it is day 33 of the search here, past the expected life of the batteries. they say they can last 30 to 35 days. okay, let's grant it. captain matthews of the u.s. navy says he believes the pingers are still alive at this point even though the ship has gone back and can't find the signal it picked up a few days ago. how long can the search realistically go on with the expectation that the batteries will be found and heard? >> he said 15 days which to me seemed rather excessive, frankly. they have a vehicle on board that very ship, on board the ocean shield. an unmanned vehicle that can go down and start painting the ocean floor with sonar. and i suspect there will be pressure to deploy that sooner. my experience with lithium batteries, they tend to quit rather quickly. what an amazing stroke of luck that we caught the last of the pings, maybe that happened within five days. there is going to be a lot of pressure to deploy that unmanned