1441: Turnabout

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Turnabout
Whenever I miss a shot with a sci-fi weapon, I say 'Apollo retroreflector' really fast, just in case.
Title text: Whenever I miss a shot with a sci-fi weapon, I say 'Apollo retroreflector' really fast, just in case.

[edit] Explanation

In the comic, two people are engaging in a battle with laser guns. One appears to gain the upper hand as he jumps on a desk, as the other's shot goes wide. He delivers the classic line "Any last words?" and is answered with the confusing phrase "Apollo retroreflectors". The earlier wild shot, reflected off the moon, promptly lances down from space and hits him in the back.

A retroreflector is a device or surface that reflects light back at its source. The Apollo 11, 14 and 15 moon missions placed several such devices on the surface of the Moon to help scientists on Earth measure the distance between the two bodies using laser ranging.

The title text mentions that you would need to say "Apollo retroreflector" really fast, because from Earth you would only have about 2.5 seconds before the light is reflected back to its source.

It is worth noting that the number of this comic is 1441: a 'reflective' palindromic number.

[edit] Transcript

[Two people engage in battle using handheld laser guns.]

[Person 2's shot misses, Person 1 jumps on a desk.]

Person 1: Any last words?

Person 2: "Apollo retroreflectors"

Person 1: What?

[Person 1 is hit in the back by the reflected shot.]

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Discussion

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)


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