Failin.gs - <AUTHOR> http://failin.gs/

<comment><USER2> Many peoples' personal weakpoint: Listening too much to what other people think about them.

This website has all the attributes to become a viral Facebook/Twitter hit, and it's clearly been designed to achieve this.

But why not give it a miss, and focus on what you're doing in your life instead of on what other people think of you. Especially when they don't even have the courage to say it to your face.

<comment><USER3> Well, sometimes there is something that only other people can see. I think there are some opinions about my traits that I happily ignore, I know what's best for me, but certain things about me bother _me_ , not just others. Particularly, being somewhat anxiety prone, things like, "am I worrying about this too much or not enough?".

I'm actually quite glad this is up, I'd considered that something like it would be useful.

EDIT: Oh wait I got it all wrong. This is asking your friends for anonymous feedback? Yikes, no, I don't want to hear what they have to say. I thought this was an anonymous Q/A thing. Like Vark for personality flaws.

<comment><USER4> There is a saying that every man is a coin viewed from a fixed position. The face of himself that he sees no one else can see, likewise, he sees the face of everyone else that they cannot see. And thus, no man knows another as that other believes himself to be.

</comment></comment></comment><comment><USER5> In the old days of LiveJournal (decade ago) there was some brutal honesty meme which was supposed to be 100% anonymous. I made like 50 (exaggeration) different surveys and then made 50 different "private" posts of the link to each individual friend. Of course to everyone it looked just like a friends- only link and they assumed everybody was going to the same anonymous /aggregated survey.

I told them all pretty quickly afterwards about my silliness and put only mildly incriminating questions in the survey, just enough to make them worry about the other memes they'd been filling out.

Of course I also confirmed that one friend was head over heels in love with me. I so happen to be married to that darling girl nowadays.

Moral: If you're filling these out, don't assume it's 100% anonymous to the person you're writing about. They could be sneaky.

<comment><USER6> No sneakiness here! While we track visitors and users in order to look out for abuse, this data is not and will not be made available to profile users.

<comment><USER5> I think you misunderstood the exploit for identifying the anonymous comments. It works with pretty much any survey where you can individualize communications:

I create 20 accounts on your service. I put my picture on all of them. I send out a different link/profile to each one of my 20 friends and track which one went to which person.

I then compare notes to see who said what.

Note that it's also really easy to do this using a URL shortener service that keeps track of times clicked, user agents, referrers, and IP addresses:

<http://➨.ws/anonymous_survey>

By using the timestamps you provide for the comments, I can tell which of my friends most likely made each comment.

</comment></comment></comment><comment><USER7> This reminds me of the old Calvin & Hobbes strip where Calvin is selling "a swift kick in the butt" for $1.00. Business is slow and Calvin says, "I don't understand it, everybody I know needs what I'm selling!"

<comment><USER8> Good call - <http://bit.ly/9BYtb9>

</comment></comment><comment><USER6> I helped co-create this site and was surprised to find it linked here. It started as a fun project with a friend: a humorous idea that, as the attention it's gotten has shown, is apparently controversial, as well.

I have to say, though, that what's surprised me most about its reception is that anonymity doesn't make users as vicious as many might think. I've been pleased with how many "failings" posted are sweet compliments; playful inside jokes; and well-worded, well-meaning suggestions.

If anyone would like to try it out, I've made a promo code, "HACKERNEWS". We'd love any suggestions and/or feedback.

<comment><USER9> I got an invite today. At first I thought "Oh crap, someone has something they want to post about me!!!"

Then I remembered I requested an account last week :)

That initial invitation email kinda weirded me out. However, as someone who has had a blog for going on 9 years, this is an interesting new way to play with personal transparency.

Feel free to tell me I suck at leaving comments on HN, just post it here: <http://failin.gs/profile/jaxn>

<comment><USER6> Thanks for joining! Please let us know what you think after using it a little while. We'll leave you a note for your profile if we don't hear from you ;)

</comment></comment></comment><comment><USER10> I love the idea. It's very good for people who can take criticism. It's up to you after all which criticism to ignore and which to take seriously. It should be made easier for other to post opinions about you by integrating this into some famous application (e.g. facebook app, blog widget, etc).

<comment><USER6> There's JavaScript embed code for blogs, and links for tweeting and posting to Facebook, but we agree, and we'll be working (as we find time) on better integration with other services.

</comment></comment><comment><USER11> Possibly the unhealthy thing about this is the anonymity, and it might not be very successful either, because of human nature.

I think most people are subject to being categorised one of two ways.

CATEGORY 1 (Confident Achievers): Largely oblivious to their own flaws (This won't easily help them because they'll challenge the answers). If the truth does break in it can be very painful for this type of person.

CATEGORY 2 (Reflective Thinkers): All too aware of their own flaws (And this won't help them; it will only make them feel more insecure).

I'd have to admit to being in the second category, and wouldn't for a second believe it's superior to the first (just different).

Which category are you, or are there more categories?

</comment><comment><USER12> I remember how reading that Facebook was engineered to give you the most positive experience. This feels like the total opposite sort of thing.

I don't think it will be a huge success, though, because as much people say that they want constructive criticism, what they really want to hear is how great they are. Going to this site would just be disappointing and frustrating for most people.

<comment><USER6> My friend (and the co-creator of the site) likes to point out that Facebook, Twitter, et al., are ego-strokers, and he wanted to make an ego-buster.

I don't think either of us expected it to become as successful as it has already. It's all just been a bonus.

</comment></comment><comment><USER13> Formspring, but in a different context. And that's no bad thing.

(See also: [http://jonathandeamer.com/2009/08/19/daily-booth-4chan- impor...](http://jonathandeamer.com/2009/08/19/daily-booth-4chan-importance- context-restrictions/))

</comment><comment><USER14> This seems like it would be an all too entirely unpleasant experience. :( The thing is, the way I see it, for me, the friends whose opinions I really trust and value are the same friends who are going to straight-up tell me to my face if I have some flaw that needs addressing, whether I want to hear it or not, because they have my best interests at heart. As for everyone else's opinions, or the nit-picky little things that we all tend to overlook in each other, anyway, then I just don't see those as needing to be brought to the surface, because it serves no good.

<comment><USER6> > the friends whose opinions I really trust and value are the same friends who > are going to straight-up tell me to my face if I have some flaw that needs > addressing, whether I want to hear it or not

This has been one of the biggest "why?"s we've gotten. I don't think it's that simple, though. Telling a person their flaws requires timing, braveness, and an open mind on the part of the listener.

In an ideal world, people would be receptive to honest criticism, and people would be honest in what they feel is worth criticizing.

The site, though, provides a platform where the profile user is requesting feedback that a good friend may not have thought worth bringing up, had never had the right moment to bring up, or may have been afraid to bring up and hurt the person's feelings (and their friendship). When the platform is there, it's easier to break the ice.

</comment></comment><comment><USER15> this site straight up weirds me out... that's all i got

<comment><USER16> Agreed. It's strange to try to put a positive spin on everyone's shortcomings.

<comment><USER6> Well, it's certainly not for everyone, but shortcomings are only shortcomings as long as you agree with them and don't care to work on them.

</comment></comment></comment><comment><USER17> Signed up to have a play around, and was happy because for once I managed to get the "dan" username. Hooray!

Then I realized my profile was at failin.gs/profile/dan. And they automatically picked up my gravatar. Yikes.

Deleted the account and rejoined with something more obscure....

<comment><USER18> Your gravatar is tied to your email address.

</comment></comment><comment><USER19> Well, I guess it's official, people have lost the capacity for introspection.

<comment><USER6> Not a substitute, but a complement.

</comment></comment><comment><USER20> Great idea. I think I'm still too self-absorbed to actively ask for critiques on my personal character though. Maybe I'll be mature (brave) enough to do this in a couple more years.

<comment><USER21> But this is perfect for the self-absorbed! It gets everyone thinking and talking about you and your imperfections.

</comment></comment><comment><USER8> What's stopping a person from creating a profile for someone (maybe someone who's "unpopular")??

Seems like it could devolve into juicycampus.com for... everyone.

<comment><USER6> This is definitely a concern. We're working on a lot of anti-abuse features that will roll out, though, before it leaves private beta.

</comment></comment><comment><USER22> Small bug, times appear in GMT, not my local TZ...

<comment><USER6> Haven't had time to finish the JavaScript component to this. Working on it!

</comment></comment><comment><USER23> Sounds like a personal single-purpose version of Rypple (<http://rypple.com/>)

</comment><comment><USER24> A startup that tried something like this: <http://hikkup.com/>

</comment><comment><USER25> I think I'll recognize all of my friends with their writing styles and ideas...

</comment><comment><USER26> Post up your worst enemies.

</comment><comment><USER27> love to try this. codes?

<comment><USER6> Try "HACKERNEWS".

</comment></comment><comment><USER28> This place is turning into Digg.</comment>


Are We Living in a Computer Simulation? - <AUTHOR> http://www.scientificamerican.com/article/are-we-living-in-a-computer-simulation/ <comment><USER3> I am definitely in the this idea is nuts camp. It's the equivalent of a couple of cell in Conway's game of life trying to figure out what computer architecture the program is running on, who build the computer and what our universe looks like. Arguments like simulating ancestors and whatnot implicitly assume that the computer owners are in some sense similar to us which seems totally unjustified, we have certainly simulate way more things that are different from us than similar to us. What justification do we have that concepts like space and time and simulating something and ancestors even make sense in the outer universe?

Or mathematics. Mathematics is of course good at describing our universe, we created it for that. Well, that is probably a bit too simplistic but anyway. And what would you expect the outer universe to be like? A structureless random mess without rules that could be described by mathematics? How would you make a simulation in such an environment? If you have some time to kill or want to write a science fiction novel, go ahead, think about it, but there are certainly more relevant problems to our existence than pondering whether we are one or a billion levels deep in a stack of simulations.

<comment><USER4> All of which is true. But I think there's a more subtle problem: if you could simulate evolving creatures in a universe, how could you tell if they were truly sentient?

Being sentient as an experience is completely different to appearing to show sentient behaviour. You can make a model of sentience that's as complicated as you can invent, and you'll still have no idea whether or not a modelled sentience is having a sentient experience of the universe around it, or whether it's faking its responses mechanically.

The corollary is that having a model isn't enough to simulate a universe, You also need some way of knowing when sentience has been achieved.

Nothing in our current technology is anywhere close to even beginning to understand how to do that.

<comment><USER5> > if you could simulate evolving creatures in a universe, how could you tell > if they were truly sentient?

I think that AlphaGo is sentient in the domain of Go play. In other words, AG was conscious in that space of table positions and game strategies. A number of Go experts were so impressed that they said they could hardly tell which is the human and which is the computer. They gained so much respect for it that they awarded it the highest dan rating. I'd award it a Turing Test pass, at least on Go play.

To answer your question, I'd take the same approach as Turing: if it behaves like a human or better, then it is conscious in that particular domain. The difference from common machine learning applications was reinforcement learning - the fact that it was embedded in an external world, interacted with it and the opposing player and learned from experience - it behaves essentially like us, in a loop of perception-decision-action. And we are like it, if you look down the stack, we too are just a pattern of chemical reactions and electric currents that have no innate subjective feeling to them. There is no "unobtainium" or "magic fairy consciousness dust" in our brains either, and we shouldn't try to essentialize consciousness, it is not a pure essence like space and energy, it's an emergent quality.

<comment><USER6> Great post. I just wanted to add that space and energy could very much be emergent phenomenon, as well. Take for example Wolfram's conjecture that the universe might be modeled as a causal network [1], in which our 4D spacetime emerges from the connections between nodes, and energy/particles emerge from the complicated dances of knots in the network. It might sound pretty far fetched, but it seems to me at least as reasonable as the universe being modeled by a small set of equations.

[1] [http://blog.stephenwolfram.com/2015/12/what-is-spacetime- rea...](http://blog.stephenwolfram.com/2015/12/what-is-spacetime-really/)

</comment></comment></comment></comment><comment><USER7> I love contemplating this idea, but really hate when people write about it. They always talk about "The Matrix" or being "Video Game Characters", which really muddies the water. Of course a lot of people will reject the idea when presented like this. The Matrix, for one, is real humans in a real universe being plugged into the simulation of the real universe, which seems absurd. The idea of being inside a video game detracts from people's inherent feeling of free will and self awareness, because it seems to imply they are either a pre-programmed NPC or a character being controlled by some consciousness outside of the simulation. I feel like this flawed first impression makes them less likely to entertain the idea.

At least the way I think about it, these analogies are neither accurate to the theory nor necessary to explain it to the layman. Let's look at it academically. If our technology had the capacity to completely simulate any sort of universe, you can bet a least one research team would do just that. Well, if you, like me and many others, think of the intelligent mind simply as a very powerful and self-aware computer capable of learning and abstract thought, and if the so-called universe simulated by researchers has a model of matter capable of creating the logical gates needed to replicate such a computer, and the simulated universe contains natural processes by which these logical gates might evolve, then you must agree that it is possible intelligent life may emerge in such a simulated universe -- no matter how different, similar, big, or small it is in comparison to our own. Then, following the same reasoning, you must also agree that there is the slightest possibility that the nested universe may produce one or multiple collections of intelligence capable of the same thing.

In this thought experiment, the simulation isn't imprisonment, doesn't violate a sense of self-awareness or free will, and doesn't even rule out the concept of a god or ultimate creator. It simply abstracts the container in which our universe lives from something mysterious to something relatively relatable to our current technology.

Another interesting thought is if we ever become capable of simulating such a universe, it seems much more likely than not we're also a simulation, since there's a possibility for each simulation to produce it's own simulation or collection of simulations.

<comment><USER8> > Another interesting thought is if we ever become capable of simulating such > a universe, it seems much more likely than not we're also a simulation, > since there's a possibility for each simulation to produce it's own > simulation or collection of simulations.

There's a lot of "ifs", though, for the argument to work:

The simulations must support a higher density of life than the universe does. If you need a planet the size of Jupiter and a hundred years to simulate one second of life on Earth, then each nested layer of simulation is going to make the number of simulated humans _smaller_. It seems highly dubious to me that simulations could be dense enough: if you can build a simulator capable of evolving a million life forms, couldn't you slash all the overhead of environmental simulation and use these same resources to build _ten_ million life forms that interface with the real world directly (imagine nano-life, if that helps)?

There must be sound economic reasons to build these simulations. Otherwise, too few of them will exist, and they will not be run for long enough. I can think of a few reasons, like research or entertainment, but I do not think they would suffice. Specialized, focused simulations are useful. Simulating whole universes is overkill. It's a waste of resources.

<comment><USER9> There is no reason to assume that the same physical rules and limitations of our own universe apply to the universe that is simulating us. Our universe could be a drastic simplification of the "real" one, indeed this simplification is the kind of potential evidence the article mentions us looking for.

I remember reading once that the limitation on speed of light could be a performance optimisation. Isolating each "light cone" of local spacetime allows the simulation to be distributed and run on separate compute clusters, because it limits things to local interactions rather than universal ones.

Things in superpositions only becoming "set" after observation... that is just lazy evaluation. It's fun to think about.

<comment><USER7> >I remember reading once that the limitation on speed of light could be a performance optimisation.

>Things in superpositions only becoming "set" after observation... that is just lazy evaluation.

I've always thought about it this way also, I'd love to get a source on where you read it so I can see a different take than my own.

Some other things to consider:

1\. Planck length is the most granular unit or pixel the computer can measure.

2\. The time it takes to move one Planck length at the speed of light is the time of one iteration of the simulation's "main loop".

3\. The reason time dilates as you approach the speed of light is because the faster a particle moves, the more the main loop must access that particle, and the more the particle's state may be in a "being processed" lock where it can't be mutated by anything else.

Just some thing I've always thought about when trying to see if I could use code patterns and processes to quantify the behavior of the universe. Of course, I wouldn't say I believe these things as fact or anything, just awesome to think about.

<comment><USER8> > The reason time dilates as you approach the speed of light is because the > faster a particle moves, the more the main loop must access that particle, > and the more the particle's state may be in a "being processed" lock where > it can't be mutated by anything else.

There's a simpler reason, I think. Any mechanism or "clock" must have moving parts of sorts (atoms, exchange particles like photons, etc.) which means that when functioning or "ticking", some parts move faster than some other parts. But if the mechanism is moving at the maximum speed, it can only be the case that some parts move at c, and others move slower, but these slower parts can never catch up, so the clock disintegrates. It can only remain whole if all parts move at maximum speed, which means it is static: it is frozen in time.

I imagine that given a speed distribution for all components of the mechanism, there would be a smooth time dilation effect as the speed of the whole mechanism increases. I'd have to calculate. In any case, I think time dilation is basically _necessary_ in a system with a maximum speed. I'd expect to see something similar in cellular automata, regarding complex objects that can move at various speeds.

</comment></comment></comment></comment></comment><comment><USER10> Doesn't look like they added anything to the debate to me. But given that it has been going on 2500+ years I suppose that is not surprising. :)

[https://en.wikipedia.org/wiki/Allegory_of_the_Cave](https://en.wikipedia.org/wiki/Allegory_of_the_Cave)

See also, [https://en.wikipedia.org/wiki/Brain_in_a_vat](https://en.wikipedia.org/wiki/Brain_in_a_vat)

<comment><USER11> There's certainly been something changed, if not added- the idea is slowly getting more pessimistic. Plato thought we could get out of the "cave" simply through sustained rational thought. Brains-in-vats thinkers at least said we were still true beings in the "real" world, even if deluded ones. But simulationists think we're _entirely_ beings of the "lower realm."

</comment></comment><comment><USER12> > "You're not going to get proof that we're not in a simulation, because any > evidence that we get could be simulated," Chalmers said.

This is where the argument starts to sound like creationist claims that god put the bones of dinosaurs on Earth just to test our faith.

<comment><USER13> As someone with a conservative upbringing, I can't say I've heard that argument. In my experience the most common explanation is that the dinosaurs died in Noah's flood along with the rest of the animals. The dinosaurs that survived on the ark were unable to adapt to the new environment and went extinct shortly after. While I don't doubt the "God put dinosaur bones here to test our faith" argument has been used by Christians, I can't imagine it's very prevalent.

<comment><USER14> I heard it as a mormon growing up.

<comment><USER15> I don't think I ever heard this growing up as a Mormon, at least not as something considered as a serious belief. My Aunt quipped once how silly it was that my Granpda (also a Mormon) believed that 'the Jews planted dinosaur bones to discredit Christianity' \- he's dead now and I don't know if he actually believed that, but it's possible that he did.

My experience growing up as a Mormon is that questions of how exactly God created the world are mostly left up to science. I haven't seen any hints of evolutionary science being considered 'taboo' with any seriousness in quite a long time.

</comment></comment></comment></comment><comment><USER16> It would have been interesting to hear Wolfram's take on the debate. The debate revolved around "why would future intelligent beings want to simulate lesser intelligent beings from the past?". But the broader picture is that given enough time, "intelligence", which really means "computation", is an emergent phenomena of the universe at large. Given enough time, the universe will simulate itself.

We perform computations in the same sense that complex weather patterns do - there's nothing intrinsically special about our ability to compute. So it's naive to think that we're the ones being simulated - the _universe_ may be simulated, and we are but one emergent property of that universe.

<comment><USER8> A universe can't really "simulate itself". There is inherent overhead to simulation, so a _perfect_ simulation of a physical system would have to be larger and slower than the system it's simulating.

Any simulation worth running would be an approximation of the real thing, with many corners cut. Because of butterfly effects, any approximative simulation will diverge from the original, and the more corners you cut, the faster that will happen (so ancestor simulations would require near perfect accuracy, so they would probably be prohibitively expensive).

If we are a simulation, our parent universe would be several orders of magnitude more complex than this one. It's not clear to me why such a simulation would be made (what purpose it would serve to the parent universe).

<comment><USER17> That's not necessarily true in discrete systems. For example we can cache results of common interactions for reuse. See HashLife and relatives, for example: a vastly more efficient way to compute game of Life without considering one cell at a time, but giving identical results.

<comment><USER8> I'm aware, but I think the efficiency of these methods is rather circumstantial: they work well because of the way our computers are organized. What you are comparing are two simulation methods, with are _both_ very far removed from what they simulate.

Instead, imagine implementing HashLife _inside_ a Game of Life universe. It is possible, because the system is Turing complete, but the overhead would be horrific: probably thousands of cells for each cell you try to simulate. You would have to duplicate the cache all over the place to minimize roundtrip costs, each cell would be a whole machinery to allow signals to be routed there, plus logic to handle synchronization issues between each "unit", and so on.

It's a very neat idea that works very well with our computer systems, but if you were to implement it using the resources of the simulated system, it would be a catastrophe. And similarly, I don't think you could build a physical "cache" that can simulate physical interactions faster than they happen, except in a few contrived cases.

</comment></comment></comment></comment><comment><USER11> > "What happens," Tyson said, "if there's a bug that crashes the entire > program?"

What if there's a bug in the simulation, and the whole computer goes up in flames- but then the experimenter restores from a backup, fixes the bug, and re-runs the simulation with the same random seed. Things proceed again exactly as before, and pass the bug-triggering point without incident. Do we notice anything happened?

<comment><USER18> Who (and where) is this experimenter? What if he (and his world) is also simulated?

What _is_ real?

<comment><USER19> >Who is this experimenter?

The Creator.

>Where is this experimenter?

Right here. Right now. Everywhere. All time. No time. Outside this Universe. Inside this Universe. We are inside of him. The universe is just a small part of him. He has no definable form. This Universe, and all these things that exist in the present moment, are part of his form. All things that have existed, and all things that will exist, that's just a small part of his form. Even things that don't exist are another small part of his form. Time is a restriction that he puts on this universe. Time is just another part of him, a part of him where he chose to limit and restrict himself to the rules of time that he himself made up. He has no restrictions, no limits.

>What if he (and his world) is also simulated?

He is already everything and nothing. Nothingness is already part of him. There's no world where he lives in, because that already is a part him. There is nothing beyond him. Because that nothingness beyond him, is also part of him. The things that exist are part of him. The things that don't exist are also part of him. He encomapss everything and nothing, all of infintity and all of the void, all of extistance and all of non-existance. All time and all space. No time and no space. All those things are just parts of him. He is sum the whole of all those finite, infinite, time, timeless, outside, inside, everywhere, nowhere. He is not limited in anyway. He is unlimited every everyway.

He is the most foundemental of all. Everything existed because he pretend that it does. Earth exist because he pretended that billions of years ago, star dust gather to form a planet called Earth. Earth goes around the sun because he pretend that Earth follows a rule he made up called Gravity.

When an object push another object, he:

1\. Pretend that there are two objects there. 2\. Pretend that one object is pushing on another object. 3\. Pretend that the other object have moved according to a made up rule that he made up: Newtown Force. 4\. Pretend that there's a scintist and pretend that the scientist "did" see and measured those object moved.

Most of all, he:

5\. Pretend that there's a guy here typing this out. 6\. Pretend that this guy typing this out have conscious and free will. In other word, I am just something he made up and pretend to exist. My free will is just him pretending I have free will. I am only typing this because he is pretending that I am. It is him who actually have free will. Free will and conciousness are fundenmental.

It's just like when you're a little kid, and you have a toy soldier, and you pretend that he's a Knight. You pretend that he as a sword and a shield. You pretend that there's a dragon and you pretend that the dragon is attacking a pretend village. Then you pretend that he fight and slayed the dragon with his pretend sword. And the pretend village made him into a pretend king.

Everything is just him pretending. Nothing really exist. He just acts like it exist. And everything have to act like everything exist. Just like the toy solder have to act like a dragon exist, because you act pretend that the dragon exist.

</comment></comment></comment><comment><USER20> Wouldn't it be amazing if some poor grad student in the future had to explain to his supervisor that his simulation of the past failed because the people in the simulation figured out that they were being simulated? That would cause so many moral issues: do you kill your experiment, or do you let it run until big freeze?

</comment><comment><USER21> I thought SMBC had a fun comic in response

[http://www.smbc-comics.com/index.php?id=3931](http://www.smbc- comics.com/index.php?id=3931)

<comment><USER22> I was anticipating this one: [http://www.smbc- comics.com/?id=2535](http://www.smbc-comics.com/?id=2535)

</comment></comment><comment><USER23> Whenever I see an article that has much lower upvotes than comments I wonder why HN doesn't just automatically upvote an article when someone makes an initial comment (if they haven't already upvoted the article).

If you are interested enough to post a comment then you probably should upvote the article, even if you don't agree with it. Why? Because it's likely generating a good and interesting discussion. This article is a great example of this phenomenon.

</comment><comment><USER24> Unlikely. The universe has too much gratuitous detail at the subatomic level. Nothing below the electron level is really necessary. At the macro scale, the universe is way too big and mostly empty. If this is a simulation, it's inefficient by tens of orders of magnitude.

If the simulation oversimplifies on the boring parts, we probably would have picked up on that by now. Although it does make you think about the Copenhagen Interpretation.

<comment><USER25> This is one of my favorite joke theories about relativity. More mass increases the complexity of the simulation, slowing down time.

<comment><USER26> One of my favorites is the speed of light is simply how fast information can be passed around processers in a distributed universe simulation.

</comment></comment></comment><comment><USER27> The premise is absurd if considered superficially and irrelevant if discussed in detail.

The further you pursue such possibilities, the less significant they become, because you reach the boundaries of human epistemology.

The difference between simulated and "real" reality is beyond the scope of the senses and deduction. We would have to be outside the world to know the truth, and this is of course impossible.

<comment><USER28> "epistemology" \-- every time I see this word (normally in @nntaleb's tweets) I look up google for meaning of this word, get a sense, and then soon forget :-)

</comment></comment><comment><USER29> > "What happens," Tyson said, "if there's a bug that crashes the entire > program?"

Why do we assume that it's written in C, as opposed to - say - Erlang? ;)

<comment><USER30> better than java , otherwise it would be realllly slow. C and Assembly is at least fast

<comment><USER29> I'd prefer slow to "in the best case, everything blows up at once - in the worst, there's a memory error that if exploited, turns your world into a dystopia".

<comment><USER31> "There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.

There is another theory which states that this has already happened."

\- Douglas Adams

</comment></comment></comment></comment><comment><USER32> The simulation hypothesis is, sadly, perhaps the only self-consistent solution to the Fermi Paradox, one that doesn't require very unlikely propositions.

[https://www.exratione.com/2015/05/the-cosmological- noocene/](https://www.exratione.com/2015/05/the-cosmological-noocene/)

All of the other suggestions require all intelligent life without any exceptions in our past light cone to behave in a consistent way, i.e. fail to build obvious megastructures, fail to come calling, etc, so as to leave everything with the appearance of being natural. The Fermi Paradox is more the Wilderness Paradox in nature. Given that a tiny faction within any sufficiently advanced civilization could on their own generate self-replicated probes that converts the observable universe to computronium, and that some portion of humanity will do that if not stopped, and that we appear in no way to have exceptional origins or be in an unusual region, that really suggests there is something fundamental that we don't yet understand.

<comment><USER33> Why simulate a very atypical world if the vast majority of intelligent-life developing worlds are much younger than ours?

</comment></comment><comment><USER34> For me it is clear that we will be doing our own simulations in the future. In short here's how I see our path in relationship with technology and it's rapid advancement:

human > transhuman > energy (in the grid): immortality at this stage > long period of answers about our universe, research and exploration > boredom > nostalgia > depression > take part in simulations where you dive in but to fully enjoy the "animalic" experience you have to forget who you were and start fresh. There are some experiences that only in relationship with death (and knowing that your existence is short) produce really positive effects. This story can get long and is filled with "ifs" but I don't dismiss the idea...at all.

</comment><comment><USER35> There is no such thing as a perfect computer that runs eternally or that can simulate something with an infinite degree of precision.

If we lived in a computer simulation, we would have noticed unusual meta- physical glitches as discrepancies within the 'order of things'.

For example, if the simulator used floating points, we would actually notice that numbers end up loosing precision after a certain amount of decimal points. We would probably have tons of theories about that and wonder why the metaphysical rules that are involved in counting suddenly change at specific precisions. etc.

no glitches = no simulation

There are many more problems with this premise but to me, these types of questions are a waste of intellectual energy so I'll leave it at that I guess, have fun.

<comment><USER36> But the simulation doesn't have to be perfect. It doesn't have to be complete. Maybe only you and your friends are actually being simulated, and everything else is just a partial stub. Maybe only the relevant parts are rendered.

I actually read Nick Bostrum's original paper and it's a pretty interesting read. Basically it looks at the long tail end of things. When you predict things waaay into the future, you tend to gain accuracy for macro predictions.

For example: our sun will most likely run out of energy and die out one day. The plate border in East Africa will most likely break apart at some point causing that continent to split.

The big one: humanity will one day go extinct. ... or...we'll expand to Mars and other parts of the solar system and thrive for millions of years. There are other options of course (we get blown back to the stone age, some humans survive and technology has to restart from a few thousand years ago...repeatedly...until we either leave this planet or go extinct).

If our machine understanding continues to grow, we should be able to eventually make machines that can simulate parts of the world we're in. So either we've already done that (some other we), and we (you and I we) are the products of their simulation ... or we'll go extinct one day.

...or simulating this world, perfectly or imperfectly, isn't possibly at all. ... and we'll go extinct one day.

<comment><USER28> >Maybe only you and your friends are actually being simulated

Why waste so much resources, when it can be just _You_ being simulated?

</comment></comment></comment><comment><USER37> You have to wonder about this. If it is a computer simulation then there is a God that is running the universe in a computer. Evolution is based on object oriented programming where one object inherits the class of the last object but modified in some way. Did God run Bingbang.exe or some other program to create the universe simulation. Then things all fell into place and sped up for God until life developed on one planet.

If it is a computer simulation it has more storage than any computer he have now because of all the galaxies of stars and their own solar systems to keep track of. Does life exist on some other planet? We don't know until we get better telescope technology to get a better look at planets.

I do think we live in a computer simulation because there are so many things in the universe that can kill us, yet we survive to an old age for most of us. That means there is some unknown force that prevents most of us from dying. Everything in the universe can be simulated using Math for the laws of physics and other sciences. Very much like a computer uses math for video game simulations.

It could be that we exist in this universe and our real bodies are in a different universe Matrix style and when we die we wake up in the other universe, and this universe is like training for the other universe that we can't see because all around us is this simulated universe.

</comment><comment><USER38> There is a rather interesting science fiction movie, called "The Thirteenth Floor", that explores this concept, in fact if I remember correctly it talks about nested simulated worlds.

This makes perfect sense to me, if the theory that we are living in a simulated universe is correct, the exact same logic would apply to the beings that are running the programs to simulate us and so on, ad infinitum.

<comment><USER39> There were a couple different movies that explored this theme around the time The Matrix came out. eXistenZ is another one that I enjoyed a lot, where video games become completely immersive, but there's still a few tropes like vapid NPCs and generic place names that kind of give it away.

<comment><USER40> There was a late night TV show. 80s Twilight Zone or something of similar vintage.

Height of the Cold War, on the brink of Nuclear War which after a series of cock-ups arrives and MAD results. Camera pulls back to reveal "Game Over", then further to show two alien teens at an arcade machine. A short exchange and another coin in the slot to start at pre-life. Show ends.

Was refreshingly well done.

</comment></comment></comment><comment><USER41> If we are simulated, it'd be interesting to know how optimized the simulation is.

Maybe the simulation is reminiscent of _The Matrix_ in that reality is essentially an elegant artificial abstraction that acts as glue tying together the perceptions of each simulation participant.

Perhaps a proper, low-level simulation isn't computationally prohibitive, but simulating the rest of our universe is. In that case, the cosmos itself may be an illusion despite an otherwise interference-free simulation.

Or, perhaps the entire cosmos is simulated just as we are—including the hundreds of billions of galaxies present in the observable universe. This would heavily imply that computational resources are not finite.

I'd argue that regardless of whether we're in a simulation or not, the sheer vastness of the observable universe heavily suggests that space may in fact be infinite—which by extension creates the potential for simulations to exist at grand—or even infinite—scales.

</comment><comment><USER42> If we were in a simulation and the simulation would fail to realize its purpose if a sufficiently large number of beings in the simulation became aware of the simulation and changed their behavior, how smart would it be to try to get more and more people interested in the issue and look for "smoking gun" evidence? ;=-)

<comment><USER43> That's the basic religion of Iain M Banks later culture novels.

<comment><USER44> iirc, 'Surface Detail' explored this in depth from one society's use of a 'virtual hell' afterlife to instill behavioral control in 'the real'. My favorite Culture character's view on the subject was expressed in 'Matter', the previous novel in the series, by ex SC agent Xide Hyrlis. In Hyrlis's view, the characters were experiencing the base level of reality based on an a moral argument because "... only reality produced ultimately by matter in the raw can be so unthinkingly cruel." and that to be otherwise "... god or programmer, the charge would be the same - that of near infinite sadistic cruelty."

</comment></comment></comment><comment><USER45> Our entire universe can be represented as a collection of bits of information. The real question is whether that information can be compressed or not. If it can be, that means you could store our universe digitally, if it can't, that means it has to exist in analog. If you can store it digitally, then it almost certainly is somewhere.

I remember reading about how NES and other cartridge game systems are harder to emulate than disc-based systems like the PSX. The reason is that cartridges are more than just flat data storage, they have chips and other electronics on them that screw with the emulation.

I'm inclined to believe (and I believe it's actually been proven) that quantum information is incompressible, that would make any algorithm that would simulate it to have the same time and space requirements as the physical system.

</comment><comment><USER46> I suspect that the proof against would be along the lines of:

'The theoretical minimum computer for simulating any 1 particle at realtime is at least X particles big. If it would be 1 particle it would not be a simulation. If it would take less it would not be able to capture all possible states. Eventually, every realistic simulation of a universe will either be orders of magnitude less complex than reality or will be orders of magnitude slower than realtime. In both cases realistic simulations of ones universe own past will never be possible and hardly worthwhile and thus we probably don't live in one.'

This also says that computing power cannot grow indefinetely.

<comment><USER47> This argument breaks down if we consider that we don't know anything about the "host" universe.

It is as if Minecraft beings reasoned that it would be impossible to simulate them, as the redstone circuits required would be much larger than the observable universe. Which is fine, except we have nanoscale transistors.

<comment><USER46> Minecraft is many orders of magnitude less complex than our universe. We could be in a simulation, but then the parent universe would be orders of magnitude more complex and we would not be a significant simulation of a civilization's past as the original argument goes.

Of course we might be entertainment, but to explain this universe you would then have to explain the way more complex universe in which we run. We cannot proof this is not so, but now it seems pretty similar to the god hypothesis.

</comment></comment></comment><comment><USER48> For those of you who haven't read this short story (universe simulation is the theme), I highly recommend it:

[https://qntm.org/responsibility](https://qntm.org/responsibility)

</comment><comment><USER49> If I play out a few steps of Conway's game of life by hand on a go board, is that little universe any more real for my moving the stones around?

I think the only thing running the simulation does is let me, an outside observer, see it. If sentiant gliders show up at some time step, they are there thinking their pre-determined thoughts whether I get to that point or not. They exist in the rules and initial conditions, not in the stones and grid lines.

So if we could be living in a simulation, I don't see the need for a computer, the program is all you need.

</comment><comment><USER50> Hilary Putnam says that we aren't.

Basically, if we really were brains in vats, then "we are brains in vats" couldn't ever be true, because the referents of our discourse wouldn't have any causal connection to real brains and real vats, and so it wouldn't even be possible, if one were a brain in a vat, to think the thought or propound the proposition "I am a brain in a vat", and so, it's necessarily false that we are brains in vats.

ieas.unideb.hu/admin/file_2908.pdf

<comment><USER51> This is a fascinating argument, but not because it tells us much about whether we are brains in vats. Instead, it tells us something deep and interesting about linguistic meaning, and the mysterious relationship between statements and propositions.

Putnam is not actually saying that we aren't brains in vats. Rather, he is saying that we cannot form accurate and meaningful statements to that effect if we are.

The argument, as I understand it, turns on a statement's ability to refer. Putnam's point, as you nicely summarized it, is that in order to accurately describe the world (I make a point here of not talking about whether the statement is true) a statement has to be causally related to the things it describes in the right way. This seems plausible.

But this is different (on must theories) from saying that the abstract proposition that might be represented by such a statement cannot be true. It could be! The puzzle is just whether you could form a linguistic statement to properly express that proposition due to the reference problems Putnam points out.

Putnam's own example demonstrates the point. A bunch of ants cannot draw an image that represents Winston Churchill in the grass, because they cannot know what Winston Churchill is or (probably) what he looks like. Any similarity between an ant-made image, and a real image of Winston Churchill has to be merely coincidental. Ants cannot close the causal link that we normally require in order to say that an image "represents" something. But this doesn't mean that there is no such thing as an image of Winston Churchill. Or that an ant-made imagine cannot resemble Winston Churchill. It just means that ants can't form a _representation_ of him!

Likewise, our putative inability to form an accurate statement to the effect that we are brains in a vat does not mean that we aren't brains in a vat. An omniscient being (perhaps the one who put us in the vats!) might, for example, read our silly HN posts about brains in vats and say, "gee, its incredible that this series of symbols actually matches the symbols that you would use to form a true statement statement about the world, if only the speaker were in the necessary causal relation to my vats in order to truly say such a thing." Likewise, we say about the ants "gee, its amazing that they managed to make an imagine resembling Winston Churchill even though they don't know what he looks like and therefore can't truly be said to have 'represented' him."

(There is a parallel line of argument that you might run about our ability to _know_ something, since knowledge, it is often said, has to be related to the external world in a certain way in order to be more than a mere belief.)

In any case, classic Putnam.

<comment><USER52> From the first episode of The Magicians, two students reason about being a brain in a vat:

Quentin: "Am I hallucinating?"

Elliot: "If you were, would asking me help?"

So, I either I don't understand Putnam's argument or it's plainly wrong.

I recognize that when we say "We are brains in the vat" it seems, at the surface, self-referentially false. Because if we are brains in a vat, we wouldn't have the experience of being brains in a vat--- we'd have the experience of walking around and being people. But I can make a statement like: "Despite my experiences, I think that I am a sentient being that is contained inside a vat."

His argument that the word "vat" refers to different things in "vat-English" and normal English doesn't matter. The concept held behind vat & brain are fundamental enough that they would be self-generating among a community of sentient beings. If we say: "I am a sentient meatcomputer inside a vase filled with liquid food" we may be saying something different, but we are still expressing the core idea.

Even though the simulated world might be vastly different than the host world, language allows abstractions such that we can make the statement.

Putnam goes on to entertain the idea of a twin earth where beeches and elmes are switched, or a world where water has a different chemical forumula than H2O. That is a better starting point, but it doesn't help. I can simply generalize my statement: "I am a sentient being experiencing a hallucination, and the brain which executes my thoughts are self-contained in an environment I cannot perceive, but which nurtures my brain while networking stimulus with it."

I'd like to add a thought experiment to this. Imagine you have two vastly different communities with vastly different chemistry, and possibly operating with more than 3space and 1time dimensions. What would happen if, by the act of an Angel, both communities were given the rules for chess?

The names of the pieces don't especially matter--- if one community never had a bishop, we can simply pick a different word. Or call it piece #4.

With enough games played and thought put into it, the communities would discover tactics. They would compare and contrast the Queen's Pawn vs King's pawn. They would figure out 3-move checkmate. They would understand why en passant was a good rule to be added. And despite have different words and names for all of these concepts, these concepts still refer to the _same things_. Even if one world played chess with stone pieces, and the other world used leashed rabbits with hats.

A great example of this is when I went to China and play Go (or Weiqi, as they call it). I spoke 10 words of mandarin, and they spoke zero english. I was able to play a couple of games without having any shared language about the game. In the second game, an older chinese guy would sometimes yell at me and move the stone I had just played--- essentially saying: "no, that's not the best move, HERE it is." I didn't always understand why it was the best move, but often it was plainly clear that I was incorrectly read the truth of the board.

So. The act of thought supersedes what we immediately refer to in language, by it's ability to abstract. boom!

<comment><USER53> In your thought experiment, you are presupposing many common factors; we can understand this better perhaps because you are positing "3+ dimensions" so we can think "the dimensions we see plus a couple more" which makes it seem like the other community is a superset of ours.

Likewise, in your former, generalized statement, it works if you continue to think of "our universe". The entire notion of anything remotely resembling a brain, or anything like what we understand to be cause and effect (like, nurturing something to keep it functional, or even the very concept of "functional"...) existing in the host environment (whatever that means! :) ) makes the abstract statement devoid of meaning.

</comment></comment></comment></comment><comment><USER54> Are we living in a computer simulation that is running atop another computer simulation and so on in regress ad infinitum? Does asking questions like this even mean anything? Maybe.

</comment><comment><USER55> > "I was driven to error-correcting codes—they're what make browsers work. So > why were they in the equations I was studying about quarks and electrons and > supersymmetry? This brought me to the stark realization that I could no > longer say people like Max are crazy."

Is he loosely associating mathematical constants with arbitrary error codes that we made up in computing?

<comment><USER56> He is not. An error code is a way to refer to an error. Error-correcting code is something else entirely; it is a way to encode information in which small errors in the transmission of the information can be detected and possibly corrected.

For a simple example: I want to send you 5 bits of data, and you receive 01101. You assume (but cannot prove) that you got the right data; maybe a bit was flipped somewhere and I actually sent you 11101!

So you and I agree that we'll include a parity bit in our messages. If I'm sending you an odd number of 1-bits, the parity bit will be 1. If I'm sending you an even number of 1-bits, the parity bit will be 0.

So now, I send you five bits of data, plus one parity bit. You get the message 011011. You see that you have fives bits, 01101, and a 1 for the parity bit, which means that you should be expecting an odd number of 1-bits. That is what you have, so you can assume that as long as no more than 1 bit can be flipped in transit, you have the data with no malformations.

This concept can be extended to detect more errors (what if two bits get flipped) and to detect where the errors take place, which helps to correct them. That's why it's called error-correcting code.

<comment><USER55> And what this has to do with "quarks and electrons and supersymmetry"?

<comment><USER56> Hell if I know, man. If I did, I'd have included it in my explanation! But there was a pretty fundamental misunderstanding of what was being said, and I felt like it was worth explaining what I knew so that at the very least, incredulity was being expressed for the correct reason.

</comment></comment></comment></comment><comment><USER5> If we are, then it means computer simulations aren't infused only with computing power, but also consciousness, as we are self evident proof of. It's a simulation with consciousness, a completely different thing than what we usually simulate (weather, proteins, old software on emulation)

<comment><USER57> We might be a bug.

</comment></comment><comment><USER58> Meta: as per usual, I'm finding the HN discussion far more stimulating than the original article.

</comment><comment><USER59> I'm not a physics genius. But to me it seems like the enthusiasm for this theory is based on some very old cultural assumptions about man vs. nature.

For example:

> "If I were a character in a computer game, I would also discover eventually > that the rules seemed completely rigid and mathematical," said Max Tegmark, > a cosmologist at the Massachusetts Institute of Technology (MIT). "That just > reflects the computer code in which it was written."

Computers are not exempt from nature, of course. The reason a computer works is because the physical laws of our universe can be described mathematically. If quantum theory didn't work mathematically, then neither would a computer.

So Tegmark is probably assigning the correlation the wrong way. A computer can only exist in a universe with mathematical physical laws; therefore the detection of mathematical laws doesn't tell us whether we're in a computer ourselves.

Likewise:

> Furthermore, ideas from information theory keep showing up in physics. "In > my research I found this very strange thing," said James Gates, a > theoretical physicist at the University of Maryland. "I was driven to error- > correcting codes—they're what make browsers work. So why were they in the > equations I was studying about quarks and electrons and supersymmetry?

Information is also not exempt from nature; it is a physical thing that is subject to the same laws of the universe as anything else. And what we call information theory arose from our study of real physical systems, like telegraphs and telephones.

Now, maybe information theory will turn out to be a better mathematical framework for describing the laws of the universe. But that does not mean that it is any more likely that we're living in a simulation. One mathematical framework is not more "natural" than another. And there are plenty of examples of where a math framework developed in one context became useful in another.

We use computers, and I think we still see ourselves as somehow distinct from the rest of nature. This lends itself to a somewhat supernatural way of thinking, like "I use a computer to manage information, so therefore if everything is information, then there must be a super-me running a super- computer."

But taking scientific theory at face value, a computer running SimCity is just as natural as a cat, or a palm tree swaying in the breeze. If our theory says that everything is information, then so are we, and so are our computers--so there is no need for anything else to explain that.

</comment><comment><USER60> If we are, let's hope they don't accidentally reboot the computer.

</comment><comment><USER30> Aghhh not this again. This is pseudoscience/creationism marketed to scientists. It's impossible to flasify this, since any evidence for or against simulation can be a part of the simulation.

<comment><USER61> > This is pseudoscience/creationism marketed to scientists.

It's not science at all, pseudo- or otherwise. It's philosophy. And I see no link to creationism. If we're in a simulation, it's not turtles all the way down. Somebody's running the simulation. The same ontological questions we grapple with now simply apply to that person instead of to us.

<comment><USER62> Heh - no reason for that to be true. The folks running the simulation could be very unlike us - maybe N-dimensional beings, or they exist across multiple universes, or heck maybe in a 2-dimension world. I can simulate more dimensions on my computer than I exist in! Why couldn't they?

Anyway their ontological questions might not be anything like ours. Perhaps they ARE god, and don't need to wonder about that.

<comment><USER45> > Perhaps they ARE god, and don't need to wonder about that.

If they were, how would they know?

<comment><USER62> Can God make a rock so big, that even God can't move it?

</comment></comment></comment></comment></comment><comment><USER63> Surely the energy demands for such a simulation would be... astronomical.

<comment><USER64> If that wasn't a pun, it was an accurate point.

<comment><USER63> Both? :)

</comment></comment></comment><comment><USER65> I thought the answer would be no because there are computable and non- computable functions. If we are in a simulation then we should not be able to reason about them.

Also then p!=np.

</comment><comment><USER66> [http://www.imdb.com/title/tt0139809/](http://www.imdb.com/title/tt0139809/)

</comment><comment><USER67> Are we living in a computer simulation? No.

Can I prove that? No. Is it false even though I can't prove it? Yes.

Not everything that cannot be disproven should be taken seriously.

</comment><comment><USER68> One way to prove this, is for us to create a simulated world smart enough that can discover itself and make its own simulated versions.

</comment><comment><USER69> Rene Descartes proposed this question in his "Meditations" essay (the one where we get "cogito ergo sum" from).

<comment><USER70> Actually, "cogito ergo sum" comes from "Discourse on the Method".

</comment></comment><comment><USER55> Is that Scientific American bringing up some sort of science/philosophy on a "creator" (a.k.a. God)?

</comment><comment><USER71> I love it. Tyson just said that there is a 50% chance that the intelligent design people are right.

</comment><comment><USER72> hmm... hail you mighty big creators of the simulation I live in - <USER2> provide me with some cheat codes so i can get some more money, women and toys - also to unleash the wrath of gozilla on a random city of sim earth :D Sounds like a fine religion to me :)

</comment><comment><USER73> If we do, then it's a very advanced one.

But does it really matter? does REAL free will really exist?

</comment><comment><USER74> Seriously? I can't believe the SciAm actually published this article.

</comment><comment><USER75> No but we are living in a mental simulation.

</comment><comment><USER76> Relevant Movie: The Thirteenth Floor.

</comment><comment><USER77> Is there life after death?

</comment><comment><USER78> So is there some super-universe version of HN where people are arguing about implementation details of our simulated reality?

<comment><USER28> Yes. And they are all discussing beneath a 'Show HN' link with 500+ points. I am wondering if that show HN simulation demo is in JavaScript as well? Hopefully in WebAssembly by now (or by then, based on perspective)

</comment></comment><comment><USER79> Once I start seeing Hungry for Apple ads then I'll know for sure.

<comment><USER80> My man!

<comment><USER81> Slow dowwwwwnnnn!

<comment><USER82> You don't knooowwwwww me!</comment></comment></comment></comment>


Live Sails.js Course - <AUTHOR> https://courses.platzi.com/classes/develop-apps-sails-js/live/

<comment><USER2> My Sails.js wishlist:

\- Support for transactions

\- Predictable data binding for raw SQL queries (and just a more verbose DSL for the ORM in general - recently used Laravel and I was in awe of how much better it was -- I mean I can't even ask a database how many cats with blue eyes Suzie has without loading the rows into memory)

\- Better support for database migrations, and better support for individual databases (generally improved adapters for each database -- composite indexes, and proper data types are two examples here)

\- Support for deep relational data fetching

\- Support for a LINQ-like IQueryable style of queries (perhaps using promises) -- for those unfamiliar with using LINQ (and specifically do DB operations), LINQ allows you to write and operate on queries with deferred execution until such point that the data is made available. What this roughly translates to is writing code and having it be turned into SQL by the ORM and only querying the database once the entire query has been built.

\- Better sockets integration

\- Integrated cache

I think this should speak volumes about Sails' readiness for production. I don't mean to harp on Balderdashy, they've done great work - but there's so much more to do. Right now if I wanted to start a new project I'd have a hard time choosing Sails over Laravel. They may be different languages but for many use cases I've seen the same or better performance from Laravel on HHVM. I honestly don't know how anyone can say they're loving it in production while these problems have remained unsolved. Every time I need to do something in my Sails application that strays from the most basic of operations, I end up having to write raw SQL or write a module in order to use sockets in any meaningful way. Personally, I'll be sticking to smaller Node.js libraries for a while yet. Not because I think Sails is bad, but because it's simply not ready.

<comment><AUTHOR> Sails is very modular, if you wanted to replace the ORM with something else you could just replace the Waterline hook. Waterline is still pretty young and all of these features would be great to get added! We are always looking to add new contributors if anyone would like to help move some of these features along.

<comment><USER2> Thanks Cody, I appreciate the reply.

<comment><AUTHOR> Yeah no problem. If you want to go into some more details about production issues my email is in my profile.

</comment></comment></comment></comment><comment><USER3> Couple of things here:

1\. The site and the courses look great but, why can't I sign up without a Facebook or Twitter account? This one issue was enough for me to leave the site. I compartmentalize my web affairs for many reasons and keeping my online accounts separate is very important for me. I'm writing this to encourage you (and others) to reconsider this practice.

2\. I can see the icon that says "Beginner," but that doesn't tell me much. In your FAQ, I would recommend expounding on this. Beginner is too ambiguous.

</comment><comment><USER4> I'm really glad to see this. I've build a few apps with Sails.js and I LOVE it, but the documentation isn't great, and there hasn't been too many solid learning resources. This is good news.

<comment><USER5> Why are they bothering to teach a class on it before writing the documentation?

</comment></comment><comment><USER6> I'm tuned in and loving the interactive experience so far. Congrats to Team Platzi on creating something that will truly change the future of online learning.

</comment><comment><USER7> The livestreaming of the class is over now. But we'll upload the recordings ASAP to: [https://courses.platzi.com/classes/develop-apps-sails- js/](https://courses.platzi.com/classes/develop-apps-sails-js/)

All your feedback will be welcome, thanks!

</comment><comment><USER8> What's the cost?

<comment><USER9> Christian from Platzi. We're creating livestreamed classes with great companies doing stuff for devs, designers and makers. We've had Sam Altman talking about Startups and the guys from Gitlab. Today we have Mike McNeil teaching Sails.js. What else would you like to learn?

<comment> mycroft-holmes The cost.

<comment><USER7> It's truly free. Is that weird?

<comment><USER10> Free isn't weird, but it was no where to be found in that response.

</comment></comment></comment></comment></comment><comment><USER11> Does anyone have any experience with sails?

<comment><USER12> I've used sails in production on a couple of apps and it's mostly pretty good but there are a couple of annoyances that will inevitably get ironed out as it develops. For me the most irritating thing is being unable to write good unit tests for controllers that use models as sails models are scoped globally and controllers have to be objects which makes injecting mocks difficult. It's great for getting a prototype up and running quickly, but if you're planning on building a big production app, a better longer term strategy would be building an express app from good open source components. (ie using sequelize for ORM). As has been mentioned elsewhere the documentation isn't always consistent and you sometimes find that a waterline function in the documentation has been deprecated in the current stable version, so be prepared to get to know the source well. In any case, it's a great effort and is a great time-saver on getting something live quickly.

<comment><USER13> Why not place the model usage in services and use the services in the controllers?

<comment><USER12> While that is a nice separation of concerns (Angular-style), it doesn't solve the problem for unit testing the controller because you still won't be able to inject a mock service into the controller without some beforeEach global variable hackery.

</comment></comment></comment></comment><comment><USER14> Hi guys. Interesting format. Are you going through YC at the moment? What are your future plans?

<comment><USER7> We had a live class with Sam Altman two weeks ago. And Gitlab and Sails.js this week. We're almost there for classes with Docker, RethinkDB and Stripe.

And then, we hope to do a full course on either React.js and JS app dev or Social Media Marketing and Community Management. Still debating that. What do you guys think?

<comment><USER15> Just a heads up re: English in the FAQ. You want to use "paid" not "payed." [https://courses.platzi.com/frequently-asked- questions/#como-...](https://courses.platzi.com/frequently-asked- questions/#como-funciona)

<comment><USER7> AAAAAAAaaoook, yeah, we can fix that. It seems we have more weird issues in our FAQ besides that. Thank you wyclif, we'll fix it asap.

</comment></comment></comment></comment><comment><USER16> Too bad it seems you can only join with Tweeter or FB account.

<comment><USER9> We're working on more options. Should we include github or an email/password login first?

<comment><USER17> Email / password please, before anything else. As a rule I don't signup any service unless it makes me create an account separate from any other one I have. My password manager remembers them for me (keepassx).

</comment></comment></comment><comment><USER18> The join button is completely broken in Chrome beta.

<comment><USER19> It's also broken in Chrome v40</comment></comment>


Show HN: Open source hyper-live chatroom using WebSockets, Node.js, and Vue.js - <AUTHOR> https://github.com/sdegutis/editfight-hyperchat <comment><USER2> Reminds me of the good old days with Powwow. I've seen this idea come and go (and even wrote my own version), but I've found that although this kind of letter-by-letter communication is literally 3-5x more efficient, only a small percentage of users choose efficiency at the cost of displaying their poor typing and spelling skills.

About efficiency, if you think I'm exaggerating, imagine for a moment that phone calls didn't exist, but that every phone conversation required recording and sending a voice mail. Imagine how ridiculously slow and inefficient that would be. Well, that's instant messaging, the most inefficient method of communication ever devised. Millions of users stare at their Slack chats, waiting for "So and so is typing" for minutes, until finally So and So just gives up and ends up writing nothing at all. ;)

<comment><USER3> Oh man, Powwow. I had completely forgotten about that. I believe ICQ had a similar live mode too. Thanks for the nostalgia trip :)

</comment></comment><comment><USER4> Again, Great project! Would be interested to see how it evolves and would like to incorporate in a site myself.

</comment><comment><USER5> You've been spamming the same site repeatedly for days. It's currently on the front page of /show multiple times.

<comment><AUTHOR> I didn't reapiZe that sorry. I would delete this but it's deler button js. Missing

<comment><AUTHOR> Sorry, my iPhone keyboard needs a reset badly. Yeah I posted this once last week and it hit FP, and then I made a lot of changes since then and open- sourced it (by popular demand), so I'm linking to the source code now. And admittedly I lost track of posting it in between then and now, so that was totally my mistake. Wow, now that I look at how it's on Show multiple times, that's really embarrassing. Okay good call, I made a mistake; I'll do my best to avoid that mistake in the future. Thanks.

</comment></comment></comment><comment><USER6> It says: "license: tbd"

Which means, this defaults to full copyright. It is not Open Source.

<comment><AUTHOR> The source is open for you to look at, I haven't decided on further permissions. That's why I felt comfortable using the phrase "open source" :)

Plus it's not a very complicated website. Took me like a day to make. So there's really hardly any use in having it open sourced in the sense that people can use my code. It's probably easier to just write it yourself :D

</comment></comment><comment><USER7> what does hyper-live mean ?

<comment><USER8> Test it and I think you will understand. Simultaneously real-time typing for all involved...

<comment><USER9> Mobile support ... ?

<comment><AUTHOR> I made this with using my iPhone as a major use-case so yep full iPhone support. Don't have an Android to test with though.</comment></comment></comment></comment>


Anatomy of LinkedIn Options Bet That Probably Lost Money: Chart - <AUTHOR> http://www.bloomberg.com/news/articles/2016-06-13/anatomy-of-linkedin-options-bet-that-probably-lost-money-chart <comment><AUTHOR> posted in reference to [https://news.ycombinator.com/item?id=11895582](https://news.ycombinator.com/item?id=11895582)</comment>


A Haskell program to illustrate the state verification problem in economics - <AUTHOR> https://github.com/jmoy/costlyState

<comment><USER2> Cool. I find I understand things better after seeing them as code, particularly Haskell, the learning curve is steeper at first but I seem to find far fewer surprises in the long run.</comment>


A mirror flips left and right, but not up and down - <AUTHOR> http://physics.stackexchange.com/questions/8227/a-mirror-flips-left-and-right-but-not-up-and-down <comment><USER2> The various feynman "fun to imagine" videos, one of which is linked by the answerer, are amazing. I advise you to watch all of them as soon as you can. They're all up on youtube as linked on stackexchange, or you can see them on the BBC's site here: <http://www.bbc.co.uk/archive/feynman/>

Also, feynman's explanation is much more intuitive and more easily understood than the one given on stackexchange. As you might imagine. Also it comes replete with the inevitable feynman tales of intellectual dickswinging that we have all come to know and love.

<comment><USER3> Feynman says some interesting stuff but none of these explanations have yet satisfied me. Sure, I get it that a mirror technically does not rotate the image, it does the near/far thing instead, flips the nose, flips the north/south, however you want to put it.

But, this the fact remains: I hold an object in front of me (there is no mirror anywhere). IF I want to see/simulate what the object will look like in a mirror, I rotate it LEFT TO RIGHT (on the vertical plane, around the line that is parallel to my body no matter whether I am standing or laying down). I cannot rotate it any other way and get the same effect. WHY is that?

EDIT: Whoops, you guys are all right, I'm an idiot. Here I am sitting at my desk with quite literally nothing but bisymmetric objects around me- for a second there I went a little crazy. Thanks for setting me straight

<comment><USER4> Rotating an object left-to-right most certainly won't show you what it looks like it a mirror. It shows you the back of the object (assuming that the front of the object was previously facing you).

Here's an experiment to demonstrate that left-to-right rotation is not what a mirror does.

1\. Take an object and hold it so that the front is facing you (pick a side and call it the front if there's not an obvious "front").

2\. Rotate the object left to right so that you are looking at the back.

3\. Write your name on the back of the object (the side currently facing you).

4\. Rotate the object right-to-left so that the front is once again facing you.

5\. Go to a mirror and hold the object so the front is facing you.

6\. Look at the object in the mirror.

Does the object in the mirror look the same as when you did the left-to-right rotation? No. You can see the back of the object, but your name is backwards. What you're seeing in the mirror is not a left-right rotation. That's an explanation that your brain applies to the situation, but it's not what actually happens.

A similar experiment is to hold a coffee mug and stand in front of a mirror. Grasp the mug by the handle with your right hand. Look in the mirror. Where is the handle? _It's still on your right_. The coffee mug in the real world has the handle on your right, and so does the coffee mug in the reflection. There is no left/right reversal.

Edit: You're not an idiot. The mirror's behavior is simple, but it's also very non-intuitive. If it were intuitive, people wouldn't ask the question.

</comment></comment></comment><comment><USER5> Mirror's don't flip left and right. We implicitly compare a mirror image to the original by rotating the object, and naturally we maintain top/bottom orientation, this gives the appearance of "flipping" the object left to right. However, if you use vertical rotation to super-impose the object on its mirror image you'll see that it seems to have been flipped top-to-bottom instead.

<comment><USER6> The way I see it, the mirror does flip up and down, at least by the measure of the same experiment used to prove that it flips left and right.

To prove that it flips left and right, imagine a vertical pole between you and the mirror. The pole has a card attached to it with the front facing the mirror. The two dots, red and blue are painted on the card and you can see their reflection in the mirror.

In the reflection, the blue dot is on the right and the red dot is on the left.

If you rotate the pole so that is facing you and you can now see the front of the card you see that the blue dot is really on the left and the red dot on the right.

This proves that the mirror flips left and right.

To prove that it flips up and down, imagine the same pole in front of you with the card facing the mirror, but this time the pole is horizontal.

in the reflection you see that the blue dot is at the top and the red dot is at the bottom.

If you rotate the horizontal pole so that the card is now facing you, you see that the blue dot is really at the bottom and the red dot at the top.

<comment><USER7> _"If you rotate the pole so that is facing you and you can now see the front of the card you see that the blue dot is really on the left and the red dot on the right.

This proves that the mirror flips left and right."_

All it proves is that you've rotated the card. You've done the flipping, not the mirror.

Now, without doing any rotation to the card, if the card is seen from the perspective of the mirror, the blue dot is on the left, and the red on the right.

Depending on which perspective you're looking at an object from, one side will be on your left, and the other on your right. But no flipping takes place, unless you either move yourself to a different perspective, or rotate the object. A mirror does neither. It just reflects back exactly what's in front of it.. so you see whatever's on your right on your right, and whatever's on your left on your left. There is no flipping.

</comment></comment></comment><comment><USER8> Hold a book in your hands while standing in front of a mirror. Now turn the book around so you can read it in the mirror. The text is backwards. But how did you rotate the book? Sideways? If you had flipped it over vertically, the text would be upside down instead of backwards. You are the one who reversed the book, not the mirror.

<comment><USER4> Exactly. Stand in front of a mirror holding a sheet of transparency (such as you would use for an overhead projector) in front of you so that you can read it. Look at the transparency and note that you can read the words. Now look at the transparency in the mirror and note that you _can still read the words_.

If you rotate the transparency (left/right, up/down, corner/corner, whatever) so that you can no longer read it directly, you'll see that the same rotation has occurred in the mirror.

</comment></comment><comment><USER9> Mirrors don't flip left and right, or up and down. They flip front and back.

<comment><USER10> This is the first part of the answer. The second part is that, since we define the left and right on an object relatively to its front and back, flipping the front and back also swaps how left and right are defined. There is no confusion with top and bottom as they are not defined relative to front and back.

<comment><USER9> Absolutely true.

</comment></comment></comment><comment><USER11> Mirrors don't flip anything.

Oversimplification (ignores angle of light from object observed to eye), but here:

Imagine standing in front of a mirror, both arms straight out. A photon leaves your left index finger, travels straight to the mirror, and is reflected straight back.

Now imagine photons leaving all your parts, traveling to the mirror, and reflecting straight back.

That's all.

<comment><USER12> That doesn't answer the question, though. You have to explain why that means my right hand appears to be on my left side.

<comment><USER11> The question is "Why is it that when you look in the mirror left and right are flipped, but not the up and down?"

When I look in the mirror I see my right hand exactly where it should be, on the right side of the mirror. If I approach the mirror and then touch it, my right hand touches the right hand image in the mirror, as do my forehead and toes respectively.

Someone who asks this question, after understanding what's happening with the light, appears to expect that the left hand with the watch (for example) in the mirror should be on the same side of the mirror as the real left hand with the watch _if_ the observer turned himself 180 deg (away from the mirror). That's a psychological phenomenon, not a physical one, and I don't know why we do that.

One way to answer, then, is that mirrors don't flip anything, our brains do it, and erroneously.

</comment></comment></comment><comment><USER13> Skipping all the details, it's because you have a left eye and a right eye, not an up eye and a down eye.

<comment><USER14> The effect does not go away if you only have (or use) one eye.

<comment><USER15> Turn the mirror 90 degrees and nothing happens. Turn your head 90 degrees and it flips up and down.

</comment></comment></comment><comment><USER16> The technical-interview answer:

"Mirrors don't reverse left and right. They reverse in and out."

Then tell the interviewer that only an idiot would look at a local coordinate frame and think it's a global one. Just what is he insinuating? This had better not be one of those "stress interviews" people talk about. There's no way in hell you're going to work for a company that will screw around with you on day one just to see how you'll react.

Works every time.

</comment><comment><USER17> i never understood the question: how could anybody ever even think that a mirror flips left and right? there is no emperical way to observe this behaviour (with a single flat mirror).

<comment><USER18> This is one of those Feynman questions where understanding the question requires a certain way of thinking that discards common sense. Similar to his "Why is the wall not see-through?" question.

The way I think about is: "When you are looking at a mirror, and you blink your left eye, mirror-you blinks his right eye. But when you are laying on your side looking at a mirror, and you blink your top eye, mirror you blinks his top eye."

<comment><USER17> still don't get it: when i blink my left eye, mirror me blinks his left eye.

maybe this question would make sense, if i would see myself as the center of the universe, all creation and all there is - but there is a pretty high chance that i ain't. (and even then i'm not sure if this question would make sense)

<comment><USER19> The question itself stems from confusion about what's being seen. It's not uncommon, especially with children, for people to become slightly confused while using a mirror. For instance, on seeing some smudge on their left cheek trying to wipe it from their right cheek. Once they start moving of course the error becomes obvious. Their initial understanding of the image is really what the image would be if you had a camera facing you and then used a video display as your mirror.

<comment><USER20> I have this problem all the time! I even shave by touch and then check in the mirror whether I've missed a spot rather than shave while looking in the mirror because I can't avoid being confused about this. I __can __, while looking at the mirror, __reason __about which way I need to move my hand to get at a certain spot on my face's reflection, but it's much faster to stop looking at the mirror and let (correct) instincts kick in.

<comment><USER21> I had my tongue pierced a few years back and even now (not that I do it very often), when looking in a mirror to put the ball back on the 'stick' (I don't know what it's called!) I drive myself nuts.

In one hand I'm trying to hold/'point' the 'stick' and in the other hand, not only am I trying to get the ball to the end of the stick, but at the same time trying to rotate it so that the hole in the ball lines up with the end of the stick. Everything points, moves and rolls totally against what I think it should be doing.

I, like you, find it easier to just do away with the mirror and try and work it out myself.

Having said that, this whole conversation has made me really _think_ about the mirror and so I'm hoping that next time, it won't be so hard!

</comment></comment></comment></comment></comment></comment><comment><USER22> Assuming a mirror's face is its front:

Photons bounce off the right side of you, strike the left side of the mirror, and then reach your eyes. Similarly for the left side.

Photons bounce off the top side of you, strike the top side of the mirror, and then reach your eyes. Similarly for the bottom side.

<comment><USER11> I think this explanation is based on the (erroneous) tendency of people to think of what they see in the mirror as themselves turned around.

Look at the desk in front of you. The right hand drawer is near your right hand. The left hand drawer is near you left hand. Now why did you just call the right side of the mirror, which is near your right hand, as the left side?

<comment><USER22> It assumes that the mirror's face is its front, making the right side of the mirror near your left hand. I only described it this way to reduce word count. We can say something similar using your more precise terms-- "near left/right hand".

I did not describe the mirror "turning you around". If it was yourself turned around, you'd see photons from your doppelganger's right hand near your left (as is the case when you face someone). Since it's a reflection, which does not turn anything around (as you said), your image of your left hand is near your actual left hand. To wrap it all up-- the reflection of your head is near your head, and your feet is near your feet. This is why you are reversed left- right, and not top-down in a flat mirror.

</comment></comment></comment><comment><USER23> My high school history teacher asked this same question (yes, it is that old) and my answer at the time was: Left and right are assigned relative to where you are facing, while up and down are not regardless where you're facing.

The same part of your body is reflected at the same side in the mirror (paint your cheeks with different colors; the mirrored cheeks have the same color on the same side as the normal). However, we CALL the cheek left or right depending on where we are facing. The mirrored image reverses the facing so its left and right are ASSIGNED that way, though it's the same physical cheek.

Up and down are absolute regardless of where we face. A mirrored image only changes the "facing" aspect so up and down don't change.

<comment><USER24> You know, that was exactly my answer as a teenager as well, and the answer I thought I knew when I clicked on this thread, but I don't think it's a sufficient explanation. Even if you assigned up and down as relative, no vertical flipping appears to take place.

I believe InclinedPlane's answer [1] is much better. We implicitly perceive the reflection as having rotated as a human would, by turning around on his or her feet.

However, if instead the reflection is perceived as having rotated vertically, with the human flipping over onto his or her head, the image is actually flipped vertically.

So the answer is actually that the image in the mirror is either flipped horizontally _or_ vertically, depending on one's perception of how the mirror image got there in the first place.

While the local/global orientation explanation does show that there are no inconsistencies, and the lack of a relative orientation for 'up' clouds things a bit, it doesn't actually explain at all _why_ we naturally look at the image and decide it's flipped horizontally.

[1] <http://news.ycombinator.com/item?id=2790792>

<comment><USER23> Left and right has one frame of reference - facing. Up and down has another frame of reference - room ceiling/floor. Mirror inverses the facing frame of reference but not the room frame of reference.

Left and right, up and down are just convention in our mind. We human use facing to assign left and right, and use ceiling and floor to assign up and down. There is no switching sides in the mirror in reality. You red hand (if you color it) is on the same side inside or outside of the mirror, just as your head and feet are on the same side inside or outside of mirror.

We just assign a new left/right to the mirrored image because we see where the facing in the mirror is; however, our head is near the ceiling and feet are still on the floor so the room frame of reference hasn't changed, and thus up/down are labeled the same in the mirror.

The point my history teacher trying to make via this exercise was to say most stuffs (in history particular) were relative in a frame of reference. It's the same event but through a different angle would be called different thing, when moved to a different frame of reference. The mirror exercise is the terrorist/freedom fighter argument in physical illustration.

</comment></comment></comment><comment><USER25> Stop using the words "left" and "right" or "up" and "down". You're confusing yourself thinking about "right" hand or "left" hand. In mirror you's world, those words have different meanings.

Instead, put a paper bag on one hand and stick your hands out. Look in the mirror. Your "bag" hand and mirror you's "bag" hand are both pointing the same way!

Now stick the bag on your foot. Look, mirror you's bag foot and your bag foot both point the same way!

Now stick the bag on your head. Look, mirror you's bag head is in the dark!

But seriously, everything in the mirror is oriented congruently with this "side" of the glass. The appendages wearing a bag always match up. "Bag hand" and "not bag hand" match just like head and feet do.

</comment><comment><USER26> It's too bad the question, repeated in the title, is phrased in such a way that it will perpetuate the myth that mirrors flip left and right. I wouldn't mind some editorializing so the title no longer claims the switch as fact.

</comment><comment><USER27> It's because mirrors are magic.

On the serious side, this would be an interesting question to ask a child. We can all reason the answer from our knowledge of physics and the rules of the world in general (where there are no cool explanations for this), but a child has no such constraints. Their imagination runs free, and they fill in the blanks from their own knowledge of the world, which may include magic, super powers, or whatever realities they came in contact with in their short life.

<comment><USER20> The heartless bastards that down voted you obviously haven't spoken to young children and heard their charming, clever and totally wrong explanations for things. If they had, they would probably agree it's an interesting question to ask them.

</comment></comment><comment><USER28> I will try my short explanation that I have been telling myself since the first time I heard this question. Imagine a mirror on the ceiling. From the same understanding that we are judging the image to be flipped left to right, we will now notice that the image is flipped top to bottom.

Explanation: Imagine a stick without width whose image is reflected in the mirror on the ceiling. If we superimpose the image on the stick, haven't we flipped top and bottom?

</comment><comment><USER29> To go along with fun mirror-things to think about, how about this one:

Stand in front of a mirror. Note the lowest point on your body that you can see in the reflection, whether it's your waist or thighs, or whatever. Now, no matter how close you get to the mirror or how far you step back, that will always be the lowest point on your body in the reflection. (e.g., you'll never be able to see your toes, if you couldn't initially.)

<comment><USER2> LIES! I just tried this, the visible portion increased by about a 50cm when I stepped back about 3m.

I guess this is because my big mirror isn't exactly flat to the wall. Come to think of it, it isn't even completely flat.

<comment><USER29> Ha, good point. I neglected to include that the mirror must be flat....

I'm glad you tried it, though! My friend told me this and I just didn't believe it until I tried it for myself.

</comment></comment></comment><comment><USER30> I think a more interesting question is how the rear view mirror works. What I mean is how does a perfectly clear image become slightly dimmer when you adjust the angle of the mirror? I've seen that since I was a child but I've never understood why it works.(I never got past calc based physics in college so if the answer is obvious I apologize.)

<comment><USER4> I'm assuming you're talking about what happens when you flip the manual "dimming" switch on the mirror.

I'm pretty sure you're looking into a mirror that actually has two reflections. One of them is already dim, and it's dominated by the brighter one so you don't normally see it. (Sometimes in the right light you can see both reflections at once.) The two reflections are offset, so that when the bright reflection is showing you the view out the rear window, the dim reflection is showing you a few degrees lower, probably the back seat. When you flip the dimming button, the mirror turns upward a few degrees, so that the dim reflection is now showing you the view out the rear window. You can't see the bright reflection any more because it's now showing you the roof inside the car, which is pretty dark in relation to the rear window. Now the "dim" reflection is actually bright enough to dominate.

I assume that this is accomplished with some sort of double mirror, where the "bright" mirror is closer to you, and some light leaks through it to hit the "dim" mirror behind. These could be made into a single unit with no actual space between them. It just needs two layers of reflective material that are at slightly different angles.

<comment><USER31> Or materials with different angles of refraction - which is what I always thought. (I don't actually know.)

</comment></comment></comment><comment><USER32> when you have mirror in front than, left and right are not changed on mirror image but front and back. including side mirror and bottom mirror it goes like this: Front miror: front/back:yes, top/down:no, left/right:no Side mirror: front/back:no, top/down:no, left/right:yes Bottom mirror: front/back:no, top/down:yes, left/right:no

so i guess this question is like asking: why is 1 + 1 always equals 3 but no 4?

such question can have two meanings:

1: person reqly thinks that 1+1 = 3, answare is in the mindset of person that asked question

2: person is just making sounds taht resembles those of human talk (like parrots) and this is not even question. but mimicing (common in nature)

</comment><comment><USER33> My answer (Andy) explains how it's really the photograph that is flipped. When we say the mirror flips the left-right directions, we're accidentally referring to the absence of the familiar rotation of the photograph.

</comment><comment><USER34> I find a nice way of look at it is to think of it as looking at the back of a two-dimensional 'slice' of what is in front of the mirror.

</comment><comment><USER35> If you stand on a mirror it does flip up and down.

</comment><comment><USER32> actually it does flip up and down, you just have to put the mirror on the ceiling. or on the floor.

so to conclude; by definition of this question the result is fixed, you are allowed to fix y- axis but not x-axis when you are translating mirror image to real world image.

</comment><comment><USER36> The book "Good and Real" opens with this thought experiment and has a good discussion.

</comment><comment><USER37> Imagine you are a starfish.

</comment><comment><USER38> isn't it simply because our eyes are in horizontal plane. If they would have been in vertical plane we would see upside down in mirror.

</comment><comment><USER39> In a mirror you see what the mirror is seeing.

</comment><comment><USER18> nice try, feynman

</comment><comment><USER40> When looking at a mirror a human will imagine a clone has gone over to the other side, _rotated around the vertical axis_ , then _inverted along the horizontal axis parallel to the mirror_. That last part is the perceived "flip" but it is a direct consequence of the imagined axis of rotation. If you imagine a being who is accustomed to a horizontal axis of rotation in their movement, you can see how they would imagine their clone going to the other side of the mirror, rotating around the horizontal axis, then inverting along the vertical axis parallel to the mirror. They would then ask why a mirror flips up and down, but not left and right, for they are accustomed to up and down switching after a rotation, where we are accustomed to left switching with right. (In fact I suspect we identify "up and down" as strongly with this invariant as we do with gravity.)

Any being with freedom of action along some plane, who is accustomed to rotation around an axis perpendicular to that plane, will experience much the same thing: a rotation around some axis parallel to the mirror, followed by an inversion around the axis parallel to the mirror and perpendicular to the rotation. They will then perceive a "flip" along that axis of inversion.

The question reveals a lot about the biases of the the person doing the asking.

</comment><comment><USER41> If your eyes were stacked one above the other, then the mirror would flip up and down.

<comment><USER42> try shutting one eye and see if you still believe that</comment></comment>