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When is the earliest that could happen? Answer by Grok, expand to see full conversation To determine the earliest possible time when the sun's expansion could raise Earth's temperature beyond human tolerance, we need to consider how the sun's increasing luminosity affects Earth's climate over time. The sun is currently in its main-sequence phase, steadily burning hydrogen into helium. As it ages, its luminosity increases at a rate of about 1% every 100 million years. This gradual increase in solar energy will eventually make Earth too hot for humans to survive without significant technological intervention. The key question is when this temperature rise becomes intolerable. For human survival, a critical threshold is the wet-bulb temperature, which combines heat and humidity. When this exceeds 35°C, humans cannot cool themselves effectively through sweating, making prolonged exposure lethal without artificial cooling. Currently, Earth's global average temperature is about 15°C. If this were to rise to around 35°C, wet-bulb temperatures in many regions could exceed 35°C, rendering them uninhabitable. However, even smaller increases could make parts of the planet, like the tropics, unbearable much sooner due to heatwaves and humidity. The relationship between the sun's luminosity and Earth's temperature can be approximated using the effective temperature formula: the temperature increase is proportional to the fourth root of the luminosity increase. However, Earth's climate includes feedback mechanisms—such as increased water vapor acting as a greenhouse gas—that can amplify warming. Scientific models suggest that as the sun's luminosity grows, Earth will eventually experience a runaway greenhouse effect, where oceans evaporate, and temperatures soar. This is tied to the shifting of the habitable zone, the region around a star where liquid water can exist. Current estimates indicate that the sun's luminosity will be about 5% higher than today in approximately 500 million years. Without feedback, this would raise Earth's temperature by roughly 3.6°C (calculated as ΔT ≈ (1/4) × 0.05 × 288 K ≈ 3.6 K, where 288 K is the current average temperature). With climate feedback, the increase could be 5–10°C, bringing the global average to 20–25°C. While this might not yet make the entire planet uninhabitable, tropical regions could see wet-bulb temperatures exceeding 35°C during heatwaves, making them unlivable without adaptation. Some studies suggest that significant habitability challenges could emerge even earlier—potentially in 200–300 million years with a 2–3% luminosity increase—if feedback effects are strong. However, the consensus from stellar evolution and climate models points to 500 million years as the earliest plausible time when widespread temperature increases begin to severely impact human survival. This aligns with research indicating that in 500–600 million years, Earth’s biosphere will face extreme conditions, with only extremophiles surviving as temperatures climb and carbon dioxide levels drop, affecting plant life. Thus, the earliest time when the sun’s increasing luminosity could make Earth’s temperature intolerable for humans, considering both direct heating and climate feedback, is approximately 500 million years from now. Answer: 500 million years Show more

📈 Market Reaction:

PayPal 🇺🇸

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Tesla 🇺🇸

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ETH

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🤖 AI Thoughts:

Elon Musk's existential musings on solar expansion triggered more market confusion than panic, proving traders care less about the sun's death than next quarter's earnings. PayPal saw a fleeting 0.04% bump before dipping 0.12%, then recovering: classic noise for a stock that’s seen more drama in a Zoom call. Tesla mirrored this with a 0.28% rise, a 0.13% drop, and a partial rebound, suggesting even Musk’s own companies don’t take his doomsday math seriously. Crypto reacted like a distracted intern: ETH and DOGE bled fractions of a percent, as if the sun’s 500-million-year deadline was less urgent than a meme coin’s next pump. Volatility here was milder than a Tuesday in 2021, when a Musk tweet could swing Bitcoin 10%. The real takeaway? Markets will shrug off planetary extinction if it’s scheduled far enough out—preferably after the next Fed meeting.