Hypertexthero / Linked List / January 2015

Linked List: January 2015

Sunday, 25 January 2015

How Accurate Is That Number? ✶

From the transcript of Charles Bailyn’s ASTR 160: Frontiers and Controversies in Astrophysics Lecture 2: Planetary Orbits (emphasis mine):

Student: How accurate is that number?

Professor Charles Bailyn: How accurate is that number? It’s accurate to about one digit, which is why I only wrote down one digit of accuracy out front. This is a pro–excellent question thank you very much. This is appropriate because remember I’m using 7 times 10 minus 11 for G, where it’s actually 6.6. So, I’m already about 10% off from there. I did my little calculation to come up with one year equals 3 times 107 seconds. That’s about accurate to one digit or so. And so the whole thing is done to one digit accuracy. If you’re dealing with one digit accuracy, it is true that 7 divided by 4 is 2. It really is true, because if that wasn’t true, then you would have to have more digits on your unit for G or something like that. In particular, let me make an official rule for this course. Three equals π, equals the square root of 10, all right. That will solve an enormous amount of arithmetic problems and it will not get you into any serious trouble. So, we don’t have to worry about the .14159 and however many more digits you all memorized it to. And when you multiply it together you get ten. Yes?

Student: Are you expecting this kind of calculation for problem sets?

Professor Charles Bailyn: Yes. The question was, “Am I expecting this kind of calculation for problem sets?” The answer is “yes.” Here’s the rule about calculators. Let me put it this way: You can only use calculators if I can’t tell that you’ve done it. So, that means you can check your work to make sure you’ve it right or something. But if you start coming up with numbers like 7.1516397, that’s eight digits of accuracy and I’m pretty sure you haven’t worked it out yourself. So important, no calculators on the tests, okay? So, get some practice doing this kind of thing. And this will–this I promise you will be useful to you in everyday life because this is how you catch the politicians doing screwy things with big numbers. You do it in your head in scientific notation and you figure out whether the answer is meaningful or not.

This whole business of significant digits, I think, is badly distorted; by the way, it’s taught in high school. In high school you, and also I should say in laboratory courses sometimes at the college level, you often get situations where people say–give you a whole sheet of rules on how to figure out how many significant digits you have. This is nonsense. All you have to do is behave like a human being. We say to each other, I’ll meet you in the dining hall in ten minutes. That doesn’t mean–that means something different from I’ll meet you in the dining hall in eleven minutes and twenty-six seconds. Even if the person happens to show up in the dining hall in exactly eleven minutes and twenty-six seconds. Ten minutes means I’ll meet you there in ten minutes, we all know what that means. I’ll meet you there in eleven minutes and twenty-six seconds means you’re a character in a bad spy novel who’s just synchronized his watch. So, this shows up in science fiction too.

I don’t know how many of you are Star Trek fans, I certainly am [laughter]. And in all the different Star Trek movies [inaudible comment]–thank you. In all the different–a friend [referring to person who made comment]. In all the different Star Trek movies there’s always a second in command who isn’t a human being, right? A Vulcan or an android or some damn thing or another. And to emphasize the non-humanness of these characters, what they do is they make them use too many significant digits. And so that makes them inhuman and so the captain will say, “When are we landing on omicron M?” The second in command will say, “Well, we should assume standard orbit in 2.6395 minutes,” emphasizing somehow superior brain power or something. But it’s nonsense because it takes the guy ten seconds to say that sentence, so what is this time calculated to a 100th of a second? Does it start from when he begins the sentence? From when he ends the sentence? What’s the other end of that time interval? Can you say you assume standard orbit to the 100th of a second? What does that even mean? When you start beaming down? When you end beaming down? Also, keep in mind it takes more than a 100th of second for the sound to travel from his lips to the captain’s ears, so the whole thing is just nonsense. And so, you don’t need any special rules, just behave like a human being; don’t behave like an android. So, no androids. And that’s the only rule I’m going to give you [laughter]. These two are the only rules I’m going to give you about significant digits, just do the right thing, okay.

Two rules:

  1. 3= π= 10
  2. No androids!
Our Solar System and the Pluto Problem ✶

From lecture 3 in professor Charles Bailyn’s ASTR 160: Frontiers and Controversies in Astrophysics:

Bailyn first reminds us of the scientific method and that astronomy is an observational science. He then talks about classification and the six categories of objects in the Solar System:

  1. Sun (a star).
  2. Inner, sometimes called terrestial or rocky, planets.
  3. Asteroids.
  4. Outer, also known as Jovian, planets.
  5. Trans-Neptunian, or Kuiper Belt, objects.
  6. Comets in the outer region, or Oort cloud.

Chapter 5. Classification and Interpretation of Celestial Objects 00:35:13:

So, here are the six categories that I would claim exist in the Solar System. And here’s my problem with the whole Pluto debate. The Pluto debate was basically about whether these guys are going to count as planets. But the thing is, “planets” is already a bad description, because it contains two quite different categories; namely, these inner terrestrial planets, and the outer Jovian planets. So, it seems to me that arguing whether category five should be part of some category that already contains two fundamentally different kinds of objects is kind of a strange argument to be having. Either we should split these two things off from each other, or, if we’re going to join these two kinds of the categories, fine, bring in anything you like. I don’t care, add the asteroids, too. And, in fact, in the original proposal, one of the asteroids qualified as well. And so, it doesn’t seem to me that this controversy was really paying justice to an appropriate classification of the things in the Solar System.

We’ll soon find out much more about Pluto when NASA’s New Horizons spacecraft passes by in July 2015!

Sunday, 18 January 2015

2015 International Year of Light ✶

On 20 December 2013, The United Nations (UN) General Assembly 68th Session proclaimed 2015 as the International Year of Light and Light-based Technologies (IYL 2015).

This International Year has been the initiative of a large consortium of scientific bodies together with UNESCO, and will bring together many different stakeholders including scientific societies and unions, educational institutions, technology platforms, non-profit organizations and private sector partners.

In proclaiming an International Year focusing on the topic of light science and its applications, the United Nations has recognized the importance of raising global awareness about how light-based technologies promote sustainable development and provide solutions to global challenges in energy, education, agriculture and health. Light plays a vital role in our daily lives and is an imperative cross-cutting discipline of science in the 21st century. It has revolutionized medicine, opened up international communication via the Internet, and continues to be central to linking cultural, economic and political aspects of the global society.

Columbia Astronomy Public Outreach ✶

Free lectures followed by guided stargazing with telescopes (weather permitting) at Columbia University.

Comedy Subverts the World of Hollow Power ✶

Max Cabanes:

It is our job to recognise the absurd, and to ridicule what is already absurd.

…

Subversion is subliminal, a state of mind, and for this reason the suppression of free speech is an expression of the way in which people are ground down economically, and the repression of humour is part of that economic repression.

Willem:

There are people attacking us who have never seen it, or think it’s only concerned with Islam. The fact is they don’t know how to read cartoons. There are people who, even if they are illiterate, know how to view a cartoon. And there are clever people with an agenda who just don’t have the culture to understand our laughter. And among the second group are these people like your prime minister and all the others calling themselves Charlie. It’s completely ridiculous, first because in the end they don’t want us, and they don’t want to be Charlie – how could they be? They hate us! And second because they are pretentious, and all pretention is false. When the king employed a fool to laugh at him, the fool was the only one allowed. Now they want no one to laugh at them, but we are free and we do. And if you abolish humour, or kill the funny people, there is nothing left – nothing.

Zineb el-Rhazoui:

People say we should respect religion, but our attitude to religion is the same as it is to any other ideology.

Thursday, 15 January 2015

The Turn-Verizon Zombie Cookie ✶

Wednesday, 14 January 2015

Every Few Years People Remember Websites Should Be Simple and Simplicity is Hard ✶

UX Check is a Google Chrome browser extension that helps identify usability issues based on Jacob Nielsen’s1 website usability principles:

  • Visibility of system status: The system should always keep users informed about what is going on, through appropriate feedback within reasonable time.
  • Match between system and the real world: The system should speak the users’ language, with words, phrases and concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order.
  • User control and freedom: Users often choose system functions by mistake and will need a clearly marked “emergency exit” to leave the unwanted state without having to go through an extended dialogue. Support undo and redo.
  • Consistency and standards: Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions.
  • Error prevention: Even better than good error messages is a careful design which prevents a problem from occurring in the first place. Either eliminate error-prone conditions or check for them and present users with a confirmation option before they commit to the action.
  • Recognition rather than recall: Minimize the user’s memory load by making objects, actions, and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate.
  • Flexibility and efficiency of use: Accelerators – unseen by the novice user – may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions.
  • Aesthetic and minimalist design: Dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility.
  • Help users recognize, diagnose, and recover from errors: Error messages should be expressed in plain language (no codes), precisely indicate the problem, and constructively suggest a solution.
  • Help and documentation: Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user’s task, list concrete steps to be carried out, and not be too large.

  1. I remember reading that Nielsen consulted with Google for a day when they were starting out, and his recommendations helped define the simplicity of the site in the beginning: the logo, a search bar and a few footer links. ↩︎

Sunday, 11 January 2015

Set Firefox Display to Retina Resolution ✶ 
about:config
layout.css.devPixelsPerPx 1