mohsen sazegara, thank you forjoining us tonight. thank you for having me. does truth matter?ur leaders to tell the truth, and is there something materially different about truth in the technological age? there's so much stuff out there. how do we gauge what's true, half true, or false? in the past month, new phrases have entered the political lexicon, in particular, "fake news" and "alternative facts". but what if there's another, explosive ingredient in this febrile mix — the ability, literally, to manipulate the words coming out of someone‘s mouth? here's our technology editor, david grossman. how do we know that something happened? that what we are seeing is real? that we are not being fooled by fakes? some tv trickery is pretty familiar to us. this technology, green screen or colour separation overlay, has been around in some form for decades. it allows us to convincingly give real people backdrops of virtual worlds for them to interact with. however, we are about to cross the threshold into a new world where it is possible to convincingly recreate known real people — fam