yep, i looked him up on wikipedia as well tried a search on http://americanloons.blogspot.co.nz/?search=Robert+Gentry#uds-search-results but got no results (could be because it's not a basic html page and therefore is against the religion of my browser)
have watched the first video and he certainly doesn't appear to be without credentials.
i would like to see a debate or discussion between him and a suitably qualified geologist/physicist
there is this page here that appears to refute, or cast a shadow of doubt over, the polonium halos argument http://www.talkorigins.org/faqs/po-halos/gentry.html
the article mentions the migration of of radon-222 gas (a precursor of an isotope of polonium), and the an explanation to refute it.
after some consideration, i assumed that a pack of these gaseous radioactive atoms has to become trapped (stationary) in the rock at a particular point so that they can create the concentric circles as the alpha particles are emitted in random directions, but at a specific distance, eventually forming a sphere then, the reason why you don't see any halos further along the fracture is because the gas is moving?
does this not refute the explanation in the video that suggests that there should be "polonium" halos all the way along the fracture?
