Hacker News Reader

fferenon The world that Twitter never made

+1, Full screen video works about 10% of the time on my phone.

fferenon Trends in menstrual bleeding changes after SARS-CoV-2 vaccination

Note that this is Science Advances, a much less prestigious journal than Science proper.

fferenon What are the odds that some idiot will name his mutex ether-rot-mutex (2017)

Exactly what I was thinking. I remember I once used "ana" everywhere in a program to avoid this.

I totally disagree. I find more mystery in large, industrial spaces than the rustic kitchen in the painting. I can easily picture "spirits dancing" in supermarket aisles and warehouses. The popularity of Liminal spaces [1] suggests that many people agree. Different aesthetics for different times.

[1] https://twitter.com/SpaceLiminalBot

fferenon Why we need Lisp machines

I have had the same thoughts before and come to a similar conclusion. I believe it's not about the language. It's about the features: runtime code editing, single address space, program interoperability. Lisp could be replaced with C or anything else. Unfortunately this is the hard part. No one is about to design completely new hardware or architecture for this, as it makes no economic sense. So we just get a shiny new language every few years, and nothing really changes.

fferenon How my genius roommate changed my perspective

I did similar things many times, though not as sophisticated. Using a chair on a table as a standing desk, etc. It's fine but at some point becomes an eyesore and makes you want some proper things.

fferenon Show HN: Relativity: A Modern Primer

I see. I don't know of a great answer, but it comes down to the constant speed of light. The simplest clock is two parallel mirrors with light bouncing back and forth. If someone is moving, then the light seems to take longer to bounce between them, so their clock appears slower. Wiki has a a good explanation:

https://en.wikipedia.org/wiki/Time_dilation#Simple_inference

In the hypothetical party scenario, you could demonstrate with your hands or some objects as mirrors.

Not the most satisfying answer, but if relativity was super intuitive, I probably wouldn't have written this book :)

fferenon Show HN: Relativity: A Modern Primer

Thanks! I don't believe these two concepts are related. You get back to the same point because the earth is _globally_ a sphere. However, time dilation and length contraction are _local_ concepts: they happen even for very small motions.

I guess a global object in spacetime analogous to a sphere in space is the hyperboloid t^2 - x^2 = r^2. Moving on this hyperboloid corresponds to changing boost velocity. But unlike a sphere, it is not closed, so moving in one direction does not get you back to the same point.

May add to this answer later.

fferenon Show HN: Relativity: A Modern Primer

This is fair enough. Hopefully some will still find it useful. I will note that I took a special relativity course in university that did things the "slow and intuitive" way, and many years later realized I still had some fundamental misconceptions about it. Eventually learned it the right way mostly by osmosis. More examples and motivation doesn't necessarily lead to correct understanding.

fferenon Show HN: Relativity: A Modern Primer

Any particular suggestions? Although it is compact, I have tried to carefully choose the wording and arrange the sections so each concept builds on the last. Also, I intentionally avoid unnecessary mathematical abstraction; for example, the abstract definition of manifolds using coordinate charts, and tangent vectors as differential operators. This really tripped me up when trying to learn GR from standard textbooks.

fferenon Mental health impacts of a big tech job

Perhaps this is unique to Apple? Even during my interview they were very explicit about having to work above and beyond. Ended up choosing somewhere else.

fferenon Getting Color Output out of a TI-99/4A

When I was a teenager with a TI-84 calculator, I used the trick of blinking the screen quickly at a fixed duty cycle to get "grayscale" from the black and white screen. Good times...

fferenon Why does F = ma?

Indeed, it is at the start of the book. It also relies on the assumption that the Lagrangian is invariant up to a total time derivative under Galilean transformations, which leads to `dL/d(v^2)` being a constant (1/2 m). This is, I believe, the most fundamental way to look at it. Otherwise you could ask why the Lagrangian can't have other terms like v^4.

fferenon Lionel Trilling’s Hottest Takes

When I read this I literally hear the music :)

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

fferenon LiChess: Learn from your mistakes

> I tested the new feature on my favorite opening: 1.e4 e5 2.f4!, a.k.a. the mighty King Gambit. Stockfish hates it, and asked me to review it like it was a mistake! Yet it's considered playable. Actually Carlsen played it against Arionian in 2015.

Not acceptable, Mr Stockfish!

Actually, the King's Gambit has been (essentially) solved: https://en.chessbase.com/post/rajlich-busting-the-king-s-gam...

There is only one move that doesn't lose by force after 2. ... exf4, and that is the strange-looking 3. Be2. Does that mean this opening is a "mistake"? Well, maybe not, obviously a human wouldn't know the perfect lines, but personally I wouldn't play it :)

Either way, I'll certainly be using this feature a lot. Kudos to the folks at Lichess.

fferenon Ask HN: What are some examples of successful companies rejected by YC?

I think the point there is to know how to do those geological tests :)

fferenon Who's downloading pirated papers? Everyone

As a grad student at a university with ample access to journals, I still use sci-hub occasionally, as many journal sites are surprisingly unreliable (cough IEEE, cough Nature).

fferenon The Hardest chess problem in the world?

It's a bishop, not knight.

fferenon Stanford engineers' breakthrough heralds super-efficient light-based computers

I uploaded the paper for anyone interested: https://drive.google.com/file/d/0B2R-ri3N25FnWHBWRzNlak01WEE...

fferenon The Effect of Physical Exercise on the Concentration of Individuals with ADHD

That's kinda what the study finds: the worst group was the non-ADHD group that exercised.

fferenon Metasurface Solves Calculus Problems as Analog Computer

Basic idea:

- A lens acts as a Fourier transform on an optical signal.

- d/dx is multiplication by ik in the frequency domain.

- They made a spatial reflection profile r(x) ~ ix using an array of nanobricks of different sizes (optimized with simulation)

- Optical signal -> lens -> reflection from metasurface -> lens = spatial derivative.

I have the paper if anyone wants it and doesn't have access.

fferenon Show HN: Play music by typing

Someone should make a keyboard that assigns nice sounding intervals to the most common digrams/trigrams so that typing normal text produces better music.

fferenon Always Talk to Strangers

Hello, dallen33!

fferenon The Axiom of Choice is Wrong (2007)

This is what I was thinking. Since there are only a countably infinite number of prisoners, you can't assign each one an equivalence class.

fferenon Bizarre Soft Robots Evolve to Run

I thought that at first too, but then I thought maybe most of the support is inside, not visible.

fferenon Pharo 2.0 Released

This is just the download page, the front page has more info: http://www.pharo-project.org/home

fferenon Mercator Puzzle

I think it's because the mercator projection distorts size, while the pieces try to stay the same (real-world) size as you move them. I didn't make the game, I just found it.

fferenon What one book could give me a new, useful superpower?

I'll take this opportunity to once again plug Strang's excellent linear algebra series [1] with associated textbook [2]. Also right now I'm working through some Cornell lecture notes [3] (that read a lot like a textbook) on manifolds and differential forms. It's meant for college sophomores and juniors who have taken linear algebra and vector calculus, though it provides a very good calculus supplement in the appendix. For me, it's perfect: the tone is informal enough to provide motivation to continue, but the definitions and proofs are fairly rigorous. It's about the only self-study math text that I think I might finish.

Hope this helps, not sure if it's over/under your level.

[1]: http://ocw.mit.edu/courses/mathematics/18-06-linear-algebra-...

[2]: http://www.amazon.com/exec/obidos/ASIN/0980232716/ref=nosim/...

[3]: http://www.math.cornell.edu/~sjamaar/papers/manifold.pdf

fferenon Alone Together, Again

This is basically how I live my life. Throughout high school and freshman year college (I'm 19) I was always so concerned about things that were utterly unimportant in hindsight, like not offending people, making friends, not being a shut-in (I've always been an introvert). I've found that simply not caring about stuff has made the biggest improvement in my life satisfaction.

For example, I tried to make friends in the first week of college by talking to random people. I joined some clubs and went to events. This completely failed, I didn't click with anyone; these kinds of things didn't fit with my personality. All of my current friends I've met serendipitously. And, because I stopped caring so much about it, I think I have much better social skills now.

Kind of fits with the Daoist philosophy of wu wei: http://en.wikipedia.org/wiki/Wu_wei

EDIT: hah, looks like someone else made the same connection :D