. >> so you've interviewed all kinds of people including jane goodall who word the foreword, but the one i want to start with is mark robert, he is one of my absolute favorites and explain to people who mark roeber is. >> he used to be a nasa scientist and then he went to apple and started a youtube channel. if you haven't heard of him, and if you have teenagers and friends ask them about the shipping boxes where it explodes in their car or the squirrel olympics. he has about 30 million subscribers on youtube and his story is remarkable because of the career trancings he made and at the end of the interview he said he still does want to be a physics teacher and this coming week on friday in austin, texas, in south by southwest it will be mark roeber and guy kawasaki on stage. >> can you imagine him being your physics teacher? i did have a physics teacher that would often come in character and whatever it happened to be and he would not break character. if you told him -- ask him what the quiz was for a bathroom pass he would say why would i know that information and he was one of the