It’s nearly impossible to read the comments on a NASA social media post about the moon these days without encountering something along the lines of “If the Hubble Telescope can see galaxies billions of light-years away, why can’t it image Apollo hardware on the moon?”
The answer is angular size, a combination of an object’s physical size and distance. Simply put, distant galaxies span an angle substantially larger than the largest lunar castoffs.
By the numbers: A Milky Way-sized galaxy (100,000 light-years across) at a distance of 13 billion light-years (roughly as far as the most remote galaxies imaged to date), would have a width-to-distance ratio of 1:130,000. The discarded bases of the Lunar Excursion Modules (LEMs) — which did triple duty as descent engine, landing gear, and launchpad for the crew capsule to lift off from the moon at the end of each mission’s moonwalks — spanned around 23 feet. With the moon averaging around 239,000 miles distant, their width-to-distance ratio is 1:55,000,000 (422 times smaller than the aforementioned galaxy).
Since a telescope’s ability to discern detail is proportional to the diameter of its primary optics (Hubble’s being just under eight feet), it would take a telescope with a mirror spanning six city blocks to show Apollo castoff equipment at a similar level of detail as seen in a Hubble image of one of the most remote galaxies.
It saddens me greatly that anyone can doubt the greatest technological achievement in human history, using arguments that can be debunked by middle-school-level mathematics. NASA historian James Oberg describes these naysayers as “cultural vandals,” defacing the efforts of the thousands who worked to put twelve brave astronauts on the moon and bring them (and a scientific bonanza of samples and data) home safely.
Next column: Who names the stars?