explain xkcd - User contributions [en]

User talk:Srimech

2020-03-12T12:47:41Z

Srimech: Undo revision 188542 by 172.68.239.89 (talk) (Spam)

XKCD 505 was my inspiration to start making mechanical computers. https://www.youtube.com/watch?v=-1nbC6IfMm0

User talk:Srimech

2016-02-16T23:44:49Z

Srimech: Created page with "XKCD 505 was my inspiration to start making mechanical computers. https://www.youtube.com/watch?v=-1nbC6IfMm0"

XKCD 505 was my inspiration to start making mechanical computers. https://www.youtube.com/watch?v=-1nbC6IfMm0

Talk:505: A Bunch of Rocks

2016-02-16T23:37:58Z

Srimech: Comment about digital physics

;Weird thing with lines in it
probably has something to do with relativity -- two objects moving, arriving at different points at the same time, or maybe a diagram of spacetime. [[Special:Contributions/66.202.132.250|66.202.132.250]] 16:44, 10 June 2013 (UTC)

It's a [https://en.wikipedia.org/wiki/Feynman_diagram Feynman Diagram] [[Special:Contributions/206.174.12.203|206.174.12.203]] 19:24, 10 June 2013 (UTC) Toby Ovod-Everett

:I did add the incomplete tag because this comic and also the explain is still really complex. More important: People without a proper physics background never will understand. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 21:01, 10 June 2013 (UTC)

There is a short story called "SOLE SOLUTION" by Eric Frank Russell which is quite similar to the one in the story. Just in case that matters.{{unsigned|Maob}}

Re Rule 34 - the point is that this comic _is_ cellular automaton porn (as are the YouTube videos of Minecraft calculators and the like). Rule 34 works, bitches! {{unsigned ip|141.101.98.241}}

Not sure what's incomplete about the explain. <small>[[User:MrGameZone|0100011101100001011011010110010101011010011011110110111001100101]] ([[User talk:MrGameZone|talk page]])</small> 22:56, 11 February 2014 (UTC)

Yo ''calculus'' is the latin word for pebble! I learned this and had to come straight to this page! ahhh connections! [[Special:Contributions/173.245.50.88|173.245.50.88]] Sawyer Biddle

As it turns out, Rule 110 seems to be a ''really bad'' way to simulate a universe- you would be much better off using a {{w|Tag_system|Cyclic tag system}}, since Rule 110 takes dozens of generations and potentially hundreds of cells to simulate one step in such a system, or a more sophisticated cellular automaton, such as {{w|Wireworld.}} --[[User:Someone Else 37|Someone Else 37]] ([[User talk:Someone Else 37|talk]]) 05:12, 9 March 2014 (UTC)

To whoever objected to panel number references, does what I did with first words fix that? {{unsigned ip|199.27.128.99}}

Well, that's a pretty unfair comparison in the last panel, the protag is immortal after all, if I'm immortal I might do the same thing, but hey we got a much shorter life to live {{unsigned ip|103.22.201.168}}

The diagram to the right of the Epitaph of Stevinus looks like a system of coupled pendula, often used in math physics courses to illustrate Lagrangian mechanics. Also may relate to elasticity theory. See for example here: http://demonstrations.wolfram.com/ThreePendulumsConnectedByTwoSprings. [[Special:Contributions/108.162.221.96|108.162.221.96]] 03:23, 12 November 2014 (UTC)
:If this is true (which seems like the most probable solution so far) then what do the symbols inside the boxes represent?{{unsigned ip|108.162.216.209}}
:: Spring constants, masses, lengths, etc [[Special:Contributions/108.162.221.220|108.162.221.220]] 18:11, 12 November 2014 (UTC)
::: The symbols on the top seem to be K and the bottom W. W is often used for angular momentum and K for potential energy. If you are not exactly right you are very close to being so.[[Special:Contributions/108.162.216.209|108.162.216.209]] 13:45, 1 December 2014 (UTC)
:The "diagram to the right of the Epitaph of Stevinus", also described as "A weird diagram with lines in it", or "partitioning of phase space into fundamental cells", or " system of coupled pendula, often used in math physics courses to illustrate Lagrangian mechanics", can be described more literally: ''There is are two horizontal rulers with divisions 13 pixels apart and 17 pixels apart, respectively; and diagonal lines showing the correspondence between the first four markings of the upper ruler with those on the lower. The intervals seem to be labeled.'' Returning to speculation, I think this suggests an illustration of '''Length contraction (Lorentz coordinate transformation) in Special Relativity'''. [[User:Mrob27|Mrob27]] ([[User talk:Mrob27|talk]]) 20:22, 28 November 2014 (UTC)
:: That seems highly unlikely due to the top labels on this graph. In your explanation they can’t represent anything relevant. Also if this diagram is used to represent spatial contraction, it does not do a good job of it. [[Special:Contributions/108.162.216.209|108.162.216.209]] 13:45, 1 December 2014 (UTC)
::: I imagined the labels were, top row: O', x', (2x)'; bottom row: O, x, 2x, Δv; or perhaps top row: Δx₁', Δx₂', Δx₃'; bottom row Δx₁, Δx₂, Δx₃, 0.7c. I don't think Randall put enough thought into those tiny squiggles for us to be able to use pixel-counting as a hint to which labels interpretation is more likely… but what of it? We can make up labels that fit any interpretation. I did say "Length contraction (Lorentz...)" was just ''speculation''. I do like the "four pendulums coupled by springs" idea, though the horizontals look too ruler-like to me. It might be better just to say "two horizontal ruled lines linked by some diagonals" ! [[User:Mrob27|Mrob27]] ([[User talk:Mrob27|talk]]) 17:00, 1 December 2014 (UTC)
:::: You are totally right, this one may always be pure speculation. Though I am pretty sure the bottom points are labeled w, the top is by no means clear. [[Special:Contributions/108.162.216.209|108.162.216.209]] 20:46, 1 December 2014 (UTC)
::::: I propose that we change it again, from (current text: "A depiction of length contraction, with two lines of the same length locally but different lengths as one is viewed in motion") to something like ''"A depiction of length contraction with two rulers in relative motion, or of several pendulums coupled by springs"''. Or mention the pendula idea first, I don't want to decide. [[User:Mrob27|Mrob27]] ([[User talk:Mrob27|talk]]) 02:20, 2 December 2014 (UTC)
:::::: Though it's in panel before that one, there's the text "and then some" referencing going beyond what we currently know in a field - could it ''possibly'' be that this is supposed to represent something we haven't derived yet? -- [[User:Brettpeirce|Brettpeirce]] ([[User talk:Brettpeirce|talk]]) 10:44, 2 December 2014 (UTC)
:Also, I'd like to point out that all three diagrams unify the theme of "working out the kinks in quantum mechanics and relativity": The first illustrates a region of the bell curve where a particle might occasionally fall if it is about to exhibit quantum tunneling; the second relates to perpetual motion, thus hinting at general questions like "does quantum mechanics or relativity allow us to violate the laws of thermodynamics in any way?", and the third is from special relativity. [[User:Mrob27|Mrob27]] ([[User talk:Mrob27|talk]]) 20:22, 28 November 2014 (UTC)
:: Having studied (and knowing the fundamentals about what profile is needed to create a device that performs quantum tunneling) I have never seen this graph as a representation of this, and frankly it makes no sense. If this diagram was an energy band the hole or electron would have no need to tunnel to go up or down the energy band as it is a gradual slope. If a device had a profile like this, it would not result in a significant number of tunneling events, especially at the positions that are marked on the diagram. For this to occur there would need to be a peak between the two points, and the points would need to be at similar heights (energy levels). [[Special:Contributions/108.162.216.209|108.162.216.209]] 13:06, 1 December 2014 (UTC)
::: Yes, you're right: all we know is that it's a bell curve (normal distribution), and mentioning "tunneling" might make the reader think we were saying it is a potential function. I was reading a bit much into it. Why are there two vertical dotted lines at roughly +σ and +2σ? I thought they indicated a "range" as if the graph were illustrating some discussion of things that fall within that range. I also incorrectly remembered what the Epitaph of Stevinus was about, so thanks for the corrections :-) [[User:Mrob27|Mrob27]] ([[User talk:Mrob27|talk]]) 16:57, 1 December 2014 (UTC)
:::: I think we could reasonably add that the function represents a probability distribution of a partial, therefore tying in the quantum aspects. with a minor explanation of the probibility of 1 and 2 sigma. [[Special:Contributions/108.162.216.209|108.162.216.209]] 20:46, 1 December 2014 (UTC)
::::: I do think it was okay without the extra text referencing quantum mechanics. I was just trying to find a way to relate the image to the words… but there are so many ways to relate the normal distribution to anything in science :-) [[User:Mrob27|Mrob27]] ([[User talk:Mrob27|talk]]) 02:20, 2 December 2014 (UTC)

The bigger picture that's missing on this explains it that this comic seems to suggest that Cueball is God, as in being stuck in Eternity who happened to build a simulated universe, which we all live in. Seeing how he addresses the reader "So if you see a mote of dust vanish from your vision in a little flash or something I'm sorry. I must have misplaced a rock sometime in the last few billions and billions of millennia." {{[[Special:Contributions/141.101.105.238|141.101.105.238]] 10:25, 12 November 2014 (UTC)}}
: I understand that English might not be your first language, but please clarify. The explanation covers Cueball being godlike. How can we add something that is already covered? Do you require further detail? Are you disagreeing with this assessment? Are you considering this observation irrelevant as your summary for your first comment "added not about Cueball being God" seems to imply? If so why?[[Special:Contributions/108.162.216.209|108.162.216.209]] 17:57, 12 November 2014 (UTC)
:: nm. I blatantly overlooked the exisiting sentence in the explanation. i blame the layout of this page. inline text that spans the whole available screen width is not pleasant to read on large displays ;) ...as for my English... the confusion stems from my bad keyboard/typing. it was meant to read "added notE about Cueball" for instance, or "as in A being stuck". [[Special:Contributions/141.101.105.233|141.101.105.233]] 08:15, 13 November 2014 (UTC)
:::you could shrink your window and display narrower lines of text(?) -- I guess it comes down to preference for masochism(?)... idunno. I think one of the most confusing parts of your question (and which may have contributed most to the ESL idea) is "missing on this explains it that...". Also, "as in being stuck" makes more sense than "as in a being stuck", though it seems you're suggesting otherwise (?) and I don't see any text mentioning added not(E) about Cueball) -- oh wait; is this a troll? -- [[User:Brettpeirce|Brettpeirce]] ([[User talk:Brettpeirce|talk]]) 15:14, 14 November 2014 (UTC)

Who or what is Nugui and why is it relivent.[[Special:Contributions/108.162.216.209|108.162.216.209]] 17:57, 12 November 2014 (UTC)

is randall not assuming that his universe (and by implication ours) is finite? if not, one iteration of the machine would still take infinite time. --[[Special:Contributions/141.101.98.201|141.101.98.201]] 12:42, 26 November 2014 (UTC)
: I think it's good enough to assume that the universe is finite, but really really huge. Hypothesizing that adding one particle to the model requires twice as many cells in the cellular automaton, that means that Cueball's cellular automata rows could be about 2^(10^80) cells long, allowing simulation of a physics system containing 10^80 particles. Of course, each planck-time would require 2^(10^80) steps of simulation in the CA. If 10^80 isn't big enough for you, then just make it 10^1000 or Graham's number, or anything finite. [[User:Mrob27|Mrob27]] ([[User talk:Mrob27|talk]]) 16:57, 1 December 2014 (UTC)
:: Don't forget that Rule 110 has 000 -> 0. Cueball can just add columns on either side as his universe expands, consequently taking more and more time to compute steps as the number of columns increases. {{unsigned ip|108.162.216.42}}

Did anyone notice that the binary numbers pointing to the particle are both 42? [[Special:Contributions/108.162.241.16|108.162.241.16]] 19:26, 27 November 2014 (UTC)
:I did now. :) But, somewhere, he left out the towel. [[User:Jarod997|Jarod997]] ([[User talk:Jarod997|talk]]) 14:33, 1 December 2014 (UTC)

Just as a curiosity -- there is a somewhat similar concept in "Permutation City", a book by Greg Egan. {{unsigned ip|141.101.88.211}}
:And dust is probably a reference to Dust Theory: http://gregegan.customer.netspace.net.au/PERMUTATION/FAQ/FAQ.html {{unsigned ip|141.101.98.187}}

I don't understand how it's possible to simulate a universe this way. Assuming that quantum mechanics is correct, and some forms of particle decay are truly random, wouldn't it be impossible to simulate this with a purely deterministic system? [[User:KingSupernova|KingSupernova]] ([[User talk:KingSupernova|talk]]) 15:30, 1 December 2015 (UTC)
: The universe Cueball is simulating would have to conform to [[wikipedia:Digital physics|digital physics]]. I can't speak about the fine points of quantum mechanics, but observably random events in a simulated universe could be the result of a pseudorandom number generator with a very large state. [[User:Srimech|Srimech]] ([[User talk:Srimech|talk]]) 23:37, 16 February 2016 (UTC)

Talk:1474: Screws

2015-01-16T12:28:18Z

Srimech: Sorry, that was redundant. Undo revision 82843 by Srimech (talk)

This page is now on the first page of google for "uranium screw". [[User:Mrmakeit|Mrmakeit]] ([[User talk:Mrmakeit|talk]]) 05:31, 16 January 2015 (UTC)

I don't think that patent is the right one, it seems to describe a uranium decontamination procedure, not a screw made of uranium like in the comic. [[User:LeoDeQuirm|LeoDeQuirm]] ([[User talk:LeoDeQuirm|talk]]) 05:46, 16 January 2015 (UTC)

I'm pretty sure the "uranium screw" is just a reference to the fact that the head of the screw appears to have split in two ("fissioned"), as opposed to a normal flat head screw that still has the edges connected. [[User:Sam887|Sam887]] ([[User talk:Sam887|talk]]) 05:50, 16 January 2015 (UTC)

Just a shot in the dark here, but a company that sells uranium ore and radiological equipment happens to also sell screws for one of its Geigers that look just like the screw cross-section in the comic. [http://www.uraniumrocks.com/products/replacement-circuit-board-mount-screws-for-victoreen-cdv-700-short] [[User:Conqu2|Conqu2]] ([[User talk:Conqu2|talk]]) 06:01, 16 January 2015 (UTC)

I was wondering if the "uranium screw" was referring to the Demon Core -- two hemispherical domes that Louis Slotin was holding apart with a screwdriver. Then I remembered the Demon Core was plutonium, not uranium. [[Special:Contributions/173.245.48.119|173.245.48.119]] 06:49, 16 January 2015 (UTC)

There are ferrous alloys containing (depleted, of course ;-) uranium for "increase[d] toughness and strength". [http://en.wikipedia.org/wiki/Ferrouranium] [[User:Knob creek|Knob creek]] ([[User talk:Knob creek|talk]]) 09:21, 16 January 2015 (UTC)

I think the be was going for apple's pentalobe screw with the 5 ponted star {{unsigned ip|108.162.238.162}}

I don't think the uranium screws are named for their use in stuff to do with uranium, as I have both seen and used screws that look like that before. It's basically a flat head screw whose divot extends all the way across the face of the screw. I agree more with the previous commentor who notes that the screw looks like it has fissioned. [[Special:Contributions/108.162.237.182|108.162.237.182]] 06:34, 16 January 2015 (UTC)

An actual rivet is neither a screw nor a bolt; it's a fastener that is placed and then has one end plastically deformed -- traditionally by a rivet gun, but more often in smaller sizes by some sort of press or clamp. (Pop rivets are hollow, and are deformed by pulling a cone-sheaped wedge into the open end of the hollow core.) There's no way to remove one except to destroy it (drill it out or cut one end off). The item pictured could also be the head of a carriage bolt, but that's no help if you can't get at the other end of the bolt. Randall is slightly pessemistic, though: there *are* some "security" screws and bolts that use a slightly-elliptical domed head that's hard to tell from a rivet; they can be unscrewed, but only with a matching slightly-elliptical socket. [[Special:Contributions/199.27.133.70|199.27.133.70]] 06:35, 16 January 2015 (UTC)

All of which can be removed by a sonic screwdriver. Totally a real thing. {{unsigned ip|173.245.50.86}}

Could the "cursed -1" be a Nethack reference? I don't know if Dungeons and Dragons has the "blessed/uncursed/cursed" status, but in Nethack cursed items with negative enchantments (denoted "cursed -whatever") are a pretty common occurrence. [[Special:Contributions/199.27.133.25|199.27.133.25]] 07:31, 16 January 2015 (UTC)

In Nethack, Cursed objects cannot be removed. Seems appropriate. At first I thought it was a pozidrive screw head. Posts on the fission screw head: where have you seen screws whose divot does *not* extend across the head? {{unsigned ip|199.27.128.230}}

[[User:Kreuiter|Kreuiter]] ([[User talk:Kreuiter|talk]]) 08:03, 16 January 2015 (UTC)from wikipedia: Louis Philippe Joseph d'Orléans (13 April 1747 – 6 November 1793) commonly known as Philippe, was a member of a cadet branch of the House of Bourbon, the ruling dynasty of France. He actively supported the French Revolution and adopted the name Philippe Égalité, but was nonetheless guillotined during the Reign of Terror

I don't think it is specifically a reference to Nethack as a lot of ol games (both video and tabletop) use the mechanic of non removable cursed objects. It is common enough in my opinion that we could argue about until we are blue in the face and get nowhere. {{unsigned ip|108.162.237.193}}

uranium screw may be a reference to [http://en.wikipedia.org/wiki/Louis_Slotin#Criticality_accident Louis Slotin], who died when he was using a screw driver to seperate two halves of a plutonium sphere as part of a science demonstration, and triggered a large burst of radiation when his hand slipped.
--[[Special:Contributions/108.162.216.59|108.162.216.59]] 08:28, 16 January 2015 (UTC)

I'm thinking it might benefit the article to include a place in the wikitable for the correct term for each drive socket. Of course their are not correct terms for each of them. Not to mention rivets and Phillip's heads don't even have drive sockets. [[Special:Contributions/173.245.56.189|173.245.56.189]] 09:04, 16 January 2015 (UTC)BLuDgeons

If you suggest cursed-1 is because if misuse - I in first place thought of [http://en.wikipedia.org/wiki/List_of_screw_drives#Pozidriv] as the cursed one - because Philipps and Pozidriv are slightly incompatible and causes damage. [[Special:Contributions/108.162.254.18|108.162.254.18]] 09:09, 16 January 2015 (UTC)

:+1, the cursed one looked to me like pozidriv at the first glance, and it's really cursed as interchanging them leads to damage ... And the most fun is when you get some Chinese crap that looks like pozidriv but it doesn't fit so you use philips which doesn't quite fit too but at least it can be inserted and you end up damaging both the driver and the screw :-/ --kavol, [[Special:Contributions/108.162.254.96|108.162.254.96]] 10:02, 16 January 2015 (UTC)

Is it really true that Phillips head are 'commonly used in construction'? At least in Europe they were replaced by Pozidriv in the 1990's and these days by Torx. {{unsigned|Popup}}

Maybe this depends on the quality of the product? If i look around, i find lots of products held together by phillips screws and only a few (usually more hi-tech and expensive) one with torx screws. [[User:Knob creek|Knob creek]] ([[User talk:Knob creek|talk]]) 09:28, 16 January 2015 (UTC)

:er, what do you call "a product"? - If "construction" is mentioned, I imagine things like wooden skeleton of a roof, fastening of windows/doors, self-tapping screws, wallplug screws ... and it's almost 100% pozidriv and torx here in central Europe. ("Almost" accounts for imports by non-european companies.) If I imagine metal constructions, from racks to bridges, hex and inbus (= hex slot) prevail. --kavol, [[Special:Contributions/108.162.254.96|108.162.254.96]] 10:02, 16 January 2015 (UTC)

Perhaps a reference to http://xkcd.com/927/ - Standards? [[Special:Contributions/141.101.79.61|141.101.79.61]]

Phillips screws have a larger number for larger size, not smaller.

Talk:1474: Screws

2015-01-16T12:27:25Z

Srimech: Posidriv

1270: Functional

2013-09-27T11:05:20Z

Srimech: Adding a further explanation of the title text

{{comic
| number = 1270
| date = September 26, 2013
| title = Functional
| image = functional.png
| titletext = Functional programming combines the flexibility and power of abstract mathematics with the intuitive clarity of abstract mathematics.
}}

==Explanation==
{{incomplete|if that's the recursion pun I think it is, Randall needs a caning.}}

'''TL;DR:''' After [[White Hat]] questions his faith in {{w|functional programming}}, [[Cueball]] says that "tail recursion is its own reward." This implies the equivalent sentence "tail recursion is an end unto itself," and that's where the pun lies. Tail recursion refers to when a function finishes by going back and calling itself, forming a loop. If you aren't groaning by now, read on.

Recursion refers to functions that invoke themselves at some point to perform a smaller part of their computation - except where the task at hand is simple enough not to require it.

For example, the {{w|factorial}} function has a recursive definition:

factorial(n) = 1 if n = 0
factorial(n) = n * factorial(n - 1) if n > 0

which can be coded as:

factorial(n):
if n == 0:
return 1
else:
return n * factorial(n - 1)

{{w|Tail recursion}} refers to a recursive function whose final operation is to invoke the function itself - crucially with no subsequent computation involved. This means that instead of pushing each level of recursion onto the stack, the compiler can simply arrange for the recursive call to jump to the start of the function with the new parameters - effectively turning a recursive call into an iterative loop, whilst retaining the simplicity of a recursive call.

The efficiency and elegance are the literal rewards of tail recursion.

The {{w|greatest common divisor}} function can be coded as:

gcd(a, b):
if b == 0:
return a
else:
return gcd(b, a % b)

Here, the recursive call to gcd is tail recursive since its the last step of the function.

The first example is not tail recursive because the multiplication cannot be evaluated until after its right operand has been calculated. This next example performs its multiplication before the final step - the recursion - and is, thereby, tail recursive.

factorial2(n, acc):
if n == 0:
return acc
else:
return factorial2(n - 1, n * acc)

factorial(n):
return factorial2(n, 1)

The technique used here is to use a helper function with an additional argument called an accumulator which will accumulate results from previous calls to the function. It is often used to implement tail recursive or iterative versions of recursive functions. This is not applicable for all recursive functions, though.

Cueball is making the pun that "(functional programming) is an end unto itself", which would be both figuratively and literally correct.

The title text describes that to {{w|Abstract mathematics|abstract mathematicians}} functional programming is both powerful and flexible, as well as intuitive and clear since it comes very close to the way mathematicians usually describe functions. On the other hand to non-mathematicians, functional programming can be exactly the opposite (thus being non-intuitive and unclear as abstract mathematics appears to them).

The title text is also a reference to a common saying about C (An {{w|Imperative programming|imperative programming}} language): "C combines the flexibility and power of assembly language with the user-friendliness of assembly language".

==Transcript==
:[White Hat stands behind Cueball, who is sitting at a computer]
:White Hat: Why do you like functional programming so much? What does it actually ''get'' you?
:Cueball: Tail recursion is its own reward.

{{comic discussion}}
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Cueball]]
[[Category:Programming]]
[[Category:Recursion]]