A different approach at convincing someone why 0.9 repeating is equal to 1

For some reason some people have an extremely difficult time accepting that 0.9 repeating is equal to 1. Not that it merely "approaches" 1, but that it's exactly equal to 1. They are just two different ways to write down the same value.

Some people are so incredibly obsessed with trying to prove that they are not equal that they will go to incredible lengths to try to do so. They will start arguing semantics, they will try to muddle the definition of an infinitely repeating decimal, and some may even attempt to invent completely new mathematics in order to somehow make the two things not equal. They are so obsessed with this that there's absolutely nothing you can tell them that would convince them otherwise. Nothing. You can try, but you will fail.

Regardless, even if it's rather moot (and will never, ever convince these people), here are two slightly different approaches at showing the equality of the two things. Instead of trying to prove it yourself, try to make them do the work.

Approach 1: Repeating decimal patterns as a fraction

It's a well-known result that every real number which decimal representation has an infinitely repeating pattern starting at some point after the decimal point is a rational number, and this is actually relatively easy to prove. And, in fact, this is a (well-known) one-to-one relationship: In other words, if the decimal representation of a number has an infinitely repeating pattern after the decimal point (not necessarily starting immediately after the decimal point, but from some point forward after that), it is a rational number, and if it doesn't have such a pattern, it's an irrational number.

This can be more succinctly (and mathematically) expressed as: A real number is rational if and only if its decimal expansion is eventually periodic.

And since such a value is a rational number, it can be written as a fraction, ie. the ratio between two integers. And, indeed, all values whose decimal representation has an infinitely repeating pattern starting at some point after the decimal point can be written as a ratio of two integers, ie. a fraction.

As an example 0.4 repeating is a rational number and can be written as 4/9.

Since this is a proven mathematical fact (and it's actually relatively easy to prove yourself), that means that 0.9 repeating is also a rational number which can be written as a fraction, ie. the ratio between two integers.

So the question is: Given that proven mathematical fact, find out what those two integers are. In other words, what is the fraction that gives 0.9 repeating.

If you want to present the argument to someone succinctly, it could be something like this:

"It's a known result that a real number is rational if and only if its decimal expansion is eventually periodic. This is easy to prove. That means that 0.9 repeating is a rational number. This also means that, as a rational number, it can be written as the ratio of two integers. Calculate what those two integers are."

Approach 2: Calculate the difference

If two values are equal, then their difference, ie. one subtracted from the other, is 0, pretty much by definition.

If two values are not equal, then their subtraction will differ from 0, again pretty much by definition.

Thus, if the real number 1 is different from the real number 0.9 repeating, calculate their difference, ie. the result of their subtraction. If they are indeed not equal, then the result has to be a real number that's different from 0. What is that real number?

(Note: There is no such a thing as "the smallest real number larger than zero". Such a thing does not exist, and it's logically and mathematically impossible to exist, especially in the set of real numbers. This is a quite famous and extremely trivially provable fact of arithmetic.)

This could be succinctly presented as:

"By axiomatic definition, if two real numbers are equal, their subtraction results in 0. Conversely, if two real numbers are not equal, their subtraction results in a non-zero real number. Calculate the subtraction of 1 and 0.9 repeating."

Why is the triple-slit experiment so uninteresting to scientists?

Some time in the early 2000's I read an article about how a laboratory had conducted a three-slit version of the famous double-slit experiment for the first time in literally 200 years that the double-slit experiment was a thing that physicists were interested in. The experiment appeared to confirm the predictions.

Even then, the experiment was flawed: It turned out that one of the slits didn't close completely, and left a tiny gap even when it was supposed to be closed. But instead of fixing the mechanical issue and redoing the experiment, they just mathematically compensated for the flaw.

For reasons that were never explained in the article.

All of the above is completely incomprehensible to me.

The double-slit experiment is one of the most famous experiments in quantum mechanics, and in fact in the entirety physics. It's one of the most studied and researched experiments in human history. Thousands and thousands of research papers have been written about it, and it's one of the most fundamental experiments that underline the entirety of quantum mechanics and particle physics, and has immensely profound implications to our understanding of the universe. It's an experiment that has been repeated probably hundreds of thousands if not millions times over the last 200 years. Expensive high-tech labs conduct the experiment, physicists conduct the experiment, physics students conduct the experiment, probably by the thousands every single day.

The double-slit experiment is probably one of the single experiments that has received most work and research in the entire history of humanity.

Thus, one would think that the triple-slit version of the experiment would be of similar interest to physicists.

But astonishing that doesn't appear to be so. It took a whopping 200 years before someone did the experiment in a laboratory setting. And this even though the technology to do so has existed for something like a hundred years. It took 200 years for anybody to do the experiment and publish a paper about it. The article quite specifically mentioned that this was the first time that anybody had done so.

And even then, the experiment was flawed, but apparently the authors were so uninterested in the entire thing that they couldn't even be bothered to fix the flaw and run the experiment again. That's how utterly unimportant they seemed to think it was.

On top of that, this paper in question, as well as the article talking about it, was not considered any sort of landmark experiment worthy of notoriety. The paper (and article) in question appears to be so non-notorious, so forgotten, that I can't even find it anymore, no matter how much googling I do. From all I have found, it appears to have completely disappeared from the internet.

I cannot even begin to comprehend this. This complete and utter lack of any interest in the triple-slit experiment, considering how fundamental and ground-breaking the double-slit version is. It just doesn't make any sense.

The vast majority of black holes do NOT have an accretion disc

The video game Elite: Dangerous depicts the Milky Way galaxy, including the numerous black holes that are known to exist there. If you go to such a black hole, it will be essentially invisible, the only way that it exhibits itself is by how it distorts the background (ie. gravitational lensing.)

Many people believe this to be unrealistic because they have this misconception, no doubt spread most prominently by movies like Interstellar, that all black holes have a very prominent bright accretion disc around them. In fact, when mentioning black holes, most people probably envision the image of the black hole in Interstellar in their minds.

In fact, there are some YouTube videos that take footage from Elite: Dangerous depicting a black hole and adding an accretion disc in post-processing, and the comment section of such videos will invariably be full of people commenting on how much more realistic it looks and wishing that the game implemented that kind of visuals.

The problem? The way that the game depicts stellar-mass black holes is actually realistic!

The fact is that stellar-mass black holes do not have any sort of visible accretion disc. They are too small for that. They are, indeed, pretty much like the game depicts them: Completely invisible, them being "visible" only in how they distort the background. There's nothing visible orbiting them.

If a stellar-mass black hole has a very closeby normal star, gas from the star may be falling into the black hole in a spiral pattern forming a sort of accretion disc, but even then it would be extremely faint, probably too faint to be seen by eye.

Only supermassive black holes in the centers of galaxies (and a few other places) may have a prominent visible accretion disc. And even with those it's theorized that not all of them might have one (for example, it's currently unknown if Sagittarius A*, the supermassive black hole in the center of our Milky Way galaxy, has a visible accretion disc. It's not a given that it has one.)

In other words, the depiction of the black hole in the movie Interstellar is not unrealistic either, but that's because it's a supermassive black hole, not a stellar-mass one.

Why are there so many underground bunkers nobody knows anything about?

There are countless stories and accounts of people wandering in some forest and randomly encountering some, often quite unassuming and inconspicuous, small concrete structure with a door or entrance, and if they get inside they often find some kind of long-abandoned bunker complex (sometimes relatively small, sometimes surprisingly huge). In the era of YouTube videos about these have become more and more abundant, with people finding and exploring these bunkers.

Almost invariably these bunkers have been completely cleared out and abandoned for many decades. Very rarely is there any furniture or machinery inside, with perhaps the exception of some decrepit tables, chairs, and so on.

What are these bunkers, and why are they completely unmarked, and why doesn't anybody know anything about them, before they are found?

The answer is in a way a bit boring, but also in other ways interesting.

It shouldn't be very surprising that these are military bunkers from the second World War and the subsequent Cold War era. For several decades after Word War II there was a real imminent threat and fear of a nuclear war or, at a minimum, some kind of invasion and war similar to and even worse than those.

The military forces in many countries, especially in the United States, in Europe and in the entirety of the Soviet Union, but also many other countries, prepared for such a nuclear war by building underground military bunkers at strategic locations, spread all through the country (so that nuclear blasts would only cripple a minimal part of the military forces).

The Soviet Union in particular, as well as some European countries, really loved to build these underground bunkers, for all kinds of purposes, which is why they are so common all around in former Soviet countries. These were not merely just underground command centers, but all kinds of bunkers were built for all sorts of purposes, such as storage of supplies and ammunition, shelter for troops and, most dangerously, nuclear waste storage (as nuclear research and nuclear power plants were extremely common in the Soviet Union, and all that waste material had to go somewhere.)

The interesting question is why there are so many bunkers (probably thousands of them) that have been completely abandoned and forgotten? Indeed, a good majority of these bunkers are completely unknown to authorities, and they have no idea that they are there, until someone randomly finds one. One would think that the government would know the location of all these bunkers, but they don't. It may seem unfathomable how the military can build a huge bunker, and then just forget about it so fundamentally that nobody even knows where the majority of these bunkers even are.

However, it's not that strange.

Most of these bunkers were built in high secrecy, for rather obvious reasons. The less likely that foreign enemies knew about the location and nature of these bunkers, the better. The construction and details of these bunkers were of course documented, so that they could be strategically used, but these documents were usually highly classified, and only a very limited amount of people had access to them.

Once a bunker was abandoned because there was no need for it anymore, the documents were sealed and archived in some secret archives somewhere, along thousands and thousands, tens of thousands, of other documents. Pretty much effectively all information about the bunker was buried where nobody would find it anymore.

How about the people who were in those bunkers? Rather obviously they were also bound to secrecy, and most of them wouldn't even remember the location and details of some random bunker somewhere in the middle of nowhere after twenty, thirty, fifty years. The people who built the bunker and those who were most intimately knowledgeable of it got old, they retired, they died. Only very few people alive today were connected to the construction and running of that random bunker in the middle of nowhere. And most of those few people wouldn't even remember where it was, even if they wanted to tell about it.

Thus, we have ended up in a world that has thousands and thousands of fortified underground abandoned military bunkers who nobody knows anything about, and any documentation about them is either deeply buried in some secret archive (alongside tens of thousands of other documents) or even completely destroyed (as many of these documents have been destroyed by the passage of time or even fires, water damage, mold, etc.)

It's likely that there are thousands of such bunkers out there that are still to be found, and literally nobody has visited in something like 50 years.

The morality of killing bad guys vs good guys in video games

Back in the day, quite a long time ago, I was playing the original Fable: The Lost Chapters game. Unlike most other RPG-like games, it has side quests that can be considered "good" and others that can be considered "evil" (and which affect your morality stats in the game). A good quest is for example helping someone, while an evil quest involves for example stealing something or, in the absolute worst cases, massacring an entire village of innocent people who have done nothing wrong.

One of the problems with the design of the game is that the quest list didn't really make it crystal-clear which side quests are of the "good" kind and which are of the "evil" kind. So at one point I accidentally accepted an evil side quest without realizing that it was such. And it wasn't just an innocent "steal candy from a baby" type of evil, but literally a "massacre an entire village of innocent people" mission.

Well, no big deal, just cancel the quest? Turns out that once you have accepted a quest you can never get rid of it. At least in the original game there literally is no way of getting rid of a quest that you have accepted. Nothing. The only way is to load a save that you had made before accepting the quest. The problem? I had since long overwritten that save, and didn't have one. The only way around this would have been to start a completely new game.

Well, what's the problem? Just ignore the quest and never do it.

Problem was: The village in question connected two areas of the game, and there was no way around it in order to get to the other area, and traversing between the two areas was mandatory to advance in the game. And the kicker? Once you entered the village in question, the quest would start, and there's no way of just ignoring it. You literally cannot leave the village without completing the quest! The game just tells you that you can't leave because you have an unfinished quest there! You are stuck! The only way to get "unstuck" is to load a save from before you entered the village, but that just puts you back there.

Yes, the game was literally designed (I don't know if deliberately or just because of lack of thought) so that if you had accepted a quest that involved doing something in such a village, you literally could not traverse through the village without doing the quest. The "optional" side quest becomes a mandatory quest, if you want to advance in the game.

And to put even more salt to the wounds, if you actually started killing people in the village, they would cry and ask you in desperation why you are doing that.

This game design was completely asinine: If you accidentally accepted a particular side quest that was this morally evil and bankrupt, it had the side effect of indirectly becoming a mandatory quest because you couldn't bypass it and thus you couldn't advance in the game without completing it, and there literally is no way to cancel or ignore the quest, once accepted. And to punish you even more, you have to witness the suffering of the innocent NPCs in order to complete the quest, and there's no way around it. And the thing is that the quest descriptions don't always make it clear if it's this kind of evil quest or not.

But this has got me thinking many times: Why do I have a problem in killing certain fictitious non-playable characters that are nothing but pixels on a screen (and thus they don't exist as real sentient feeling beings), while I have zero qualms about killing certain other non-playable characters (in some games even quite brutally so)?

From an ethical point of view, at least one line can be drawn: If the NPCs are trying to kill me, then it becomes morally justifiable to engage in self-defense. Likewise if the NPCs are threatening other innocent NPCs it's morally justifiable to stop them from doing so.

However, that's not all possible situations that can happen in such games. Sometimes, for example, you may approach an "enemy" NPC from behind, without him noticing, and killing him by shooting or stabbing him in the back, without even knowing if he was going to attack you or not.

Most games make it relatively clear whether such an NPC would attack you for sure if he sees you by, for example, establishing that NPCs wearing certain unforms or certain clothes will always automatically attack you, without exception. Likewise a common game design is that all NPCs within a certain clearly delimited area will always attack you without exceptions (while NPCs outside of that area will not). Thus, it makes it morally easier to kill them before they see you, because you know that they would attack you anyway, so you don't have to actually test and make sure that's actually the case.

In a few games it may be less established. Sometimes it may be harder to distinguish between NPCs that are "enemies" and will automatically attack you, and those who are not. In fact, when this is sometimes the case in some rare games, I myself usually do hesitate before going into a killing spree and usually prefer to wait to see if the NPC will attack me before I respond in kind.

But it's an interesting psychological question what makes many/most people behave like this. These people know perfectly well that these are just some pixels lighting up on a screen, depicting completely fictitious non-existing non-sentient non-feeling imaginary beings, and it makes literally no difference to anything whether you simulate "killing" them or not. Yet these people, including me, still hesitate killing "innocent" people, even if they are completely fictitious and simulated.

I think that there's more to this than just weird psychology in play. Regardless of whether these people are fictitious or not, it can erode one's principles, morality and sense of psychological well-being to act in a manner that goes contrary to one's moral and ethical values. It can feel bad, even knowing that no real being was hurt in doing so. In fact, it's not true that no real being was hurt: There was one real being who was slightly hurt by these evil acts: You yourself. Doing bad things to innocent people can feel bad, and that hurts. It obviously doesn't hurt even nearly as much as if you were to do it to a real person, but a hurt is a hurt nevertheless, big or small.

Maintaining your moral principles even in a completely simulated fictitious setting can also work as a safeguard against you losing or eroding those moral principles. Who knows what will happen to your moral principles in real life, if you slip up on them in these video games? Will you become more and more desensitized to evil acts over time, slowly but surely, if you just keep doing these simulated evil acts yourself? It's not completely impossible. Even if simulated, doing evil acts can have negative psychological consequences, like so many other things may.

Why did Nikhil Kamath cheat against Anand in a chess charity event?

In June of 2021 the biggest online chess website, chess.com, organized a live simultaneous exhibition charity event. One of the strongest players in the world, a former world champion and (at the time) the strongest player in India, Viswanathan Anand, played a simultaneous match against several high-profile celebrities and other people.

One of these people was Nikhil Kamath, a compatriot of Anand, and one of the richest people in India. He is not a very strong chess player, quite a beginner in fact. Thus, it immediately rose everybody's eyebrows when he easily beat Anand in their match, his level of play being absolutely beyond anything that a beginner player could ever manage to do. It was immediately apparent that he had used a chess engine to cheat in the match (and further analysis of the game confirmed what was already immediately obvious.) He himself quickly confessed to doing so.

This, quite naturally, caused huge controversy, as not only is cheating in chess in this manner extremely frowned upon, but on top of that he did so in a charity event, and against one of the strongest and highest-profile players in the world, a former world champion.

But why? Why would someone cheat like this, especially in such a high-profile event like this, against such a high-profile player? What was going through his head?

Rather obviously I cannot read minds and thus there's no way for me to know for certain what he was thinking, but this is what I'm hypothesizing:

People who are not familiar with chess and chess tournaments, who might have never played the game or have only played extremely little, and have no experience at all on tournaments and online play, often do not understand how serious of a thing it is to use a chess engine to cheat in a game.

In fact, some time ago a friend of mine, when the topic of online chess came up, presented me with his novel idea and asked me if it would be possible to use a chess program to tell you what to play when playing online against someone. From his tone and how he explained his idea, it was very clear that he had absolutely no idea nor concept of how common cheating in this manner online is, and how frowned upon it is. He seemed to be genuinely and extremely naively asking this as if it had been a novel idea he came up with, and clearly had no idea how common it was, or what kind of repercussions it would have if done.

Of course I cannot possibly know for sure, but I have my suspicion that something similar happened with Mr Kamath: It may well be that, being a rather beginner player, he just didn't understand how serious it is to use a chess engine to cheat, especially against such a high-profile strong player as Anand.

Maybe he thought that it would be a fun little way to make things interesting. Like perhaps some kind of small little innocent prank. Wouldn't it be interesting and amusing if out of the blue one of players in the simultaneous match played very strongly and even beat the world champion? Now that would be something to tell stories about later! What a little innocent joke that he did, pranking the former world champion like that. Surely they would be laughing at it afterwards. And, on top of that, the game itself would probably turn out interesting!

He probably didn't know, and the idea didn't cross his mind, nor did he do any kind of research beforehand, about how huge of a faux pas this kind of cheating is, and how frowned upon it is, how disrespectful and inappropriate it is, especially in this kind of even against this kind of high-profile player. The enormous backlash after the game probably came as a surprise to him. It was probably something he didn't think about much before the event, and only later did he realize what a stupid mistake had made when the entire thing blew up in his face.

It's easy to say "he should have known, or even at least done a quick google search about the subject", but when you are not an aficionado of something, such things don't necessarily occur to you. It just doesn't cross your mind to check, or to think that hey, maybe I'm doing something that I shouldn't be doing.

The complicated nature of professional sumo wrestling

 

Sumo is the national sport of Japan. Despite what someone who has never really seen much of it and has very little knowledge about it might hastily think, it's a highly technical form of wrestling that requires enormous amounts of strength and highly polished technique. It doesn't matter how big, heavy and strong you are, if you don't have the technique you will be on the ground very quickly.

Professional sumo wrestlers in Japan, ie. rikishi, go through grueling training, usually 5 to 6 hours of hard training every single day, to build up strength, stamina and technique. All professional rikishi in Japan belong to an official sumo stable (a "sumo school" or "private sumo club" of sorts). Professional sumo is divided into six divisions, and all rikishi from division 6 to division 3 are mandated by their stable to live within the premises of the stable, where they get accommodation, food and a small allowance for daily expenses, and where they have to train every day, five to six hours a day minimum. It is, actually a very hard and grueling life. And it's pretty much their entire life, if they want to continue being professional sumo wrestlers.

The good

So why go through all this? What motivates people to enlist in these sumo stables?

For starters, sumo in Japan is extremely prestigious. Its history goes back literally centuries and it's extremely rich in culture, customs and traditions, both secular and practical, as well as religious (the entire sport being deeply rooted in Shintoism, and full of Shintoist beliefs, practices and traditions.)

All rikishi are considered celebrities of sorts in Japan. Obviously the higher-ranked you are, the more of a celebrity. There is great prestige in the job. Sumo tournaments are watched by thousands in the arena itself and millions through TV, and rikishi are admired and respected, and they often get all kinds of side gigs in all kinds of events.

Of course the job itself is a very stable form of livelihood: The professional rikishi are provided with accommodation and food at no expense of their own, plus a small allowance for daily expenses if in divisions 6-to-3. If a rikishi manages to climb to division 2 or better, it comes with a big amount of perks, including an actual sizeable salary and freedom to live wherever he wants (ie. he can either keep living at the stable, at no extra expense, or choose to move to live somewhere else, as long as he is available for daily training of course.) Needless to say, rikishi in division 2 and especially the highest division, division 1, are the most famous national celebrities and get the most admiration and most gigs.

This actually causes for bouts in divisions 3 and 2 to be extraordinarily fierce: Everybody in division 3 is trying to climb to division 2 and get all the perks that come with it, while everybody in division 2 is desperately trying to avoid dropping back to division 3. While quite obviously division 1 bouts are the most prestigious, it's the two next divisions that tend to have the most fierce, brutal and spectacular fights, with everybody desperately trying to avoid division 3.

There's also a strong sense of camaraderie within a stable: All the rikishi living in a stable have a strong common culture, and they usually are very close friends with each other, and have a lot of trust in each other, and everybody is there to support everybody else.

From the point of view of the wider public, rikishi are generally seen as "gentle giants" of sorts. While in the ring the fights can be absolutely brutal, outside the ring they are known for being very friendly, calm, polite, and role models to look up to, and they are often called to events, TV shows, schools, and other places, where they are usually treated like celebrities (especially if they are in the highest divisions.) In fact, rikishi are officially forbidden from participating in any fights or altercations outside the ring (such as for example a bar fight). Breaking this rule may result in sanctions and even expulsion.

The bad

Sumo wrestlers tend to be morbidly obese. It's not a requirement for them to gain weight, but you'll have a very hard time having any success if you don't, because the weight is an obvious advantage in wrestling. There have only been a handful of rikishi during the last 50 or so years that have weighed under 120 kg and have reached the salary divisions (ie. division 2 or 1.) It's not impossible, and there are examples (most notoriously Enhō Yūya, who is very short and weighed less than 100 kg when he reached division 1), but it requires extreme strength and skill to pull off, so much so that extremely few people have ever succeeded.

Even though rikishi tend to be very trained and very strong, morbid obesity tends to cause all kinds of problems regardless. No matter how well trained and how strong you are, no matter how strong your muscles and tendons are, the enormous weight puts a lot of strain on joints and ligaments. Not only do rikishi often have mobility problems (eg. good luck trying to run a 100m sprint, or even climbing a set of stairs), but injuries are extremely common.

Indeed, injuries are almost guaranteed in professional sumo. They almost come as an expected job hazard. Not only are the wrestlers severely overweight, putting extra strain on their joints and ligaments, and also making falls all the more dangerous (as bone fractures become more likely), but the wrestling itself tends to be extremely brutal, with very few restrictions on what can and cannot be done, which in itself increases the likelihood of injuries significantly.

If you watch any amount of professional Japanese sumo, you'll notice that at least half of the rikishi will be wearing some kind of bandages, supports and tapes, to either try to protect themselves from injury, or more commonly because of an injury that they are still recovering from.

In fact, by far the most common reason for a rikishi to fall to lower divisions is because of injuries. Professional tournaments do not give any concessions for injuries. If you don't participate, you lose by default, and thus can drop to a lower division if it happens enough times. There have been even cases of rikishi from division 1 dropping all the way to division 5 because of a severe enough injury that kept them from tournaments for a very long time. It's all an uphill battle from there (especially if the injury is of the sort that never really heals fully.)

Dropping from division 2 to division 3 is a major blow to the life of a wrestler. He will be once again obligated to move to live in the stable (if he was living in his own home), and he will not receive a salary anymore, instead just getting the small allowance. There's also numerous other perks of divisions 2 and 1 that are not given to the lower divisions, and thus lost if dropping to division 3 or lower. If a rikishi refuses to move to the stable, it may result in sanctions and even expulsion, ending his career, and potentially causing public shame. Many a rikishi in the two highest divisions has retired early because of injuries, before he drops to the lower divisions. After all, it's better to end in a high than either suffer the loss of perks or reputation by being expelled because of not complying with the rules.

The ugly

One thing I have not mentioned about the limitations of divisions 3-6 and the perks of divisions 1 and 2: That of marriage.

You see, rikishi in divisions 3-6 are not only obligated to live in the premises of the stable, but they are forbidden from getting married, or having any romantic relationships of the sort. One of the huge perks of getting to division 2 is that this restriction is dropped, and the rikishi is freely allowed to marry and move to his own home.

However, if he does that, dropping back to division 3 is even more of a huge blow: While such a rikishi is allowed to remain married (even the stables aren't that cruel), he will essentially stop being able to provide for his family because his salary will stop, and the small allowance of division 3 is not even close to enough. This can cause huge problems for that family, especially in Japan. And, indeed, early retirements due to injuries that put the wrestler in danger of dropping to division 3 are most common when said wrestler is married.

There's also an unhealthy attitude towards injuries. For the longest time, and to a large extent even to this day, if a rikishi gets injured on the ring, especially if it's during a tournament, he is supposed to just "toughen up" and walk out on his own, regardless of how bad the injury is. For the longest time there wasn't even any medical staff present in the vicinity to help him. This no doubt has worsened the severity of injuries many, many times. Only very recently (less than 10 years go) were the rules changed so that medical personnel are present at the events and a wrestler could be carried out in a wheelchair or stretcher if he was unable to walk, or even get direct medical help right there besides the ring if the injury is extreme.

But that's not even the ugliest part of professional sumo culture.

You see, even though there's a strong sense of camaraderie among the members of a sumo stable, there's still likewise a very strong pecking order: Those in higher divisions have more perks than those in lower divisions, and the former can often boss the latter around as they wish. There are all kinds of daily chores and tasks that need to be done in the premises of a stable, and the more disgusting chores (such as cleaning an outhouse) are rather obviously given to the members of the lowest divisions. In fact, part of the in-stable sumo culture is a form of hazing and bullying (the extents of which depends highly in the particular stable and its internal culture.) The members of the highest divisions may come up with disgusting tasks for the members of the lowest divisions just for the sake of it. This is generally considered part of the training itself, a form of "toughening up" the newcomers, and also a sort of perk for raising up in the ranks. Some of the hazing stories at the worst stables are just horrendous.