and abrahm lustgarten, a reporter at "pro-publica" and author of "run to failure: bp and the making of deepwater horizon disasr." we asked both the department of justice and b.p. to join us. they declined our invitation. john young, an initial reaction to today's settlement? >> well, it's the first major step, and let's not forget the 11 workers who lost their lives and their family members who lost loved ones but the fact that it's the largest criminal fine in u.s. history i think is appropriate in light of the fact that the b.p. oil disaster was the largest environmental disaster in u.s. history. but, agin it's just a first step. the civil awards and damages that need to be assessed against b.p. so that we're made whole down here in louisiana and in the entire gulf coast. >> brown: we'll come back to that but let me ask abrahm lustgarten of the criminal indictments in particular of the company as well as several individuals. >> yeah, i mean, i have to agree i think this is a very significant step and most significant, in my opinion, is the indictment of three senior b.p. managers. b.

is the primary party of responsibility. >> brown: abrahm lustgarten, john young, thank you both. >> thank very much, have a good evening. >> suarez: find an updated timeline with all of our reporting starting in april 2010. you can still use our widget to calculate how much oil spilled into the gulf. >> suarez: now, we turn to a story about the power of sleep and what it may do for you-- physically and intellectually. 's auestion researchers have long explored. "newshour" science correspondent miles o'brien gets a first-hand look at how some of our thinking on the subject may be changing. >> reporter: now this gives new meaning to the term power nap and i am fairly certain it's not the best way to dress for some rest, but this is what scientists-- actually their guinea pigs-- must do to try and answer a stubborn mystery: why do we sleep? >> the basic driving, evolutionary pressure for sleep is still a debate and i don't even know if we've discovered it yet. >> reporter: robert stickgold has as good a chance as anyone at finding the answer. he is a professor of psychiatry at harvard medica