explain xkcd - User contributions [en]

Talk:2217: 53 Cards

2019-10-21T21:17:30Z

162.158.165.118: Refuting claim against dark matter

"This page was last edited [tomorrow]." Okay, good to know. Tomorrow starts three hours from now, my time. This comic reminded me of this article: https://arstechnica.com/science/2019/10/corkscrewing-bouncy-ion-drive-would-provide-thrust-in-different-universe/ [[Special:Contributions/172.68.38.88|172.68.38.88]] 00:44, 19 October 2019 (UTC)

I can do this, but my flowchart would be different and involve secretly inserting a joker, using the shuffling as cover for the move.
Collect a deck of 52 cards and have a spectator count the cards. - Secretly hide a joker from the deck in your off-hand (the one without the deck). - Shuffle the cards, letting the hidden card drop on top of the deck. - Keep shuffling, so the inserted joker is well mixed into the deck. - Have a spectator count the cards, looking only at the backs. - 53.
[[User:Nutster|Nutster]] ([[User talk:Nutster|talk]]) 04:56, 19 October 2019 (UTC)

Actually this is also what encryption scientists have to face talking to not so few encryption enthusiasts who just invented their own encryption method[[Special:Contributions/162.158.234.112|162.158.234.112]] 07:01, 19 October 2019 (UTC)
:Ohg V unir na haornnoyr pvcure! [[Special:Contributions/162.158.158.253|162.158.158.253]] 13:52, 19 October 2019 (UTC)
:The difference is that those "own excryption methods" usually work ... not well, but at least little. Now, the algorithms which claim to compress ANY input to smaller size, those tend to be suspicious ... -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:15, 19 October 2019 (UTC)

Wait, isn't perpetual motion (w.r.t. a inertial reference frame) possible, at least according to Newtonian mechanics? Just launch something into space at high enough speed and "watch" it wander away forever. Extracting (an unbounded amount of) energy from that object is a totally different story... --[[Special:Contributions/162.158.234.94|162.158.234.94]] 10:11, 19 October 2019 (UTC)
:Not really, as even in vacuums particles randomly come into existence. Eventually enough would be in the path to slow it to a stop. [[Special:Contributions/162.158.62.151|162.158.62.151]] 17:37, 19 October 2019 (UTC)
::Not in Newtonian mechanics. Those random particles are result of quantum physics - and in quantum physics, EVERYTHING is possible, just unlikely (there is extremely small but nonzero probability that all particles in macroscopic object would exhibit tunneling effect moving them in same direction, for example). -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:15, 19 October 2019 (UTC)
:Vacuum fluctuation (particles), i.e. quantum weirdness, cannot cause trouble. This is because all working QFT, where these vacuum fluctuations appear, take as assumption the strict local conservation of energy-momentum 4-vector, which is the generalisation of what our OP is asking about. This is a fundamental backbone of all modern physics, not just Newtonian mechanics, and the only known violation is in cosmology. Needless to say, when we talk about perpetual motion machines, we have to start by omitting this trivial class. That is, we do not call systems that achieve perpetual motion by exploiting the conservation of linear or angular momentum alone, as perpetual motion machines. Some machines of that form that convert the energy and momentum from one part to the other could be a perpetual motion machine, because in those cases it is possible for the efficiency of conversion to be imperfect, in which case it will always practically be imperfect, leading to the eventual failure. Luckily, on Earth and in practice, there is no need to be careful, because even the linear or angular momentum special case, would be interacting with air---the best vacuum we can get, are still not perfect; it is not perfect even in actual space outside Earth. It just doesn't exist anywhere. [[Special:Contributions/162.158.165.118|162.158.165.118]] 20:49, 21 October 2019 (UTC)

Getting a 53 card deck from a 52 card deck is easy. First, cut the deck twice. Then, shuffle all parts together; be sure to suffer thoroughly. Finally, take off the top 5 cards, sneak in the Joker on the bottom while nobody's looking, and put the five cards at the "middle". Because of skewed philosophy, you will have gotten a 53 card deck![[Special:Contributions/162.158.122.186|162.158.122.186]]

“The amount of energy necessary to refute bullshit is an order of magnitude bigger than to produce it.” -Alberto Brandolini [[User:Menoshe|Menoshe]] ([[User talk:Menoshe|talk]]) 22:03, 19 October 2019 (UTC)

Note that while it shouldn't be possible to obtain energy from nowhere, there ARE methods which makes hard to find where the energy comes from, and some may be useful (say, perhaps as a new kind of battery?). Also, anything involving not-completely-understood phenomena, like black hole for example, might actually generate energy from source we don't know about yet (parallel universe or something like that). Meanwhile, lot of theoretical designs of perpetual motion machines without working prototype only contain steps which can't possibly get energy anywhere and are completely useless ... -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:15, 19 October 2019 (UTC)
: Black hole physics are one of the best understood. No part of understanding them requires parallel universes. The thing that is really a headache in General Theory of Relativity is that we still do not have a good, localised, way to express the energy stored in the gravitational field. Landau-Lifshitz pseudo-tensor is proved to be unique given the assumptions, but starts with a subtraction of the matter stress-energy tensor, and violates precisely this comic---it says that some gravitational wave situations don't carry away energy, when in fact we know those have to carry away energy. Better defined notions, like ADM energy, are global energy, not localised energy, so that we do not know what they mean, practically. However, even though we are still not fully understanding what mathematical quantity would correctly map to gravitational field energy in the theory, we still do know that it has to be gravitational field energy, and that it has nothing to do with parallel universes. Just to hammer down the singular mistake in your nice comment. [[Special:Contributions/162.158.165.118|162.158.165.118]] 21:01, 21 October 2019 (UTC)

In the picture it seems that he cuts the cards into a pile of 21 cards and 38 cards (thus making 59 cards) I'm sure that helps his argument (or he can't count.
: Yeah, I noticed that mismatch too! Actually, I interpreted the "cut" as referring to that one old trick where rectangular objects (usually banknotes) would be cut in half and then rearranged with small pieces missing, making one more object than there used to be. This of course would not be a case of "rearranging and shuffling". (If you're wondering why this doesn't work for ''actual'' banknotes, that's because the existence of serial numbers makes this trick far harder, and the ''repeated'' serial numbers on most modern notes make it effectively impossible. But back in the 19th century this actually used to be a problem.) --[[Special:Contributions/172.69.54.33|172.69.54.33]] 19:26, 21 October 2019 (UTC)

Perpetual motion is so easy that we've already done it. The universe isn't going to stop expanding anytime soon, afterall. Also, Voyager (and some other space probes). Everything is perpetual motion in space at solar escape velocity until/unless it hits something. [[Special:Contributions/162.158.214.88|162.158.214.88]] 18:35, 20 October 2019 (UTC)
: This case is by definition excluded from the discussion of perpetual motion. See above for my longer version on it. [[Special:Contributions/162.158.165.118|162.158.165.118]] 21:03, 21 October 2019 (UTC)

You can always rearrange the matter making up the 52 cards, into 53 smaller cards. [[Special:Contributions/108.162.212.17|108.162.212.17]] 19:21, 20 October 2019 (UTC)

It's easy to prove, using the Banach-Tarski theorem [[User:Cellocgw|Cellocgw]] ([[User talk:Cellocgw|talk]]) 12:39, 21 October 2019 (UTC)
:If you show me how to dissolve the cards into subatomar theoretical dots by shuffling, I agree. --[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 13:36, 21 October 2019 (UTC)

Sigh... I really don't like having to keep challenging Kynde, who I believe is a well-intentioned contributor... but as soon as I saw the rewritten explanation with confusing phrasing and broken English, I knew that it was him who did it, and honestly... it just makes the article worse. It's harder to read and comprehend, contains irrelevancies, and swings between explanatory points incoherently. It was, honestly, okay as it was (specifically [https://www.explainxkcd.com/wiki/index.php?title=2217:_53_Cards&oldid=181494 this version]). I don't really know what to do about it. I'm of the "be bold in making edits" school of wiki-ing, but I don't want to just flush away other people's well-meant contributions. [[User:Hawthorn|Hawthorn]] ([[User talk:Hawthorn|talk]]) 15:01, 21 October 2019 (UTC)

Unfortunately, plenty of physicists make the same mistake, losing sight of the fact that math is only a model that must conform to reality, a-la Zeno's Paradox. That's how you end up with silly claims of "if you can [go faster than light] [travel through a wormhole between two distant points in an expanding universe] you'll go backward in time". Or how about the pseudoscience of explaining failed models by assuming that there must be "dark" matter or energy, instead of acknowledging that the model, itself, must be fundamentally wrong the way an actual scientist would. — [[User:Kazvorpal|Kazvorpal]] ([[User talk:Kazvorpal|talk]]) 16:53, 21 October 2019 (UTC)
: What are the chances that the global scientific community, who are setup to attack each other to win funding, would require outsiders to tell them that dark matter and dark energy are indications that their models are "fundamentally wrong"? It just goes to show how rarely you talk to scientists. Cosmologists are always apologising for not knowing what dark energy is, treating them only as the cosmological constant (other alternatives are always explored, but none offer significant improvements upon cosmological constant simplicity). But the dark matter situation already merit a few observational wins, and are starting to look more and more like postulating neutrinos, which is a winning precedent. For two examples, firstly, we have observed localised dark matter causing gravitational lensing. Secondly, we see some galaxy collisions that have dark matter in the wrong place due to the collisions. These evidences are enough to convince most astrophysicists that the basic picture seems correct. Other than this, you should also work on understanding more about how theory and experiment interact in physics, before commenting more upon the matter. [[Special:Contributions/162.158.165.118|162.158.165.118]] 21:17, 21 October 2019 (UTC)

Well, since it's a non-closed system that is receiving energy... and matter is just solidified energy... :) I'm going to say that Cueball is right so long as his flowchart also contains a StarTrek replicator somewhere. [[Special:Contributions/172.68.90.64|172.68.90.64]] 20:08, 21 October 2019 (UTC)SiliconWolf

Talk:2217: 53 Cards

2019-10-21T21:03:54Z

162.158.165.118: Another definition of perpetual motion clarification

"This page was last edited [tomorrow]." Okay, good to know. Tomorrow starts three hours from now, my time. This comic reminded me of this article: https://arstechnica.com/science/2019/10/corkscrewing-bouncy-ion-drive-would-provide-thrust-in-different-universe/ [[Special:Contributions/172.68.38.88|172.68.38.88]] 00:44, 19 October 2019 (UTC)

I can do this, but my flowchart would be different and involve secretly inserting a joker, using the shuffling as cover for the move.
Collect a deck of 52 cards and have a spectator count the cards. - Secretly hide a joker from the deck in your off-hand (the one without the deck). - Shuffle the cards, letting the hidden card drop on top of the deck. - Keep shuffling, so the inserted joker is well mixed into the deck. - Have a spectator count the cards, looking only at the backs. - 53.
[[User:Nutster|Nutster]] ([[User talk:Nutster|talk]]) 04:56, 19 October 2019 (UTC)

Actually this is also what encryption scientists have to face talking to not so few encryption enthusiasts who just invented their own encryption method[[Special:Contributions/162.158.234.112|162.158.234.112]] 07:01, 19 October 2019 (UTC)
:Ohg V unir na haornnoyr pvcure! [[Special:Contributions/162.158.158.253|162.158.158.253]] 13:52, 19 October 2019 (UTC)
:The difference is that those "own excryption methods" usually work ... not well, but at least little. Now, the algorithms which claim to compress ANY input to smaller size, those tend to be suspicious ... -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:15, 19 October 2019 (UTC)

Wait, isn't perpetual motion (w.r.t. a inertial reference frame) possible, at least according to Newtonian mechanics? Just launch something into space at high enough speed and "watch" it wander away forever. Extracting (an unbounded amount of) energy from that object is a totally different story... --[[Special:Contributions/162.158.234.94|162.158.234.94]] 10:11, 19 October 2019 (UTC)
:Not really, as even in vacuums particles randomly come into existence. Eventually enough would be in the path to slow it to a stop. [[Special:Contributions/162.158.62.151|162.158.62.151]] 17:37, 19 October 2019 (UTC)
::Not in Newtonian mechanics. Those random particles are result of quantum physics - and in quantum physics, EVERYTHING is possible, just unlikely (there is extremely small but nonzero probability that all particles in macroscopic object would exhibit tunneling effect moving them in same direction, for example). -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:15, 19 October 2019 (UTC)
:Vacuum fluctuation (particles), i.e. quantum weirdness, cannot cause trouble. This is because all working QFT, where these vacuum fluctuations appear, take as assumption the strict local conservation of energy-momentum 4-vector, which is the generalisation of what our OP is asking about. This is a fundamental backbone of all modern physics, not just Newtonian mechanics, and the only known violation is in cosmology. Needless to say, when we talk about perpetual motion machines, we have to start by omitting this trivial class. That is, we do not call systems that achieve perpetual motion by exploiting the conservation of linear or angular momentum alone, as perpetual motion machines. Some machines of that form that convert the energy and momentum from one part to the other could be a perpetual motion machine, because in those cases it is possible for the efficiency of conversion to be imperfect, in which case it will always practically be imperfect, leading to the eventual failure. Luckily, on Earth and in practice, there is no need to be careful, because even the linear or angular momentum special case, would be interacting with air---the best vacuum we can get, are still not perfect; it is not perfect even in actual space outside Earth. It just doesn't exist anywhere. [[Special:Contributions/162.158.165.118|162.158.165.118]] 20:49, 21 October 2019 (UTC)

Getting a 53 card deck from a 52 card deck is easy. First, cut the deck twice. Then, shuffle all parts together; be sure to suffer thoroughly. Finally, take off the top 5 cards, sneak in the Joker on the bottom while nobody's looking, and put the five cards at the "middle". Because of skewed philosophy, you will have gotten a 53 card deck![[Special:Contributions/162.158.122.186|162.158.122.186]]

“The amount of energy necessary to refute bullshit is an order of magnitude bigger than to produce it.” -Alberto Brandolini [[User:Menoshe|Menoshe]] ([[User talk:Menoshe|talk]]) 22:03, 19 October 2019 (UTC)

Note that while it shouldn't be possible to obtain energy from nowhere, there ARE methods which makes hard to find where the energy comes from, and some may be useful (say, perhaps as a new kind of battery?). Also, anything involving not-completely-understood phenomena, like black hole for example, might actually generate energy from source we don't know about yet (parallel universe or something like that). Meanwhile, lot of theoretical designs of perpetual motion machines without working prototype only contain steps which can't possibly get energy anywhere and are completely useless ... -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:15, 19 October 2019 (UTC)
: Black hole physics are one of the best understood. No part of understanding them requires parallel universes. The thing that is really a headache in General Theory of Relativity is that we still do not have a good, localised, way to express the energy stored in the gravitational field. Landau-Lifshitz pseudo-tensor is proved to be unique given the assumptions, but starts with a subtraction of the matter stress-energy tensor, and violates precisely this comic---it says that some gravitational wave situations don't carry away energy, when in fact we know those have to carry away energy. Better defined notions, like ADM energy, are global energy, not localised energy, so that we do not know what they mean, practically. However, even though we are still not fully understanding what mathematical quantity would correctly map to gravitational field energy in the theory, we still do know that it has to be gravitational field energy, and that it has nothing to do with parallel universes. Just to hammer down the singular mistake in your nice comment. [[Special:Contributions/162.158.165.118|162.158.165.118]] 21:01, 21 October 2019 (UTC)

In the picture it seems that he cuts the cards into a pile of 21 cards and 38 cards (thus making 59 cards) I'm sure that helps his argument (or he can't count.
: Yeah, I noticed that mismatch too! Actually, I interpreted the "cut" as referring to that one old trick where rectangular objects (usually banknotes) would be cut in half and then rearranged with small pieces missing, making one more object than there used to be. This of course would not be a case of "rearranging and shuffling". (If you're wondering why this doesn't work for ''actual'' banknotes, that's because the existence of serial numbers makes this trick far harder, and the ''repeated'' serial numbers on most modern notes make it effectively impossible. But back in the 19th century this actually used to be a problem.) --[[Special:Contributions/172.69.54.33|172.69.54.33]] 19:26, 21 October 2019 (UTC)

Perpetual motion is so easy that we've already done it. The universe isn't going to stop expanding anytime soon, afterall. Also, Voyager (and some other space probes). Everything is perpetual motion in space at solar escape velocity until/unless it hits something. [[Special:Contributions/162.158.214.88|162.158.214.88]] 18:35, 20 October 2019 (UTC)
: This case is by definition excluded from the discussion of perpetual motion. See above for my longer version on it. [[Special:Contributions/162.158.165.118|162.158.165.118]] 21:03, 21 October 2019 (UTC)

You can always rearrange the matter making up the 52 cards, into 53 smaller cards. [[Special:Contributions/108.162.212.17|108.162.212.17]] 19:21, 20 October 2019 (UTC)

It's easy to prove, using the Banach-Tarski theorem [[User:Cellocgw|Cellocgw]] ([[User talk:Cellocgw|talk]]) 12:39, 21 October 2019 (UTC)
:If you show me how to dissolve the cards into subatomar theoretical dots by shuffling, I agree. --[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 13:36, 21 October 2019 (UTC)

Sigh... I really don't like having to keep challenging Kynde, who I believe is a well-intentioned contributor... but as soon as I saw the rewritten explanation with confusing phrasing and broken English, I knew that it was him who did it, and honestly... it just makes the article worse. It's harder to read and comprehend, contains irrelevancies, and swings between explanatory points incoherently. It was, honestly, okay as it was (specifically [https://www.explainxkcd.com/wiki/index.php?title=2217:_53_Cards&oldid=181494 this version]). I don't really know what to do about it. I'm of the "be bold in making edits" school of wiki-ing, but I don't want to just flush away other people's well-meant contributions. [[User:Hawthorn|Hawthorn]] ([[User talk:Hawthorn|talk]]) 15:01, 21 October 2019 (UTC)

Unfortunately, plenty of physicists make the same mistake, losing sight of the fact that math is only a model that must conform to reality, a-la Zeno's Paradox. That's how you end up with silly claims of "if you can [go faster than light] [travel through a wormhole between two distant points in an expanding universe] you'll go backward in time". Or how about the pseudoscience of explaining failed models by assuming that there must be "dark" matter or energy, instead of acknowledging that the model, itself, must be fundamentally wrong the way an actual scientist would. — [[User:Kazvorpal|Kazvorpal]] ([[User talk:Kazvorpal|talk]]) 16:53, 21 October 2019 (UTC)

Well, since it's a non-closed system that is receiving energy... and matter is just solidified energy... :) I'm going to say that Cueball is right so long as his flowchart also contains a StarTrek replicator somewhere. [[Special:Contributions/172.68.90.64|172.68.90.64]] 20:08, 21 October 2019 (UTC)SiliconWolf

Talk:2217: 53 Cards

2019-10-21T21:01:43Z

162.158.165.118: Clarifying black hole physics

"This page was last edited [tomorrow]." Okay, good to know. Tomorrow starts three hours from now, my time. This comic reminded me of this article: https://arstechnica.com/science/2019/10/corkscrewing-bouncy-ion-drive-would-provide-thrust-in-different-universe/ [[Special:Contributions/172.68.38.88|172.68.38.88]] 00:44, 19 October 2019 (UTC)

I can do this, but my flowchart would be different and involve secretly inserting a joker, using the shuffling as cover for the move.
Collect a deck of 52 cards and have a spectator count the cards. - Secretly hide a joker from the deck in your off-hand (the one without the deck). - Shuffle the cards, letting the hidden card drop on top of the deck. - Keep shuffling, so the inserted joker is well mixed into the deck. - Have a spectator count the cards, looking only at the backs. - 53.
[[User:Nutster|Nutster]] ([[User talk:Nutster|talk]]) 04:56, 19 October 2019 (UTC)

Actually this is also what encryption scientists have to face talking to not so few encryption enthusiasts who just invented their own encryption method[[Special:Contributions/162.158.234.112|162.158.234.112]] 07:01, 19 October 2019 (UTC)
:Ohg V unir na haornnoyr pvcure! [[Special:Contributions/162.158.158.253|162.158.158.253]] 13:52, 19 October 2019 (UTC)
:The difference is that those "own excryption methods" usually work ... not well, but at least little. Now, the algorithms which claim to compress ANY input to smaller size, those tend to be suspicious ... -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:15, 19 October 2019 (UTC)

Wait, isn't perpetual motion (w.r.t. a inertial reference frame) possible, at least according to Newtonian mechanics? Just launch something into space at high enough speed and "watch" it wander away forever. Extracting (an unbounded amount of) energy from that object is a totally different story... --[[Special:Contributions/162.158.234.94|162.158.234.94]] 10:11, 19 October 2019 (UTC)
:Not really, as even in vacuums particles randomly come into existence. Eventually enough would be in the path to slow it to a stop. [[Special:Contributions/162.158.62.151|162.158.62.151]] 17:37, 19 October 2019 (UTC)
::Not in Newtonian mechanics. Those random particles are result of quantum physics - and in quantum physics, EVERYTHING is possible, just unlikely (there is extremely small but nonzero probability that all particles in macroscopic object would exhibit tunneling effect moving them in same direction, for example). -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:15, 19 October 2019 (UTC)
:Vacuum fluctuation (particles), i.e. quantum weirdness, cannot cause trouble. This is because all working QFT, where these vacuum fluctuations appear, take as assumption the strict local conservation of energy-momentum 4-vector, which is the generalisation of what our OP is asking about. This is a fundamental backbone of all modern physics, not just Newtonian mechanics, and the only known violation is in cosmology. Needless to say, when we talk about perpetual motion machines, we have to start by omitting this trivial class. That is, we do not call systems that achieve perpetual motion by exploiting the conservation of linear or angular momentum alone, as perpetual motion machines. Some machines of that form that convert the energy and momentum from one part to the other could be a perpetual motion machine, because in those cases it is possible for the efficiency of conversion to be imperfect, in which case it will always practically be imperfect, leading to the eventual failure. Luckily, on Earth and in practice, there is no need to be careful, because even the linear or angular momentum special case, would be interacting with air---the best vacuum we can get, are still not perfect; it is not perfect even in actual space outside Earth. It just doesn't exist anywhere. [[Special:Contributions/162.158.165.118|162.158.165.118]] 20:49, 21 October 2019 (UTC)

Getting a 53 card deck from a 52 card deck is easy. First, cut the deck twice. Then, shuffle all parts together; be sure to suffer thoroughly. Finally, take off the top 5 cards, sneak in the Joker on the bottom while nobody's looking, and put the five cards at the "middle". Because of skewed philosophy, you will have gotten a 53 card deck![[Special:Contributions/162.158.122.186|162.158.122.186]]

“The amount of energy necessary to refute bullshit is an order of magnitude bigger than to produce it.” -Alberto Brandolini [[User:Menoshe|Menoshe]] ([[User talk:Menoshe|talk]]) 22:03, 19 October 2019 (UTC)

Note that while it shouldn't be possible to obtain energy from nowhere, there ARE methods which makes hard to find where the energy comes from, and some may be useful (say, perhaps as a new kind of battery?). Also, anything involving not-completely-understood phenomena, like black hole for example, might actually generate energy from source we don't know about yet (parallel universe or something like that). Meanwhile, lot of theoretical designs of perpetual motion machines without working prototype only contain steps which can't possibly get energy anywhere and are completely useless ... -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:15, 19 October 2019 (UTC)
: Black hole physics are one of the best understood. No part of understanding them requires parallel universes. The thing that is really a headache in General Theory of Relativity is that we still do not have a good, localised, way to express the energy stored in the gravitational field. Landau-Lifshitz pseudo-tensor is proved to be unique given the assumptions, but starts with a subtraction of the matter stress-energy tensor, and violates precisely this comic---it says that some gravitational wave situations don't carry away energy, when in fact we know those have to carry away energy. Better defined notions, like ADM energy, are global energy, not localised energy, so that we do not know what they mean, practically. However, even though we are still not fully understanding what mathematical quantity would correctly map to gravitational field energy in the theory, we still do know that it has to be gravitational field energy, and that it has nothing to do with parallel universes. Just to hammer down the singular mistake in your nice comment. [[Special:Contributions/162.158.165.118|162.158.165.118]] 21:01, 21 October 2019 (UTC)

In the picture it seems that he cuts the cards into a pile of 21 cards and 38 cards (thus making 59 cards) I'm sure that helps his argument (or he can't count.
: Yeah, I noticed that mismatch too! Actually, I interpreted the "cut" as referring to that one old trick where rectangular objects (usually banknotes) would be cut in half and then rearranged with small pieces missing, making one more object than there used to be. This of course would not be a case of "rearranging and shuffling". (If you're wondering why this doesn't work for ''actual'' banknotes, that's because the existence of serial numbers makes this trick far harder, and the ''repeated'' serial numbers on most modern notes make it effectively impossible. But back in the 19th century this actually used to be a problem.) --[[Special:Contributions/172.69.54.33|172.69.54.33]] 19:26, 21 October 2019 (UTC)

Perpetual motion is so easy that we've already done it. The universe isn't going to stop expanding anytime soon, afterall. Also, Voyager (and some other space probes). Everything is perpetual motion in space at solar escape velocity until/unless it hits something. [[Special:Contributions/162.158.214.88|162.158.214.88]] 18:35, 20 October 2019 (UTC)

You can always rearrange the matter making up the 52 cards, into 53 smaller cards. [[Special:Contributions/108.162.212.17|108.162.212.17]] 19:21, 20 October 2019 (UTC)

It's easy to prove, using the Banach-Tarski theorem [[User:Cellocgw|Cellocgw]] ([[User talk:Cellocgw|talk]]) 12:39, 21 October 2019 (UTC)
:If you show me how to dissolve the cards into subatomar theoretical dots by shuffling, I agree. --[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 13:36, 21 October 2019 (UTC)

Sigh... I really don't like having to keep challenging Kynde, who I believe is a well-intentioned contributor... but as soon as I saw the rewritten explanation with confusing phrasing and broken English, I knew that it was him who did it, and honestly... it just makes the article worse. It's harder to read and comprehend, contains irrelevancies, and swings between explanatory points incoherently. It was, honestly, okay as it was (specifically [https://www.explainxkcd.com/wiki/index.php?title=2217:_53_Cards&oldid=181494 this version]). I don't really know what to do about it. I'm of the "be bold in making edits" school of wiki-ing, but I don't want to just flush away other people's well-meant contributions. [[User:Hawthorn|Hawthorn]] ([[User talk:Hawthorn|talk]]) 15:01, 21 October 2019 (UTC)

Unfortunately, plenty of physicists make the same mistake, losing sight of the fact that math is only a model that must conform to reality, a-la Zeno's Paradox. That's how you end up with silly claims of "if you can [go faster than light] [travel through a wormhole between two distant points in an expanding universe] you'll go backward in time". Or how about the pseudoscience of explaining failed models by assuming that there must be "dark" matter or energy, instead of acknowledging that the model, itself, must be fundamentally wrong the way an actual scientist would. — [[User:Kazvorpal|Kazvorpal]] ([[User talk:Kazvorpal|talk]]) 16:53, 21 October 2019 (UTC)

Well, since it's a non-closed system that is receiving energy... and matter is just solidified energy... :) I'm going to say that Cueball is right so long as his flowchart also contains a StarTrek replicator somewhere. [[Special:Contributions/172.68.90.64|172.68.90.64]] 20:08, 21 October 2019 (UTC)SiliconWolf

Talk:2217: 53 Cards

2019-10-21T20:49:56Z

162.158.165.118: Clarifying definition of perpetual motion, relative to momentum conservation

"This page was last edited [tomorrow]." Okay, good to know. Tomorrow starts three hours from now, my time. This comic reminded me of this article: https://arstechnica.com/science/2019/10/corkscrewing-bouncy-ion-drive-would-provide-thrust-in-different-universe/ [[Special:Contributions/172.68.38.88|172.68.38.88]] 00:44, 19 October 2019 (UTC)

I can do this, but my flowchart would be different and involve secretly inserting a joker, using the shuffling as cover for the move.
Collect a deck of 52 cards and have a spectator count the cards. - Secretly hide a joker from the deck in your off-hand (the one without the deck). - Shuffle the cards, letting the hidden card drop on top of the deck. - Keep shuffling, so the inserted joker is well mixed into the deck. - Have a spectator count the cards, looking only at the backs. - 53.
[[User:Nutster|Nutster]] ([[User talk:Nutster|talk]]) 04:56, 19 October 2019 (UTC)

Actually this is also what encryption scientists have to face talking to not so few encryption enthusiasts who just invented their own encryption method[[Special:Contributions/162.158.234.112|162.158.234.112]] 07:01, 19 October 2019 (UTC)
:Ohg V unir na haornnoyr pvcure! [[Special:Contributions/162.158.158.253|162.158.158.253]] 13:52, 19 October 2019 (UTC)
:The difference is that those "own excryption methods" usually work ... not well, but at least little. Now, the algorithms which claim to compress ANY input to smaller size, those tend to be suspicious ... -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:15, 19 October 2019 (UTC)

Wait, isn't perpetual motion (w.r.t. a inertial reference frame) possible, at least according to Newtonian mechanics? Just launch something into space at high enough speed and "watch" it wander away forever. Extracting (an unbounded amount of) energy from that object is a totally different story... --[[Special:Contributions/162.158.234.94|162.158.234.94]] 10:11, 19 October 2019 (UTC)
:Not really, as even in vacuums particles randomly come into existence. Eventually enough would be in the path to slow it to a stop. [[Special:Contributions/162.158.62.151|162.158.62.151]] 17:37, 19 October 2019 (UTC)
::Not in Newtonian mechanics. Those random particles are result of quantum physics - and in quantum physics, EVERYTHING is possible, just unlikely (there is extremely small but nonzero probability that all particles in macroscopic object would exhibit tunneling effect moving them in same direction, for example). -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:15, 19 October 2019 (UTC)
:Vacuum fluctuation (particles), i.e. quantum weirdness, cannot cause trouble. This is because all working QFT, where these vacuum fluctuations appear, take as assumption the strict local conservation of energy-momentum 4-vector, which is the generalisation of what our OP is asking about. This is a fundamental backbone of all modern physics, not just Newtonian mechanics, and the only known violation is in cosmology. Needless to say, when we talk about perpetual motion machines, we have to start by omitting this trivial class. That is, we do not call systems that achieve perpetual motion by exploiting the conservation of linear or angular momentum alone, as perpetual motion machines. Some machines of that form that convert the energy and momentum from one part to the other could be a perpetual motion machine, because in those cases it is possible for the efficiency of conversion to be imperfect, in which case it will always practically be imperfect, leading to the eventual failure. Luckily, on Earth and in practice, there is no need to be careful, because even the linear or angular momentum special case, would be interacting with air---the best vacuum we can get, are still not perfect; it is not perfect even in actual space outside Earth. It just doesn't exist anywhere. [[Special:Contributions/162.158.165.118|162.158.165.118]] 20:49, 21 October 2019 (UTC)

Getting a 53 card deck from a 52 card deck is easy. First, cut the deck twice. Then, shuffle all parts together; be sure to suffer thoroughly. Finally, take off the top 5 cards, sneak in the Joker on the bottom while nobody's looking, and put the five cards at the "middle". Because of skewed philosophy, you will have gotten a 53 card deck![[Special:Contributions/162.158.122.186|162.158.122.186]]

“The amount of energy necessary to refute bullshit is an order of magnitude bigger than to produce it.” -Alberto Brandolini [[User:Menoshe|Menoshe]] ([[User talk:Menoshe|talk]]) 22:03, 19 October 2019 (UTC)

Note that while it shouldn't be possible to obtain energy from nowhere, there ARE methods which makes hard to find where the energy comes from, and some may be useful (say, perhaps as a new kind of battery?). Also, anything involving not-completely-understood phenomena, like black hole for example, might actually generate energy from source we don't know about yet (parallel universe or something like that). Meanwhile, lot of theoretical designs of perpetual motion machines without working prototype only contain steps which can't possibly get energy anywhere and are completely useless ... -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 22:15, 19 October 2019 (UTC)

In the picture it seems that he cuts the cards into a pile of 21 cards and 38 cards (thus making 59 cards) I'm sure that helps his argument (or he can't count.
: Yeah, I noticed that mismatch too! Actually, I interpreted the "cut" as referring to that one old trick where rectangular objects (usually banknotes) would be cut in half and then rearranged with small pieces missing, making one more object than there used to be. This of course would not be a case of "rearranging and shuffling". (If you're wondering why this doesn't work for ''actual'' banknotes, that's because the existence of serial numbers makes this trick far harder, and the ''repeated'' serial numbers on most modern notes make it effectively impossible. But back in the 19th century this actually used to be a problem.) --[[Special:Contributions/172.69.54.33|172.69.54.33]] 19:26, 21 October 2019 (UTC)

Perpetual motion is so easy that we've already done it. The universe isn't going to stop expanding anytime soon, afterall. Also, Voyager (and some other space probes). Everything is perpetual motion in space at solar escape velocity until/unless it hits something. [[Special:Contributions/162.158.214.88|162.158.214.88]] 18:35, 20 October 2019 (UTC)

You can always rearrange the matter making up the 52 cards, into 53 smaller cards. [[Special:Contributions/108.162.212.17|108.162.212.17]] 19:21, 20 October 2019 (UTC)

It's easy to prove, using the Banach-Tarski theorem [[User:Cellocgw|Cellocgw]] ([[User talk:Cellocgw|talk]]) 12:39, 21 October 2019 (UTC)
:If you show me how to dissolve the cards into subatomar theoretical dots by shuffling, I agree. --[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 13:36, 21 October 2019 (UTC)

Sigh... I really don't like having to keep challenging Kynde, who I believe is a well-intentioned contributor... but as soon as I saw the rewritten explanation with confusing phrasing and broken English, I knew that it was him who did it, and honestly... it just makes the article worse. It's harder to read and comprehend, contains irrelevancies, and swings between explanatory points incoherently. It was, honestly, okay as it was (specifically [https://www.explainxkcd.com/wiki/index.php?title=2217:_53_Cards&oldid=181494 this version]). I don't really know what to do about it. I'm of the "be bold in making edits" school of wiki-ing, but I don't want to just flush away other people's well-meant contributions. [[User:Hawthorn|Hawthorn]] ([[User talk:Hawthorn|talk]]) 15:01, 21 October 2019 (UTC)

Unfortunately, plenty of physicists make the same mistake, losing sight of the fact that math is only a model that must conform to reality, a-la Zeno's Paradox. That's how you end up with silly claims of "if you can [go faster than light] [travel through a wormhole between two distant points in an expanding universe] you'll go backward in time". Or how about the pseudoscience of explaining failed models by assuming that there must be "dark" matter or energy, instead of acknowledging that the model, itself, must be fundamentally wrong the way an actual scientist would. — [[User:Kazvorpal|Kazvorpal]] ([[User talk:Kazvorpal|talk]]) 16:53, 21 October 2019 (UTC)

Well, since it's a non-closed system that is receiving energy... and matter is just solidified energy... :) I'm going to say that Cueball is right so long as his flowchart also contains a StarTrek replicator somewhere. [[Special:Contributions/172.68.90.64|172.68.90.64]] 20:08, 21 October 2019 (UTC)SiliconWolf

1928: Seven Years

2017-12-14T05:06:58Z

162.158.165.118: Added some explanation to Panel 10

{{comic
| number = 1928
| date = December 13, 2017
| title = Seven Years
| image = seven_years.png
| titletext = [hair in face] "SEVVVENNN YEEEARRRSSS"
}}

==Explanation==
{{incomplete|May require explaining the activities shown, as in the explanation for [[1141: Two Years]].}}
[[Randall]]'s wife was diagnosed with cancer in late 2010, a matter he has discussed in the comic [[:Category:Cancer|multiple times before]]. Here, motivated by the seven-year period between the American solar eclipses of {{w|Solar eclipse of August 21, 2017|2017}} and {{w|Solar eclipse of April 8, 2024|2024}}, we see them reminiscing the seven years prior to the first eclipse, leaving an open question to what the next seven years will bring.

The title text is most likely a continuation to panel 15 concerning hair regrowth, in which she references the horror movie ''The Ring''. "The little girl from ''The Ring''" refers to {{w|Sadako Yamamura}}, the antagonist of the {{w|Ring (novel series)|''Ring'' series}} by {{w|Koji Suzuki}}, and popularized in a {{w|The Ring (2002 film)|2002 movie}}.

This comic is a continuation of [[1141: Two Years]], which is shown as the first eight panels, slightly grayed out.

[[Image:seven years key.png|right]]

Some explanations:

*Panels 1–8: See [[1141: Two Years]]
*Panel 9: Randall and Randall's wife (with her hair noticably longer) are walking through a forest.
*Panel 10: Randall's wife is sitting down, not in the forest anymore. She is concerned because she has pain in her toe and worries that this is an early sign of her cancer spreading again. Randall points out the simpler explanation- that she stubbed her toe the previous day, and the pain is likely a result of that. This panel shows the paranoia that comes from cancer remission, as earlier explained in [[931: Lanes]].
*Panel 11: Randall and his wife are going spelunking. The guide is gesturing deeper into the cave while Randall and his wife are climbing down.
*Panel 12: Randall's wife stands on a rock above an alligator in a swamp, photographing the alligator. Randall is on a balcony behind safety railings.
*Panel 13: Randall's wife sits on an examination bed, listening to a doctor holding a clipboard.
*Panel 14: Randall and his wife stand above a deep pond full of fish and other objects. Randall's wife is piloting a wired underwater camera with lights.
*Panel 15: Randall and his wife are standing next to each other. Randall's wife has shoulder-length hair covering most of her face.
*Panel 16: A line of six people, including Randall and his wife, stand and watch the solar eclipse.
*Panel 17: The sky has been brightened.
*Panel 18: Randall and his wife are walking together and holding hands.
*Panel 19: Still walking, Randall and his wife think together about a timeline. Seven years have passed since 2010, represented with a solid line from the past to 2017; seven years in the future will be 2024, represented with a dotted line into the future and surrounded by three question marks.
*Panel 20: The pair keeps walking.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[The first eight panels, used earlier in the comic 1141: Two Years, are in gray color.]

:[Randall and Randall's fiancée sit on a bed, Randall's fiancée is talking on the phone. The person she is talking to, a doctor holding a clipboard, is shown inset.]
:Randall's fiancée: Oh god.

:[Randall and Randall's fiancée sit together while Randall's fiancée, now bald, is receiving chemotherapy. They are both on their laptops.]
:IV pump: ... Beeep ... Beeep ... Beeep ...

:[Randall and Randall's fiancée (who is wearing a knit cap) are paddling a kayak against a scenic mountain backdrop.]

:[Randall and Randall's fiancée sit at a table, staring at a cell phone. There is a clock on the wall. Her head is stubbly.]
:Randall's fiancée: How long can it take to read a scan!?

:[Randall and Randall's fiancée are back at the hospital again, Randall's fiancée receiving chemo. They are playing Scrabble.]
:Randall: "Zarg" isn't a word.
:Randall's fiancée: But ''caaaancer.''
:Randall: ...Ok, fine.

:[Randall and Randall's fiancée (wearing a knit cap) are listening to a Cueball-like friend. A large thought bubble is above their heads and it obscures the friends talk. The text below, split in three is the only part there can be no doubt about:]
:Friend: So next year you should come visit us up in the mounta
::a
::and
:Randall and Randall's fiancée (thinking): '''"Next year"'''

:[Randall and Randall's fiancée are getting married, with a heart above their heads. Randall's wife's hair is growing back.]

:[Randall and Randall's wife (wearing a knit cap) stand on a beach, watching a whale jump out of water. This is the last gray panel, with an additional label in normal black color.]
:''Fwoosh''
:Label: Two years

:[Randall and Randall's wife (with her hair noticably longer) are walking through a forest.]

:[Randall's wife is sitting down, not in the forest anymore.]
:Randall's wife: My toe hurts and I found a report of a case in which toe pain was an early sign of cancer spreading.
:Randall: Wait—didn’t you stub your toe yesterday?
:Randall's wife: Yes, but what if this is unrelated?

:[Randall and his wife are going spelunking. The guide is gesturing deeper into the cave while Randall and his wife are climbing down.]

:[Randall's wife stands on a rock above an alligator in a swamp, photographing the alligator. Randall is on a balcony behind safety railings.]
:Randall: When they estimated your survival odds, I think they made some optimistic assumptions about your hobbies.

:[Randall's wife sits on an examination bed, listening to a doctor holding a clipboard.]
:Doctor: This is probably nothing.
:Doctor: But given your history, we should do a full scan.
:Doctor: We'll call with the results in a few days. Try not to worry about it until then!

:[Randall and his wife stand above a deep pond full of fish and other objects. Randall's wife is piloting a wired underwater camera with lights.]

:[Randall and his wife are standing next to each other. Randall's wife has shoulder-length hair covering most of her face.]
:Randall's wife: Hard to believe—six years ago, I was bald. But today, after a long struggle, I finally look like the little girl from ''The Ring''.
:Randall: That's, uhh... good?
:Randall's wife: ''Hissssss''

:[A line of six people, including Randall and his wife, stand and watch the solar eclipse.]

:[The sky has been brightened.]
:Figure with blonde hair: ''Wow.''
:Randall's wife: Yeah.

:[Randall and his wife are walking together and holding hands.]
:Randall's wife: That was incredible.
:Randall's wife: When's the next one?
:Randall: In seven years.
:Randall: Wanna go see it?

:[Still walking, Randall and his wife think together about a timeline. Seven years have passed since 2010, represented with a solid line from the past to 2017; seven years in the future will be 2024, represented with a dotted line into the future and surrounded by three question marks.]

:[The pair keeps walking.]
:Randall's wife: Yeah.
:Randall's wife: I'll do my best.
:Randall: It's a date!

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Hairy]]
[[Category:Multiple Cueballs]]
[[Category:Comics featuring Randall Munroe]]
[[Category:Comics featuring real people]]
[[Category:Cancer]]
[[Category:Romance]]
[[Category:Total Solar Eclipse 2017]]