Difference between revisions of "Talk:1441: Turnabout"

Explain xkcd: It's 'cause you're dumb.
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Superimposing the 3rd and 5th panels over each another shows the beam does not come back exactly to its source
 
Superimposing the 3rd and 5th panels over each another shows the beam does not come back exactly to its source
 
http://xbehome.com/uploads/retroreflector.png [[User:Defaultdotxbe|Defaultdotxbe]] ([[User talk:Defaultdotxbe|talk]]) 08:09, 31 October 2014 (UTC)
 
http://xbehome.com/uploads/retroreflector.png [[User:Defaultdotxbe|Defaultdotxbe]] ([[User talk:Defaultdotxbe|talk]]) 08:09, 31 October 2014 (UTC)
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Can anyone comment on how likely/unlikely it would be to accidently hit a retroreflector on the moon? The moon takes up only a very small proportion of the sky (when visible at all of course), and so the likelyhood of that wild shot even hitting the moon at all has to be pretty low. (I'm sure there was a What-If on this...) A theoretical laser beam covers only a minute area of the lunar surface, furthing lengthening the odds of hitting a reflector. Would be great to have some numbers though.. --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 09:22, 31 October 2014 (UTC)

Revision as of 09:22, 31 October 2014

In the few seconds the photons take to get to the moon and back, the earth has moved enough on its axis that the reflected beam from a perfect retroreflector is not gonna hit the protagonist.

The retroreflectors for the Apollo missions were deliberately spoiled so they return six slightly offset beams, angled such that photons from one of them will go back near enough to the source.

Oh, and of course there's also the whole r^4 thing too. ‎108.162.250.208 (talk) (please sign your comments with ~~~~)

Citation needed. And did you mean the inverse square law? 103.22.201.195 07:37, 31 October 2014 (UTC)
Since you acknowledge that the reflectors for the Apollo missions were constructed to take this into consideration and the photons will return near enough to the source, the cartoon is still valid.  Now, whether the photons would retain sufficient energy upon their return to cause harm when they did not have enough power to destroy the reflector in the first place is a subject for another discussion .108.162.216.94 07:49, 31 October 2014 (UTC)

Superimposing the 3rd and 5th panels over each another shows the beam does not come back exactly to its source http://xbehome.com/uploads/retroreflector.png Defaultdotxbe (talk) 08:09, 31 October 2014 (UTC)

Can anyone comment on how likely/unlikely it would be to accidently hit a retroreflector on the moon? The moon takes up only a very small proportion of the sky (when visible at all of course), and so the likelyhood of that wild shot even hitting the moon at all has to be pretty low. (I'm sure there was a What-If on this...) A theoretical laser beam covers only a minute area of the lunar surface, furthing lengthening the odds of hitting a reflector. Would be great to have some numbers though.. --Pudder (talk) 09:22, 31 October 2014 (UTC)