Hacker News Reader

vilhelm_son UK and US say Russia fired a satellite weapon in space

> The US said the Russian satellite system was the same one it raised concerns about in 2018 and earlier this year

vilhelm_son Stacked images of the comet, photobombed by Starlink satellites

I guess the most basic way to stack (just add the images together) would leave them in, but

> Almost every modern astronomical post-processing program has a rejection process (sometimes referred to as sigma-reject) to remove unwanted signals, though the exact sequence will depend on which program you use.

https://skyandtelescope.org/astronomy-blogs/imaging-foundati...

vilhelm_son Swedish epidemiology boss says questioned Covid-19 strategy seems to be working

> there's something else going on: either it's way more infectious (but less dangerous) than realised, or more likely, a very large proportion of people have baseline immunity to the infection. It spreads rapidly through those who had no previous immunity and then burns out.

I don't think this can be the explanation, because it would not account for how geographically localized it was in Sweden. The Stockholm metro area got hit heavily, but the rest of the country was comparatively spared, and it never became big in southern Sweden. If people had prexisting immunity to coronaviruses you'd expect the immunity to be equally distributed, so it should burn through the entire country.

To me, that sounds more like there was an outbreak that started in Stockholm, but then they added social distancing measures which were enough to slow it down...

vilhelm_son Do Colorless Ideas Sleep Furiously? (1997)

In 1985 some students at Stanford organized a competition:

> you were asked to compose not more than 100 words of prose, or 14 lines of verse, in which a sentence described as grammatically acceptable but without meaning did, in the event, become meaningful. The sentence, devised by Noam Chomsky, was: colourless green ideas sleep furiously.

Four winning entries here: http://archives.conlang.info/ga/farzhi/shiarweilwoen.html

vilhelm_son Debunking the Myth of 10% Brain Usage

I think the page is saying that the largest injuries destroyed less than 10% of the brain, leaving more than 90% intact. 50% is more than that.

vilhelm_son Debunking the Myth of 10% Brain Usage

> If we are using only 10% of our brains, that means a person would be fine if the other 90% of the brain got removed [...] There are instances in history when people were injured and got parts of their brain removed (although not as close as even 10%)

Actually you can do much better. There are people who had 50% of their brain removed and were fine. [https://en.wikipedia.org/wiki/Hemispherectomy]

And there are examples of people who lost up to 95% of their brain and still seem pretty normal. (Actually, some are claimed to be be smarter than average, leading to the suggestion that the rest of the brain is just cramping our style, but that's probably an exaggeration.) [https://www.gwern.net/Hydrocephalus]

vilhelm_son Why Does DARPA Work?

My impression is that it's not at all that consistent. The total spending is constant at a few billion per year, but what that gets spent on depends entirely on the taste of the program managers, which in turn depends on the darpa director. The program managers only serve for a few years at a time, and the director for a bit longer, so it can change drastically. I think the trends are typically last a decade: in the 1980s after the success with the F-117, they were funding all kinds of airplane projects. Also in the 1980s they funded a lot of AI research, until they suddently didn't (the "AI winter"). In the 1990s, they were into networked combat simulators and command & control systems.

Starting around 2010, DARPA suddenly began to fund a lot of computer science research on formal verification. I was a phd student at the time, and it was pretty striking, programming language theory used to be a really fringe subject, and now suddenly it was awash in cash and all the professors could hire huge herds of postdocs. But some of those professors also told me that I should not expect it to last: sooner or later there will be new people in DARPA and all the money will instantly stop.

vilhelm_son Discovering Dennis Ritchie’s Lost Dissertation

"How to Program an Infinite Abacus" defines register machines (a.k.a counter machines), and shows that they coincide with general recursive functions. "The complexity of loop programs" defines loop programs, and shows that the coincide with primitive recursive functions. (A key difference is whether loops are bounded or not.)

vilhelm_son Helium shortage has ended, at least for now

How do you get this number? Googling a bit, the D-T reaction produces 17.59 MeV per helium atom, so it should yield

17.59 MeV / (helium-4 atomic mass) = 0.117 TWh/kg

in thermal energy per kg of helium produced. The U.S. electricity production in 2019 was 4,118 TWh [1] and 4118 TWh / 0.117 (TWh/kg) = 35,196 kg.

If we assume some inefficency in the thermal->electricity conversion, I guess it should produce at least 70,000 kg/year.

[1] https://www.eia.gov/tools/faqs/faq.php?id=427&t=3

vilhelm_son Why Our Intuition About Sea-Level Rise Is Wrong

It seems this would made the effect from the icebergs bigger rather than smaller, because the gradient decays by r^3 instead of r^2, so the distance is more important?

Like, the gravitational acceleration is a = GM/r^2 while the gradient is da/dr = -2GM/r^3

So for moon vs glacier at 1000km you'd get

- 2 * (Gravitational constant) * (mass of moon) / (391184 km)^3 = - 1.638×10^-13 reciprocal seconds squared

- 2 * (Gravitational constant) * (1e19 kg) / (1000 km)^3= -1.335×10^-9 reciprocal seconds squared

vilhelm_son As Qualified Immunity Takes Center Stage, More Delay from SCOTUS

Qualified immunity is not constitutional. It supposedly derives from the common law, so congress can change it through ordinary legislation.

vilhelm_son The Vintage Beauty of Soviet Control Rooms (2018)

In fact one of the photos in this collection is from the American ship NS Savannah (launched in 1959)... it's not easy to spot which one is the odd one out!

vilhelm_son The Vintage Beauty of Soviet Control Rooms (2018)

Indeed, one of them is a subway control panel, and another one a railway panel. :) [See http://blog.presentandcorrect.com/27986-2 for the links to original image sources.]

vilhelm_son Gitlab phished its own work-from-home staff, and 1 in 5 fell for it

It depends on what your threat model is. If you are a high value target, clicking on a link could definitely get your hacked through a browser vulnerability, e.g. https://blog.coinbase.com/responding-to-firefox-0-days-in-th... and https://www.theregister.co.uk/2016/10/20/alleged_dnc_hackers... .

Most people are probably not worth the effort of this, but I could imagine a source code hosting company could be, as a step to try to compromise some other software...

vilhelm_son Show HN: A dependently-typed programming language with static memory management

I would guess the main problem is that this approach will be slow, since it keeps making copies of all data. If you have a garbage collector you can just pass pointers around.

vilhelm_son Emptier US roads more lethal in coronavirus pandemic, report says

On the plus side, we got a new Cannonball Run record: 26 hours across the continent, which works out to an average of 107 mph including stops...

https://www.whichcar.com.au/news/the-cannonball-run-record-h...

vilhelm_son Chernobyl and the Cost of Lies (2019)

But that's just even more arbitrary, right? It just means nobody knows how many deaths it caused, and there is an uncertainty of an order of magnitude based on how the effects of very low doses.

vilhelm_son Chernobyl and the Cost of Lies (2019)

I think it's worth noting that the UNSCEAR report also said 5000 more deaths among less exposed people (so 9000 in total), it's all rather arbitrary.

vilhelm_son Why Don’t We Use Chemical Weapons Anymore?

Even the most long-lasting ones will still evaporate in a few weeks. (Of course, if it's inside a bottle it will not evaporate, and if it's inside a city you probably want to decontaminate it rather than wait).

vilhelm_son Ventilator maker: we can ramp up production five-fold

One possible scenario is that the pandemic dies down when the weather gets warmer and then comes back for a second wave in fall. (Several historical flu pandemics behaved like that.) Should that turn out to be the case, it would still be useful to build up a stockpile of ventilators to use 6 months from now.

vilhelm_son Fulfillment by Amazon suspends non-essential inbound shipments

Well, on the other hand, it seems like because Amazon is so centralized, they had a lot of capacity which they can now re-purpose. Previously they were shipping both non-essential stuff (books, vinyl records, etc) and essential (food, medicines), and now all those resources can go into essential things.

If the vinyl record shops had a completely separate fulfillment system, there would be no easy way to repurpose it to ship essential items, so we would be in a worse position.

vilhelm_son Koenigsegg’s 2.0-liter no-camshaft engine makes 600 horsepower

I guess he means it can run on ethanol produced from biofuel.

vilhelm_son Soviet radar hidden in Chernobyl’s shadow [video]

Apparently it never worked properly (from https://www.tandfonline.com/doi/abs/10.1080/09636412.2017.13...):

> Meanwhile, the top Soviet EW warning commanders called OTH radar “virtually useless.”[88] Danilevich agreed, arguing that LUA was impossible before the development of satellites: “there were only above-the-horizon systems; there were no over-the-horizon systems ... These systems were not sufficiently reliable. They did not allow the reliable detection of launches. The only way to reliably determine the beginning of an attack is through human intelligence, but it is dubious that such data could be obtained.”[89] Apparently OTH radar operators would consult public reports about planned NASA space launches and then claim that they had tracked a launch on the appropriate day. But the ruse became obvious when weather delayed a launch.[90]

[88] Fischer, “The Soviet–American War Scare of the 1980s,” 502. [89] Hines interview with Col. Gen. Danilevich, 24 September 1992, in Hines, Mishulovich, and Shull, “Soviet Intentions 1965–1985, Vol. II”, 41. [90] Bruce G. Blair, The Logic of Accidental Nuclear War (Washington, DC: Brookings Institution Press, 1993), 205.

vilhelm_son Superdeterminism may help us overcome the current crisis in physics

That's the whole point right? The hope is to figure out what the hidden variables were, to make better predictions than quantum mechanics could. To un-hide them, as it were.

vilhelm_son Superdeterminism may help us overcome the current crisis in physics

No, you actually can. The authors of this article discuss the issue more in their longer paper here: https://arxiv.org/abs/1912.06462

The idea is that superdeterminstic theories are deterministic, while quantum mechanical measurements are random, so you should be able to set up an experiment where QM predicts you would just get random results, but actually you get the same result each time.

vilhelm_son Warren Abstract Machine

"[S]econd, we couldn't understand how the WAM worked. We read all the papers but the explanations seemed to be written only for people who already understood how the thing worked." ---Joe Armstrong (from "A History of Erlang")

This has been my experience also!

vilhelm_son The neuroinvasive potential of SARS-CoV2

> According to the complaints of a survivor, the medical graduate student (24 years old) from Wuhan University, she must stay awake and breathe consciously and actively during the intensive care. She said that if she fell asleep, she might die because she had lost her natural breath

Sounds like something from a horror movie!

vilhelm_son Was Knuth Really Framed?

I don't think there is such a sharp distinction between writing and using tools. You could take the 9-command pipeline, paste it into a shellscript, and now you have a new tool.

And isn't this how most programming is done? Typically your program relies on a set of libraries, but the methodology of writing the library looks very similar to the methodology of writing the client code; at the end of the day, it's all programming.

If literate programming is great, then I would expect it would be great everywhere. And if decomposing your program into a few steps and piping together already-written software for those steps is great, then I would expect you should try to use that style of programming as widely as possible.

vilhelm_son What happens if I don't fill out my census form? (2019)

https://gwipp.gwu.edu/counting-dollars-2020-role-decennial-c...

They calculate that in 2017 there were $1,504,191,364,000 in Federal spending guided by the census numbers, which is about $4,600 per capita.

In this paper [1] they look at some specific programs:

> Five grant programs administered by the U.S. Department of Health and Human Services (HHS) use the Federal Medical Assistance Percentage (FMAP), based on the 2010 Decennial Census population count, to determine reimbursements to and payments from each state government (totaling $286.1 billion in Fiscal Year 2015). The five FMAP-guided programs are Medicaid, the Children’s Health Insurance Program, Title IV-E Foster Care, Title IV-E Adoption Assistance, and the Child Care and Development Fund. In Fiscal Year (FY) 2015, reimbursements to and payments from state governments under these five programs totaled $286.1 billion (48.1% of all federal grants to states and 13.0% of all state budgets).In FY2015, 37 states forfeited a measurable amount of funds for each person missed in the 2010 Census.

> Among these 37 states, the median FY2015 loss per person missed in the 2010 Census was $1,091. FY2015 loss per person missed ranged from $533 for Utah to $2,309 for Vermont. The median state is Tennessee.

[1] https://gwipp.gwu.edu/sites/g/files/zaxdzs2181/f/downloads/G...

vilhelm_son Radical hydrogen-boron reactor leapfrogs current nuclear fusion tech?

There are various proposed schemes for doing so: https://en.wikipedia.org/wiki/Direct_energy_conversion

In principle this could be more efficient than a heat engine, although the Wikipedia page seems to say that an "economically feasible" version would have around 60% efficiency, which is the same as a combined-cycle power plant.