Hacker News Reader

jarviston Sustainable energy without the hot air (2008)

No, the wind analysis was not reasonable for the time - he used data from a previous generation of turbines (and in turn, the next generation of turbines were certain to be 40% bigger & etc.), from a wind farm that had quite flukey winds.

I saw him present 18 years ago, and asked him why: he said that he didn't want to rely on any predictions or models, but only discuss real data. Which is sort of defendable as a position, but ignored the fact that renewable energy was progressing so incredibly fast, and that these engineering predictions were not speculative but very much concrete.

Similarly the silicon solar panel industry in 2008 had a roadmap to get to £1/Wp over the next few years (which they did, and which led to the ~2012 explosion in solar installations), by mass producing the 'expensive' ~20% efficient (mono-crystalline silicon) technology. Mackay uses a 10% figure throughout.

So overall this was a bit like making predictions in the year 2000 assuming everyone will be stuck on 56k dial-up forever, because most people are on 56k dial-up.

These biases are present in all of the discussion of renewable technology, yet nuclear gets a free-ride / magical thinking in terms of uranium extraction, waste disposal and cleanup. And then there is the persistent obsession with land use in the book.

This led me to the conclusion (which I still hold) that this was an example of the tail wagging the dog: David MacKay wanted the 'obvious' physicists answer of nuclear power to be the natural conclusion, and by construction made it so in his book. Just because you are a Bayesian does not mean that you are unbiased!

David MacKay was an amazing scientist, but I do not think this book is accurate (even for its time), or that useful in public understanding of what we now call 'Net Zero'. It certainly popularised the idea of actually thinking through individual energy budgets, which can only be a good thing, but it was a massive missed opportunity to treat heat (chemical) energy (maximum entropy) and electrical (which can directly do work) as equivalent, just because they have the same unit.

Later on, as the 'Climate Tsar' he made a web app where you could play with the future balance of generation with a simulated model of the UK, and set your own costs for the different technologies, which I thought was much more useful. You could choose your own energy mix, and understand some of the tradeoffs.

And yes, very sad that he died so young. In the context of this book it would have been interesting to see how he dealt with the increasing mismatch of reality and his predictions as time passed.

jarviston Allow babywearing carriers on planes

I dunno, I flew UK-IRL this summer and in both directions I just threaded the baby-belt (standard issue here, the cabin crew hand them out before the safety briefing) around the carrier and the sleeping baby.

In a full on crash situation infants are not going to do well, so optimising for much more likely turbulence injuries (for which having the baby strapped as securely as possible is definitely a good idea!) seems more important.

jarviston Carbon-aware electricity pricing, measured daily on 38 grids

These approaches always measure the wrong thing though - the average carbon cost of electricity.

What you need to know is the marginal carbon cost, which will be much less variable as almost all dispatchable generation is fossil.

So yes, you should avoiding adding load when there is a severe supply crunch and the marginal power is generated by gas peaker plants (often gas turbine based), and use power when renewable generation is otherwise being curtailed, but most of the time the grid is firmly in the middle regime with a fairly average marginal cost.

jarviston Kenji/Serious Eats – 30-Min Pressure Cooker Pho Ga

The statement that electric pressure cookers measure pressure absolutely (i.e. not relative to local pressure) was news to me, and definitely a good hack to know if you're living at altitude.

jarviston Writing by hand is good for your brain

For my textbooks, I use little record cards. I write the book reference on the top line, then whatever notes or quotations etc. If it's a heavily referred to book, I sometimes use different colour cards to mean different things.

When I return the book to the library etc., I take all my record cards out and put them in a little perspex index box.

Sometimes I use the record cards to then start some more detailed notes in a notebook; sometimes the record cards refer to a page in my notebooks where I've attempted a derivation etc.

jarviston uBlock filter list to hide all YouTube Shorts

I've always had watch history off, but my searches now return a couple of pages of short form nonsense, before my actual results.

jarviston At 17, Hannah Cairo solved a major math mystery

Absolutely. Key for me was to invite children's friends (and family) along, host it in our house and make it a recurring weekly thing. The books (presumably you also have these from the MSRI's 'Mathematical Circles Library') are great, but week-to-week I've found the free online NRICH resources much more directly useful: https://nrich.maths.org/about-nrich

jarviston Math from Three to Seven

It's been really rewarding. I definitely recommend jumping in. I started with my reception-age child (+ school friends), and have just extended it to their younger sibling (+ friends from nursery). Your 3.5 year old will have started the EYFS (Early Years Foundational Stage) syllabus at nursery if they attend (which is also what they do in the 'Reception' year at primary school, before starting the national curriculum in the first year), so they will now be exposed to counting and comparisons. The perfect time to get started, in other words!

The NRICH material is really good: https://nrich.maths.org/teachers/early-years

There's some NRICH funded research that showed that exposure to symmetry and reasoning at this level was much more predictive of future abilities than numbers and counting. I think when parents try and help at the early stages, they often try to e.g. get their kids to count to 100, which is conceptually identical to counting to 10.

For number fluency there is the free White Rose '1 minute maths' app, which does a very nice job of gamifying subitising & etc. A lot of primary schools in London seem to have adopted the White Rose teaching resources. https://whiteroseeducation.com/1-minute-maths

jarviston Math from Three to Seven

Practically speaking (running a little maths circle in the UK for my children, and some of their friends from nursery and primary school), I have found the Nrich website to be the single best source of resources: https://nrich.maths.org/about-nrich

There is also https://parallel.org.uk/ by Simon Singh, but this is aimed at ages ~10+.

The book by Rozhkovskaya has some really nice activities in it. https://www.amazon.co.uk/gp/product/1470416956

The book by Zvonkin described in the article is a very good motivator, particularly for the honest descriptions of lessons gone badly wrong, and staying up late cutting out pieces of cardboard! But it's quite difficult to use as a teaching resource.

jarviston Feynman’s Razor

What do you not like about Feynman's "little arrows" / rotating clock hands in the QED book? I can't think of a more simple metaphor for the exponential of a complex phase, exp(i omega t). I suppose you could try and do it with more commonplace trigonometric functions, but then you lose the simple vector interpretation of adding the contributions. Or are you arguing that you should always try and teach complex numbers and the Euler identity to avoid strained analogies?

jarviston Standard Ebooks' 1,000th title: Ulysses

That's great! Their motivation & updates seem very sensible. Calculus Made Easy is a very nice compact book for university students who have started to forgot their high school training, and I will certainly point people in the direction of this project.

jarviston Ultrasonic Coffee

Water is incredibly efficient at transmitting sound.

jarviston Ultrasonic Coffee

The mug will attenuate almost all the signal. Maybe try with a disposable plastic cup?

jarviston Picotron Is a Fantasy Workstation

This is super useful to know about! The sprite designer & waveform editor / tracker is a really good creative introduction to computers for small children. And you can jump straight in to doing this with the above web link.

(For those new to Pico-8, hit 'esc' from the Lua console to bring up the editor tools, then click on the icon in the top right.)

jarviston The London office where swinging pendulums keep cyber threats at bay

But it is theatre. A single £0.01 Zener diode can generate vastly more guaranteed (by quantum mechanics!) randomness, without all the possibility of failure, entropy leaking etc.

jarviston Children need risk, fear, and excitement in play

Yes, but what you are missing is that behaviour has changed! We have that level of net road deaths today, given that kids are being driven everywhere.

So you can't state from your data that it has got safer: you need the child deaths/km or deaths/hr walking.

jarviston Canned air is unexpectedly supersonic [video]

The speed of sound does not depend on pressure, only temperature.

I suspect this is occurring because the (sonic) flow through the nozzle cools as it expands, therefore the speed of sound drops, making the same flow now supersonic in the cooled gas.

jarviston The humble brilliance of Italy's moka coffee pot (2018)

There's also a fantastic Youtube video in a neutron beam facility of a Moka pot, in which you can see the full process of brewing. The water and plastic handle appear 'black' as hydrogen scatters neutrons so strongly.

https://www.youtube.com/watch?v=VESMU7JfVHU

jarviston The humble brilliance of Italy's moka coffee pot (2018)

A key quality of life improvement for me was to realise that you can eject the grounds from the filter funnel by putting the tube to your lips and blowing gently, ejecting the coffee puck into the food waste / compost bin. The Moka pot then becomes an almost zero-cleanup way of making coffee.

You need to do this after the pot has cooled enough that the aluminium won't burn your lips, but soon enough that the coffee grounds haven't continued to swell and wedge themselves in place.

jarviston If humans went extinct, what would the Earth look like one year later?

I'm certain all the reactors will SCRAM (shut down the nuclear chain reaction), but then every large (i.e. all) power reactors need active cooling to remove the decay heat and prevent a core meltdown. (This is what happened at Fukushima - even with all the staff on site, they couldn't cope with a station 'blackout' (no external power grid) event.)

jarviston If humans went extinct, what would the Earth look like one year later?

Strangely this piece doesn't mention nuclear power plants: with 400 or so operational nuclear power plants worldwide, that's a lot of core meltdowns.

Similarly I would imagine there would be a lot of oil in the sea, if suddenly all the oil rigs and refineries were instantly abandoned.

jarviston What scientists must know about hardware to write fast code (2020)

My experience is a first implementation / novice programmer will write Julia code of a similar speed to python. But then an intermediate Julia programmer can adapt that same code to be of order C / Fortran performance, without stopping the novice programmer from being able to work on the code base. So it's this ability to iteratively improve and collaborate across very different skill sets that's really important.

This is quite a different situation to traditional scientific computing.

jarviston U.K. rejoins Horizon Europe research funding scheme

Why would you want control? That means more bureaucracy you need to do yourself.

In the UK (and I believe everywhere with a well functioning research culture), the 'Haldane principle' means that research funding is decided by researchers (not politicians / the civil service). https://publications.parliament.uk/pa/cm200809/cmselect/cmdi...

Funding UK science via the ERC, means you are making use of the network effects for peer review & processes. So the individual funding applications are being reviewed to a higher standard, and better decisions are made about what science to fund.

jarviston Show HN: IncarnaMind-Chat with your multiple docs using LLMs

https://github.com/whitead/paper-qa

>This is a minimal package for doing question and answering from PDFs or text files (which can be raw HTML). It strives to give very good answers, with no hallucinations, by grounding responses with in-text citations.

jarviston Google releases Bard to a limited number of users in the US and UK

Interestingly, in the UK I get this:

Me: As a part of Google, do you have my personal info?

Bard: I do not have your personal information. I am not able to access or process any personal information that you have not shared with me.

GDPR legislation saving us from AI?

jarviston Thousands of scientists publish a paper every five days (2018)

It's certainly not perfect (still a bit coarse, doesn't state what % of the work is done, doesn't state which parts of the paper the author worked on), but CRediT statements are gaining increasing traction in the published literature: https://credit.niso.org/

jarviston The Home Computer Generation

I don't think this is true, at least in the UK. The BBC computer literacy project meant that there were BBC Model Bs in every UK school, with tie-in educational materials. In the early 90s my entire class at a run of the mill state primary school took turns pair-programming LOGO on the school's BBC Micro. I don't think you can get more ubiquitous than every single human having programmed a loop and subroutine.

jarviston Pen and paper exercises in machine learning (2021)

Well write it up and put it on the ArXiV / send it to the author for version 2!

jarviston Zotero 6

The web plugin actually falls back to 'web page with snapshot' if it can't detect a journal paper, which in many ways is better than trying to drag around big PDF binaries.

jarviston Show HN: EBNF Specification of the BBC Shipping Forecast

You're also missing 'soon' and 'imminent' (along with 'later' have a very specific and important meaning).

And no 'sea states'? Currently there's 'Very rough or high, occasionally very high later in northwest Rockall.'

Nice stuff!