Hollywood is wrong about aliens. They don't have oddly shaped heads, bulging eyes or even an eery green hue. Dimitar Sasselov is pretty convinced of that.
He's not even sure we'll know them when we see them. Prof Sasselov, an astrophysicist, thinks that if life exists elsewhere - and he believes it does - it will likely be based on different building blocks than ours, and so may not even be recognisable as life.