Ever since humans first looked up at the night sky, we have wondered whether we are alone in the universe. Dreams of life beyond Earth pervade literature, TV shows and drive Hollywood blockbusters – but the truth of life beyond the Earth continues to evade us.

n the coming decades, however, we face the very real prospect of discovering Earth-like planets orbiting distant stars and being able to search for life upon them.

But before we look at what we think are the various ingredients needed to contribute to the recipe of a perfect world, we need look at the history of the search for life elsewhere in the universe.

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