Kosmologi-joke

Reklamer
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Klammer

Jeg har tidligere haft diskussioner med mine kolleger og venner om den bedste måde at placere klammer i kode, heldigvis er der dog ingen der har insisteret på denne måde:

På den anden side, hvis man er Python udvikler der er tvunget til at bruge et andet sprog er det nok naturligt.

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Paradokset ved falsk positiv

Fra Cory Doctorow’s “Little Brother“:

Say you have a new disease, called Super-AIDS. Only one in a million people gets Super-AIDS. You develop a test for Super-AIDS that’s 99 percent accurate. I mean, 99 percent of the time, it gives the correct result — true if the subject is infected, and false if the subject is healthy. You give the test to a million people.

One in a million people have Super-AIDS. One in a hundred people that you test will generate a “false positive” — the test will say he has Super-AIDS even though he doesn’t. That’s what “99 percent accurate” means: one percent wrong.

What’s one percent of one million?

1,000,000/100 = 10,000

One in a million people has Super-AIDS. If you test a million random people, you’ll probably only find one case of real Super-AIDS. But your test won’t identify one person as having Super-AIDS. It will identify 10,000 people as having it.

Your 99 percent accurate test will perform with 99.99 percent inaccuracy.

That’s the paradox of the false positive. When you try to find something really rare, your test’s accuracy has to match the rarity of the thing you’re looking for. If you’re trying to point at a single pixel on your screen, a sharp pencil is a good pointer: the pencil-tip is a lot smaller (more accurate) than the pixels. But a pencil-tip is no good at pointing at a single atom in your screen. For that, you need a pointer — a test — that’s one atom wide or less at the tip.

This is the paradox of the false positive, and here’s how it applies to terrorism:

Terrorists are really rare. In a city of twenty million like New York, there might be one or two terrorists. Maybe ten of them at the outside. 10/20,000,000 = 0.00005 percent. One twenty-thousandth of a percent.

That’s pretty rare all right. Now, say you’ve got some software that can sift through all the bank-records, or toll-pass records, or public transit records, or phone-call records in the city and catch terrorists 99 percent of the time.

In a pool of twenty million people, a 99 percent accurate test will identify two hundred thousand people as being terrorists. But only ten of them are terrorists. To catch ten bad guys, you have to haul in and investigate two hundred thousand innocent people.

Guess what? Terrorism tests aren’t anywhere close to 99 percent accurate. More like 60 percent accurate. Even 40 percent accurate, sometimes.

What this all meant was that the Department of Homeland Security had set itself up to fail badly. They were trying to spot incredibly rare events — a person is a terrorist — with inaccurate systems.

Is it any wonder we were able to make such a mess?

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Bitcoin og “penge”

Michal Zalewski’s “The Deal With Bitcoin“, læst sammen med David Graeber’s “Debt: The First 5000 Years“, burde læses af alle. Jeg tror at Bitcoin’s betydning er overvurderet, men sammen med Graeber’s bog får man en bedre forståelse af hvad penge, og valuta, er.

In essence, BTC is a global, decentralized fiat currency: it has no (recoverable) intrinsic value, no central authority to issue it or define its exchange rate, and it has no anchoring to any historical reference point – a combination that until recently seemed nonsensical and escaped any serious scrutiny. It does the unthinkable by employing three clever tricks:

  1. It allows anyone to create new coins, but only by solving brute-force computational challenges that get more difficult as the time goes by,
  2. It prevents unauthorized transfer of coins by employing public key cryptography to sign off transactions, with only the authorized holder of a coin knowing the correct key,
  3. It prevents double-spending by using a distributed public ledger (“blockchain”), recording the chain of custody for coins in a tamper-proof way.

Jeg er enig med Zalewski i at blockchain ikke er så vigtig ift. Bitcoin, men mener at der stadig er masser af potentiale i grundprincippet i en blockchain. Måske tager jeg fejl, for som Kai Stinchcombe skriver i “Ten years in, nobody has come up with a use for blockchain” (selvom at det er fokuseret rigtig meget på Bitcoin’s implementering):

There are four additional problems with a blockchain-driven approach. First, you’re relying on single-point encryption — your own private keys — rather than a more sophisticated system that might involve two-factor authorization, intrusion detection, volume limits, firewalls, remote IP tracking, and the ability to disconnect the system in an emergency. Second, price tradeoffs are entirely implausible — the bitcoin blockchain has consumed almost a billion dollars worth of electricity to hash an amount of data equivalent to about a sixth of what I get for my ten dollar a month dropbox subscription [min fremhævelse]. [Thirdly], systematically choosing where and how much to replicate data is an advantage in the long run — the blockchain’s defaults on data replication just aren’t that smart. And finally, Dropbox and Box.com and Google and Microsoft and Apple and Amazon and everyone else provide a set of valuable other features that you don’t actually want to go develop on your own. Analogous to Visa, the problem isn’t storing data, it’s managing permissions, un-sharing what you shared before, getting an easy-to-view document history, syncing it on multiple devices, and so on.

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En oplevelse med Chromecast

Vi har suppleret vores Samsung / Apple hjem med en Google Chromecast. Det kører OK og jeg er sikker på at det kun er et spørgsmål om tid før vi alle har fundet ud af hvordan det skal bruges. Jeg har bare haft en meget mystisk oplevelse…

Den starter med at jeg fra min telefon sætter en Youtube video i gang på Chromecast. Det virker fint.

Derefter starter min søn et antal Youtube videoer fra hans tablet. Det virker fint.

Jeg er i mellemtiden i gang med noget andet på min telefon og opdager at der er skruet op for lyden på den. Jeg skruer derfor ned … og min søn siger at nu forsvandt lyden på Chromecasten.

Jeg lukker derfor Youtube-app’en på min telefon, tager tabletten og skruer op for lyden på den. Hvorefter lyden på min telefon, ikke på Chromecasten, skrues op.

?!?

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En dialog og lidt udefrakommende lyde

På vej med min dreng til skole:

– Far, hvad er det for en lugt?

– Hvad for en lugt?

– Den der ulækre lugt…

– Jeg kan ikke lugte noget… Måske kommer det udefra?

Et par kilometer senere lyder der er klunk fra forenden af bilen. Jeg tænker, det lyder også dyrt.

– Ekploderede den nu?

Jeg drejer fra hovedvejen og opdager i den forbindelse at jeg ikke længere har servostyring.

– Jeg er bange for at bilen er gået i stykker.

– Fedt

lyder det sarkastisk fra min dreng. I det mindste har han det ikke fra fremmede.

Og det var historien om hvordan han fik en fridag, og at min mekaniker igen har min Berlingo.

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Hvad er der galt med dette kort?

Og læs så Brian Romer’s “Mapbreaking“.

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Klimaforandringer

Jeg ved godt at jeg har oliefyr og kører i en dieselbil. Samtidig ved jeg også godt at hvis vi skal have noget som helst håb om at kunne få de menneskeskabte klimaforandringer under kontrol er vi nød til at bringe vores samlede CO2 bidrag til atmosfæren ned på 0. Jeg tror ikke det er muligt.

Så her er to forskellige vinkler: En prognose (ScienceBlog’s “93% risiko for global opvarmning over 4°C i dette århundrede“) og et håb (Bill Gates’ “4 signs of progress on climate change“).

Pudsigt at bogen “Toward the year 2018“, fra 1968, hvor Thomas Malone spekulerer over om “large-scale climate modification will be effected inadvertently” af et højere CO2 niveau. Han forudser at det vil være være nødvendigt at etablere en international, ikke-politisk, organisation med faktisk magt til at bekæmpe en sådan global opvarmning. Hvilket nok forklarer vores nuværende situation.

Hvis man vil forstå et par af måderne hvorpå klimadebatten kører af sporet, så kan man passende læse “How Big Oil Lost Control of Its Climate Misinformation Machine” og “How Climate Change Deniers Rise to the Top in Google Searches“.

Og bagefter kan man reflektere over hvor mange mennesker der tror at Bjørn Lomborg benægter menneskeskabte klimaforandringer, når det han skriver f.eks. er kan læses i “Innovation needed to fight climate change“.

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Opdragelse

Ryan Sohmer, “Smashing All The Screens“:

I will gladly put my kid into acting lessons, have him learn video production and see how youtube works through my friends and colleagues, but I will not let him post himself on youtube. Or facebook, or Instagram.

For 2 reasons-

1, The internet is a scary place and my son, when he’s an adult has the right to create his own digital profile;

2, I don’t want my kid to turn into a Logan Paul-like asshole.

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Mens vi står på resterne af fortidens massemedier…

En af de største udfordringer i meningsdannelse pt., er at vi naturligt søger ind i vores egne ekkokamre. Jeg kan dog godt lide sober, faglig diskussion med folk jeg er uenig med.

Mainstream media did not reflect reality for countless unreflected, underrepresented, and underserved communities; now, thanks to the net, we can better hear them. And mainstream media did not uniformly inform the entire nation; we just couldn’t know who all was uninformed, but now we have a better sense of our failings.
[…]
The mass is dead. I don’t regret its passing. In some ways, we need to learn how society managed before media helped create this monster. In other ways, we need to recognize how we can use new tools — the ones the bad guys have exploited first — to better connect and inform and manage society. Let’s begin by recognizing that the goal is not to create one shared view of reality but instead to inform discussion and deliberation among many different communities with different perspectives and needs. That’s what society needs. That’s what journalism must become
— Jeff Jarvis, “Death to the Mass(es)!

Læs også hans “Democracy Dies in the Light“, endnu en gang om journalisme.

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