Alternate Day Fasting Improves Physiological and Molecular Markers of Aging [pdf] - <AUTHOR> https://www.cell.com/action/showPdf?pii=S1550-4131%2819%2930429-2 <comment><USER2> I fast, on average, once a week. At least once a month, I try to do an extended fast (2-5 days) to force ketosis. I also do intermittent fasting basically daily (I only eat between 12-8). Been doing this for about 4 years now. Some anecdata:

\- Fasting > 24 hrs paradoxically gives you an extreme boost of energy and mental focus. I especially love how my olfactory sense is _extremely_ heightened. It's pretty cool and even after all these years doesn't get old.

\- Fasting is not a panacea. Depriving yourself of nutrients or eating garbage is still a bad idea even if you fast or do IF. Unfortunately, eating healthy is hard and kinda' sucks. Egg whites and chicken + broccoli gets old pretty fast.

\- Fasting >7 days is a bad idea unless you know what you're doing. This is when your muscles and vital organs start contributing as an energy source (e.g. they also start breaking down).

\- Your body is clever, so extended fasts will start putting you into "starvation mode" and you'll lose some of the benefits.

\- There have been NO STUDIES on long-term fasting (e.g. over the course of an adult lifetime). This is a big warning sign to just be careful and not overdo it. Different people have different tolerances. Talk to your doctor.

\- Even on fast days, make sure you take vitamins (I take Fish Oil, Zinc, a Multivitamin and Magnesium)

<comment><USER3> Are you fit? as in, do you lift weights or are active in sports that require strength?

I ask because I wonder about the effects of extended fasts on muscle loss/retention, a big problem cutting weight for some people is that they get rid of some muscle mass along with the calories they wanted to eliminate.

<comment><USER2> I did for a few months this year, but I've been lazy over the summer. I'm 155lb, 6'0, so fairly skinny, maybe at around ~15% BF. I noticed that fasting doesn't help with BF at all unless I eat very clean and lift. I was at 170lb, around ~28% BF earlier this year and had to work my ass off to get my body fat percentage down.

<comment><USER4> > I noticed that fasting doesn't help with BF at all unless I eat very clean > and lift.

So what happens? You lose muscle and fat in the same ratio? Or do you keep the fat?

<comment><USER2> I feel that my body kind of adjusts to the fasting and I just don't lose much of anything.

<comment><USER4> That sounds to me like "I eat more to make up the calories when I'm not fasting".

</comment></comment></comment></comment></comment></comment><comment><USER5> This fasting caused a 37.4% reduction in caloric intake. It raises the question of whether it was the fasting itself or merely the overall caloric reduction that made the real difference.

<comment><USER6> I wondered this as well. In many of the intermittent fasting studies they kept caloric intake the same and showed that the benefits applied even when taking caloric restriction out of the equation.

<comment><USER7> A lot of diets, especially IF style diets, are pretty much just tricks to get you to eat less calorie wise. Intermittent fasting does this by just setting the simple rule, only eat during a relatively small window of time. It's easier to eat less during that period because there's only so much you can comfortably eat in that time. (Granted you can totally fit a whole day's intake in the IF period but it's harder).

<comment><USER8> Is there really no difference between eating 1500 calories at once vs. over the course of 5 meals?

Of course, there is no weight loss without a calorie deficit, but are all calorie deficits equivalent on magnitude alone? I struggle with the notion that the timing does not matter at all, and much of the suggested benefits of controlling the timing focus on other metrics beside immediate weight loss.

The "wisdom" of the late 90s was that six or so small meals were better than one large meal, with respect to weight loss. Now it appears some experts would argue the opposite. Is it all just a bunch of smoke and mirrors over calories in > calories out?

<comment><USER9> "Is there really no difference between eating 1500 calories at once vs. over the course of 5 meals?"

Digestion - and the ramping up of your entire metabolic process - is not a minor task. It is an all-hands-on-deck marshaling of a number of bodily processes that preclude other processes that you might like your body to engage in.

If you are firing up this mechanism every three hours - insulin response, spiking your blood sugar, moving your stomach and bowels, etc., then you never give your body time to do any other housekeeping tasks.

Think of food intake as an _interrupt_ , in computer science parlance. What happens to process performance when you're throwing interrupts ?

IANAD.

<comment><USER4> > then you never give your body time to do any other housekeeping tasks.

Do you have any links to describe what other tasks it would want to be doing in that time and which are blocked by an insulin spike?

<comment><USER9> [https://osher.ucsf.edu/patient-care/integrative-medicine- res...](https://osher.ucsf.edu/patient-care/integrative-medicine- resources/cancer-and-nutrition/faq/cancer-and-fasting-calorie-restriction)

"...it is theorized that cancer cells do not respond to the protective signals generated by fasting, thus leaving them vulnerable to both the immune system and cancer treatment. This process is known as differential stress resistance (DSR). Short-term starvation (STS), fasting for 48 hours, causes a rapid switch of cells to a protected mode, which is capable of protecting mammalian cells and mice from various toxins, including chemotherapy."

(et. al)

I read it as cleanup/housekeeping tasks that aren't high priority, relative to processing food inputs. When freed from those tasks, the body can concentrate on housekeeping.

<comment><USER4> That's not housekeeping though, that's in the case of fighting cancer. And based upon the mechanism you lay out, that's with outside intervention. That doesn't seem to expand out to "general housekeeping" when you're also dealing with medical science trying to kill cancer without killing you.

</comment></comment></comment></comment></comment></comment></comment></comment><comment><USER10> Been doing intermittent fasting for a long time now and have been doing ADF for the last few months.

I lost fat and retained lean muscle while \- eating between 3000-6000 calories on eating days \- running 30-35 miles per week \- weight lifting 3x per week

Here is a reddit post about my progress with some documentation including pics of recent DEXA scans.

[https://www.reddit.com/r/leangains/comments/cliuqk/been_prac...](https://www.reddit.com/r/leangains/comments/cliuqk/been_practicing_alternate_day_fasting_for_about_6/)

<comment><USER11> Congratulations on your accomplishments. Can I ask how you manage to choke down 6000 kcal on eating days? Even when I'm really hungry I can't physically force myself to eat that much. It makes me feel sick and my digestive system is at the limit.

<comment><USER10> I'm one of those people that eat quickly and a lot, so I've just become accustomed to eating big meals.

That being said, I also eat significant amounts of junk food. Slice of cake is like 500-800 calories. No problem. I can do that x 3 after a meal of normal stuff. Junk is easy to throw down and calorie dense. Also, its fun to eat.

Now 6000 calories of salad and lean meats? That would be difficult...

</comment></comment></comment><comment><USER12> >For healthy, non-obese adults, ADF is safe to practice for several months

They might just be saying this because they didn't test any further, but does anyone know any reasons why it might stop being safe after several months?

<comment><USER13> IMO it's not unsafe. The longest supervised fast was a whole year long. The person was obese and only supplemented vitamins if I remember correctly.

Fasting is how we evolved to eat. We didn't have Costco and fridges 10k years ago.

<comment><USER14> [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2495396/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2495396/)

Note, however, he died relatively young although he did live a few decades after the fast [https://en.m.wikipedia.org/wiki/Angus_Barbieri%27s_fast](https://en.m.wikipedia.org/wiki/Angus_Barbieri%27s_fast)

</comment></comment></comment><comment><USER15> Sample size was small for the ADFs (approx 40). They were compared to control of 60. I didn't drill deep enough to see age and/or gender breakdown.

That said, fasting as pro-health tool keeps coming up and the gist time and again seems to say it yields a positive.

</comment><comment><USER16> We have neighbours with twins aged 7 who raise their kids at home on a raw food diet. They eat lots of nuts, fresh fruit, fermented beans and garden vegetables. They conserve vegetables and fruit using lacto-fermentation.

The kids are much smaller and thinner than normal kids their age. Up until recently I used to pity these _poor, starving_ kids. I compared them to our kids, who are athletic, tanned, well built.

But recently I started asking myself if this is not the other way around. Maybe if we didn't have the luxury of cooking, transformed food and western supermarkets we'd have been much smaller. Maybe this means that we _all_ in the 1st world eat too much.

I'm starting to think that maybe we're not really better off having our stomachs full basically the whole day long, especially if you consider that most of us do very little physical activity if at all...

<comment><USER17> Hey ciconia, I wanted to drop you an email on an unrelated note, but was unable to find contact info. So please check out this comment: [https://news.ycombinator.com/item?id=20852873](https://news.ycombinator.com/item?id=20852873)

(Other readers, please accept my apologies for hijacking the subthread.)

</comment></comment><comment><USER18> I've been fasting weekly for a long time (after starting with intermittent fasting). I'm glad to see an article like this because I've been waiting to try fasting every other day. My subjective observation is that there is a misconception of what the body does with nutrients and that is why in general people won't think of even trying to fast ever.

To use contrasting analogies, it seems in general the perception is that the body works like a car and you have to re-fuel it every few hours in order to keep going. However, from my experience I think the body is more like a factory that creates its own energy. It needs materials, from which a part is used for energy, but thanks to having storage, you have plenty of supplies to keep going until the next shipment of resources arrive. In other words, fuel is burned in proportion to the user of the car, but factories don't necessarily use their materials as soon as it receives the shipment. Factories can store resources and their use is scheduled for a later use.

Therefore it is better to optimize for quality of materials, rather than frequency of consumption! Your body will use the materials it gathered from the past few days of consuming food (no citation here, but again just my experience), and the only problem of not eating is the BRAIN's expectation of eating food every day and that feeling of satiation, which is basically a hit of dopamine and not a true sign of wether you need materials and/or energy to survive.

</comment><comment><USER19> Be careful If you are going to try fasting. If you read carefully, fasting increases PUFAs on the serum and if you have plenty of PUFAs in your body, it could kill your thyroid and metabolism.

Before trying fasting be sure to have at least a month of healthy eating and try sipping unsweetened lemon juice while you fast.

</comment><comment><USER20> Here is a different link - [https://link.springer.com/article/10.1007/s12325-018-0746-5](https://link.springer.com/article/10.1007/s12325-018-0746-5)

<comment><USER21> This is a different article altogether (which may be what you mean).

Here's a link to a webpage for the OP article: [https://www.sciencedirect.com/science/article/abs/pii/S15504...](https://www.sciencedirect.com/science/article/abs/pii/S1550413119304292?via%3Dihub)

</comment></comment><comment><USER22> I am happy to see another study that indicates good results.

I have stopped fasting, even though I believe in the benefits.

Now, I just make sure that every day I have at least a 12 hour contiguous period of not eating. This is really easy to do, for example, finishing dinner by 6:30pm and not eating until 7:30am the next day gives me a 13 hour period for resting my digestive system and giving my cells some time to repair rather than absorb nutrients. Easy, and with a mostly vegan diet except with lean meat about two times a week, I feel great.

For me, it is best to stay on an easy program, something that I can do long term.

</comment><comment><USER23> I was heading to the gym near the Twitter HQ in SF yesterday and saw Jack Dorsey walk past. He looked extremely thin and borderline sick to me. I think he does more extended fasts over the weekend but it's a bit unnerving when someone in a position to influence behavior like he is seems to be taking fasting to an extreme.

<comment><USER24> I've seen a lot of people say stuff like this, but it's kinda gross. If you want to criticize things someone has said about their diet and health practices, that's fine (and hopefully, you'll cite sources for why they're wrong), but if you're going to make it about how they look, and make your own diagnosis about their health, that's not really OK.

You don't know anything about the guy's health. He may actually be sick, wholly unrelated to his diet. He could be dealing with an eating disorder (which may be related to his diet, but millions of people have fasted regularly without having an eating disorder...there are lots of ways people cover for eating disorders). And, maybe he's in great health and your beliefs about what "healthy" looks like are wrong ("put some meat on your bones" is not great health advice for most people, but it's a common refrain).

I don't really know anything about what he's said about diet or fasting. But, I know that bringing his appearance and health into it are not shedding light on the subject, they're just conflating appearance with health and well-being in ways that aren't useful.

<comment> core-questions > that's not really OK.

This kind of word policing is even less OK. It's not "gross" to make a comment about something you see and have opinions about, especially for a public figure. You're not shedding light on any subject, either, all you're doing is being offended-on-behalf of someone else; the world's got enough of that and it doesn't seem to be making any positive difference at all.

<comment><USER24> The comment I responded to did not add substantively to the discussion, and I pointed out why.

I am not "policing" anything. I have no power to arrest someone or censor someone for being an asshole online. I expressed an opinion about the kind of community I'd like to be a part of. Also, it seems like you're doing what you're criticizing me for. I _don 't_ think the world's got enough of minding one's own damned business regarding people's health, body, and appearance, and that having more of it _would_ make a positive difference. This conversation is about the science of fasting, not whether Jack Dorsey looks thin.

<comment> core-questions > Also, it seems like you're doing what you're criticizing me for.

Sure, but only in a meta-sense to curb the proliferation of the technique. I'd liken it to nuking would-be nuclear powers to prevent further problems.

And maybe, _just maybe_, Jack Dorsey should eat a sandwich.

<comment><USER24> > I'd liken it to nuking would-be nuclear powers to prevent further problems.

So, when you wrote this, did the idea of using nuclear weapons preemptively seem like an obviously good idea, to you?

</comment></comment></comment></comment></comment></comment><comment><USER25> If I eat two meals in one sitting and then wait 23 hours before my next meal is this a form of intermittent fasting? I still get the same amount of calories as a normal person but there's a long period where I get nothing.

(I've been skipping breakfast my entire life so I don't really get the 3 meal thing.)

<comment><USER26> Yes, it's known as 23:1 Intermittent Fasting or more commonly OMAD, one meal a day.

<comment><USER25> Is it? The thing is I'm eating two meals in one sitting so it's still two meals a day. I typically thought intermittent fasting meant one meal per day. Does what I'm doing still count?

<comment><USER26> I think the amount of food doesn't matter, I would say if it's in one sitting it count as one meal. People that do OMAD usually eat much more than what they would eat in a normal meal, otherwise it wouldn't be sustainable in the long term.

Intermittent Fasting just means there is a 12+ hour period between the last meal of the day and the first meal of the next day. The most typical form is two meals a day in 16:8 fashion.

</comment></comment></comment></comment><comment><USER27> Is this new knowledge?

It sounds pretty similar to what was discovered in BBC's "Eat Fast Live longer" and that's a good few years old.

[https://vimeo.com/259080453](https://vimeo.com/259080453)

</comment><comment><USER28> It's interesting, but as a hobby and primary physical outlet I'm very involved in cycling. I don't race, but I ride with racers, and keep up.

I do not think I could balance fasting with 1,500 calorie efforts. ;)

<comment><USER29> Funny enough in the 70s and 80s (and into the early 90s in some rare cases) it was fairly common for cyclists to cut weight like boxers.

I think its fair to assume that caffeine and amphetamines were used to achieve those results and not strict fasting regimes...

<comment><USER28> Sure. I think that's still done -- I mean, look at top-tier racers.

But fasting and cutting weight are different ideas.

<comment><USER29> I just meant that cutting calories while cycle training has a long history (though I would describe it as healthy)

<comment><USER28> Diet modification during training typically still involves eating more calories than a sedentary person.

<comment><USER29> I know less about cycling diets than I do fighter camps but it is incredibly common for fighters to eat at fasting levels while continuing to train. The strict weight requirements cause that.

I was of the impression that it used to be the case that cyclists did this but that it was out of fashion now.

In any case lots of people do 1500 calorie efforts at fasting intake levels. It's not healthy long term but it's completely 'normal' for done athletes.

</comment></comment></comment></comment></comment></comment><comment><USER30> Mirror: [https://www.gwern.net/docs/longevity/2019-stekovic.pdf](https://www.gwern.net/docs/longevity/2019-stekovic.pdf)

</comment><comment><USER31> A -37% change in caloric intake (Fig. 2B) produces only a -4.5% change in body mass (Fig. 3A)? Seems odd no? Or am I mis-reading something?

<comment><USER32> This change was reported over 4 weeks, or 28 days.

For a 180lb person consuming, on average, 1900 kCal/day, a 37% drop in calories is a 703 kCal/day deficit below their initial equilibrium. This is 19,700 kCal over four weeks. Divided by 3600 kCal/lb, this is about 5.5 lbs. 4.5% of 180 lbs is 8.2 lbs. So, we're in the ball park. A 3-lb deficit from reduced inflammation (water) seems reasonable.

For a higher initial weight, you can get the numbers to agree exactly. I'm 6' and 182 lbs., which is just barely overweight. In the U.S., were I live, I look pretty "fit" by comparison with the average person. (I'm not, but that's another story.) According to [1], Austria, from where the participants were likely sourced, is only slightly leaner than the United States.

Therefore, their numbers seem to line up. Westerners are stuffing themselves.

[1] [https://www.indexmundi.com/blog/wp- content/uploads/2013/04/w...](https://www.indexmundi.com/blog/wp- content/uploads/2013/04/weight-of-the-world.jpg)

</comment></comment><comment><USER33> Does this increase risk of gallstones?

<comment><USER34> Yes it does. See - [https://news.ycombinator.com/item?id=20813736](https://news.ycombinator.com/item?id=20813736)

<comment><USER35> >..."might increase the risk of gallstone disease"...

I do 18:6 intermittent fasting and I did have a gallstone episode. My intuition is that fasting precipitated the expulsion of stones that had formed prior to the onset of my fasting regimen. Also, while practicing intermittent fasting, I think I have a tendency to overeat during my main meal of the day, maybe as a subconscious attempt to avoid feeling hungry later on. To avoid overeating, I need to be mindful to stop eating while I still feel slightly hungry.

The following blog post is consistent with my experience: [https://gallstonesdiet.net/can-intermittent-fasting-cause- ga...](https://gallstonesdiet.net/can-intermittent-fasting-cause-gallstones/)

<comment><USER26> > To avoid overeating, I need to be mindful to stop eating while I still feel > slightly hungry

For me the trick is to eat really slowly, even if I'm hungry.

</comment></comment></comment></comment><comment><USER36> Does fasting bring about any significant changes at the cellular level?

</comment><comment><USER37> why is this dated Sept 3rd 2019 (the future)?

<comment><USER38> They publish biweekly, this might be a pre-release from next week's issue.

</comment></comment><comment><USER20> Add (PDF) to the tile please (looks like its a direct link to a PDF)

<comment><USER39> Updated. Thanks!</comment></comment>


Linux: Linus Says, Linux Not Designed; It Never Was - <AUTHOR> http://kerneltrap.org/node/11

<comment><USER2> One of the things I respect about Linus is that he's such a gifted troll. :)

<comment><USER3> Linus is right here. Kernel is not a Business Requirement. He was scratching his Technical itch.

<comment><USER4> The best kind of troll, the one who is correct. Or is that the worst?

</comment></comment></comment><comment><USER5> It is interesting to read this and compare with _Worse is Better_ : <http://www.jwz.org/doc/worse-is-better.html>

Note that all of the ways the worse, less designed solution (Unix, C), are better boil down to being better from an adaptation/colonization/survival perspective. In other words the rise of Unix/C is computer evolution in action.

Linus just recognizes that that applies to Linux as well.

<comment><USER6> Absolutely , that was the first thing that came to my mind - this is Worse is Better and taking a further leap its a result of Release Early and Release Often.

<comment><USER7> You can use asterisks to get italicized text: <http://news.ycombinator.com/formatdoc>

<comment><USER6> Thanks.

</comment></comment></comment></comment><comment><USER8> Probably worth pointing out that this article is from 2002.

<comment><USER9> Just a meta-question here: Is pointing out the date of something worth 25 upmods? I mean, when so-and-so got to the forum and saw that...

 _Probably worth pointing out that this article is from 2002._

...was only upmodded 24 times, did he say to himself:

 _Only Twenty-Four upmods? This deeply insightful bit of time-tellery is worth Twenty-Five if it's worth a farthing! I shall upmod at once!_

<comment><USER10> You're reading too much into it. The points just indicate that around 25 people didn't realize the article was from 2002 until they read the comment so they upmodded

</comment></comment></comment><comment><AUTHOR> Pretty fantastic look into how Linus see's technology design, versus evolutionary engineering. F'ing awesome.

Linus' outlook on optimal engineering reminds me of Kevin Kelly's swarm and emergence writings.

<comment><USER11> Don't tar Linus' acerbic pragmatism with KK's technobabble idealism.

</comment></comment><comment><USER12> The Designers of UNIX are called Ritchie and Thompson.

Linux is a re-implementation of that design.

<comment><USER13> This quote by Linus applies:

 _But that's like saying that you know that you're going to build a car with four wheels and headlights - it's true, but the real bitch is in the details._

<comment><USER12> Go read an old unix source and tell me if you think it's just the four wheels and the headlights that were common.

Sure there are details, lots of them. Many of those were copied.

And linux didn't even get all of them right, even copying is hard work.

So it's an evolution of the original design.

Especially now, two decades later.

</comment></comment></comment><comment><USER14> Linus: "Quite frankly, Sun is doomed. And it has nothing to do with their engineering practices or their coding style."

This was in 2001. How does one get such prophetic skills.

<comment><USER15> Everything is doomed if you wait long enough.

<comment><USER16> That's exactly right. On top of that Sun had just lost 80% of its market capitalisation and there was a general sense of doom in the tech industry back then.

</comment></comment></comment><comment><USER17> The first Linus comment on that page is the best comment post I have ever read.

It make so much sense ! I can see clearly now !

</comment><comment><USER18> Natural evolution is best? One word: wheel . . .

Linux _as a whole_ was not designed -- that is easy to accept, and also that it is a strength.

However, design is not so entirely opposed to evolution as might be inferred. Design seems essentially to have some iterative character too. It always entails a some series of ideas, rejections, and then further adjusted ideas. That is deliberately controlled, but it still has _variation_ and _selection_ \-- so the possibility of blending between design and evolution is very reasonable.

And given the wheel example, artificial design has something to offer too.

(I think Torvalds' view is consonant with this. -- I mean, is he not overall offering some combination of evolution and design?)

<comment><USER19> Your wheel example is not good.

Before wheels, I'm pretty sure people used tree trunks to drag heavy objects from A to B. And I'm pretty sure the wheel's inventor hasn't envisioned the average consumer car we have today either.

Linus's point is that design happens at a micro-level, but at a macroscopic level the direction of a successful project should be made by trial and error with a feedback cycle.

To put things in perspective ... Linux is not designed for servers, it is not designed for desktops, it is not designed for real-time systems, it is not designed for mobile phones. When people wanted to use Linux for such stuff, they took it and modified it to their will, and the parts that slowed them down were eventually removed / refactored.

That's actually very true if you look at the history of many successful projects. And that's evolution more than design. "Release early and often" is exactly about this.

<comment><USER18> > Your wheel example is not good.

Well, no it isn't too good. But it does basically fit: It is a small feature of larger systems, as you describe, and it has been done better by artificial design.

</comment></comment></comment><comment><USER20> This surprised me:

"Take TCP for example. The TCP protocol is specified in a series of documents. If you make a formally correct implementation of the base TCP RFC you won't even make connections. Much of the flow control behaviour, the queueing and the detail is learned only by being directly part of the TCP implementing community. You can read all the scientific papers you like, it will not make you a good TCP implementor."

\- Alan Cox

</comment><comment><USER21> It's interesting that Linus believes that Linux is the most widely deployed Unix. I would have guessed that MacOS X might have surpassed it by now.

Edit: Oops...this is from 2001

<comment><USER22> Well, firstly that post was written eight years ago. Secondly, OS X might surpass it on Desktops, but what about servers, computing clusters and so on?

<comment><USER23> Not to mention phones, TiVos, netbooks, routers, Kindles, NAS devices...

<comment><USER24> OS X is on a lot of phones though (the iPhone)

<comment><USER25> linux is on most wireless access points, routers, etc :/ That's a lot of units.

</comment></comment></comment></comment></comment><comment><USER26> Evolution isn't that impressive. Humans could build human-level AIs if we had millions of years too.

</comment><comment><USER27> reminds me of yesterday's font page submission on poor use of analogies. not saying it is, but i can't help seeing the connection...oh god! may _this_ is a bad analogy. will it never end!!

<comment><USER28> Sounds interesting. Link?

Not that we really need to analyze it. Theres 50 reasons why this is a bad analogy.

</comment></comment><comment><USER29> That which works well beats that which looks good.

Take quantum for example: When Dirac was asked, "What's the answer to the measurement problem?" his response was, Quantum mechanics is a provisional theory.</comment>


Heinz Wolff has died - <AUTHOR> http://www.bbc.co.uk/news/uk-42378765 <comment><USER2> For all we have some pretty good science programming in the UK, what with Jim Al-Khalili, Brian Cox, Sky at Night and more, we're missing the Heinz Wolff and Johnny Ball style characters who bring their subjects alive for children.

It'd be great to have a science-based equivalent to Horrible Histories.

<comment><USER3> For older children or adults, "Everyday Miracles" had only 2 episodes but they were both pretty good. Also the presenter was really doing experiments and going around factories where they make stuff showing exactly how things are made.

[http://www.bbc.co.uk/programmes/b04fh5tf](http://www.bbc.co.uk/programmes/b04fh5tf)

</comment></comment><comment><AUTHOR> I recall meeting him at a Royal Society Christmas lecture when I was a teen. I was sat in the front row - and he asked for a volunteer. Needless to say, muggins volunteered - to stick his naked hand in a flask of liquid nitrogen, it transpired.

And this is how I first experienced the Leidenfrost effect, and understood just how effectively boiling liquids can self-insulate.

He was an astoundingly good teacher, and an inspiration, to me, at least.

<comment><USER4> That could have gone quite wrong no?

<comment><AUTHOR> He was very clear about dipping my hand in slowly, and not moving it at all, as that would've shaken off the boundary and resulted in frostnip - but this was the 90's, when getting kids to put their hand in cryo was just one of those things you do.

</comment></comment></comment><comment><USER5> A number of episodes of The Great Egg Race are available on the BBC Archive: [http://www.bbc.co.uk/archive/great_egg_race/](http://www.bbc.co.uk/archive/great_egg_race/)

Wonderful stuff. RIP.

Oh - he was a contestant an episode of on The Adventure Game, which is now available on DVD. Stands up very well to the test of time.

</comment><comment><USER6> Very sad news. "The Great Egg Race" was a TV show I often think would lend itself well to revival.

<comment><USER7> Hear hear on both counts.

Its gentle rivalry and lack of melodrama would be great to see again. It would need a new presenter now of course, and they'd be pretty big shoes to fill.

</comment></comment><comment><USER8> This is very sad news.

I loved seeing Heinz Wolff on TV as a child for two reasons.

First, like Johnny Ball, it was great to see a quirky, odd shaped personality on TV instead of the usual slick drama school, artsy or journalist types.

For a nerdy kid like me Heinz was a wonderfully fun roll model.

Second, Heinz was German. In a country where sections of the media* still go on about the Second World War at every political dealing with modern Germany, Heinz was a well known "nice German".

People like Heinz Wolff, Bauhaus and Kraftwerk made me a deutschophile. The irony that he came to England from Germany as a Jewish refugee is not lost on me.

*(My family lost my grandfather and two others fighting but it's ridiculous how the tabloids still blame current generations of Germans for the past whilst pushing their own dodgy agendas).

</comment><comment><USER9> That's rather sad. I was one of the children that he inspired with his remarkable works. I shall off to Youtube to re-watch some.

</comment><comment><USER10> A very sad loss, and it's a great shame that we didn't get more of The Great Egg Race. I met him briefly while working as an assistant at Space School at Brunel University one year.

</comment><comment><USER11> I once attended a lecture he gave to an international audience. However the Americans in the room complained that they couldn't understand anything he said.

</comment><comment><USER12> Bear to the right!

</comment><comment><USER13> Lets pray that he is in a better place

</comment><comment><USER14> I did not really know much of him, but enough, that this sentence

"A Jewish refugee, Wolff moved to the UK from Berlin at the age of 11 on the day World War Two broke out in September 1939"

annoyed me very much. F____ stupid Nazis. By wanting to make Germany great again, they destroyed so much of it ...</comment>


Ask HN: Formalities that should be discussed when starting on a group project? - <AUTHOR>

I am about to dedicate a good chunk of my time and money to working on a promising project. The idea was purely of my own invention. I've bounced the idea off a couple people who have reacted very positively and have expressed interest in working with me on it (without me asking explicitly for their involvement).
If I decide to pursue the project with others, are there any formalities that should be addressed -- for example, regarding ownership, patenting, etc. What kinds of agreements should be discussed before we begin investing time and money into the project? Does it need to be formally documented in a particular way? Do I need to involve a legal professional? If some issues do not need to be addressed at the very beginning, then when should they be addressed?
Are there standard procedures/recommendations that should be followed? Where can I get this information?
Up till now, I have only had text conversations (I've made sure to keep time-stamped logs of our conversations). We don't have anything tangible -- no prototypes or design notes.
It would be frustrating to encounter any dilemmas later on that could have been "prevented" by having established some formal agreements. "Cover my ass" might be one way to put it. I'd like to get these matters out of the way before I put in time and money.
Perhaps I am naive but I see real promise in what we are about to work on. <comment><USER2> I don't know about the details of the paperwork.

But a usual complain is the distribution of the equity. Imagine that three year later one of the developers-founder will write a post from a throwaway account saying that he worked for three years and someone offered only a 5% equity, and he fells scammed. (Probably, in this case a 5% is very low.)

Another point to consider is vesting, because another developer-founder will quit the second week, and he will share a 20% of the company forever.

Do you want more equity because it's your idea and you are investing money? Are you going to code? Are you going to bring clients/users?

Some ideas from Joel Spolsky: "Joel's Totally Fair Method to Divide Up The Ownership of Any Startup"

[http://www.brightjourney.com/q/forming-new-software- startup-...](http://www.brightjourney.com/q/forming-new-software-startup- allocate-ownership-fairly)

Discussions of this article in HN (with some additional ideas, support and counterpoints):

[https://news.ycombinator.com/item?id=2445447](https://news.ycombinator.com/item?id=2445447) (436 points, 1158 days ago, 67 comments)

[https://news.ycombinator.com/item?id=3489719](https://news.ycombinator.com/item?id=3489719) (328 points, 876 days ago, 93 comments)</comment>


Jun Fukuyama's P≠NP Page - <AUTHOR> http://junfukuyama.wordpress.com/ a new serious proof claim on P!=NP has been put forward by a Phd mathematician/computer scientist Jun Fukuyama last July 1 and has received very little public attention since then.
http://www.linkedin.com/pub/junichiro-fukuyama/36/2b9/88b
rumor is that its been submitted to a journal. it uses a known plausible approach based on monotone circuit theory for which there are some long established existing proofs of circuit lower bounds (dating to a celebrated 1985 proof by Razborov). Fukuyama has published several papers in computer science. it would be great if the online community could give this some attention as with the Deolalikar proof from 2.5yrs ago. <comment><USER2> Very briefly:

Context: Some problems are easy, and known to be easy. Some problems appear to be hard, and yet easy to verify alleged solutions. That seems odd - let's have a closer look.

Example:

Consider being given a network and asked if there's a path that visits every node exactly once and returns to its starting point. (This is the task of asking if a Hamilton Cycle exists). If the network is big enough, deciding if this can be done can be really hard. However, checking if someone has successfully done it is easy.

Motivation for a definition of NP:

A problem for which it is efficient (for which read "polynomial") to check a purported solution is said to be in "NP". Knowing whether a Hamilton cycle exists in a network is one of many, many such problems.

Definition: A problem is in "NP" if there is a polynomial time algorithm to test an alleged solution.

Definition: A problem is in "P" if there is a polynomial time algorithm to solve it.

Lemma: All problems in "P" are also in "NP". Proof left to the interested reader.

(Note: technically we are dealing with Decision Problems - problems where the answer is always Yes or No. For example, I didn't ask you to find a Hamilton Cycle, I only asked if there was one. Sometimes the Decision version can be ramped up into actually finding the solution.)

Note that easy problems (for example, finding a cycle that visits every edge exactly once - an Euler Cycle) is also "NP", but it's not a hard NP problem - it's actually in "P". This point confuses a lot of people. NP does not automatically mean hard - that comes in a minute.

Another example:

Similarly, factoring a large integer can be really hard, but if someone claims to have a factor, checking it is as easy as doing the division.

Comparing problems:

Cleverly, it can be shown that if you can solve the Hamilton Circuit problem efficiently, that can be converted into a way of solving the factoring problem. In some very real sense, the Hamilton Circuit problem is harder than (or equal to) the factoring problem.

Finding:

There are many, many NP problems that have been shown all to be equivalent to each other, all to be easy to check solutions, and yet no algorithm for solving in polynomial time known. Such problems are call NP-Complete (NPC) because an efficient algorithm for any of them will completely solve all the NP problems.

So:

* A problem is said to be in "P" if there is an algorithm that takes instances and produces answers in polynomial time.

* A problem is said to be in "NP" if there is an algorithm that takes only polynomial time to check a purported solution for correctness.

* It is unknown if there are any problems that are in "NP", but not in "P".

That is the P vs NP question, and the Clay Mathematics Institute has offered $10^6 for its resolution. You could do this by showing that there is a polynomial time algorithm for any of the NPC problems, or by showing that no such algorithm exists.

Summary:

* P problems are "easy"

* NPC problems are thought to be hard

* There are lots of NPC problems, and solving any one of them would solve all NP problems.

* Integer factoring (IF) is thought to be outside P, but not as hard as NPC.

* There are problems that are harder than all NPC problems, these are called NP-Hard.

So we think that

      P < IF < NPC={ Clique, 3SAT, G3C, Knapsack, Ham, ...} <= NP-Hard

But we don't know if these are, in fact, all different. The submitted link is to a paper that says yes, they are all different.

I hope that helps.

<comment><USER3> Why do they call it decision problems, if it's really about finding a solution that is much more than a boolean (like a path, ...)?

The whole idea of "verify" versus "find" makes no sense for problems with a yes/no answer, because if you can verify a boolean answer in polynomial time, you can always find the solution in polynomial time too, after all there are only two possible solutions so you need to verify only one to find the answer.

If you need extra data to prove this "yes" in polynomial time, then the answer isn't a boolean anymore, but a boolean plus the extra data, so how can you still call that a yes/no problem?

<comment><USER4> _...if you can verify a boolean answer in polynomial time, you can always find the solution in polynomial time too, after all there are only two possible solutions so you need to verify only one to find the answer._

It doesn't work that way. The common characteristic of NP-complete problems is that there are an exponential number of possible solutions, but verifying that a purported solution is a solution takes only polynomial time.

For example consider SAT (see <http://en.wikipedia.org/wiki/Boolean_satisfiability_problem> for more). This is the problem of deciding whether there is a set of possible variable values that make a given Boolean equation evaluate to _True_. For an equation of length n there are in general O(n) variables, and therefore 2^O(n) possible sets of true/false values that the variables can have. So a brute force search takes exponential time.

But if you give me an equation, AND a set of values for the variables that you claim will result in the final expression evaluating to _True_ , I can verify it in time O(n).

Does that answer your question?

</comment></comment></comment><comment><USER5> Before anyone gets too excited, I would caution that there there is a long history of failed attempts at this problem, and an equally long history of premature announcements. On the surface, here is what is encouraging about this one:

\- The author is a theory professional and not an amateur or a crank

\- The author frames this as a possible proof where he's seeking feedback on the method, rather than declaring a solution up front

\- The author builds on existing theory in a formerly mainstream approach that has been shown to have problems (circuit lower bounds)

\- Looks like a serious and well-considered proof effort

Here is why HN should hold off on any excitement:

\- This style of proof was found to be unworkable in the past. In particular, approaches to proving circuit lower bounds in this manner were shown by Razborov and Rudich to be "natural proofs" in the 1990s, which is a category of proof strategy that cannot demonstrate P/NP. It's not explained why this strategy does not succumb to the same problem -- though the author surely has some reasoning around it. (see point 6 of Scott Aaronson's "8 signs a proposed P/NP proof is wrong": <http://www.scottaaronson.com/blog/?p=458>. You might also see this comment from /r/math: [http://www.reddit.com/r/compsci/comments/14mqqt/anyone_have_...](http://www.reddit.com/r/compsci/comments/14mqqt/anyone_have_the_math_to_check_out_this_p_np_proof/c7elwbz)) ).

\- There is a very good community framework for evaluating proposed solutions when the author's ready. Possibly the author has already submitted the work to a journal, but it's not clear that he's confident enough yet to invite more active discussion on his effort from the theory community. I can't find any discussion of it online. It's likely he's pursuing these on his own, and conceivably flaws have been found since the summer.

\- The author does not declare this as a completed solution in the same way that Deolikar did two years ago. In that case, his announcement led to an analysis by the theory community online that led to discovery of core errors. We can wait here 'til the author gives a bit more information.

\- This proof joins dozens of other announced solutions to P/NP in both directions (see, for example, <http://www.win.tue.nl/~gwoegi/P-versus-NP.htm>) which emerge quite regularly, and close attention paid to each will leave no time for original research :)

<comment><AUTHOR> hi AK. maybe consider blogging about this? this is a well written but superficial analysis. scott aaronson insists on his blog that a proof should explain why it succeeds against "known barriers" eg razborov/rudich Natural Proofs. but this is really an optional requirement of a proof. moreover the actual barrier to "natural proofs" is very subtle and basically insists that a proof, if it exists, should have a certain "intrinsic complexity" in its constructions, and that many such constructions in the literature for class separations do not have this "intrinsic complexity". but new researchers are just suggesting that this only requires some new "intrinsic complexity" function that hasnt been seen before; but that such functions do exist, they just dont seem to be used in proofs that we know of. eminent authorities in the field such as Lipton have argued that the near 20yr old Natural Proofs may be overdramatized as a real barrier.

here is liptons blog on the subj: [http://rjlipton.wordpress.com/2009/03/25/whos-afraid-of- natu...](http://rjlipton.wordpress.com/2009/03/25/whos-afraid-of-natural- proofs/)

here is chow in AMS:

"Nevertheless, it is my personal opinion that the optimistic approach is the right one; that is, the Razborov–Rudich result should be regarded as a hint, and not a barrier, to separating complex- ity classes. The only real barrier is our lack of imagination."

<http://www.ams.org/notices/201111/rtx111101586p.pdf>

<comment><USER5> I may have come across as insistent on clearly stating ways around the natural proofs barrier because this is Hacker News, where folks are liable to jump to conclusions, and not, say, <http://cstheory.stackexchange.com>. Given the large number of attempts against P vs. NP, frequently by folks who are not active in complexity theory, it's often better to try to understand these ideas on theory sites.

You make an reasonable point, vis-a-vis Chow; rather than being regarded as an absolute barrier for lines of reasoning involving circuit complexity, the requirement of being a sufficiently complex proof may provide a jumping-off point for uncovering a working method.

</comment></comment></comment><comment><USER6> A great site with 95 documented attempts at proving P ?= NP is over at <http://www.win.tue.nl/~gwoegi/P-versus-NP.htm>, for those interested in the subject.

</comment><comment> B-Con From other people's research ( [http://michaelnielsen.org/polymath1/index.php?title=Jun_Fuku...](http://michaelnielsen.org/polymath1/index.php?title=Jun_Fukuyama%27s_P%E2%89%A0NP_Paper) ) he seems to have a credible background.

Although I find it interesting that he works for Toyota:

> My name is Jun Fukuyama. I'm currently a researcher at Toyota InfoTechnology > Center. I'm visiting WINLAB and Civil Engineering department at Rutgers > University, working on algorithms and mathematical analysis related to > vehicular communications and mobility modeling.

Unless he's been doing this research in his spare time, it seems like an odd fit for Toyota to dedicate research to. Obviously large companies employ theory-oriented researchers, but when I think Toyota I don't really think about very abstract computer science. I'm curious if there are any particular applications for the company one way or the other.

<comment><USER7> Toyota actually has opened a school in Chicago specifically for computer science, in conjunction with the University of Chicago:

[http://en.wikipedia.org/wiki/Toyota_Technological_Institute_...](http://en.wikipedia.org/wiki/Toyota_Technological_Institute_at_Chicago)

<comment><USER8> I go to UChicago; that place is sort of like an eerie mystery box that nobody ever goes to or talks about. I didn't even find out about it's existence until my 3rd year here. My one friend who's been in there described the experience as really bizarre; it left him half convinced that its actually a front for some sort of Israeli money laundering operation.

<comment><USER9> They have some very prominent machine learning folks there and I went to the Machine Learning Summer School they hosted a few years back. Seemed legitimate enough to me!

</comment></comment></comment></comment><comment><AUTHOR> hi all. meant to post a comment but didnt understand this hackernews interface so far, am brand new to this site. fukuyama states on his web page he's worked on P vs NP for over 10 yrs, both inside and outside of his professional jobs which include research and teaching. the web page is a proof [claimed/attempt] that P!=NP posted on Jul 1. unfortunately its gotten very little to no online attention since then, at this point so far. he doesnt seem to have announced it anywhere in cyberspace, only created the blog.

<comment><USER10> If you don't mind me asking, how and when did you find his blog post?

</comment></comment><comment><USER11> I wish I had the mathematical background to comprehend this. It's very involved. My understanding is that he has shown that CLIQUE (a known NP- complete problem) takes exponential time and thus is not solvable in polytime, this would mean there is a problem outside of P but inside of NP, and this P != NP.

<comment><USER12> If a problem is NP complete then there is an algorithm to solve it in nondeterminstic polynomial time. Any nondet algorithm can be transformed to an exp poly time algorithm (just run through each of your poly time algorithms one by one) so showing CLIQUE has an exp algorithm doesn't help at all. We want a lower bound.

<comment><USER13> Yes, that's what he is saying, _every_ CLIQUE algorithm takes at least exponential time.

<comment><USER12> Oh ok, I thought the first post was referring to a single algorithm, not every possible algorithm. My mistake.

<comment><USER11> Sorry, if I could I would edit it to be more clear. We definitely need to show that no algorithm can exist with poly runtime for all inputs.

</comment></comment></comment></comment></comment><comment><USER4> I googled to see if Terry Tao had weighed in yet. He has not that I've seen.

However [http://vzn1.wordpress.com/2012/12/08/outline-for-a-np- vsppol...](http://vzn1.wordpress.com/2012/12/08/outline-for-a-np-vsppoly- proof-based-on-monotone-circuits-hypergraphs-and-factoring/) suggests that this looks like a serious attempt. (Of course most serious attempts will fail.)

</comment><comment><USER14> Can we get a laymans explanation of what this is about? I understand what p np is, but don't really understand what this person is claiming. Is this some kind of claim about the overall concept of p np? Or proving a specific case?

<comment><USER15> If I understand it right he showed that Clique cannot be solved in polynomial time, since any NP complete problem is at least as hard as Clique none of those problems can be solved in polynomial time. So he used Clique to draw general conclusion that P!=NP.

<comment><USER16> This only works if all NPC problems can be converted to CLIQUE?

<comment><USER17> All NP problems can be converted into the other NP problems, therefore if you can prove it for one NP problem, you prove it for all NP problems.

<comment><USER18> You missed a few words. Any NP-complete problem can be converted into any other NP-complete problem in polynomial time.

<comment><USER17> Right, oops.

</comment></comment></comment></comment></comment></comment><comment><USER10> Note: For the moment, I will assume that the NP != NC and above results are correct enough to consider the validity of the latter portion of the paper.

As far as I can tell (from my initial reading), the author (and many many commenters here) seem(s) to be confusing polynomial time (P) with polynomial circuit size (P/poly). These are completely different complexity classes in style and probably in power, too. Last time I checked, there was not a good characterization of P in terms of circuit complexity (the attempt at doing so is P/poly). So, logically, comparing P and NP is not even possible without additional knowledge about P. The exception to this being showing that X != NP where P <= X <= NP.

For reference: P <= BPP <= NP

We know that BPP (a randomized version of P) is (non-strictly) contained in P/poly. We also know that proving P = BPP (which is conjectured to be true by most) requires these classes require superpolynomial lower bounds for Boolean|Arithmetic circuit size. As far as I know, proving an exponential lower bound for an NP-complete problem doesn't immediately rule that P != NP since P !=> only polynomial size circuit size (the circuit size only relates to the size of the advice function). P might not contain problems that require exponential circuit size, but this fact is not stated, proven, nor reference by the author here.

Simply put: The author assumes that P != NP follows immediately from Theorem 6.1. This is not as obvious as they might think it is; many additional details are needed.

Admittedly, I have not rigorously studied or concluded anything from the flattening process the author proposes. I honestly don't believe I have to. Skimming over it, I don't see any way that P is characterized in terms of polynomial circuit sizes (which probably is an assumption as powerful as P!=NP) here. I also do not see any mention of P/poly, which I believe the author is attempting to use.

For a paper approaching the P vs NP issue using circuit complexity, I would expect this much. Because of the lack of even a mention of BPP, P/poly, and others, I would be highly surprised if many of these results in the paper hold at all. Though, hopefully, I might be wrong.

EDIT: Accidentally used circuit depth when I was really thinking of size.

<comment><AUTHOR> "as far as I know, proving an exponential lower bound for an NP complete problem doesnt immediately rule that P!=NP". that statement is _FALSE_. P!=NP is exactly a consequence of proving exponential lower time bounds. actually P!=NP would be a consequence of even proving somewhat weaker _superpolynomial_ time bounds on any NP complete problem...

<comment><USER10> I was clearly referring to exponential circuit sizes (note the sentence before it), not exponential time.

By the way, you can edit your original reply to contain more information rather than just making a bunch of new ones.

<comment><AUTHOR> oops. thx for info. didnt notice that. new to this. sorry for multiple replies that should just be edits.

</comment></comment></comment></comment><comment><USER19> For a popular treatment of the subject and the consequences, see this film (I assume the first film ever made about P=NP and it was released just this year): <http://en.wikipedia.org/wiki/Travelling_Salesman_(2012_film)>

I just finished a section on NPC problems in my algorithms class (working on a masters). For years, I've been confused about the true meaning of P, NP, and NPC. Feels weird saying it, but I am so glad I've finally got a good grasp on at least the definitions. One of the most gratifying moments in the class was doing homework problems that required proving various problems were in NPC.

</comment><comment><USER20> Btw., what about Vinay Deolalikar's proof now?

The last update I could find: [http://rjlipton.wordpress.com/2011/08/11/deolalikars- claim-o...](http://rjlipton.wordpress.com/2011/08/11/deolalikars-claim-one- year-later/) <http://news.ycombinator.com/item?id=2891710>

<comment> iso-8859-1 It is incorrect. I guess that after he realized it himself, he got discouraged and didn't bother to tell people about it.

</comment></comment><comment><USER11> Has this been submitted to a journal or the Clay Institute or any peer review yet?

</comment><comment><USER21> I'm interested in knowing how many of you on here are going to read this in one sitting. Not that it would be sufficient to analyze it for bugs, but because you're that interested.

<comment><USER22> If I had the mathematical background necessary to understand it, I certainly would.

... and I really wish I did have the mathematical background. Anyone have any recommendations on how to go from a standard CS undergrad math background to being able to understand proofs like these?

<comment><USER23> Read it and google as you go. Math is one of the best covered topics online. For a potential millenium prize proof, it seems very approachable. That said, that's not saying much.

<comment><USER24> I find math in some cases to be really hard to Google. Particularly with expressions that I don't know the names of; I never know what to use as search terms.

</comment></comment></comment></comment><comment><USER25> There is a great udacity course with all the background to the P/NP problem: <http://www.udacity.com/overview/Course/cs313/> I found it very informative. It also has a section on "should you try solving the P vs. NP problem" and the answer is "not unless you have a lot of time, money, and though of something no one tried before, or is a math / CS professor"

</comment><comment><USER26> YES, YOUR MAJESTY!

<comment><USER27> All Hail Britannia

</comment></comment><comment><USER28> damn, there is a typo on page 32 (in paper version 1.11). Stopped reading. I'm wondering if that voids the proof. Let's the downvote begin.

<comment><USER29> This is why we cant have nice things

<comment><USER28> now the funny thing is that there is really a typo on that page, so all of the these hacker news people downvote just because I pointed out some small, but truth parth of reality.

this is called witch-hunt

<comment><USER30> Well, sure. It's more that you posted a comment not that there's a typo but that this typo makes it so unbearable to read that you were simply forced to stop. But anyway...

<comment><USER28> it will be oil on fire, and you guys will already downvoted me into oblivion, but the truth is the same, the paper has several typos, which makes in unquestionable that it did not see a spell-checker.

<comment><USER2> Spell checking math, and in particular LaTeX math, is a complete nightmare. I, for one, find that there are just as many substantive typographical errors after spell checking my papers as before, and all I've done is wasted at a minimum an hour trawling through false positives.

Besides, small typos in a paper that's substantially readable and well crafted, written by someone in a language other than their first, are scarcely a reason to stop reading.</comment></comment></comment></comment></comment></comment>


Boston YC Meetup at next weeks (5/22) WebInnovators Conf?  - <AUTHOR>

<comment><AUTHOR> Anyone want to meetup at the next Tues May 22 WebInnovators conference at the Royal Sonesta in Cambridge (6:30-9pm)? There are about 150+ people that attend, so I recommend we put a YC on the nametags to identify ourselves. The event is free, but you should RSVP at: <http://www.webinnovatorsgroup.com/>

<comment><USER2> How about putting news.yc on the nametags so as not to be confused with real YC people.

</comment></comment><comment><USER3> These events are getting pretty packed now. Maybe better to meet up before at the bar downstairs or something for those who are interestd...</comment>