Brian Greene is a national treasure of  solid information besides his opinions of zero "civilizations"that exist. I'm sure they do. Just the shear number of stars and solar systems say otherwise. Astronomers say there are more stars in just our galaxy than there are grains of sand on Earth. With that fact alone you must believe there is some civilizations out there in our galaxy never mind other galaxies ect.,(reply>), What's app scams <b>*</b> Report them. I report every single one