The Sun will lose the ability to sustain life on Earth in about 500 million years.
Why it is true
As the Sun ages, it becomes brighter and hotter, making Earth uninhabitable long before it becomes a red giant.
Source: Astrophysics
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This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.