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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 175 Add to bookmarks 2
Comments 0



fiter1 26 September at 00:54


HOW TO BE AN EFFECTIVE ENGINEER?

Programming *Product Management *

This question comes up for a lot of us as we trying to advance our career and
reach new heights. At the moment when I was challenged by it, I came across a
wonderful book by Edmond Lau "Effective Engineer".

As always going through the book, I write new thoughts down. And today I want to
share the compilation of things that I have found useful from the book. This is
by no means an ad for the book, but I think it has some really interesting
approaches for us to explore together.


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Total votes 3: ↑3 and ↓0 +3
Views 476 Add to bookmarks 0
Comments 3 +3



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 300 Add to bookmarks 2
Comments 0



Quality_department 22 September at 12:35


WHAT CAUSES TESTERS AND DEVELOPERS TO FEUD AND HOW TO AVOID IT

Иннотех corporate blog Personnel Management *IT career Reading room IT-companies
Translation

Testers and developers are the driving force of any IT enterprise. Their work
directly influences the quality of the final product. Pavel Petrov, our Lead
tester-engineer of the risk detection monitoring service for corporate clients,
shares his insights on building a productive relationship between two different
IT camps.


Read more
Total votes 3: ↑3 and ↓0 +3
Views 211 Add to bookmarks 0
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?


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Total votes 3: ↑2 and ↓1 +1
Views 262 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!”


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



ptsecurity 15 September at 08:16


PAYMENT VILLAGE AT PHDAYS 11: ATM HACKING

Positive Technologies corporate blog Information Security *IT systems testing
*Payment systems *Entertaining tasks

The Positive Hack Days 11 forum, which took place May 18–19, 2022, was truly
epic. The bitterly fought ATM hacking contest featured no fewer than 49
participants. How cool is that? The winner of this year's prize fund of 50,000
rubles, with the handle Igor, was the first to hack the virtual machines. And he
wasn't even at the event! :)

Besides Igor, eight other participants picked up prizes this year for their
VM-hacking skills. They
were: drd0c, vient, vrazov, durcm, zxcvcxzas7, asg_krd, hundred303,
and drink_more_water_dude. A big thank-you to everyone who took part, and for
those who weren't at PHDays, here are the links to the virtual machines.




Read more
Total votes 5: ↑3 and ↓2 +1
Views 277 Add to bookmarks 1
Comments 0



fiter1 11 September at 19:22


RECIPE FOR INCREASING YOUR PRODUCTIVITY

Programming *
Sandbox

Recipe for improving your productivity


Read more
Total votes 3: ↑3 and ↓0 +3
Views 1.3K Add to bookmarks 2
Comments 0



Cyber_L0rd 9 September at 14:31


MODERN MICRO-SERVICE ARCHITECTURE: KEY CHALLENGES FOR SYSTEM ANALYSTS

Иннотех corporate blog System administration *Server Administration
*Microservices *
Translation

We're continuing to explore micro service architecture. In today's blog
Alexander Solyar, Lead system architect at Innotech, describes the main
challenges analysts are facing while working with micro services. He also shares
a number of effective solutions and recommendations.


Read more
Total votes 3: ↑3 and ↓0 +3
Views 583 Add to bookmarks 0
Comments 0



Shapelez 8 September at 13:29


THE 2022 NATIONAL INTERNET SEGMENT RELIABILITY RESEARCH

Qrator Labs corporate blog Decentralized networks *Information Security *

The National Internet Segment Reliability Research explains how the outage of a
single Autonomous System might affect the connectivity of the impacted region
with the rest of the world. Generally, the most critical AS in the region is the
dominant ISP on the market, but not always.

As the number of alternate routes between ASes increases (the "Internet" stands
for "interconnected networks" - and each network is an AS), so does the
fault-tolerance and stability of the Internet across the globe. Although some
paths are more important than others from the beginning, establishing as many
alternate routes as possible is the only viable way to ensure an adequately
robust network.

The global connectivity of any given AS, whether an international giant or a
regional player, depends on the quantity and quality of its path to Tier-1 ISPs.

Usually, Tier-1 implies an international company offering global IP transit
service over connections with other Tier-1 providers. Nevertheless, there is no
guarantee that such connectivity will always be maintained. For many ISPs at all
"tiers", losing connection to even one Tier-1 peer would likely render them
unreachable from some parts of the world.


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Total votes 9: ↑9 and ↓0 +9
Views 278 Add to bookmarks 1
Comments 0



AlexMorOR 8 September at 10:32


UNITY: WHAT IS A COROUTINE AND WHY IS THERE AN IENUMERATOR

.NET *Game development *C# *Unity3D *
Translation

The title of the article is a question I was asked in an interview for a Middle
position. In this article, we will look at Unity coroutines, what they are, and
at the same time we will capture the topic of Enumerator \ Enumerable in C # and
a little secret of foreach. The article should be very useful for beginners.


Read more
Total votes 1: ↑1 and ↓0 +1
Views 459 Add to bookmarks 1
Comments 0



juliafjol 29 August at 12:16


GROW AS A UX DESIGNER BY LEARNING COPYWRITING BASICS

Web design *Interfaces *Internet marketing *Design
Tutorial

Getting a task from a client, UX designers tend to pay attention to the design
goals, not the contents of the website/app itself. There’s something completely
wrong with it because the visual part might be superb, but when it frames a
vague or wordy message, the client's goals won’t be reached.

To avoid this, a UX designer should dive deeper into the content, analyze it,
and restructure it in an interface-friendly way. It doesn’t mean doing the
copywriter’s job, it means collaborating. The reality is that sometimes the
writing team is used to praising the product (because clients like that), or
there is no copywriter involved in the project at all.

Provide proof instead of opinion

An impression is more powerful when the customer can conclude the product’s
benefits on their own. Instead of a colorful line of adjectives like “ultimate”
or “leading” you should aim at what exactly makes the product that cool. The
trick is to be precise, preferably with an example.


Get More Tips
Total votes 5: ↑4 and ↓1 +3
Views 672 Add to bookmarks 6
Comments 6 +6



AlexMorOR 27 August at 07:27


UNITY: SELECTING AND UPLOADING FILES BY USER ON WEBGL ASSEMBLY

Website development *Game development *Unity3D *WebGL *
Translation
Tutorial

In this article, we will look at a way to give the user the ability to upload
any files, such as textures. And let's touch on the topic of launching JS
functions from C# within Unity. As a result, we will get a script that, by
calling just one function, will open a window for selecting files.




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Rating 0
Views 684 Add to bookmarks 2
Comments 2 +2



Cyber_L0rd 27 August at 06:15


MODERN MICROSERVICE ARCHITECTURE: DESIGN PRINCIPLES

Иннотех corporate blog System administration *Server Administration
*Microservices *
Translation

First mentions of micro service architecture application go back to the previous
decade. Today this approach became the industry standard. Alexander Solyar, Lead
software architect at Innotech, dives into details, shares professional insights
and practical rules for working with micro services .


Read more
Total votes 3: ↑3 and ↓0 +3
Views 1.6K Add to bookmarks 5
Comments 1 +1



juliafjol 24 August at 09:38


DESIGNING CONVERTING LANDING PAGES

Web design *Design
Tutorial

It feels like everything about LPs has already been said, however, I still keep
seeing the same mistakes being made over and over again both by start-ups and
established companies. Here are some tips, backed up by my 10-year experience as
a UX/UI Director in agencies and product-led companies. These alone will give a
nice increase in your conversion rate, I guarantee. 

Use a descriptive, not a salesy hero header 

Answer the questions “What?” and “For whom?” as early on the page as possible. A
very common pattern is the largest copy being an inspirational abstract slogan
and below it in smaller font the actual statement about what the product is and
what it does. 


Get More Tips
Total votes 6: ↑6 and ↓0 +6
Views 2.5K Add to bookmarks 7
Comments 11 +11



Vitaly_net 23 August at 15:40


COLOR IMAGE CAPTURING DEVICE WITH PSEUDORANDOM PATTERNS SETS

Image processing *Machine learning *Matlab *
Sandbox

The present invention relates to an analog signal capturing devices generally
and monochrome or color image capture sensors, such as a scanner or a
Charge-Coupled-Device (“CCD”) for video and photo camera in particular, which
are almost free from moiré and aliasing. The present invention relates to
methods for enhancing the resolution of an image capture device and device for
digital color/grey image displaying also.


Read more
Total votes 1: ↑1 and ↓0 +1
Views 296 Add to bookmarks 2
Comments 1 +1



kaimi_ru 23 August at 06:24


20 YEARS OF PAYMENT PROCESSING PROBLEMS

Information Security *
Translation

Thanks to yarbabin for the logo

Electronic payment systems have existed on the Internet for a long time, and
some bugs in them are twenty years old. We've found critical vulnerabilities
allowing us to steal money and drive up the balance. Today we will analyze
typical implementations of payment processing and related security issues.



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



parthiba 22 August at 09:40


10 EASY STEPS TO BUILD AN ANDROID CHAT APP USING KOTLIN IN 2022

Instant Messaging *Development of mobile applications *Development for Android
*API *Kotlin *
Tutorial

This tutorial will guide you step by step in building an Android chat app in
Kotlin with the help of third-party messaging SDKs. The reason I chose Kotlin
for this tutorial is that - it is a lightweight programming language suggested
by Google for building apps that work on Android devices. 

In the steps ahead, I’ll show you how to develop an app in Android Studio, with
messaging features that can integrate using SDKs. I use MirrorFly’s chat SDKs
throughout this tutorial.


Read more
Total votes 4: ↑3 and ↓1 +2
Views 839 Add to bookmarks 4
Comments 2 +2


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