It is perfectly possible to resolve a (6-foot) flag with a telescope.
The article states "the Earth's atmosphere is never steady enough to allow resolution below about one arc second for most locations". But according to the European Southern Observatory one can do 1000x better:
"With AMBER on the Very Large Telescope Interferometer (VLTI), the astronomers were able to see details on the scale of one milli-arcsecond, corresponding to being able to distinguish, from the Earth, the headlights of a car on the Moon."
-- http://amber.obs.ujf-grenoble.fr/spip.php?article154
Therefore a 6-foot-wide flag ("headlights of a car") would be visible as 1 or 2 pixels with the VLTI, which is made of four 8.2 meter reflectors.
I presume the actual flag left by the astronomers was somewhat smaller, so one would need a tad better telescope, but certainly not something with a "3.5 mile diameter".
yes, but the article explicitly defines "flag being visible" as stripes of the US flag being visible. for that you would need a tad better than 6-foot resolution.
On a side node, the VLTI should be able to produce a 2x2 or 3x3 pixel image of one of the russian or american lunar landers (14-foot wide). It would be a cool thing to accomplish to demonstrate the resolution of the VLTI...
The article states "the Earth's atmosphere is never steady enough to allow resolution below about one arc second for most locations". But according to the European Southern Observatory one can do 1000x better:
"With AMBER on the Very Large Telescope Interferometer (VLTI), the astronomers were able to see details on the scale of one milli-arcsecond, corresponding to being able to distinguish, from the Earth, the headlights of a car on the Moon." -- http://amber.obs.ujf-grenoble.fr/spip.php?article154
Therefore a 6-foot-wide flag ("headlights of a car") would be visible as 1 or 2 pixels with the VLTI, which is made of four 8.2 meter reflectors.
I presume the actual flag left by the astronomers was somewhat smaller, so one would need a tad better telescope, but certainly not something with a "3.5 mile diameter".
Upvote me. HN readers need to be educated :-)