Aliens could be among us - but we just cannot recognise them, Britain's top astronomer has said.
Lord Martin Rees said the visitors might be in a form beyond human understanding. Lord Rees, president of the Royal Society academy of science and also astronomer to the Queen, said: "They could be staring us in the face and we just don't recognise them."
The respected professor went on: "The problem is that we're looking for something very much like us, assuming that they at least have something like the same mathematics and technology.
"I suspect there could be life and intelligence out there in forms that we can't conceive