The greatest long-term threats facing humanity

Can we actually say anything about the far future? If we can’t predict when it will rain next month, forecasting billions of years hence might seem impossible.

However, not everything is as chaotic as the weather: even predictions very far ahead are sometimes possible, especially in astrophysics and cosmology. We can be confident that there will be a total solar eclipse in the UK on 23 September 2090 because the Moon, Sun and Earth move in stable, predictable orbits with very minor disturbances, and the laws of gravity are now well-tested. Similarly, we can use known astrophysics to predict what will likely happen across the Universe as it expands.

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