Wendelstein 7-X achieves world record - <AUTHOR> http://www.ipp.mpg.de/4413312/04_18 <comment><USER2> Just to reiterate, Wendelstein 7-X is _not_ about fusion. 7-X is a research project about controlling a plasma. It is not meant to evaluate whether energy production is viable, neither is it setup to do so.

<comment><USER3> > 7-X is a research project about controlling a plasma.

Which is the primary impediment to developing viable fusion reactors. So yes, it is absolutely about fusion. We're not trying to contain plasma because we think it'd be a neat thing to do. We're trying to contain plasma because it's necessary for fusion.

We already know that energy production is viable if we can solve the containment problem. Saying this project "isn't about fusion" is like saying "guns don't kill people, bullets do".

<comment><USER4> > We already know that energy production is viable if we can solve the > containment problem.

No. That's only a small part of the problems. What is probably a far more difficult problem is the fact that any nuclear fusion which is remotely viable in this century will use a Deuterium-Tritium reaction. And tritium is an isotope which does not occur in nature - it is unstable. Therefore tritium has to be bred, using heavy water reactors. And lots, lots, of uranium. The idea is now to breed tritium, using neutrons from nuclear fusion, and further nuclear chemistry which is supposed to happen in a breeding blanket. But this runs into an additional problem, the deuterium-tritium reaction has no neutron surplus, as uranium fission has. And in addition to the very difficult task of exfiltrating traces of Tritium, one essentially needs a breeder technology (similar to Monju in Japan), and there are huge, unsolved material sciences problems, such as constructing a large structures which withstands very strong magnetic forces, very high temperatures, and a very high neutron flux, and this of course without any elements like carbon which will become radioactively activated.

Oh, and I forgot, the whole process is also unlikely to be clean, because of the breeder technology needed.

And all these questions are so extremely difficult, that today's large projects, like ITER, do not even address them.

More on these issues for example in the article by Michael Moyer which is contained in the page below (Michael Moyer, "Fusion's false Dawn", Scientific American 302, 50 - 57 (2010) doi:10.1038/scientificamerican0310-50 )

[http://energyskeptic.com/2014/why-fusion-is- still-30-years-a...](http://energyskeptic.com/2014/why-fusion-is- still-30-years-away/)

<comment><USER5> Tritium can be bred in any sort of fission reactor. The US has recently used light water power reactors to breed tritium for supplying the US nuclear weapons stockpile.

Lithium-7 plus a high energy neutron yields tritium, helium, and a lower energy neutron. I don't know what a practically engineered system can do, but a 14.1 MeV neutron from D-T fusion formally has enough energy to transmute 5 lithium-7 nuclei into tritium and helium (each transmutation is endothermic to the tune of 2.466 MeV).

I agree about the huge unsolved material science problems. I just don't think that tritium availability lies on the critical path of unsolved problems for industrial fusion power.

<comment><USER4> > I just don't think that tritium availability lies on the critical path of > unsolved problems for industrial fusion power.

Well.

[https://scholar.google.co.uk/scholar?hl=en&as_sdt=0%2C5&q=Sa...](https://scholar.google.co.uk/scholar?hl=en&as_sdt=0%2C5&q=Sawan+Abdou+Tritium+breeding&btnG=)

[http://fti.neep.wisc.edu/pdf/fdm1273.pdf](http://fti.neep.wisc.edu/pdf/fdm1273.pdf)

M.E. Sawan and M.A. Abdou, "Physics and Technology Conditions for Attaining Tritium Self-Sufficiency for the D-T Fuel Cycle", Presented at the Seventh International Symposium on Fusion Nuclear Technology, May 22-27, 2005, Tokyo, Japan; to be published in Fusion Engineering and Design.

Abstract + conclusions:

"There is no practical external source of tritium for fusion energy development beyond ITER and all subsequent fusion systems have to breed their own tritium. To ensure tritium self-sufficiency, the calculated achievable tritium breeding ratio (TBR) should be equal to or greater than the required TBR. The potential of achieving tritium self-sufficiency depends on many system physics and technology parameters. [...] It is clear from the above discussion that both the required and achievable TBR values depend on many system physics and technology parameters. Many of these parameters are not yet well defined. In addition, the rapidly decreasing tritium resources imply that the time window for the availability of tritium to supply fuel for the DT physics devices is closing rapidly. It is, therefore, necessary to establish without delay an extensive R&D program to determine the "phase-space" of plasma, nuclear, material, and technological conditions in which tritium self- sufficiency can be attained.

[...] Tritium self-sufficiency in DT fusion systems cannot be assured unless specific plasma and technology conditions are met. [...]

<comment><USER5> This seems to be the critical assumption in Sawan and Abdou's paper:

 _The tritium bred in the CANDU reactors is the only practical source available for ITER and other DT fusion systems [3,4]._

Citation 3 is "personal communication." 4 is this 2002 presentation: [http://www.fusion.ucla.edu/abdou/abdou%20presentations/2002/...](http://www.fusion.ucla.edu/abdou/abdou%20presentations/2002/DevPath%20Presentation/DevPath%20Presentation%20\(10-28-02\)%20FINAL2.pdf)

Page 32 of that presentation, "Tritium Supply Calculation Assumptions", says it is assumed that the following will NOT happen:

• Restarting idle CANDU's

• Processing moderator from non-OPG CANDU's (Quebec, New Brunswick)

• Building more CANDU's

• Irradiating Li targets in commercial reactors (including CANDU's)

• Obtaining tritium from weapons programs of "nuclear superpowers"

• Premature shutdown of CANDU reactors

But assumptions 3 and 4 have already been invalidated. China has added CANDU reactors since the presentation and is building a few more abroad for other countries. The United States has started irradiating lithium targets in commercial reactors.

So in my judgment, closing the tritium cycle still isn't on the critical path to fusion industrialization. There are other crucial problems to solve before "where will we get enough tritium for these fusion reactors?" becomes a crucial issue.

</comment></comment></comment></comment></comment></comment><comment><USER6> What does "At an ion temperature of about 40 million degrees" mean?

How does "ion temperature" relate to "regular" temperature?

Is it similar to how we can cool down things to fractions above absolute zero, by using lasers to reduce the movement of atoms? i.e. is the "ion temperature" a measure of how fast are they moving, as opposed to the every-day meaning of temperature as "how hot something is"?

I realize that "how hot something is" depends on how fast the atoms of said "something" are moving, but since they specify "ion temperature" I'm guessing it has a very specific meaning.

I searched for "ion temperature" but only found about Electron temperature [0].

Could someone explain it to me in lay terms? :)

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

<comment><USER7> Other replies have explained that the ions and electrons can be at different temperatures, and that is of course true. I can offer some more explanation why. While you have linked temperature to some average kinetic energy, this is not a strictly accurate notion of temperature. Temperature only means something in the context of thermodynamic equilibrium; for any system out of equilibrium, often a temperature cannot be defined, even as an average kinetic energy. The two concepts are linked to each other, in the sense that an average kinetic energy at the particle scale is a significant (and sometimes only, but not always) component of the internal energy of the system. But temperature is first and foremost an equilibrium concept.

A plasma is composed of both ions (partially ionized atoms, or if they are fully ionized, bare nuclei) and electrons. Together, they constitute two co- located but separate fluids, whose motions may be distinct; indeed, because electrons are so much lighter than ions, they respond to forces much more readily. In equilibrium, a single fluid must have sufficiently rapid interactions so that the particle distributions are driven to a Maxwellian. In that case, for a single fluid, a temperature is well defined. In the case of a two-fluid system, self-interactions (such as interactions between ions and themselves, and electrons and themselves) may be sufficient to establish two separate equilibria corresponding to each fluid; hence, the electron vs. ion temperature. Only in the case that ion-electron interactions are sufficiently rapid would those equilibria be driven together to a single-temperature fluid, in which case, Te = Ti.

This picture becomes rapidly more complicated at very high temperature (usually, around 0.1 keV or about a million K), at which point the photons being exchanged by hot charged particles become dynamically important, and a third temperature, the radiation temperature, may emerge. At this point, the plasma must be described using three temperatures - if, and only if, you are in a situation lucky enough for equilibrium to manifest. (Fortunately, equilibrium is not usually that hard to access.) In many cases, such as when the system undergoes a strong shock, the system may be driven very far from equilibrium, but only temporarily. In others, some underlying energetic process may continuously drive the system away from equilibrium, resulting in a metastable state; this is the case in stellar atmospheres, in which NLTE (non-local thermodynamic equilibrium) processes matter a great deal. Usually, physicists resort to kinetic theory to try to understand such situations.

<comment><USER6> Awesome explanation!

Thanks a lot.

It's amazing how something seemingly simple as "temperature" can be so counter-intuitive.

</comment></comment></comment><comment><USER8> If you speak German the podcast Alternativlos has a fantastic episode about Wendelstein. Highly recommended.

<comment><USER9> Did you mean this one [https://alternativlos.org/36/](https://alternativlos.org/36/) ?

<comment><USER8> That's the one.

<comment><USER10> Thanks for the tip, started out really interesting!

<comment><USER11> Even if you don't care about fusion itself, it is highly interesting in that it covers some of the engineering that went into building that thing.

<comment><USER8> And the guests are perfect. Competent and entertaining at the same time.

</comment></comment></comment></comment></comment></comment><comment><USER12> > The objective of fusion research is to develop a power plant favourable to > climate and environment. Like the sun, it is to derive energy from fusion of > atomic nuclei

While plasma containment seems like an essential step towards fusion-based energy, is fusion-based energy a desirable goal?

Right now, fission-based nuclear energy is only used as a heat source for steam-driven turbines. It's a fantastically complex and expensive way to make heat.

Is fusion energy on Earth going to do something similar? And if so, is this source of heat actually going to be cheaper than using the sun as a distant fusion reactor? (Which is what drives both solar and wind energy on Earth.) It seems quite doubtful that fusion could ever be cheaper than solar or wind energy, the tech-to-energy ratio just seems massive in comparison.

So if it's not Earth where fusion energy will be useful, how about in space? Here on Earth, the Carnot cycle is used to convert heat into useful mechanical energy, then finally electrical energy, which is usually the true goal. But the Carnot cycle requires dissipating massive amounts of heat; just as much energy is dissipated as heat as gets turned into electricity. And heat dissipation isn't such an easy thing in space, is it?

I feel like I'm missing some rather large puzzle pieces here. Without them, fusion does not really seem like an engineering goal towards a good energy source, just engineering research into better containment of difficult materials. Could somebody help enlighten me?

<comment><USER13> Just a layman. But wind and solar have big limitations. They are available only in a limited amount only under certain conditions and their variability isn't under our control. And if you think energy storage would solve all this, batteries aren't cheap. We would like to have an infinite source of energy that we can control on demand.

<comment><USER14> Oh, but a fusion power plant is gonna be cheap?

<comment><USER13> Who knows about the future. And considering the amount of energy feasible via fusion, it can be insanely cheap in terms of price per kwhr

</comment></comment></comment></comment><comment><USER15> General comparison of the two competing systems: Tokamak vs Stellerator [https://www.sciencedirect.com/science/article/pii/S2468080X1...](https://www.sciencedirect.com/science/article/pii/S2468080X16300322)

Looks like theoretically the Stellerator is superior in practice, while in practice only the Tokamak is being worked on practically.

<comment><USER16> Fortunately the ITER project does wast amount of R&D and basic engineering that solves problems common to both design. If the problems in stellators are solved and it proves to be superior to tokamak in practice there is no need to start from scratch.

<comment><USER17> There's also quite a bit of talk going on between scientists on both projects. If I remember correctly, the microwave heating design of Wendelstein 7-X also solved a few problems for ITER and in general it's more of a friendly competition.

<comment><USER18> I view it as less of a competition than as projects working on different parts of the same problem - ITER seems to be working more on the problems of managing a fusion reaction (materials, procedures, shielding, etc.), while using a better-studied containment design with lower technical risk. Meanwhile, Wendelstein is ignoring all those other challenges in order to study an alternate containment design in isolation.

</comment></comment></comment></comment><comment><USER19> Anyone interested in the subject matter would probably enjoy Omega Tau Podcast. [http://omegataupodcast.net/tag/fusion/](http://omegataupodcast.net/tag/fusion/)

</comment><comment><USER20> Whenever you're shown a new gosh-wow fusion design, ask "What is the power density of this design?"

The power density of a PWR fission reactor core is 100 MW/m^3.

The power density of ITER (gross fusion power/volume inside the cryostat) is maybe 0.05 MW/m^3.

There are fundamental engineering limits to fusion that guarantee the power density will suck compared to fission. So my default take on any fusion design is that it will never be competitive with fission, never mind the things that are cheaper than fission.

</comment><comment><USER21> How's Lockheed's Z-pinch based compact reactor?

<comment><USER22> Latest news is a patent grant to Lockheed in March. Not much else recently.

</comment></comment><comment><USER23> So where are they along the project plan to useful fusion energy? Since that is not the end goal of this project, how far along the project plan for this device are they?

I'm really well past the phase of being excited about milestones like "record for a stellarator". Put it in context, show where we are on the plan. Perhaps it's behind, but still moving forward - that's fine. Confirming things work as predicted is awesome and tells me they should be moving forward at a good pace right? So where are they on that gantt chart?

<comment><USER24> Nowhere close, but as you rightly stated, that isn't the goal of this experimental device. For what it is, which is an exploration of the dynamics of containing high temperature plasmas, it is a resounding success. What you're asking is sort of like someone asking Babbage how close he is to a Pentium 90. Babbage still did some incredible and foundational things, and it was still a world away from playing Doom.

There are a lot of issues outstanding for fusion to be a viable power source, and this reactor is simply exploring the dynamics of one of those issues. Putting aside hype and desperation, there is no chart yet. For a fusion plant to work and compete with any other plant, you need it to have good uptime, relatively low maintenance burdens in terms of downtime and costs, good output, a viable source of fuel, a fusion cycle that is safe and sustainable, and more.

As of today the d-t cycle isn't sustainable because it requires tritium, produces a lot of energetic neutrons that along with helium will undermine the reactor. The problem is that more viable fusion cycles occur at significantly higher temperatures and it's a struggle to control plasma at d-t temps. The lack of control both quenches the reaction, and exposes parts of the reactor to plasma which erodes the material. Neutron bombardment causes the metal to become brittle, and helium infiltrates and undermines it too. So a reactor would be down for maintenance a lot, which would make it difficult to work as an economically viable source of power.

As of today the tritium for the reaction has to be bred in fission reactors. There are theoretical plans to use a "blanket" impregnated with an isotope of Lithium to breed tritium within the fusion reactor, but so far no one has gotten it to sustainably work near necessary levels. As a result a fusion reactor today would require fission reactors, and it might make sense to ask why we don't just stick to the far more mature and efficient fission technology.

There are lots of other issues that aren't as big or obvious as what I've described, but ITER and desperation hype aside, there are more unsolved problems than solved. So where this reactor is concerned, be excited for what it is away from the context of "fusion any day now!" hype. Appreciate the slow, but steady progress in the context of incremental research.

If you want clean power in your lifetime, support fission plants.

<comment><USER25> Mostly agreed, but: "If you want clean power in your lifetime, support fission plants."

Not anti nuclear or anything, but you really want a large share of wind+solar. Less hard to handle waste and cheaper. Once we are approaching 80% wind+solar we can discuss how to best deal with the difficult remaining 20% (load shifting, expanded transmission grids, storage, CCX and Carbon2Gas gas plants and nuclear are all options that are possibly going to play a role).

<comment><USER26> They're only cheap and low-waste if you don't have to worry about storage, and that needs to be solved well before the 80% point. Battery manufacture is pretty dirty, and even if the environmental issues were not a concern, it's not clear that enough raw materials (rare earths, etc.) exist in the world to move the entire power grid to intermittent sources plus battery storage. And so far, no alternative storage sources have proven themselves broadly viable (pumped hydro is probably closest but requires fairly specific climate and geography).

Personally I'm with Bill Gates on this one: we basically need an innovation miracle to solve our energy and climate problems, but probably just one, and it can be in any of four or five different fields (renewables + storage, fission, fusion, biofuels, carbon capture, etc.). Success in any one of those spaces is far from guaranteed, so we shouldn't put all our eggs in one basket, and should be aggressively pursuing all of them in the hopes that at least one will pan out.

<comment><USER25> Could you please point me to reputable studies that back up your claim that storage will be needed before very high penetration?

Even for extremely high carbon reductions (95% on 1990) the best models I've seen consider transmission lines and sector coupling considerably cheaper. And these models make very aggressive assumptions on the fall of battery prices. E.g.:

[https://arxiv.org/pdf/1801.05290.pdf](https://arxiv.org/pdf/1801.05290.pdf)

Edit: The thing to look at is figure 11. on page 16. It gives a policy trade off. Given political limits on the amount of transmission grid extension (x axis) what is the cost of the economically optimal mix of technologies (y axis). Left graph shows sector coupling, right graph shows sector coupling. The second graph almost completely eliminates the need for battery storage.

Nuclear is not in this mix, partly because this is exploring policy constraints on transmission capacity in the context of Europe (and nuclear is pretty much a non-starter politically) but it clearly shows that the idea that large amounts of battery are inevitable is outdated.

I'll leave you with a quote from the conclusions:

"The All-Flex-Central scenario with optimal transmission costs just 13% more than today's system [even when excluding health benefits]"

<comment><USER26> You're right that arrangements that mostly avoid storage are _possible,_ but might not be cost efficient in a way that leads to their eventual adoption, and any mass adoption of renewables at high percentages of overall capacity requires some kind of major investment beyond the cost of generation itself, to deal with the intermittency, be it storage or transmission (and the latter is really only helpful if by "renewables" you mostly mean wind -- the intermittency of solar is obviously highly correlated over broad geographic areas). Still, I think the more interesting question isn't "could it be done" \-- it's pretty clear that it could -- but "could it be done in a manner that's cost-competitive with non-renewable technologies," and there's pretty abundant research at this point that shows that any advantages renewables have in terms of levelized cost of ownership get more than wiped out once these kinds of investments are factored in; see, e.g., [https://www.lazard.com/perspective/levelized-cost-of- energy-...](https://www.lazard.com/perspective/levelized-cost-of-energy-2017/) From the executive summary:

> Despite the sustained and growing cost-competitiveness of certain > Alternative Energy technologies, advanced economies will require diverse > generation fleets to meet baseload generation needs for the foreseeable > future

with specific numbers in the actual report.

It's easy enough to focus on Europe or the Americas where the rich have the comparable luxury of being able to overpay for generation if the political will is there, but the overwhelming majority of new generation capacity brought online globally in the next century won't be in these places, it will be in Asia, Africa, and South America, as these countries work towards developmental parity with the West. We need to come up with solutions that aren't just possible, but cheap, and deployable in places that are starting from basically nothing in terms of modern grid infrastructure, and where hyper-inefficient diesel generation is currently the norm, to the extent that electricity is broadly available at all (as is the case in large parts of Africa in particular today).

Again: this isn't to say that renewables can't work, or that any other particular technology will or won't be the solution. We just don't know yet, both in terms of feasibility and economics.

<comment><USER4> > We need to come up with solutions that aren't just possible, but cheap

Renewable energy sources are already cheaper than traditional nuclear energy, in many parts of the world already cheaper than fossil sources, and rapidly getting even cheaper:

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

And at the same time, Westinghouse had to file for chaper 11 bankruptcy because ... well, nuclear power does not seem to be so economical at all.

As an interesting side note, both nuclear power as well as renewable energy sources have the cost structure that almost all investments are up-front, while the relative amount of running costs is very small. Because in a market system, the marginal cost of production per unit determines the market price, and the market price is therefore close to zero, both technologies have the problem that they actually need subsidies and incentives to be created. In other words, while renewable power sources definitively need incentives, nuclear power also can't exist without huge subsidies.

<comment><USER26> > Renewable energy sources are already cheaper than traditional nuclear energy

Again: only when looking at the cost of generation alone. It's more expensive if you factor in the storage and/or long-distance transmission necessary for high utilization (even the study I'm responding to says so, though by a smaller amount than I've seen elsewhere -- ~13%).

> well, nuclear power does not seem to be so economical at all.

Nuclear power isn't economical under the current regulatory environment and set of political realities. There's no fundamental reason that that need be the case. More people die from wind and solar per year than nuclear (mostly installers and technicians falling off of things), and obviously both are dwarfed by orders of magnitude by coal once externalities are factored in. If we were as risk-averse with those sources as we are with nuclear, they would be expensive too. Coupled with the slowness of construction eliminating economies of scale or effective market competition, and you don't have a great situation.

<comment><USER4> I live in Scotland, and was living in Northern Germany before. We _do_ have high penetration here:

[https://www.businessgreen.com/bg/news/3029756/scottish- wind-...](https://www.businessgreen.com/bg/news/3029756/scottish-wind-power- enjoys-record-breaking-start-to-2018)

And it works pretty well. The last power failure I can remember which was in any way related to wind energy was in 2006:

[https://en.wikipedia.org/wiki/2006_European_blackout](https://en.wikipedia.org/wiki/2006_European_blackout)

(but wind energy was not the primary cause, the main cause was bad planning)

What happens at large scale is that the fluctuations induced by variable wind speeds smooth out over larger regions. And having a large, interconnected grid is usually much cheaper than battery storage.

What would also help is diversification. In Scotland, there was a fascinating project to generate electricity from wave power, the Pelamis wave power converter. It had working 500 kW installation but was scrapped then.

[https://www.youtube.com/watch?v=JYzocwUfpNg](https://www.youtube.com/watch?v=JYzocwUfpNg)

Fortunately, some Chinese companies seem to have copied the design:

[http://www.dailymail.co.uk/news/article-3832029/Chinese- wave...](http://www.dailymail.co.uk/news/article-3832029/Chinese-wave-power- device-suspiciously-similar-Scottish-machine.html)

> If we were as risk-averse with those sources as we are with nuclear, they > would be expensive too.

A wind power plant blowing up will not cause half of Europe to be contaminated with huge costs to agriculture, like it happened in 1986. You must also not forgot the extreme health costs of uranium mining.

</comment></comment></comment></comment></comment></comment></comment></comment></comment><comment><USER27> This is fantastic news!

Based on this information, I conclude that nuclear fusion is probably only about 20 years away.

<comment><USER28> Can we stop with the "fusion will always be x years away" meme? Fusion is mostly a number of invested dollars away. A big reason why we don't have fusion reactors yet is because nobody invests sufficient amounts into the necessary research. Check this graph [http://imgur.com/sjH5r](http://imgur.com/sjH5r) from the old Slashdot interview

[https://hardware.slashdot.org/story/12/04/11/0435231/mit- fus...](https://hardware.slashdot.org/story/12/04/11/0435231/mit-fusion- researchers-answer-your-questions?sdsrc=rel)

It's just disrespectful to all the brilliant physicists and engineers who work on the topic to belittle their efforts like that.

<comment><USER29> You have to admit that there is something to this meme, It seems like Fusion suffers from a lack of focus and direction. Ive heard all sorts of horror stories about physicists and engineers going off on fusion design tangents that pull funding away from more viable designs as far as energy-in/energy- out.

I understand that there is a level of experimentation and R&D that is guaranteed not to generate viable results but at some point you need to trim the fat, get everyone moving in one direction etc. This grand project has been going on for over 50 years at this point, It seems like we should at least have one design that everyone should be focusing on. If they had real, defined commercial goals (even if they miss the goals) it might be easier to secure funding because your average politician would see the benefit to them.

I'm not a nuclear engineer so take that all with a grain of salt.

<comment><USER30> It's hard to know what is a 'tangent' and what is the next breakthrough though.

As they say - if we knew what we were doing it wouldn't be research.</comment></comment></comment></comment>


Get Disciplined, Not Motivated - <AUTHOR> http://joelrunyon.com/two3/get-disciplined-not-motivated <comment><USER2> I suggest not putting too much faith in these self-help posts.

The human mind is complicated. Advice that seems helpful could in reality be harmful.

Certainly, the distinction between discipline and motivation is meaningful. And sure, all else being equal, discipline is more useful than motivation towards leading a successful life. But maybe things are not equal.

Am pretty sure there were times in my life when I worked on increasing my discipline (i.e., on cultivating productive habits) when I would have been better served by focusing on increasing my motivation (particularly, by asking what sorts of things do humans typically find motivating, which of those things have I found motivating in the past, and how might I cultivate my ability to take pleasure in one or more of things).

It is fairly clear from Einstein's writing that it was mainly motivation (and in particular curiosity) rather than discipline that fueled his career. For example, he complained in writing about the design of his PhD program because it extinguished his natural love for (i.e., his motivation to do) physics. I tend to think that it would be very unlikely for a human being to be able to exert the degree of effort Einstein exerted on his physical research using just discipline (i.e., if the human being were not motivated or energized by the process of doing the research).

I mean, if you try to increase your discipline, and your attempt succeeds, then that is great. You should make more attempts to increase your discipline even further. But I have found that there is a limit to how much I can do that. And certain self-help authors have caused me to ignore evidence that my attempts at increasing my discipline are no longer having any positive effect.

Added. Also, I think the intense concentration and intense demands on working memory and "fluid intelligence" that programming makes on a person often makes the person less aware of alternatives to willpower, sustained concentration and discipline as ways of becoming a more capable and productive person.

<comment><AUTHOR> Hollerith, I actually agree with you, but the problem with motivation is it is fleeting. how many people do you know have been _motivated_ to do something and started, but then gave up when they hit an obstacle or it got tough.

So many people bust themselves up because they think they need more motivation, but what they really need to do is transform that initial motivation into creating habits of discipline that are driven by their motivations. Then, when their motivations wane, they can keep on going.

<comment><USER2> Not all motivation is fleeting: the reason Einstein complained in writing about the few years in which his motivation had been extinguished by his experience in grad school is that during the rest of his career, his motivation to think about physics was consistently strong. And I think some of the people reading this have a consistently strong motivation to provide for their wives and children.

Sure, there are times in everyone's life when one needs to apply discipline because that is the only way to get something necessary done. And it would be foolish to neglect to apply that discipline and instead to wait for a natural human motivation to do that thing.

And sure, the ability to apply discipline is extremely valuable and one should do whatever one can to increase this ability.

And I would for example suggest to readers who have not tried it yet to see if strength training causes an increase in their ability to apply discipline _even in parts of life that have nothing to do with physical strength or stamina_ because strength training tends to improve the health of the mitochondria in the muscles, which might improve the health of the mitochondria in the rest of the body, particularly the frontal lobes of the brain, which would tend to increase ability to apply discipline because IIUC the frontal lobes are almost uniquely dependent on an adequate supply of metabolic intracellular energy.

I just want to point out to readers that there are now many many sources of information about these matters and to suggest that they be initially skeptical of any new source, particularly if he is selling something or likes giving pep talks.

</comment></comment></comment><comment><USER3> A great distinction. But I tended not to read it with physical goals in mind... I find it strange these days how many geeks seem to have heroic physical goals.

"Like every other guy on earth, I've wanted six pack abs forever."

I suppose I've wanted it at one time or another, in the abstract "that'd be nice to have" way I've wanted, say, a jetpack. But I've never been interested in putting the time or effort into achieving that level of fitness. I'd much prefer the jetpack. Or even better, learning something new.

An hour or two of hard running every few days to get a nice head-clear and endorphin rush, to be reasonably fit and healthy... then I'd much prefer to play video games and study algorithms.

<comment><USER4> IMO one is better off training to _do_ something rather than acquire a external physical characteristic. Most of the people I know who train consistently and have impressive physical achievements (a) enjoy training and (b) train for intrinsic goals, often quantifiable goals.

Like "enter competition X", "win championship Y". Or some tangible set of lifts or times in a run/row/swim, etc.

Wanting to have six pack abs is a ridiculous goal. For some, it's ridiculously easy and sets the bar way too low; for others, irrelevant or even counterproductive.

On the other hand, wanting six pack abs will get you in the right frame of mind to have a nice heart-to-heart conversation with all those skeletal women running grimly along on the treadmills for hours. They, too, depend on extrinsic motivations that are chiefly concerned with appearance.

</comment></comment><comment><USER5> My dad is the most disciplined person that I know. He got his math PhD in 2.5 years. He said that when he was in grad school, he'd wake up every morning at 4am, work without interruption until 8am, take a 1 hr nap until 9am, work until 5pm, stop work, and then sleep at 9pm. He kept a strict diet of only eating green veggies and never eating meat (plus, he couldn't afford meat).

I've never had any discipline. In college, I decided I'd finally get some discipline and I would do exactly what my dad did. I woke up at 4am every morning, took a 1hr nap at 9am, worked until 5pm, went to bed at 9pm. I wanted to be just like my hero.

In short, it was a total disaster. I was tired constantly. I slept in class all the time. I performed decently in school, but I remember it as a pretty unpleasant time. It was a pattern that was very hard to get to work inside of a college dorm where I also had a roommate sleeping in the same room. I found myself always thinking, "What would dad do?" Not, "What's right for me?" I beat myself up a lot when I couldn't live up to the kind of man my dad is.

I gave up on the idea of discipline, and it's been great for me. When I reflect on when I'm happy or unfulfilled with work, I don't think of it in terms of words like "motivation", "discipline", "inspiration", etc., because those words just express patterns and modes of approaching work that work/don't work for other people. I think, "Why am I tired?" "Why would I rather watch TV than work on my company?" "What are the short-term / long-term tradeoffs?" etc

</comment><comment><USER6> Insightful - Motivation v/s Discipline. Motivation may be a start but discipline is what carries you through. One of those articles that makes me say "I never looked at it this way".

</comment><comment><USER7> As someone who had to deal with a bit of depression in the past I think the article got things backwards. Get motivated first, and as your time becomes limited (instead of just being wasted) discipline and organization naturally follow.

<comment><USER8> I've found discipline helps most when it's not yet needed. When I have an expanse of time, it's easy to end up being unproductive without discipline. Once I'm working under the pressures of time constraint, discipline is easy because it's necessary and not really an option.

</comment></comment><comment><USER9> I believe there is a variation on this theme in the Marine Handbook. I am not sure if it is harder to see yourself as undisciplined or unmotivated though.

Strangely I get more done when I don't have enough time because I don't get to think about what I'm not going to get done, instead I'm just trying to get most of it done. That's a pretty non-intuitive result for me.

</comment><comment><USER10> This is a great post, I particularly like this quote:

        "Motivation is the start, but if it's not solidified into
         discipline,  it usually fades away into regret pretty
         quickly once you realize you never acted on it."

I think it's worth mentioning Stephen Presfield's concept of Resistance here from his book "Do the Work" [1]. I often find myself fired up with a new task, but lacking the follow though that discipline would give me. It's too easy when I want to do something that I don't know how to do (write some Haskell for example) for my little monkey brain to jump off to some interesting shiny thing (HN). Resistance explains this as a way of protecting yourself from the pain of struggling to understand and the risk of failure, by replacing it with something easy and non-challenging.

[1] Read it: <http://www.stevenpressfield.com/do-the-work/>

</comment><comment><USER11> It takes motivation to become disciplined. Once you do get disciplined though, you don't need as much motivation to continue doing what you are doing.

</comment><comment><USER12> "People often say that motivation doesn't last. Well, neither does bathing – that's why we recommend it daily." - Zig Ziglar

</comment><comment><USER13> I decided to get fit and healthy a few months ago, and boy was I motivated and stuck at it for a week or two well, but I was pretty undisciplined and slipped pretty quickly. I had to essentially codify it into a quick routine, get up and do x, after x do y, when z is true etc. Amazingly treating it essentially as a programming task helped me stick to it more, because once I'd 'written' the routine in to my life it was pretty easy to just go through it every morning.

Motivation is a weird thing, we all start with the best intentions in the world but sticking with the good habits is damn hard.

</comment><comment><USER14> This is fantastic. A must read, IMO.

</comment><comment><USER15> Take this with a grain of salt, and some science on the matter.

[http://www.iijiij.com/2012/09/01/science-shows-that-self- dis...](http://www.iijiij.com/2012/09/01/science-shows-that-self-discipline- taxes-the-soul-014481)

</comment><comment><USER16> Motivate yourself to be disciplined, and discipline yourself to be motivated. False dichotomy solved!

</comment><comment><USER17> I was motivated to share this fantastic post with other people on social networks</comment>


Postmodernism generator - <AUTHOR> http://www.elsewhere.org/pomo/
<comment><USER2> It's easy to make fun of postmodern philosophy, but no philosopher made-up postmodernism, they are just commenting or labeling phenomena already inherent in our culture, some of which is even more complex than their method of expressing it. Their comment might be somewhat cryptic, sometimes even creative, as they are always trying to cover their asses from, what they believe is, our loose and unstable language(s), but the overall message of diversity, multiplicity, the questioning of social constructions (sometimes), etc. have been essential tools in our society and cultural/social relations in postmodern culture.

I understand some of the downfalls of postmodernism and I won't defend it, but I'm not going back to rationalism, which influenced the Nazis, or Platonic or Christian Essentialism, which has marked humanity in negative ways for too many centuries, etc.

<comment><USER3> Can you point to any postmodern philosophy papers that are useful?

How about some that merely make non-obvious true points?

Or some that are at least interesting?

It probably seems like I'm bashing postmodern philosophy, but although I expect this line of thinking to end at the conclusion "postmodern philosophy is useless," I've never actually followed it myself, and I would honestly be very happy if you could answer "yes" (with examples) to at least one of the above questions. It's just that from my vantage point as a relatively uninformed outsider the field feels vacuous.

And your logic in the last sentence of your post is terrible.

<comment><USER4> It is much longer than an essay, but I would highly recommend Heidegger's _The Question Concerning Technology_.

Now as inspired as the text is, it is not a light read. But not all meaningful scholarly work needs to be written like a popular science novel. (I mean, ever try reading Gödel's famous paper?) I read Heidegger in the context of a Philosophy seminar and frankly it helps having access to secondary sources for help.

On a more positive note, Heidegger has only been called postmodernist in retrospect. At the time he was producing these essays and writings, there was no postmodernist jargon to lean on. So his writings are pleasantly free of words that only help to obscure.

</comment></comment></comment><comment><USER5> In case somebody missed it (Richard Dawkins on postmodernism):

<http://news.ycombinator.com/item?id=645178>

Edit: here's the direct link to the article: <http://www.physics.nyu.edu/faculty/sokal/dawkins.html>

<comment><AUTHOR> Oh, I didn't see that somebody has already posted this as a link in the comments. No cross-posting was intended.

</comment></comment><comment><USER6> This generator reminds me of the Paper generator by some MIT students..

<http://pdos.csail.mit.edu/scigen/>

..much more funny and even pdf direct output :D

<comment><USER7> Yes, this is funny. The existence of random paper generators for a discipline doesn't say much about the rigor of that discipline. You might be able to make some kind of argument based on how long it takes for someone trained in the discipline to detect it as randomly generated.

Of course, you could imagine building a program that creates perfectly compileable, yet randomly generated programs. These guys actually did it to test gcc's handling of the volatile keyword: <http://www.cs.utah.edu/~regehr/papers/emsoft08-preprint.pdf>

</comment></comment><comment><USER8> Ha ha ha, lets all point and laugh at the postmodernists.

Or we could just ignore them.</comment>


Amazon contractors enduring 'subhuman' conditions in Philippines - <AUTHOR> https://www.ft.com/content/8b7bc787-4f33-4909-85f0-8df36d165b69 <comment><USER2> Philippinos are some of the best people I've met. So happy.

They work insanely hard when given opportunities.

Cruise ships, middle eastern governments, and others have abused them for years.

Wish they hadn't pushed for independence. As an American state they would have prospered so much more.

<comment><USER3> > Wish they hadn't pushed for independence.

Why? They are their own people/nation? They deserve independence.

> As an American state they would have prospered so much more.

There was a racial requirement for statehood ( majority white ). It was one of the sad reasons for the extermination of the native americans. If the philippines were to become a US state, it would probably mean that most filipinos would have been killed off or pushed out of the philippines. Do you really think the filipinos would have prospered in that environment? Not to mention, they are catholics and the US historically didn't treat catholics too well.

You might want to read up on the history of the US and the US history in the philippines/pacific. It isn't pretty.

You do realize that their first attempt at independence was crushed by the US right? And for 60 years, philippines was a poor colony of the US?

[https://en.wikipedia.org/wiki/Philippine%E2%80%93American_Wa...](https://en.wikipedia.org/wiki/Philippine%E2%80%93American_War)

</comment></comment><comment><USER4> Paywall. Can anyone provide a summary?

<comment><AUTHOR> > Video footage and stills, taken at the weekend and provided to the Financial > Times, appear to show several employees sleeping on the floor at a facility > in Cebu City. One employee appears to have set up a bed on a treadmill.

> The Amazon-contracted workers at the site, which is managed by French > outsourcing company Teleperformance, provide support to customers who have > bought the US tech giant's internet-connected Ring camera systems.

> While it is typical for some Filipino call centre workers to sleep on-site > to avoid long commutes, workers said lockdown restrictions meant the > facility had been overwhelmed. Employees said they were only able to leave > the site to buy groceries or use showers at a nearby hotel.

> In a letter to their bosses, the workers say promises of adequate sleeping > arrangements have not materialised, which has led to "hundreds" of workers > sleeping in the facility, including on the call centre floor itself and in a > small gym.

> Teleperformance employees face severe penalties for talking to the media or > sharing information about their work in any way. A contract seen by the FT > suggested that workers would be considered liable for "damages" of "at > least" 500,000 pesos — roughly two years' salary — for breaking > confidentiality agreements, on top of losing their job.

<comment><USER4> What a weird situation. What causes that?</comment></comment></comment>


Show HN: Hacker-Dict.com: The Hacker Dictionary - <AUTHOR> For ClojureCup this year, we have built an online dictionary for programmers where people share information (subjective or objective) in dictionary format.
Our aim is to build an online dictionary where people can share information about the programming world.
Since the judging period is in progress, we cannot make any modifications yet, but will start making it better by introducing much needed features like editing/deleting once the ban is lifted.
Enjoy and vote for us at http://clojurecup.com <comment><AUTHOR> Clickable link is at [http://hacker-dict.com](http://hacker-dict.com)

ClojureCup web site: [http://clojurecup.com](http://clojurecup.com)

</comment><comment><USER2> This brought a smile to my face: [http://hacker- dict.com/subject/recursion](http://hacker-dict.com/subject/recursion)</comment>


Crystal - minimalistic PHP database toolkit - <AUTHOR> http://crystal.martinrusev.net

<comment><USER2> Interesting. Nice that it's detached from a framework. Would like to see model support in an objective style.</comment>


How Strenuous Exercise Affects Our Immune System - <AUTHOR> https://www.nytimes.com/2018/04/25/well/move/how-strenuous-exercise-affects-our-immune-system.html <comment><USER2> As a machinist and building maintenance engineer, I can almost guarantee any ill feeling you're experiencing after a trip to your local gym is due to the air quality.

Gyms are rarely purpose built facilities. Rather, theyre rented and renovated spaces. In turn, airflow in the structure is planned for light industrial or office space. Almost no thought goes into the fact that gyms are sometimes hundreds of occupants moving the air at two to three times what the OSHA or planning documents indicate. Paints with VoC's, sealants, and even offgassing plastics from gym mats or new equipment can turn the air quality from decent to garbage in a few hours.

I was once contracted to fix an air handler issue at a fitness center. The root cause was a set of 6 un-ventilated panini presses that were placed near the front desk as part of an effort to sell snacks and sandwiches. The added smoke and particulate had decreased the filter life and burned out a blower motor. The solution was either get rid of the electric grills, or start replacing 30 day filters every week.

<comment><USER3> You're not even mentioning CO2 concentration. I work in a large, open office with seemingly sufficient airflow, but after buying a CO2 detector on a whim I've seen that it frequently reaches 1200ppm, and you actually can tell that you feel like crap when that happens.

I can't imagine if the whole office was filled with people exercising.

<comment><USER4> What does it feel like as it starts getting higher?

<comment><USER5> I don't know, but I'd love to see some study on the impact of CO2 levels on the measures we typical care about regarding meetings: levels of alertness, qualities of social interaction, decision-making speed/quality, etc.

<comment><USER6> Harvard published an interesting one a few years ago. Having trouble tracking down the link on mobile, but here's an overview:

[https://thinkprogress.org/exclusive-elevated-co2-levels- dire...](https://thinkprogress.org/exclusive-elevated-co2-levels-directly- affect-human-cognition-new-harvard-study-shows-2748e7378941/)

<comment><USER7> Here's the study link: [https://ehp.niehs.nih.gov/15-10037/](https://ehp.niehs.nih.gov/15-10037/)

> Associations of Cognitive Function Scores with Carbon Dioxide, Ventilation, > and Volatile Organic Compound Exposures in Office Workers: A Controlled > Exposure Study of Green and Conventional Office Environments

> ... Methods: Twenty-four participants spent 6 full work days (0900–1700 > hours) in an environmentally controlled office space, blinded to test > conditions. On different days, they were exposed to IEQ conditions > representative of Conventional [high concentrations of volatile organic > compounds (VOCs)] and Green (low concentrations of VOCs) office buildings in > the United States. Additional conditions simulated a Green building with a > high outdoor air ventilation rate (labeled Green+) and artificially elevated > carbon dioxide (CO2) levels independent of ventilation.

> Results: On average, cognitive scores were 61% higher on the Green building > day and 101% higher on the two Green+ building days than on the Conventional > building day (p < 0.0001). VOCs and CO2 were independently associated with > cognitive scores.

> Conclusions: Cognitive function scores were significantly better under > Green+ building conditions than in the Conventional building conditions for > all nine functional domains. These findings have wide-ranging implications > because this study was designed to reflect conditions that are commonly > encountered every day in many indoor environments.

</comment></comment></comment></comment></comment></comment><comment><USER8> I've been running for twenty years and am currently on a half-year streak with around 15km / day. In all those years I've been sick for about two weeks all in all. Before working out, that was like the average over half a year.

Conclusion: Figure out what works for you, have a daily routine, add a bit of obsession and stop reading stories about the pros and cons of exercising.

<comment><USER9> Same with me during my peak running period last year; even when I was feeling ill or off, a run, albeit grueling at the time, always seemed to aid in my recovery (if only for the placebo of getting myself out of bed).

I really need to start doing it on the regular again...

<comment><USER10> Prior to my knee injury I was a happy runner, and I definitely found that just going for longer than 15 minutes would completely clear out my nose if I was at the congestion stage of a cold.

Of course, my nose would be congested again a few hours later, but it was still a decent motivator since I hate taking medicine.

Wish my knee would stop being shitty.

</comment></comment></comment><comment><USER11> I have one rule: I only ever do sports if I have rested well the night before. It took me until I reached my 40s to realise that lack of sleep + heavy exercise = high chance of catching a cold.

Other sure ways how I can get sick: overdo sauna after exercising and, by far the worst, overdoing cold showers (Jim Hoff anyone? - I got seriously sick experimenting with that)

I guess the overall strength of my immune system is below average :-(

<comment><USER12> There is a high correlation between insufficient sleep and catching cold. It kind of made sense but I've looked it up and found several studies supporting this.

This winter I've tried only cold showers after running outside. Cold showers as in (sometimes) my neck hurt if I did it too long. Did not catch a cold until this spring and I think this is more correlated to insufficient rest/sleep (on top of exercising) than to water temperature.

My takeaway is enough rest is not optional and cold showers are doable even in very cold water. I have no idea how hard would be a bath in water + ice.

<comment><USER13> What's the theory behind the cold shower?

<comment><USER14> for me it wakes me the f up. It's strong like having drunk coffee or something. Results may vary of course, but works wonders for me and my focus during the day.

I know of an old woman who's beed ice-cold bucketing for years and looks great and hasn't been sick in a long time. Does this with -20C outside too. Yet I find I may get sick easier if it's too cold outside and I go all out freezing shower.

<comment><USER11> I still do cold showers, but just finishing with cold water for a short interval, 20 seconds or so. That seems to be entirely beneficial (I don't remember were I read it but there's some other cold shower expert recommending not going longer than that)

<comment><USER15> I've been doing cold showers after working out ... but when I do, I'm freezing _the entire day_. Does this happen to anyone else?

<comment><USER16> Does attire affect your temperature perception? I mean, maybe you're just not wearing enough...

<comment><USER15> Nothing different than I usually wear ... t-shirt and jeans, and I keep my house at 74 degrees (it's usually a bit warmer in my office). Under normal circumstances, as you can imagine, I find it quite comfortable.

</comment></comment></comment></comment></comment></comment></comment></comment><comment><USER17> I gotta stash this one away. I often refer to the disaster of 20th century health science as scientists repeatedly gathering a single point of data and then drawing a line (or hyperplane) though it, but this is a great article clearly demonstrating an example of that, and how plausible it all seemed at the time.

(Not that it's a trend limited to the 20th century. But it seems to me to have been extremely bad in the health area in that time frame. Not uniquely so necessarily, but quite bad.)

<comment><USER18> I imagine the 20th century was the worst time for it because we had more sophisticated data collection and analysis methods, but failed to recognize our own inadequacies when using those tools to draw conclusions.

Kind of like social media algorithms today.

</comment></comment><comment><USER19> My personal experience with long (100miles+) cross-country mtb riding (with lots of climbing) is that in fact, catching a cold after such a strenuous ride is way more common than the base rate. This is also the experience reported by most professional cyclists (check TdF reports).

My under-researched model of how this happens, is that there is a lot of tear- and-wear in the muscles where the effort is happening, which leads to inflammation, and that's where the white-blood cells might end up.

<comment><USER20> runners and other endurance athletes I have met over the years, show noted skin aging after 40 years old..

<comment><USER21> That may be more due to inadequate preventative sunscreen/protective clothing per outdoor time, every one who spends time outdoors without it shows signs of skin aging like the a/b test in one, truck drivers, with the side closest to window showing significantly more wear and tear versus the interior facing side. In addition to sunscreen, there are nowadays a lot of arm/leg covering just for SPF protection even in hotter temperatures - I always wear the arm protection/eyewear when outside.

<comment><USER22> Eyewear? Like sun glasses. Do the eyes age from natural light?

<comment><USER23> Yes. Macular degeneration from uv. Sunglasses and car windscreens in the eu must protect against uv by law. Other windows not necessarily.

I have an optometrist friend who says he can tell easily in eye exam which old people have worn glasses or sunglasses and which haven't.

</comment></comment></comment></comment></comment><comment><USER24> The standout quote for me: "[immune cells] moved elsewhere, migrating to the animals' guts or lungs, portions of the body that might be expected to need extra immune help after hard exercise".

Rapidly producing immune cells during exercise, then letting them (and more) die off would be a baffling response. But pumping them into the lungs (because you've been breathing hard through your mouth) and gut (for when you make up lost energy, and maybe eat some raw meat you've been hunting)? That makes a great deal of sense.

That effect is unconfirmed in humans, but it would ground our observations in an evolutionarily-sane outcome.

<comment><USER25> Exercise pushes stuff around in your gut which is probably more directly related to the immune response than the possibility of eating raw meat.

<comment><USER26> Why would you go run (hunt) if there is still stuff (food) in your gut.

<comment><USER27> Best to hunt when you are loaded up on fuel. Don't want to be hunting when energy is low as you will most likely be less successful as your focus, patience, and response times will all be lower.

Hunting isn't like going to the store, success isn't guaranteed.

<comment><USER28> I think the opposite. People that fast for a period (> 16 hours) report improved energy levels. This may be because after a while the body enters a ketogenic state where it burns body fat, which is a great source of energy and perfect for when on the hunt.

<comment><USER29> > I think the opposite. People that fast for a period (> 16 hours) report > improved energy levels. This may be because after a while the body enters a > ketogenic state where it burns body fat, which is a great source of energy > and perfect for when on the hunt.

Ketogenesis requires over a week of carb restriction IIRC. I think fasting yields energy because the body increases various stress hormones to push you to find food so you don't starve.

<comment><USER30> No, it has to do with insulin levels. Google "Jason Fung insulin".

</comment></comment></comment></comment></comment></comment></comment><comment><USER31> This article doesnt make mention of my workout where I lift something heavy 1 time.

I had the idea that I wanted to reduce time in the gym, so I used the potential energy equation

PE= M _g_ h

I'm not getting any taller, so the only thing I could change was either the reps or mass of weight moved.

I made it my goal to lift heavy weights so I'd only need to deadlift 1 time and be able to pig out.

TBH, it works, I lose 1 lb a week eating 3,000 calories a day. We lift 2 times a week. Warm up, then do 2+ reps of a heavy set.

I dont really sweat after a workout, but I look pretty big and I'm still deadlifting 450lbs. But I only deadlift that weight 1 time a week.

Is that 'Strenuous'?

<comment><USER32> Found the fatty ;)

Ok, seriously.... math: if you eat 3000 kcal per day and lose 1 lb per week, you're burning 3500 kcal per day. This is quite a lot. It's near impossible unless you work out a lot and are veeeery muscular... or are impossibly tall... or, well, fat. (Or a combination of those.)

Take me for comparison: I am 187cm (6'1ish) tall and weigh 75kg (165 lbs), pretty much smack in the middle of the "normal weight" range. I like running, do about 50km (30 miles) per week. I count calories and let my wrist watch measure my energy expenditure 24/7\. On rest days (mostly sedentary), I burn about 2100 kcal. To get up to 3400, I have to do some sort of hard run and some lighter activity in addition, or do a long run (18km+).

Now I'm not everybody of course, but you can't be that abnormal, right? So I'm not buying your numbers.

<comment><USER33> Running is probably the worst sport as far as caloric expenditure is concerned.

A serious endurance cyclist or swimmer will certainly go through 3000 kcal on a normal training day if not more.

I've burned an estimated 5000kcal daily on the bike for weeks. What's more is I know these numbers are very accurate as we train with power meters that record our energy expenditure with minimal error.

It's important to distinguish between serious athletes and average people who exercise. It's possible that truly competitive athletes - for instance, who run 120 miles a week to your 30 - will be much more likely to get ill from their efforts. It can take serious fitness - and a mentality acquired only by years of serious training - to push yourself to the extent that you fall ill, and maybe the recreational "athlete" described in this text can't reach that point.

<comment><USER4> Why do you think cycling would burn more calories than jogging?

<comment><USER34> Jogging is very efficient, mechanically speaking. You're not going to burn a lot of calories per hour.

<comment><USER35> You need to put more effort in 1 hour cycling session to burn the same amount of calories as in 1 hour running session. Running activates more muscles.

<comment><USER36> But cycling affects largest human muscles, which work more intensively..

<comment><USER35> I was "professional" athlete many moons ago. When we measured max heart rate, we did it on a bike first and then on a treadmill running and then bike again. My max heart rate running was +5 beats allways and I was not a single case. I just couldn't get to my max heart rate while cycling.

</comment></comment></comment></comment></comment></comment></comment></comment><comment><USER37> So this is very interesting to me as a swimmer. I find that at the peak of my curve (where I train harder for the regional meet) I often get sick more often, and for far longer. In swimming, this is catastrophic to your performance for the meet, so we try at all costs to prevent illness, but it always happens to one or two of us. The question I pose, does this just apply to shot term exercise, or does intense training (5 hrs a day) for about a month have the same effect.

</comment><comment><USER38> Started doing Tabata sprints a couple years ago. Amazing how much more effective they are versus running at a slower pace for 40 minutes (my old routine).

Also, never knew this, they make self-powered treadmills which are really ideal for sprinting on. I just bought a ASUNA Hi-Performance Cardio Trainer Self Powered Manual Treadmill, it's pretty much ideal for Tabata/sprinting for a home-gym.

<comment><USER39> Effective at what?

<comment><USER38> Effective at maintaining aerobic conditioning. I wanted to get away from having to run 40 minutes 3 times a week. Doing sprints for 2-4 minutes 3 times a week is essentially the same.

Also has the added benefit over my old 40 minute jog routine of increasing my quickness. I play hockey so it was noticeable how much quicker my first 3 strides have become the past 2 years.

Pretty good read regarding all this: [http://www.bbc.com/news/health-17177251](http://www.bbc.com/news/health-17177251)

<comment><USER39> Yeah it's not surprising that slow speed jogging wouldn't improve quickness. Fast twitch vs. slow twitch and all.

</comment></comment></comment></comment><comment><USER40> I have asthma, and I think strenuous exercise is good for my lung capacity long term, but makes me feel terrible the next day or 2 days after. It's really difficult to figure out what causes my symptoms and what makes me feel better.

I wish there was a chip that monitored hormones and immune system factors, etc.

</comment><comment><USER41> Anecdotally my own experience matches that of the rodents in the experiment. I've found that when I'm getting regular strenuous exercise (I bike up a steep hill as part of my commute) I almost _never_ get sick, and can go > 1 year without so much as a sore throat. Conversely, when I'm more sedentary for months at a go, I'm more likely to become ill.

<comment><USER42> I have asthma and many allergies, whenever I have a cold, 80% chances it's gonna end up as a long and tiresome bronchitis. In HS, I decided to give no fuck, went to my 2h winter soccer practice (+ 1h total mudtrail bike to go there). That cold didnt last long and didnt end up causing bronchitis. That was surely half luck, but I always have a feeling that, to an extent, keeping your system active helps. More blood flow ? maybe trigger a more rapid and global immune response .. dunno

</comment></comment><comment><USER43> i think its not the exercise but the rest that follows after a strenuous activity that makes you prone to get sick. its been my theory that if you rest like you are on your last breath, your immune system stops being active. but if you stay active and keep moving your body like you have to survive, your immune system is boosted.

ive tested this theory time and time and seems to be on point.

there have been a number of times when i was feeling sick and instead of resting, id go out in the cold freezing and walk outside for hours. next day i would be completely healed.

but when im just home bed ridden that sickness can linger for days or even weeks.

im also a huge fan of taking cold shower the moment you feel like you are carching a cold. it works way too often to be a coincidence.

</comment><comment><USER44> >athletes are lousy at identifying whether and why they are sniffling.

Not an expert, but wonder if this is caused by a hangover from the endorphin dump from the marathon. I felt that way afterwards.

</comment><comment><USER45> Anecdotally: when I was a bike racer I noted that if I was so exhausted after a hard training ride (usually 5+ hours, >100 miles) that I was involuntarily falling asleep afterward that I would inevitably come down with a sore throat leading to a cold within 12-24 hours. 100% of the time.

I've had maybe 2-3 colds in the decades since I quit racing.

<comment><USER8> What was your hydration and nutrition like post/pre?

<comment><USER45> Hydration was completely insufficient, I realized much later. Nutrition was the typical medium-to-large meal after a shower/nap. There was often a long car ride home, an hour or so.

</comment></comment></comment><comment><USER46> I guess this research is wrong then?

[https://nutritionfacts.org/video/preserving-immune- function-...](https://nutritionfacts.org/video/preserving-immune-function-in- athletes-with-nutritional-yeast/)

</comment><comment><USER35> Anyone else noticed that endurance athletes look 10 years older ?

</comment><comment><USER47> Kudus to NYT for stating the TL;DR right at the top, instead of exhausting the reader with meaningless paragraphs.

> The review concludes that, contrary to widespread belief, a long, tiring > workout or race can amplify immune responses, not suppress them.

Would be even better if that was reflected in the title, but alas, my expectations from a modern website are not so high.

</comment><comment><USER33> This article could not be more wrong, and anyone who has been a truly serious athlete will agree with me.

There are perhaps a dozen times in my life when I was training with abnormally high intensity even for a very competitive endurance athlete and fell ill immediately afterward.

These range from 2 hr brutal races to 3-4 days of 5-7 hrs daily intense training or race efforts. I very rarely catch a cold, but it's more often than not after an effort that stands out to me as memorably difficult.

Any serious cyclist will agree with me. Even competitive high school athletes know that you are most likely to get sick right before taper.

This is an example of misinterpretation of scientific experiment, most likely by the journalists but possibly by the scientists themselves.

EDIT: I don't take issue with "immune response is heightened after exercise". I'm sure it is. I take issue with this quote: "But it is unlikely to have made you vulnerable to colds or other illnesses afterward, according to a myth- busting new review of the latest science about immunity and endurance exercise".

<comment><USER48> This is all anecdotal evidence that's pretty well countered by this statement:

> Their first conclusion was that athletes are lousy at identifying whether > and why they are sniffling. The original 1980s studies had relied on > runners' self-reports of illness. But newer experiments that actually tested > saliva showed that less than a third of marathon runners who thought they > had caught a cold actually had. Statistically, their odds of becoming sick > were about the same as for anyone else in the race's host city.

<comment><USER33> The anecdotes of hundreds of national and world class athletes I have trained, raced, and interacted with over the years is worth more than any study you can paste here, my friend.

I suppose you are unlikely to see anyone here back me up since HackerNews isn't exactly an athletic demographic.

Fever, red eyes, overflowing mucus, extreme soreness and raw throat for days or over a week - are you trying to tell me that this isn't sick? Maybe that's your normal state, but I've seen hundreds of cases of amateur and professional athletes reduced to this shortly after performing national caliber efforts.

<comment><USER49> The problem with anecdotes is there is no transparency or verifiability to that data, it's all in your inherently biased memory and mind. Real data is not perfect, but at least I can plug it into my R and see if we get the same results after analysis. If you feel passionately about it, perhaps you can create a survey instrument to gather the data about your trainees, I'd be happy to analyze that data.</comment></comment></comment></comment>


How do you find integer solutions to x/(y + z) + y/(x + z) + z/(x + y) = 4? - <AUTHOR> https://www.quora.com/How-do-you-find-the-integer-solutions-to-frac-x-y+z-+-frac-y-z+x-+-frac-z-x+y-4/answer/Alon-Amit?share=1 <comment><USER2> For anyone looking to learn more about elliptic curves, which are astoundingly "well-connected" as math topics go, here's a good book that should be accessible to anyone with some calculus under their belt:

[https://www.amazon.com/Elliptic-Tales-Curves-Counting- Number...](https://www.amazon.com/Elliptic-Tales-Curves-Counting- Number/dp/0691151199)

It's not a textbook, which is both good and bad. In my case, it did a good job whetting my appetite for more!

A really well-written and not-extremely-difficult undergrad textbook on elliptic curves:

[https://www.amazon.com/Rational-Points-Elliptic- Undergraduat...](https://www.amazon.com/Rational-Points-Elliptic- Undergraduate-Mathematics/dp/331918587X)

(Non-affiliate links, just so you know.)

<comment><USER3> These look fascinating, thanks.

I tried to crack this problem, and ended up (very naively) resorting to substituting division with modulo operation that is, a%(b+c) + b%(a+c) + c%(a+b) = 4 of which the min solution is a=1, b=2, and c=4. I am glad that the true solution involved EC which, if my understanding is correct, is basically modular operations in high-dimensional space.

<comment><USER2> Elliptic curves are "generalized modular arithmetic" only in the sense that they involve a different kind of addition law (the set of points on a nice EC is a _group_ ).

Also, you can look at the points on an elliptic curve where you allow the coordinates to be real, complex, rational, or even the integers mod _p_ (any _field_ will do), so the last choice gives you a closer link with modular arithmetic. It's best to treat ECs as their own weird, wonderful beasts!

</comment></comment></comment><comment><USER4> This is a great article. Little puzzles like these are often the gateways to enormous mathematical journeys. Here, I only wished the journey was more detailed -- you could motivate all of these operations -- but that would take many pages.

<comment><USER5> I admit, I had low expectations with it being on Quora. I was far from disappointed, though.

<comment><USER6> Really? The math content on Quora is generally top notch. It depends on who answers the question of course, but there are many high quality writers on Quora with deep understandings of mathematics.

<comment><USER7> How does Quora works? I regularly see very interesting answers there. While it looks like SO clone, its content is different. Do they pay for good answers? Or they just happen to have bright people in their community?

<comment><USER6> The difference seems to be in the culture of the community, which they've done a good job of cultivating from day 1.

Quality is valued, and so are expert opinions. I doubt they pay anybody.

</comment></comment></comment></comment></comment><comment><USER8> The Wolfram Alpha results for this one are pretty intimidating:

[http://www.wolframalpha.com/input/?i=(a%2F(b%2Bc))%2B(b%2F(a...](http://www.wolframalpha.com/input/?i=\(a%2F\(b%2Bc\)\)%2B\(b%2F\(a%2Bc\)\)%2B\(c%2F\(a%2Bb\)\)%3D4)

<comment><USER9> You can ask for integer solutions in Mathematica with

> Solve[x/(y + z) + y/(z + x) + z/(x + y) == 4, {x, y, z}, Integers]

but it gives a very long output in terms of Root[]s and conditional expressions.

<comment><USER10> I initially tried that on WolframAlpha but it doesn't understand Mathematica syntax. But one can enter it on [https://lab.wolframcloud.com](https://lab.wolframcloud.com) after creating an account.

<comment><USER11> Thanks. At least I could check the solution there and it is correct.

</comment></comment></comment></comment><comment><USER12> In the title, read "and" as "plus". (For a while I thought they meant "logical AND", given the HN context.)

<comment><AUTHOR> Yeah, I wrote "+" but HN turned it to "and".

<comment><USER13> Just for fun, what if it _is_ read as AND: that is, bitwise AND?

x/(y&z) & y/(x&z) & z/(x&y) = 4.

If the / becomes integer (flooring) division, there are many solutions, such as (6, 13, 19).

But if the division results are required to actually be integers, there are no small solutions - at least, none where x, y, and z <= 10000 (checked by brute force with minor optimization). I suspect that unlike the original problem, there are actually no solutions, but it's just a guess. Anyone want to come up with a proof? :)

<comment><USER14> Let's consider the lexicographically smallest triplet (x, y, z) such that:

x/(y&z) & y/(x&z) & z/(x&y) is even

That means that x/(y&z) is even, or y/(x&z) is even, or z/(x&y) is even.

If x/(y&z) is even, then x is even too, so x&z is even, so y is even (otherwise y/(x&z) wouldn't be integer).

Similarly, we can conclude that all x, y, z are even.

But if we substitute x=x/2, y=y/2, z=z/2, the value of x/(y&z) & y/(x&z) & z/(x&y) doesn't change.

So the (x, y, z) triplet we considered wasn't the smallest. Contradiction.

<comment><USER13> Makes sense. Nice proof :)

</comment></comment></comment></comment></comment><comment><USER15> > Next up: what is the degree of our equation? The degree is the highest power > of any term showing up. For example, if you have (a^2)b(c^4), that's a term > of degree 7 = 2 + 1 + 4

I thought that equation was degree 4, which aligns with what the author says later on. Am I missing something? It seems odd that he would write out that equation accidentally, maybe just crossed wires though. I'm sure we've all been there.

<comment><USER16> The wording in that paragraph is a bit confusing. In this context, "term" refers to the entire product, For example, the equation "(a^2)b + (b)c^4 = 0" has two terms: (a^2)b, and (b)c^4.

The degree of the entire equation is the maximum of the degree of the individual terms. However, the degree of a term is the sum of the degree of all of the factors.

For example, the equation "a+b+c=10" is degree 1, but "abc=10" is degree 3.

<comment><USER15> Ah ok so he was talking about the degree of the equation but gave an example of calculating the degree of a term, the highest of which in any equation is its degree. That makes sense, thanks for clearing it up!

</comment></comment></comment><comment><USER17> What are some other problems that appear deceptively simple, but are extremely difficult to solve?

<comment><USER18> Let n be a positive integer.

Let s(n) be the sum of all positive divisors of n. E.g., s(2) = 1 + 2, s(4) = 1 + 2 + 4, s(20) = 1 + 2 + 4 + 5 + 10 + 20.

Let H(n) = 1 + 1/2 + 1/3 + 1/4 + ... + 1/n.

Question: is it true that s(n) < H(n) + log(H(n)) exp(H(n)) for all n > 1?

(log is natural logarithm)

It turns out that this simple looking problem is equivalent to the Riemann Hypothesis, which is perhaps the most important unsolved problem in pure mathematics. Many of the best minds in mathematics have attempted it in the approximately 160 years since Riemann posed it.

What equivalent means in this context is that if the Riemann Hypothesis is true, than the inequality above is also true, and if the inequality above is true, then the Riemann hypothesis is true.

<comment><USER17> Maybe just me, but that problem does not look very simple at all. One reason OP's problem is appealing, is because the solution can be easily checked. The solution is a kind of "proof of work". You could never guess the solution without a deep understanding of the problem. But once found, the solution is immediately verifiable.

For many problems one can easily guess the solution, without necessarily knowing the proof (like Fermat did). The answer is almost certainly negative, and a complete solution requires a very long and tedious proof that cannot be checked without a deep understanding of the field and many years of collective effort.

I am specifically interested in problems which can be understood by a child, have hard solutions which cannot be easily guessed, but are easily verified (ex. factoring the product of two large primes). It seems like these problems would make good candidates for one-way-functions, like the diophantine equations and ECC. But elliptic curve cryptology is too difficult to describe to a child.

<comment><USER19> Quite easy to explain given a few graphs. The explanation boils down on how hard is to accurately draw a curve of such an elliptic function at big x (P3) and then figure out which two other points intersect with a given line near. You can even show it on a big whiteboard.

You can even show how easy out would be for a simple curve where the left part is an easy equation.

The hard part is what makes an equation easy to solve. (And how some elliptic are broken.) It takes at least some high school math to hint at this.

</comment></comment></comment></comment><comment><USER20> Agree, good article. Thanks to it I think I understand more why cryptography based on elliptic curves (like Curve25519) is considered pretty safe for now.

</comment><comment><USER21> x = 702

y = -390

z = 858

[ [http://www.wolframalpha.com/input/?i=(702%2F(-390%2B858))%2B...](http://www.wolframalpha.com/input/?i=\(702%2F\(-390%2B858\)\)%2B\(-390%2F\(702%2B858\)\)%2B\(858%2F\(702%2B-390\))) ]

Found the above solution using a hillclimbing algorithm.

[http://codepad.org/PixRUl0N](http://codepad.org/PixRUl0N)

<comment><USER22> The question asks for positive solutions, which turns out to be a bit harder!

<comment><USER21> Sorry...I was only going off of the title of the thread.

</comment></comment></comment><comment><USER23> A bit tangential but I wonder if something like that could relate to the slightly odd collection of fundamental particles we find in physics. They have properties that have to come out integral like spin x 2 and charge x 3 and have odd values like muons and tao particle being basically electrons but approx 200 and 3500 times heavier.

</comment><comment><USER24> I wonder if a SAT solver would be able to solve this faster than brute force.

<comment><USER25> Yes. You can try the following smt2 script with yices2 [0]:

      (set-logic QF_UFNIA)
      (declare-fun x () Int)
      (declare-fun y () Int)
      (declare-fun z () Int)
      (define-fun left-side () Int
      (+ (+
        (* (* x (+ x z)) (+ x y))
        (* (* y (+ y z)) (+ x y)))
        (* (* z (+ y z)) (+ x z)))
      )
      (define-fun right-side () Int
      (* (* (*
        4
        (+ y z))
        (+ x z))
        (+ x y))
      )
      ; disallow division by zero
      (assert (not (= 0 (+ y z))))
      (assert (not (= 0 (+ x z))))
      (assert (not (= 0 (+ x y))))
      (assert (= left-side right-side))
      (check-sat)
      (get-model)

Run this by calling _yices-smt2_ on it.

[0]: [http://yices.csl.sri.com/](http://yices.csl.sri.com/)

<comment><USER16> You need to add:

        (assert (> z 0))
        (assert (> x 0))
        (assert (> y 0))

or it will give you negative solutions.

I am running this on my machine now. Will report back if it comes up with a solution.

<comment><USER26> Anything is possible, but I really doubt you'll find those 80 digit numbers. Maybe the sat solver includes some serious number theory though. I doubt it.

</comment></comment></comment></comment><comment><USER27> using the rearranged form:

        ((x + (((2*y*z) + (y*y) + (z*z) + (((z*z*z) - (z*y*y))/(x + y)))/(x + z)))/(y + z))

I find by brute force (no pride!) the first solution triplet: 35, 132, 627

Edit: of course, this is _not_ a solution. It's now just an example to others to beware of floating point errors.

<comment><USER28> That doesn't equal 4 it equals 4.00000009534. So, there is a precision issue, probably using floats to keep division results.

<comment><USER29> I once saw a youtube video which said that an object moving at 4m/s would be slowed down by [thing] by 0.00006m/s, so its new velocity would be 3.99994m/s

... except that no, its new velocity would be 4m/s. The author, a physicist, ignored sig figs. 4 - 0.00006 = 4, when you're dealing with measurements :)

<comment><USER30> sig figs are just an informal way of dealing with uncertainty that can be applied procedurally by high school students.

<comment><USER29> It's not about uncertainty, it's about precision. Unless, of course, you think that scientific notation is limited to only high schools.

<comment><USER30> What do you think the difference between precision and uncertainty is?

<comment><USER29> 'Uncertainty' is a much more ambiguous term that means many more things than 'imprecision of measurement'.

Still, I'm interested to hear why you think sig figs are high-school only when they're the standard way of writing in scientific notation. Do you genuinely think that the example I gave from the video is reasonable? It sounds like you're a theorist and have no experience in real-world application.

</comment></comment></comment></comment></comment></comment></comment><comment><USER31> Now eagerly waiting for Letsencrypt to make Elliptic curve as default. Respect to the author of the article.

</comment><comment><USER32> If you count zero as a positive number then one solution is:

0, 109552575, 29354524 :)</comment>


2D game-art tutorial – create buildings quick and easy using vectors (modular) - <AUTHOR> http://www.2dgameartguru.com/2018/03/building-2d-gameart-house-quick-and.html <comment><AUTHOR> It's been a while but here is the next 2Dgameartguru tutorial on small and simple buildings to populate town or map scenes created in vectors using mainly simple rectangles.

The tutorial is done using inkscape but can be recreated in any other vector design tool (Illustrator, Affinity Designer, CorelDraw, etc.)</comment>


On Gruber, Apple Watch, and Fanboyisms - <AUTHOR> https://medium.com/p/on-gruber-apple-watch-and-fanboyisms-20daddaebaa0

<comment><USER2> This is basically "I disagree with him, and wish he'd tone down his opinion piece. His lack of hedging words makes his article too powerful, and I wish I had the same effect on my audience".

That's neither insightful, nor contributing anything to the Apple Watch debate itself. It's just meta-attacking.

Aside: "You should read back your articles before publishing them, Mr. Gruber" certainly applies to the author, as well. I know he's not a native speaker, but a quick spelling check is easily done by software.

<comment><AUTHOR> I don't see this as a meta-attack, and imho it is interesting to point out contradictions in anyone's opinions (including mine, of course). I think Gruber makes some valid points on several ocassions, but the post is both my view of his opinion (which is also an opinion itself), and my view of the Apple Watch.

Fair point on the spell check. Just did it now, I hope it is a little bit better written now. I try to do my best, but you hit a nerve there ;) Thanks!

</comment></comment><comment><USER3> Is building Veblen goods for tasteless oligarchs really "fashion"? He's right that it's certainly not "tech".

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

<comment><AUTHOR> He says it's not tech, and then he calls it a computer. That makes no sense to me. Of course it's a Veblen good, something Ben Thompson has discussed in Stratechery...

[http://stratechery.com/2014/apple-watch-asking- saying/](http://stratechery.com/2014/apple-watch-asking-saying/)

<comment><USER4> I think conflating "tech" and "computer" isn't necessarily true these days. My Garmin watch has a very sophisticated computer inside but I'd not count that as "tech" particularly. Similarly my printer, scanner, TV, etc.</comment></comment></comment>


The tech diversity blind spot - <AUTHOR> http://eev.ee/blog/2015/11/06/the-tech-diversity-blind-spot/ <comment><USER2> Thank you for this great article. I appreciate the efforts made by people to look past themselves and the "obvious" reasons for things. Isn't that what makes good engineers good?

</comment><comment><USER3> Unsubstantive pot-stirring, followed by a Patreon link.</comment>