Some of these have been found — there are thought to be many millions in the Milky Way. There’s one orbiting the nearest star, Proxima centauri And another nearby faint star has 7 Earth-sized planets around it Will there be life on them — maybe even intelligent life? The outer three are in the habitable zone They’d be spectacular places to live. Viewed fro the surface of one of the planets, the others would loom larger than our moon does to us — swinging past fast across the sky. But they’re very un-Earthly. Probably tidally locked so that they present the same face to their star -one hemisphere in perpetual light. The other always dark. And _ the real goal, of course, is to see these exo-planets directly -- not just to infer them from their shadows . But that's hard. To realise just how hard, suppose an alien astronomer with a powerful telescope was viewing the Earth from (say) 30 light years away -- the distance of a nearby star. Our planet would seem, in Carl's famous phrase, a 'pale blue dot', very close to a star (our Sun) that outshines it by many billions: a firefly next to a searchlight. The shade of blue would be slightly different, depending on whether the Pacific ocean or the Eurasian land mass was facing them. The alien astronomers could infer the length of our ‘day', the seasons, the gross topography, and the climate. By analysing the faint light, they could infer that it had a biosphere. The James Webb space telescope may offer clues. But within 10 years, the European Southern Observatory, will hopefully have its ELT — with a mosaic mirror 39 metres across. Such instruments will be drawing inferences like this about exo-planets the size of our Earth. LIFE LIKELIHOOD Habitable doesn’t mean inhabited — but for most of us that’s the number-one question. We still don’t know the likelihood —- we know too little about how life began on Earth to lay confident odds. What triggered the transition from complex molecules to entities that can metabolise and repro