. >> suppose that nobody on earth had ever heard a piece of music then suppose beethoven fifth symphony is played over and over by invisible musicians. the physicist problem is to devise an apparatus that will polled one note from another and analyze it with invisible instruments that produce the sound, produce the rules and follow in what order it be played and how long it power of labour code is not likely he would succeed in imagining violence or clarinets or even musicians blowing into poor in spirit postulate by bodies that would meet the requirements. even with the simplification the odds of completely solving the mystery of beethoven fifth would be heavy. solving the problem of the invisible atom which is far more complex mixing with light and heat and other forms of energy and more intricate ways they of sound and more intricate ways, it is infinitely more difficult. and that is the gateway i wanted to write about your science bear the industry chronicled more than the civil war and there is a new book on link and every year. what draws you? what drives so many of us to the civi

even with this simplification the odds of his completely solving the mystery of beetho n beethoven's fifth would be heavy. solving the invisible atom which emits heat and light and other forms of energy in more intricate ways than sound is emitted by musical instruments is infinitely more difficult. and that is what these men and that was the 20th and that's why i wanted to write about the gateway through which they came, science. >> i'll go back to you for a minute, robert. barely an episode in american history more chronicled than the civil war. your book on lincoln seems pretty much every year. what -- what draws you -- what do you think draws so many of us to this civil war is this period? and specifically drew you to that period? >> it's a great question. i discuss that a lot in my book because walt had an idea about the civil war. walt was steeped in the war because he nursed these thousands and thousands of soldiers. he really knew what was going on. he saw the wounds. he knew. and he visited battlefield, too. but walt had an idea that pretty soon this war is going to be over.