[andrewas]

Dyson sphere? You mean a construct of several solar masses completely encomppasing the volume of their solar system? Now thats a job for an advanced culture. Theyd have be ultra paranoid to put that much effort into hiding.

Alien life existing at the same time a ours us quite likly - life has existed on this planet for 300 billion years, which is actualy not that insignificant a portion of the age of the universe. (for both figures the exact data does not come to hand at the moment). Intelligent life on the other hand is hugely unlikly, its only been on earth for something around 20'000 years. That is an isignificant portion of the age of the universe, although theres nothing in physics to say that intelligent life cant persist for hundreds of millions of years.

But the chances of their being a civilisation close enough to contact, advanced enough to contact, and primitve enough for us to understand, is pretty close to nothing. Theres no chance of Star Treks picture of the universe - hundreds of similar species, most at the same stage of development - being at all accurate.