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Physics

A science about the world around us

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What is to see under the Black Sun of Giedi Prime?

Level of difficultyEasy
Reading time6 min
Views667

The director Denis Villeneuve and cinematographer Greig Fraser in their Dune: Part Two movie made a curious decision to film the scenes on the surface of the Giedi Prime planet in the infrared spectrum. It turned out to have interesting aesthetics and there are some interesting related physics to discuss and speculate about how realistic the look of it is.

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Total votes 5: ↑5 and ↓0+7
Comments0

Uniform gravity, can it exist?

Level of difficultyMedium
Reading time3 min
Views1K

3.What's an ugly smiling face?

It's the cat from curved space.

V. Komen, I. Tikhonenkov

Here we are discussing in general the majority of metrics for a stationary gravitation fields in one dimension. The only accepted approach so far to apply the equations of field (A. Einstein):

10
Total votes 3: ↑2 and ↓1+2
Comments0

Uniform gravity, can it exist?

Level of difficultyMedium
Reading time3 min
Views960

Uniform gravity, can it exist?

1. The motion of a free particle-like cat

V. Komen, I. Tikhonenkov

Good morning! You've woke up. Having prepared coffee and toasts of bread you are drifting from a kitchen to a table before a large wall TV. The left hand keeps a small plate with toasts and the right one controls coffee level within your beloved mug. The life is plotted out for ten seconds to come. But Ervin is already worried that you, as usual, made conspiracy and decided not to share your breakfast with him. So the damned cat thrusts himself across you pass, hits your legs. By the next moment the plate, toasts and the mug are falling. And – yes! All those precious things reached a floor level by the same time. Physics...It's how it shows up, unexpected. And we used to identify ourselves as physicists. The unexpected thing is that we still do. It's whence our motivation originates. We cannot pass by any falling objects quietly.

15
Total votes 2: ↑2 and ↓0+2
Comments0

Let’s Discuss the Lorentz Transforms – Part the Last: The Real Derivation, or The Nail in the Casket

Reading time9 min
Views946

In this post there are a lot of references to the previous one – it is essential that you read it before getting down to this.

In my previous posts (see the list below below) I tried to express my doubts whether there is a real physical substrate to the Lorentz transforms. The assumptions about the constancy of the speed of light, the homogeneity of space-time, and the principle of relativity do not and cannot lead to the deduction of the Lorentz transforms – Einstein himself, for one, gets quite different transforms, and from those he goes over directly to the Lorentz transforms obviously missing a logical link (see Einstein p. 7, and also Part 1 of this discussion). As for the light-like interval being equal to zero, we saw that it can be attached to such assumptions only in error and cannot in itself be a foundation of a theory. I have to conclude that all that fine, intricately latticed construction of scientifictitious, physics-like arguments with the air of being profound is nothing but a smokescreen creating the appearance of a physical foundation while there is none.

What is then the real foundation of the Lorentz transforms? Let’s start from the rear end, the Minkowski mathematics. Historically, this appeared later than special relativity as a non-contradictory model of the Lorentz mathematical world; previously mentioned Varićak was among those who took part in its creation. Notwithstanding its coming later in history, it can be used as the starting point for derivation of the Lorentz transforms.

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Total votes 3: ↑3 and ↓0+3
Comments0

Let’s Discuss the Lorentz Transforms – Intermission: Rapidity, and What it Means

Reading time4 min
Views881

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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Total votes 3: ↑3 and ↓0+3
Comments2

Let’s Discuss the Lorentz Transforms – Part 1: Einstein’s 1905 Derivation

Reading time6 min
Views1.1K

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
Comments0

Let’s Discuss Relativity of Simultaneity

Reading time4 min
Views938

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 2: ↑1 and ↓1+1
Comments0

Weekend picks: A closer look at ITMO University

Reading time4 min
Views1.4K
ITMO University occupies several prominent buildings in the centre of St. Petersburg. But residents and guests alike rarely get a chance to take a look at what’s happening inside them. Articles featured in this digest will take you on a virtual tour of our labs, as well as shed some light on the work underway within our walls.

Total votes 4: ↑4 and ↓0+4
Comments0

Laser telemetry for vision correction: a complete operation with comments (not for the faint of heart)

Reading time5 min
Views986
Now I will show what doctors usually never show to patients. More precisely, it shows everything in the form of a beautiful render, from which it does not follow at all that a piece of metal will stick up in your cornea for a couple of minutes. Fortunately, you will not feel this because of the anesthetic premedication, you will not know and do not remember, because the piece of iron will be out of focus.



So, watch the video, and I will show the frames with comments. This is a real operation on a patient in a German clinic, the recording was made on a device like the “black box” of the VisuMAX device. In this case, the patient has agreed to use the recording for training purposes, usually access to such records is strictly limited.
Total votes 4: ↑1 and ↓30
Comments2

Laser that cuts inside the cornea: ReLEx procedure at the physical level

Reading time6 min
Views1.8K
The idea — to take and cut a lens in a transparent cornea — is not new. At first it was done manually, with a scalpel directly on the surface (difficult and very rough, with a sea of side effects). The first laser was used in 1979, then it was a pulsed infrared emitter with an effective pulse length of 4 nanoseconds.


Step 1: creating a plasma bubble, in fact — a microburst. Step 2: expansion of the shock and heat waves. Step 3: cavitation bubble (plasma expansion). Step 4: the formation of a parallel slice at the expense of several adjacent laser focus points.

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Total votes 7: ↑4 and ↓3+8
Comments8

Working with light: Starting your career at ITMO University

Reading time4 min
Views1.5K
One of our previous articles featured an overview of our photonics department students’ work lives. Today we’re going to expand on this topic by looking at four related MA programs: “Light Guide Photonics and Programmable Electronics”, “LED technologies and optoelectronics”, “Photonic materials” and “Laser technologies”. We sat down with some of the folks currently enrolled in these programs, as well as recent graduates, to talk about the role ITMO University played in kickstarting their careers.

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Total votes 5: ↑5 and ↓0+5
Comments0

The wave method of building color scheme

Reading time7 min
Views2.1K
image

In life we often face the challenge of choosing the right colors. This happens when we need to choose clothes suitable for each other, shoes suitable for clothes, choose different wallpapers for the children's room, makeup, choose colors for our site and much more. The process of selecting several colors that combine with each other is called the construction of a color palette (gamut).

In colouristics there are several methods for constructing a color palette (color gamma) based on the arrangement of colors relative to each other in the color circle and, usually, having the same brightness. Harmonious perception of which is not sufficiently substantiated from the physical point of view.

The wave method of building color palette based on the relationship of color and acoustic waves, and also the concept of consonance (harmony) in music theory. Below is a more detailed description of the method.

This site allows you to choose the most harmonious combination of colors for your site, clothing, interior, etc.

The corresponding article was published on the site arxiv.orghttps://arxiv.org/abs/1709.04752. Results are available on our sitewavepalette.com.
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Total votes 2: ↑1 and ↓1+2
Comments2

Lab tour: Functional Materials and Devices of Optoelectronics at ITMO University

Reading time3 min
Views1.3K
Today we’re taking a look at the Functional Materials and Devices of Optoelectronics Lab at ITMO University, the equipment it houses, and the projects underway at the facility. It is an international research facility located in the center of St. Petersburg. The staff is primarily occupied with the search for innovative materials (semiconductors, metals, and nanostructured oxides), and the manufacturing of next-gen micro- and optoelectronic gadgets. Here we take a look at the high-tech equipment it utilizes.

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Total votes 6: ↑5 and ↓1+8
Comments0

Putting theory to practice: juggling work and study at the Department of Photonics and Optical Information Technology

Reading time4 min
Views1.4K
Master’s degrees are really useful. Postgrad education allows BA holders to put their new-found skills into practice, and secure great jobs further down the road. But students often need help assessing this choice, particularly if they majored in uncommon subjects — like photonics.

To set the record straight, we talked to the people behind, and the graduates of our MA programs in photonics and optical computing. In this article you’ll learn about part-time work available for photonics students, graduates’ job-hunting prospects, and the academic career options that open up.

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Total votes 9: ↑9 and ↓0+9
Comments0

Future economics for physicists

Reading time7 min
Views1.7K

Annotation. This article gives an analogy between the forces of nature and various types of money. A justification for the "money conservation laws" is made. Explanation of the IT-money phenomenon by analogy to physics laws is given, as well as gold and currency money. The transition from the gold and currency to the gold-currency-computing economy is considered. A reasonable assumption is made that the fourth type of money after gold, securities and IT money will be so-called "citation indices" or "ratings", which are similar in their properties to stock indices.


What is money?


This article is an attempt to understand what money is from the physics and econophysics points of view. Econophysics (economics and physics) is an interdisciplinary research field, applying theories and methods originally developed by physicists to solve problems in economics, usually those including uncertainty or stochastic processes, nonlinear dynamics and evolutionary games.

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Total votes 1: ↑0 and ↓1-1
Comments0

Holographic Principle, new type gyroscope, information without light speed limit, teleportation of physical objects…

Reading time57 min
Views12K
Warning

First, all the objects and theories described in this article have the status of hypothetical at the moment. That is, the holographic hypothesis and string theories have not been experimentally confirmed many.

Second, a fundamentally new type of mechanical gyroscope with six degrees of freedom is proposed for experimental verification (base) of hypotheses. Of the two and three degrees of freedom mechanical gyroscopes known to science, this is the last of the possible types with the maximum number of degrees of freedom in the holonomic system (GYRO_6DoF).

Third, with the advent of the experimental base — the tops of the physical pyramid, string theories, and the holographic hypothesis, which is actually the foundation of the future Theory of Everything, are temporarily removed from criticism until the moment of practical implementation of the experiment and measurements.


Abstract

Even people far from physics know that the maximum possible data transmission rate of any signal is equal to the speed of light in a vacuum. It is denoted by the letter «c», and this is about 300 thousand kilometers per second. The speed of light in a vacuum is one of the fundamental physical constants. The impossibility of achieving speeds exceeding the speed of light in three-dimensional space is a deduction from Einstein's Special Theory of Relativity (SRT). Usually, when it is argued that SRT prohibits the transmission of the information above the speed of light, an implicit assumption is made that there is no other way other than to «bind information» to a photon and transmit it. However, there is another way. The well-known physical hypothesis — the Holographic Principle (a modern and widely used tool in theoretical physics) points to an interesting phenomenon: “Phenomena taking place in three-dimensional space can be projected onto a remote screen without losing information” — Leonard Susskind “The World as a Hologram ”[p. 3].

image

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Total votes 32: ↑2 and ↓30-26
Comments127
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