxygen deprivation, leading to death,” he reveals.
He adds, “The Sun’s mass loss would weaken its gravitational pull, shifting Earth’s orbit outward and causing tidal disruptions, climate instability, and increased seismic activity. Together, these changes would make Earth uninhabitable long before the Sun engulfs it.”
Gradual loss of the Earth’s water and other essential resources due to the Sun’s expansion
As the Sun expands into a red giant, Earth would face a devastating loss of water, essential for life, remarks Singh.
Water Evaporation: Extreme heat would boil away oceans, lakes, and rivers, halting the hydrological cycle and leaving the planet dry and barren. Life would become unsustainable without water for hydration and agriculture.
Ecosystem Collapse: With no water, ecosystems would collapse, leading to mass extinctions and failed agriculture. Scarce resources like arable land and breathable air would disappear, causing societal collapse as Earth becomes uninhabitable.
Loss of Other Resources: In addition to water, other essential resources, such as arable land and breathable air, would become increasingly scarce. Soil would lose its fertility as temperatures rise and water evaporates, leading to the permanent loss of agricultural productivity.
DISCLAIMER: This article is based on information from the public domain and/or the experts we spoke to. Always consult your health practitioner before starting any routine.
As the Sun grows in size, its outer layers would expand (Source: Freepik) 
Even with some protective atmosphere remaining, the intensity of solar radiation would lead to severe radiation burns, DNA damage, and a much higher risk of skin cancer. (Source: Freepik)
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