All scenarios / Space
The Sun Goes Red Giant
Guaranteed. Just not for about 5 billion years.
What it is
The Sun will end the world eventually, and this one's guaranteed. In about 5 billion years it will run out of hydrogen in its core and swell into a red giant, probably engulfing Mercury and Venus and scorching Earth.
Why it ranks where it does
Long before that, the Sun will be a problem because it's slowly getting brighter. In about a billion years, the extra heat will drive the oceans to evaporate and make Earth uninhabitable for complex life. On human timescales the chance is effectively zero, so the score rounds to 0%.
Evidence on the board
- A certainty on a timescale where the rounding error is the entire human species.
What the experts say
Astronomers are confident about this timeline because we can watch other stars like the Sun at every stage of their lives.
The long view
The Sun is about 4.6 billion years old, roughly halfway through its life as a stable, hydrogen-burning star. It's about 30% brighter than it was when Earth formed, and it keeps slowly brightening. Over hundreds of millions of years, that extra energy will speed up the weathering of rocks that pulls carbon dioxide out of the air, eventually starving plants. Any civilization that survives that long will have had a very long time to move outward. For now, the Sun's biggest threat is the one covered in Solar Superstorm.
What would move the number
Up
- Waiting about a billion years
Down
- Moving to Mars, then further out
Live signals we track
The baseline above is set from the evidence as of October 13, 2026. On the live board, your browser adjusts it in real time using these feeds. Chatter can only nudge a score in proportion to its evidence, so attention alone can't make an unlikely scenario look likely.
- Public attention: daily Wikipedia pageviews for Future of Earth
- Online chatter: Hacker News stories mentioning "red giant" this week vs. the prior eight weeks
Sources
- NASA: Sun facts
https://science.nasa.gov/sun/facts/ - NASA: Stars
https://science.nasa.gov/exoplanets/stars/ - The Conversation: Why humans have only 1 billion years left on Earth
https://theconversation.com/the-sun-wont-die-for-5-billion-years-so-why-do-humans-have-only-1-billion-years-left-on-earth-37379
Baseline scores are an editorial threat index from 0 to 100 that combines current reporting with published expert estimates. They're meant for comparing risks, not as actuarial forecasts. See how the numbers work.