knudsen: my pleasure. you for having me. ♪ stephanie: we turn to the skies were it is not just the moon orbiting the earth. laura barrÓn lÓpez reports on the growing problem of human-made debris in space. laura mankind's trash litters : our planet from local parks to the depths of the ocean. but not just on earth. debris from everything we have launched into space since the 1950's is clogging earth's orbit. space junk is threatening our technology down here and up there. for more on what's at stake and how we can manage space junk going forward, we turn to marcus holsinger, professor of aerospace engineering at the university of colorado, border -- boulder. professor, thank you for joining me. what are we talking about and how much is in earth's orbit? >> great question. so when we're talking about space debris, we're talking about mostly anthropogenic or human made pieces of debris. these are defunct satellites, rocket bodies that have been expended and left up in orbit, as well as parts of spacecraft or

and and i served with your brother on the uss mobile under ron alan knudsen. and then i went to college and started being a docent here. and met president nixon and figured out this whole dichotomy of him. and that really interested me. and then in 2009, i reconnected your brother and and you guys arranged to send me out to the navy on a guided missile cruiser, which led to me meeting the prior mayor of whittier. and he had told me that kind lost all track of everything to do with richard nixon and whittier and what made me do the math, because was really surprised because, you know, reconnecting with your brother and everything and putting putting all the pieces of the navy together and and doing map led to the book because i couldn't believe all of the information that i started discovering when i started into the oral histories. but it was the one thing that's always fascinated me about all of this research is common thread of the navy flying through of us and it's been really gratifying and very interesting. ladies and gentlemen, please join me in thanking