Talk:1441: Turnabout

2014-10-31T21:30:31Z

173.245.51.196:

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. {{unsigned ip|‎108.162.250.208}}
:Citation needed. And did you mean the inverse square law? [[Special:Contributions/103.22.201.195|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 .[[Special:Contributions/108.162.216.94|108.162.216.94]] 07:49, 31 October 2014 (UTC)
::The photons will retain the same power (more or less...), but there will be less ''of'' them. The laser (e.g. the one from the Apache Point observatory) spreads out on its way to the Moon (perfect collumation into a millimetre-wide laser beam is neither practical nor desirable, given the need to 'flood' the vicinity of the reflector in leiu of impossible accuracy, including to account for asymmetric atmospheric distortion on the beam and its return) so that only a small proportion of the beam hits a reflector unit (one of the largest being 0.6m²) and the returning beam (for reasons already mentioned) is again much wider than the collecting telescope (3.5m diameter, possibly). There's usually no more than a dozen photons (per each short pulse of the laser) that actually make the return trip to be detected, and often it's well down into single-figures, requiring many such pulses to gather enough photons to make a statistically significant analysis.
::All this, of course, does render even more ridiculous the concept of manually firing even a ''combat''-strength laser beam across the necessary void and back again to such a precise hit (and, BTW, the What-If someone was mentioning is http://what-if.xkcd.com/13/ and shows a possibly less-tightly-collumated-than-Apache-Point laser having a diameter of almost half that of the Moon itself). But what the hey? ;) [[Special:Contributions/141.101.99.112|141.101.99.112]] 10:04, 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 [[User:Defaultdotxbe|Defaultdotxbe]] ([[User talk: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...) --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 09:22, 31 October 2014 (UTC)

:: Randall covered lasers hitting the moon in [https://what-if.xkcd.com/13/ what-if 13] --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 09:45, 31 October 2014 (UTC)

What is a 'reflective' palindromic number like mentioned in an (early?) version of this explanation:
:Citation: "It is worth noting that the number of this comic is 1441: a 'reflective' palindromic number."
All I could find about reflective ~palindromes was that you should be able to mirror the number/word and still get the same. But you cannot mirror 4 into 4. So in that way it cannot be reflective... (1 maybe if the font is the correct one, else only 8 and 0 in numbers and some letters like A and X).
Of course it is a palindrome as it would read 1 4 4 1, also in reverse. But reflective - not so much?
If it is not reflective, then it has no relevance in the explain as it was this reflection that had a reference to the story... [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 10:49, 31 October 2014 (UTC)
What

:I agree, the number is a palindrome, but not a reflective palindrome. I'm not quite decided on whether the fact it is a palindrome holds any relevance, or is simply a coincidence. --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 11:10, 31 October 2014 (UTC)

I've removed a sentence about "continuity problems" and why the beam does not go right through the opponent (or hit the original shooter). No laser tag set that I know of is powerful enough to go right through someone, I imagine that would be regarded as a slight health & safety issue. You could argue that panel 1 shows the beam going through someone, but I think that is in fact behind him. As far as him being knocked over, I would guess that is to emphasise his being hit, rather than physically knocked over. --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 13:35, 31 October 2014 (UTC)
:IMO, it's not laser-tag at all, but a full-strength offensive laser-blast (of at least 'stun' level). The first 'through the body' shot is actually a miss 'in depth' (rarely for XKCD comics without other explicit perspective cues to the image, like this one, it's in the <TwilightZoneMusic+Reverb>Third! Dimension!</TwilightZoneMusic+Reverb>...), neither harming nor impeded by the attacker. The rebounded shot at the end appears to have at least caused the same attacker to lose grip of his gun, if not caused physical damage to his back. (Although I suppose he could be wearing a "shocker" or vibrating-on-hit style of laser-tag kit, or is reacting to the sound-effect arising from the unexpected "hit detection".) No doubt a combat-level laser would be dialled up to damage your target without ''necessarily'' burning straight through.
:Also (regarding another comment), while I imagine it'd be useful to wear armour designed to be reflective (or even retroreflective!) all over, it would probably be impractical, whereas the lunar retroreflector array being used might possibly itself withstand the beam for at least long enough to get a decent amount of bounce-back. Anyhow, with such Improbable Aiming Skills, I suspect at least latent and subconcious Force abilities were in play, which can handwave all such niggling problems. Right guys? (And also opens the doorway for this being a universe with full-on Stormtrooper Armour... you know, the kind that's Reactive Armour, but assembled the wrong way round so it ends up hurting you more than if you were wearing no more than woven and leather fabrics...) [[Special:Contributions/141.101.99.112|141.101.99.112]] 14:24, 31 October 2014 (UTC)

As the earth is turning, the reflected beam would hit different spot. In that 2.5 secs it would take the beam to travel back to the earth, earth would have turned 1.160km at the equator. So even if the beam would stay collimated the beam would miss coming back.

1405: Meteor

2014-08-09T19:04:03Z

173.245.51.196: /* Explanation */

{{comic
| number = 1405
| date = August 8, 2014
| title = Meteor
| image = meteor.png
| titletext = No, only LAVA is called 'magma' while underground. Any other object underground is called 'lava'.
}}

==Explanation==
This is one of [[Randall]]'s [[:Category:My Hobby|My Hobby]] comics. In this comic the author makes semantically incorrect statements to [[356: Nerd Sniping|frustrate nerds]] who know the correct word, and confuse people who don't know the precise word so they can go on to frustrate more nerds.

[[Cueball]] tells his friend (Randall) that he found a piece of a {{w|meteor}}. His friend corrects Cueball, telling him that what he found is called {{w|magma}}, and that that the phrase "a piece of a meteor" would be correct if the object was in the air, once it hits the ground it is called {{w|magma}}. In doing so Randall attempts to confuse or annoy Cueball. In truth, {{w|meteorite}} is the expression for a piece of a {{w|meteoroid}} that has landed, only while descending through the atmosphere is it called a {{w|meteor}}. Thus the first statement by Randall is a true correction of Cueball, the next is false.

The word "{{w|pedant|pedantic}}" means being overly concerned with being precise. It is usually a pejorative term used to refer to someone who is overly fussy and corrects someone's word choice even when the more ambiguous or slightly incorrect term they used was fine for informal communication. You would tend to belive a pedant, as they would usually know what they are pedantic about. So when Randall is making wrong statements that seems pedantic he may make people belive him.

The title text expands on the joke, as if the conversation had continued with a confused Cueball responding that he thought magma was underground. Randall attempts to confuse him further by talking about {{w|lava}} which indeed is the expression for magma that has reached the surface. But it's ridiculous to suggest that all other things are called lava when underground. In the sentence he also continues to imply that magma could also be found above ground (in the form of the meteorite that was the reason for the conversation).

The two sentences thus follows the same pattern with one true but pedantic part to begin with, and then a false statemt to confuse the victim.

===Meteor & Magma===
Here is a list the of terminology that is being muddled:
* The descent of a small solid body from space:
** A {{w|meteoroid}} is a small solid body travelling through space and/or the atmosphere.
** A {{w|meteor}} is a streak of light produced by a meteoroid as it burns up in the atmosphere.
** A {{w|meteorite}} is a piece of a meteoroid remaining after it strikes the ground.
* Molten rock:
** {{w|Magma}} flows underground.
** {{w|Lava}} has been extruded to a planet's surface, as through volcanic eruption.

==Transcript==
:[Cueball walks toward his friend holding a rock.]
:Cueball: Check it out - I got a piece of a meteor!
:Friend: ''Actually'', it's only called that while falling. Once it lands, it's called ''magma''.

:[Below the frame:]
:'''My Hobby: Mixing pedantic terms'''

{{comic discussion}}
[[Category:My Hobby]]
[[Category:Comics featuring Cueball]]

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Talk:1441: Turnabout

1405: Meteor