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Schlenz yesterday at 17:45


LET’S DISCUSS THE LORENTZ TRANSFORMS – INTERMISSION: RAPIDITY, AND WHAT IT MEANS

Mathematics *Physics

I thought my previous post rather funny, and was surprised seeing it initially
receive so few views. I thought the entertainment flopped, but fortunately I was
wrong. I therefore feel it my duty before my readers to address the subject of
the Landau & Lifschitz proof of the invariance of the interval.

You can find the summary of it in Wikipedia. Making their starting point the
light-like interval always being equal to zero, Landau & Lifschitz seem to make
a great fuss about it. The Wikipedia article even says: ‘This is the immediate
mathematical consequence of the invariance of the speed of light.’ No, it is
not.

I beg everyone’s pardon, but the light-like interval always being equal to zero
is nothing else but the following statement: ‘The length of a ray of light will
always be equal to the length of this ray of light’. Sounds like a cool story,
bros and sis, but I cannot see what further inferences can be drawn from it. The
‘proof’ of this truism cannot fail under any circumstances whatever – whether
you keep the speed of light invariant, or keep or change the metric of space or
time or both – or make both metric and speed of light change – the light-like
interval will remain equal to zero. I am okay with anyone wanting to prove it if
they feel like it, but you cannot make it an ‘immediate mathematical consequence
of the invariance of the speed of light’. Neither is it possible to make the
constancy of the speed of light a consequence of the invariance of the
light-like interval for the reason already mentioned: this is a truism. It does
not prove anything, nor can it be a consequence of anything. When Landau &
Lifschitz insist that this is a consequence of the constancy of the speed of
light, that is either an error or a downright subterfuge, a means employed to
create a spectre of logical connection between two unconnected notions, and
charge this ghostly connection with pretended significance. And, since the
following proof of invariance of an arbitrary interval hangs on the invariance
of the light-like interval, we can altogether dismiss it: the necessity of
introduction of such a measure as interval cannot be derived from the statement
that a length of something will be equal to itself in whatever frame of
reference it is measured.


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Comments 2 +2



Schlenz 26 September at 14:20


LET’S DISCUSS THE LORENTZ TRANSFORMS – PART 2: THE EQUATION OF THE SPHERE, OR IS
IT?

Mathematics *Physics

The previous discussion done, we have surmounted the difficult waters and are
now sailing into something much more pleasure-like and hopefully even
entertaining.

As I promised, we will be discussing the invariance of the interval, that is to
say, the following relation:


Read more
Total votes 3: ↑3 and ↓0 +3
Views 180 Add to bookmarks 2
Comments 0



Schlenz 23 September at 16:46


LET’S DISCUSS THE LORENTZ TRANSFORMS – PART 1: EINSTEIN’S 1905 DERIVATION

Mathematics *Physics

Even as I am posting this, I can see that my previous post received a hundred
and twenty plus views, but no comments yet. I am saying again that my pursuit is
not to give an answer, but to ask a question. I only wonder if there is in fact
no answer to the questions I am asking – but anyway, I will continue asking
them. If you know how to deal with the problems I am setting – or happen to
understand they are not problems at all, I will be most grateful for a
constructive input in the comments section. I am sorry to say I was unable to
make this post sound as light and unpretentious as the previous one. This one
deals with harder questions, is a little wordy, and requires at least elementary
knowledge of calculus to be read properly.

In my previous post we discussed the ‘Galilean’ velocity composition used for
introduction or substantiation of relative simultaneity. It is not the only
point where Einstein resorts to sums c + v or c – v: he does that actually to
deduce the Lorentz transforms, notwithstanding the fact that a corollary of the
Lorentz transforms is a different velocity composition which makes the above
sums null and void. It looks like the conclusions of this deduction negate its
premises – but this is not the only strange thing about Einstein’s deduction of
the Lorentz transforms undertaken by him in his famous 1905 article.

In Paragraph 3 of that paper Einstein is considering the linear function τ (the
time of the reference frame in motion) of the four variables x′ = x – vt, y, z,
and t (the three spatial coordinates and time of the frame of reference at rest)
and eventually derives a relation between the coefficients of this linear
function.


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Total votes 3: ↑3 and ↓0 +3
Views 302 Add to bookmarks 2
Comments 0



Schlenz 20 September at 12:27


LET’S DISCUSS RELATIVITY OF SIMULTANEITY

Mathematics *Physics
Sandbox

There is one only too obvious problem with relativity of simultaneity in the way
it is normally introduced, and I have never found an answer to it – what’s more,
I never read or heard anyone formulate it. I will be grateful for an
enlightening discussion.

The framework of the thought experiment introducing relativity of simultaneity
is this. Two rays of light travel in opposite directions and reach their
destination simultaneously in one frame of reference and at different moments in
the other.

For example, in the Wikipedia article on the subject you can read:

‘A flash of light is given off at the center of the traincar just as the two
observers pass each other. For the observer on board the train, the front and
back of the traincar are at fixed distances from the light source and as such,
according to this observer, the light will reach the front and back of the
traincar at the same time.

‘For the observer standing on the platform, on the other hand, the rear of the
traincar is moving (catching up) toward the point at which the flash was given
off, and the front of the traincar is moving away from it. As the speed of light
is finite and the same in all directions for all observers, the light headed for
the back of the train will have less distance to cover than the light headed for
the front. Thus, the flashes of light will strike the ends of the traincar at
different times’.

I am always not a little surprised at the modesty displayed by the authors of
such illustrations. If we grant the statement ‘the light headed for the back of
the train will have less distance to cover than the light headed for the front’
to be true – how then do we evaluate the magnitude of the effect? Or, in other
words, how much longer is one distance in comparison to the other?


Read more
Total votes 3: ↑2 and ↓1 +1
Views 263 Add to bookmarks 1
Comments 0



serenaryder 16 September at 18:38


HOW IN-APP CHATS HELP E-LEARNING PLATFORMS TO BE MORE INTERACTIVE?

Instant Messaging *Development of mobile applications *API *Software Video
conferencing

e-Learning is an extension of/ alternative to a traditional classroom setup.
e-learning, commonly known as ‘online learning’ or ‘virtual learning’ is ideally
a one-way or two-way digital communication established on a device with video
and voice call integration using internet access. The last two years made us
realize how technology can facilitate and improve communication. Digital
technology had its impact in almost every industry including the sensitive
education sector.




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gekh 15 September at 15:31


IT'S ALIVE

IT Standards *IT career Reading room The future is here IT-companies

I wonder why IT developer interviews are so strange most of the time. It feels
as if the people are looking for computer science teachers, not engineers. All
those theoretical questions that have no relation to the working reality. It is
strange to be looking for eloquent teachers, who can perfectly explain any term
or pattern, and then ask them to do the actual work. Maybe it is the imprint
from the years spent in university when the teachers looked like all-knowing
gods and seemed to solve any issue in your life. May be, may not. Anyway, these
teachers stay in unis and don't do the work.

You know, what would be my universal answer to all interview questions? “I have
no idea how and why it works, but I can use it, and I can use it for good”. This
is the reality. Actually, no one knows exactly these hows and whys. What is a
computer? What is electricity? What is an electron? No one knows for sure. But
it works and we use it.

Imagine a famous author, like Stephen King, asked a question about the
difference between deus ex machina and Mary Sue. Would his answer change the
quality of his books? He may or he may not know all those scientific literature
terms, but he can use the language and use it for good.

Every time I turn on my computer it is a wonder. I have no idea what is going
on, but it awakes, it becomes alive, and I can communicate with it in its own
sublime and subtle language.

Have you ever realised that all these electronic devices are monsters,
Frankenstein's monsters? Some pieces of dead matter were put together, and then,
with some electricity involved, it suddenly awoke. “It's alive!”. Had
Frankenstein any idea why it turned alive? Of course not, or why he was so
surprised? Every developer experiences this feeling almost every day. “It's
working!”


Read more
Total votes 7: ↑4 and ↓3 +1
Views 454 Add to bookmarks 0
Comments 0



Park_er 12 August at 08:09


CONCEPTOGRAM AS A METHOD TO CREATE MORE EFFECTIVE TECHNICAL DOCUMENTATION

Иннотех corporate blog Popular science Technical Writing *
Translation

Konstantin Kotelnik, an analyst at Innotech, ponders over making technical
documentation easier to understand for developers and helping the clip-thought
generation work effectively with large quantities of data. Read the article to
find out about the potential emergence of a graphical IT-Esperanto and the
standardisation of technical language.


Read more
Total votes 2: ↑2 and ↓0 +2
Views 561 Add to bookmarks 2
Comments 0

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Labertte 12 August at 06:54


HOW I GAVE MY OLD LAPTOP SECOND LIFE

Configuring Linux *Nginx *Laptops
Sandbox

17-19 min read

Hi y'all, my name is Labertte and I use Arch btw.
Probably like every other Linux user, I'd like to buy a ThinkPad, put some
lightweight distribution like Arch or Gentoo on it, and then go to Starbucks,
get a soy latte and tell everyone that I use "linux". But I decided to go a
little different route and give a chance to my old laptop that I was using about
five or seven years ago.


Read more
Total votes 2: ↑1 and ↓1 0
Views 1.8K Add to bookmarks 1
Comments 4 +4



burzzo 3 August at 00:13


FL_PYTORCH IS PUBLICLY AVAILABLE ON GITHUB

Mathematics *Machine learning *Artificial Intelligence

FL_PyTorch: Optimization Research Simulator for Federated Learning is publicly
available on GitHub.

FL_PyTorch is a suite of open-source software written in python that builds on
top of one of the most popular research Deep Learning (DL) frameworks PyTorch.
We built FL_PyTorch as a research simulator for FL to enable fast development,
prototyping, and experimenting with new and existing FL optimization algorithms.
Our system supports abstractions that provide researchers with sufficient
flexibility to experiment with existing and novel approaches to advance the
state-of-the-art. The work is in proceedings of the 2nd International Workshop
on Distributed Machine Learning DistributedML 2021. The paper, presentation, and
appendix are available in DistributedML’21 Proceedings
(https://dl.acm.org/doi/abs/10.1145/3488659.3493775).

The project is distributed in open source form under Apache License Version 2.0.
Code Repository: https://github.com/burlachenkok/flpytorch.

To become familiar with that tool, I recommend the following sequence of steps:


Read more
Total votes 1: ↑0 and ↓1 -1
Views 668 Add to bookmarks 0
Comments 0



Advertone 31 July at 11:15


HOW ABORTION IN THE AGE OF SURVEILLANCE CAPITALISM TURNS INTERNET INTO A
DYSTOPIA

Information Security *Cryptocurrencies
The reversal of Roe v. Wade, which launched a furious debate about abortion
rights, has a side — and a very itchy side. In June 2022, the Supreme Court
struck down federal protections for abortion rights in the United States,
turning the decision on the legality of abortion over to the state level, many
of whom had long been waiting for it: they had «trigger» laws banning abortion,
and state prosecutors were preparing to prosecute for violating or trying to
circumvent them.

Not even a week later, news emerged that the blow to women's rights might come
from an unexpected (for naive Americans who are not familiar with the «Yarovaya
Package» and other niceties of Russian legislation) side, when the willingness
to «leak» personal data even without a decision was confirmed by the developers
of major applications for women. Thus, suddenly, own gadgets and all the IT
infrastructure that surrounds the modern man for his convenience, suddenly
showed its downside: the possibility of total control over human life and
actions.




Read more →
Total votes 8: ↑8 and ↓0 +8
Views 2.3K Add to bookmarks 4
Comments 0



doroff-goroff 14 July at 11:13


STRESS-TESTING: HOW TESTERS LIVE IN A TURBULENT WORLD OF BUGS

Иннотех corporate blog IT systems testing *Lifehacks for geeks Brain Health
Translation

A tester is one of the most stressful roles in IT. You constantly need to be
concentrated and report bugs to developers in your team. Lidiya Yegorova,
Innotech’s “Scoring conveyor” team QA-Lead shared her practices on how to
minimize the stress while testing.


Read more
Rating 0
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Comments 0



alexandervolchek 12 July at 12:43


METAVERSES: HYPE OR THE FUTURE TO COME?

Decentralized networks *Machine learning *Artificial Intelligence Social
networks and communities AR and VR

Alexander Volchek, IT entrepreneur, CEO educational platform GeekBrains

Pretty much everyone in the IT community is talking metaverses, NFTs, blockchain
and cryptocurrency. This time we will discuss metaverses, and come back to
everything else in the letters to follow. Entrepreneurs and founders of tech
giants are passionate about this idea, and investors are allocating millions of
dollars for projects dealing with metaverses. Let's start with the basics.


Read more
Total votes 2: ↑1 and ↓1 0
Views 754 Add to bookmarks 4
Comments 0



BuddhaSugata 14 June at 19:40


«IF I HAD A HEART...» ARTIFICIAL INTELLIGENCE

Reading room Artificial Intelligence Science fiction

Most people fear of artificial intelligence (AI) for the unpredictability of its
possible actions and impact [1], [2]. In regard to this technology concerns are
voiced also by AI experts themselves - scientists, engineers, among whom are the
foremost faces of their professions [3], [4], [5]. And you possibly share these
concerns because it's like leaving a child alone at home with a loaded gun on
the table - in 2021, AI was first used on the battlefield in completely
autonomous way: with an independent determination of a target and a decision to
defeat it without operator participation [6]. But let’s be honest, since
humanity has taken in the opportunities this new tool could give us, there is
already no way back – this is how the law of gengle works [7].

Imagine the feeling of a caveman observing our modern routine world:
electricity, Internet, smartphones, robots... etc. In the next two hundred years
in large part thankfully to AI humankind will undergo the number of
transformations it has since the moment we have learned to control the fire [8].
The effect of this technology will surpass all our previous changes as a
civilization. And even as a species, because our destiny is not to create AI,
but to literally become it.


... more, give me more, give me more ...
Rating 0
Views 2.7K Add to bookmarks 6
Comments 0



andrey78910 9 June at 09:10


TEXT-BASED CAPTCHA IN 2022

Information Security *Machine learning *Artificial Intelligence
Translation

The first text-based CAPTCHA ( we’ll call it just CAPTCHA for the sake of
brevity ) was used in 1997 by AltaVista search engine. It prevented bots from
adding Uniform Resource Locator (URLs) to their web search engine.

Back then it was a decent defense measure. However the progress can't be
stopped, and this defense was bypassed using OCR available at those times (for
example FineReader).

CAPTCHA became more complex, noise was added to it, along with distortions, so
the popular OCRs couldn’t recognize this text. And then OCRs custom made for
this task appeared. It costed extra money and knowledge for the attacking side.
The CAPTCHA developers were required to understand the challenges the attackers
met, what distortions to add, in order to make the automation of the CAPTCHA
recognition more complex.

The misunderstanding of the principles the OCRs were based on, some CAPTCHAs
were given such distortions, that they were more of a hassle for regular users
than for a machine.

OCRs for different types of CAPTCHAs were made using heuristics, and the most
complicated part of it was the CAPTCHA segmentation for the stand along symbols,
that subsequently could be easily recognized by the CNN (for example LeNet-5),
also SVM showed a good result even on the raw pixels.

In this article I’ll try to grasp the whole history of CAPTCHA recognition, from
heuristics to the contemporary automated recognition systems. We’ll figure out,
if a CAPTCHA is still alive.

I’ll review the yandex.com CAPTCHA. The Russian version of the same CAPTCHA is
more complex.


Read more
Total votes 4: ↑3 and ↓1 +2
Views 1.2K Add to bookmarks 11
Comments 0



ritchie_kyoto 2 June at 08:49


WI-FI AND CWMP (TR-069) / USP (TR-369) PROTOCOLS: FREQUENCY OPTIMIZATION ATTEMPT

Wireless technologies *Popular science

I guess, it's not a big deal to say that Wi-Fi (IEEE 802.11 standards) is the
one of the most popular and most spread communication technology of the current
day. Especially indoors. The growing number of Wi-Fi devices still remains that
leads to the overcrowded spectrums: both 2.4 GHz and 5 GHz.


This fact means increasing of demand for some optimization routines for
utilization of resources. And therefore some RRM (Radio Resource Management)
systems become required.






Read more →
Total votes 1: ↑1 and ↓0 +1
Views 3.8K Add to bookmarks 5
Comments 0



quadcode_team 31 May at 15:31


FINTECH IN PRACTICE: HOW QUADCODE DEVELOPS TECHNOLOGY FOR TRADING AND BANKING

Quadcode corporate blog Finance in IT

Hello, I am Aleksandr Ivanov, CTO at Quadcode. We came to Habr to show the
Fintech “kitchen”; we’ve been at it for 8 years, so we can already share our
experience. In our blog we will talk about architectures, technologies, tools
and life hacks.




Read more
Total votes 2: ↑2 and ↓0 +2
Views 1.8K Add to bookmarks 2
Comments 0



parthiba 30 May at 10:18


A STEP-BY-STEP GUIDE TO INTEGRATE VIDEO CALLING FEATURES WITHIN APPS USING
WEBRTC

API *Video conferencing
Tutorial

WebRTC integrations have emerged as a game-changer in the Video Calling
Technology over the years. The protocol has redefined the way real-time video
communications take Developers can integrate WebRTCs commonly available as
JavaScript APIs to add audio and video solutions to their apps. place.
Developers can integrate WebRTCs commonly available as JavaScript APIs to add
audio and video solutions to their apps. This tutorial will take you through the
steps in developing a two-way video call between two devices. 

WebRTC (Web Real-Time Communication) is a set of rules that can establish
bidirectional and full-duplex communication between our two devices using
JavaScript. It connects your devices and enables transfer of unlimited real-time
audio and video across any operating system. However, the WebRTC agents created
for both devices do not know any information about each other inorder to
establish the media exchange. At this point, a third, mutually agreed-upon
server is introduced. This server which connects the devices to transfer data
with necessary information about the endpoints is known as the Signaling
Server. 

Before we start off with the steps, it is necessary to become familiar with the
basics of the integration process. 


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gmtd 29 May at 17:19


UTILITARIAN BLOCKCHAIN. 1. ASSETS

Decentralized networks *Research and forecasts in IT *Finance in IT
Cryptocurrencies


In the modern world, the term " **blockchain** " is steadily associated with
cryptocurrencies, NFTs, mining, trading and financial pyramids. However, even
among programmers and IT people there is not always a clear understanding of
what it is and what it is for.

This article attempts to look at this still relatively new element of the
information and human space in practical and slightly philosophical aspects.

> **Disclaimer**: The article will use simple language to explain non-trivial
concepts, so non-critical distortion of technical details is possible.

Read more →
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simonzolin 28 April at 05:14


AUDIO API QUICK START GUIDE: PLAYING AND RECORDING SOUND ON LINUX, WINDOWS,
FREEBSD AND MACOS

Programming *C *Development for Linux *Development for Windows *Sound
Tutorial

Hearing is one of the few basic senses that we humans have along with the other
our abilities to see, smell, taste and touch. If we couldn't hear, the world as
we know it would be less interesting and colorful to us. It would be a total
silence - a scary thing, even to imagine. And speaking makes our life so much
fun, because what else can be better than talking to our friends and family?
Also, we're able to listen to our favorite music wherever we are, thanks to
computers and headphones. With the help of tiny microphones integrated into our
phones and laptops we are now able to talk to the people around the world from
any place with an Internet connection. But computer hardware alone isn't enough
- it is computer software that really defines the way how and when the hardware
should operate. Operating Systems provide the means for that to the apps that
want to use computer's audio capabilities. In real use-cases audio data usually
goes the long way from one end to another, being transformed and (un)compressed
on-the-fly, attenuated, filtered, and so on. But in the end it all comes down to
just 2 basic processes: playing the sound or recording it.

Today we're going to discuss how to make use of the API that popular OS provide:
this is an essential knowledge if you want to create an app yourself which works
with audio I/O. But there's just one problem standing on our way: there is no
single API that all OS support. In fact, there are completely different API,
different approaches, slightly different logic. We could just use some library
which solves all those problems for us, but in that case we won't understand
what's really going on under the hood - what's the point? But humans are built
the way that we sometimes want to dig a little bit deeper, to learn a little bit
more than what just lies on the surface. That's why we're going to learn the API
that OS provide by default: ALSA (Linux), PulseAudio (Linux), WASAPI (Windows),
OSS (FreeBSD), CoreAudio (macOS).


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serenaryder 23 April at 19:22


THE SIGNIFICANCE OF IN-APP MESSAGING APPLICATIONS IN YOUR DIGITAL BUSINESS

Instant Messaging *Development of mobile applications *API *Software Video
conferencing

In-app messages are targeted notifications sent to customers/ users while they
are active on the website or mobile application. They are a very effective way
to engage customers as they are already within the application looking for
specific information. In-app chat applications help connect better with the
users and improve user retention as they are timely and targeted. 


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