6. Infer At what stage in the life cycle of the Sun will it be impossible for life to exist on Earth Explain.

Life on Earth will become impossible during the Sun's **red giant** phase.<br /><br />Here's why:<br /><br />* **Expanding Sun:** As the Sun runs out of hydrogen fuel in its core, it will begin to fuse helium. This process causes the Sun to expand dramatically, becoming a red giant. This expansion will engulf Mercury and Venus, and possibly even Earth. Even if Earth isn't directly engulfed, it will be incredibly close to the Sun's surface.<br /><br />* **Intense Heat:** The surface temperature of the red giant Sun will be lower than its current temperature, but its enormous size will mean it emits far more energy. This increased energy output will cause the Earth's surface temperature to soar to uninhabitable levels. Oceans will boil away, and the atmosphere will be stripped away by the intense solar wind.<br /><br />* **Loss of Habitable Zone:** The habitable zone, the region around a star where liquid water can exist on a planet's surface, will shift outwards as the Sun expands. Earth will be well inside the inner edge of this new habitable zone, making it far too hot for life as we know it.<br />