anything like this. and for us health care professionals, we have nothing to go by. what we can do is speculate and make assumptions of what could have happened, but we're all learning so much as this unfolds. and it's exciting to see that folks are doing so well. but as we mentioned before, this has been so, so traumatic, that i just will be very surprised if the miners can escape some of those psychological effects. >> you know so much of the studies i've read on people in these kind of conditions basically are astronauts or people, you know, health workers in antarctica, researchers there, people that have been in isolation. but what makes this different is that darkness these men experienced for these past 69 days. talk a little bit about how that can affect somebody, not just in the short term, but also long-term, what it does to the body, and one's mental health, to be living in complete darkness and how they worked to have a light area and a dark area, a light area using lamps