Physical Definition and 1000 Threads

Question: When thinking of continuums the most notable seems to be space-time but they also mark a simplification to reality like in continuum mechanics, often taught when learning the tensor calculus needed for general relativity. The question is that for general relativity when a geodesic...

How can space expand when space is not a physical thing? I’ve heard some say that is not expanding but rather it is getting less dense, which to me implies the same thing.

Pardon me if this is a very silly question. Although my research involves a lot of probability distributions, I consider myself a fledgling statistician. When people assign a probability distribution to a variable in a physical process, is it inherently assumed that the parameters of this...

What is physical applied mathematics?

Hi! I would like to crowdsource where can I find a large tabulation of physical and chemical data (ie. density, enthalpy and entropy; for both single-phase and saturated phases) for different fluids; preferrably for alcohols and acids. What I'm trying to look for is something similar to...

What type of chemical and physical transformation occurs in the blue sphere silica gel when it is subjected to very high temperatures above the temperature supported by it for several minutes? does it turn into a compound that will absorb and store moisture and water inside and can leak if it...

I keep coming across this descriptor, "two (or three) independent, non-interacting parts," in many books on QM (for example, Penrose's Shadows of the Mind). It is usually followed by a mathematical description (for example, state vector |A>|B>). I can wrap my mind around the quantum paradox of...

Position and momentum are the popular pairs of properties with uncertainty we often hear about, for example that we cannot know with precision where an electron is and its momentum at the same time. What are others? Such as an example of an energy and a time that we cannot know both...

Hi, I'm putting together some resources about theories and would like some help to make sure I don't make a mistake. In particular, I'd like to know if each of the electromagnetic, gravitational, mechanical and entropic processes applies to every physical process. So, for example, due to an...

I am following [this YouTube lecture by Schuller][1] where he finds the appropriate formalism for the quantum mechanics in the physical curved space. Everything makes sense to me but at the very end I see that we find the pull backed connection one-form on the base manifold. He says to the end...

If a balloon and a sweater are rubbed together, high-school science teachers like to say "the electrons transferred to the balloon in the form of static electricity." Then, it is often charming to show that two such balloons repel one another "because they have more electrons." Can we unpack...

Trying to make sense of small and large extra dimension(s) of phyiscal space in a simple intuitive example. Consider a two dimensional manifold like R2 and we are trying to add a small and a large extra dimension. Do we mean by smale extra dimension in this case something like (0,1)×R (the...

So on this page https://www.feynmanlectures.caltech.edu/I_11.html under heading 11-2 Translations first he tries to proof that there is no origin in space. Joe writes newtons laws after measuring quantities from some origin. $$m(d^2x/dt^2)=F_x$$ $$m(d^2y/dt^2)=F_y$$ $$m(d^2z/dt^2)=F_z$$ We need...

i try to understand what physical entity mass or massdensity divided by speedquadrat could be? Any ideas? thanks

I read this tweet (I omit the author for privacy), and my curiosity led me to ask questions:: Any optimization problem is equivalent to a convex (linear) one (but infinite dimensional…). The key do perform global optimization using Lasserre’s relaxation via the problem of moment (aka...

https://www.quantamagazine.org/physics-experiments-spell-doom-for-quantum-collapse-theory-20221020/ Experiments Spell Doom for Decades-Old Explanation of Quantum Weirdness Physical-collapse theories have long offered a natural solution to the central mystery of the quantum world. But a series of...

I've learned that some cosmological observations do not match with theoretical predictions leading to the hypothesis of dark matter or dark energy. Do you know references which discuss if instead the explanation could be that physical constants slowly vary in space? This seems conceptually...

I am on a journey to not just understand how to manipulate physics equations but to understand why they work , and how they describe physical phenomena. I understand how division combines physical quantities. I have this much physical quantity 'per' this much physical quantity. It puts 2...

I am having trouble to find the moment of inertia of the second rod! Is it related to the first rod?? At the beginning I thought It's not! But when took those as constant,the equation had become way much simpler and there is nothing about chaos! My approach is given below

Been a long time I studied physics that had anything to do with mechanics, so I'm now in need of memorizing almost everything. So I am seeking for some guidance here. This is "system simulation/modeling/discrete event system simulation/etc" type of subject. The first thing that I didn't...

Does Laplace's equation hold true for electrostatic potential at the location of a dipole? Or should poisson's equation be used?

Answer: Did I draw them right?

Hello, couple of questions about bubble universes and the physical constants. I understand in an eternal inflation scenario universes bubble off the original during the inflation phase. Firstly, according to this theory, does the new universe creation only happen at an early inflation phase of a...

There is something I don't understand that I want to ask quantum physics experts here: Suppose the happening of event X results logically speaking in the happening of event A. So we could for instance have the following logical implication ##X.happens \rightarrow A.happens##. If this is...

I understand what is the physical meaning of a timelike geodesic, but what is the physical meaning of a spacelike geodesic?

What's meant by 'affine' model in physical sciences? I guess it's related to some ideal or benchmark model?

Is anything in the physical universe unlimited or infinite or does Infinity only exist to make some math work? Is Infinity a real thing outside of math?

hello, i have some diffuculties with this problem, there's the point where the spring is attached to the rod and according to the equation of time period of physical pendulum , h represent the distance from the COM and the pivot point. here the pivot point is at the COM. and i know that it can't...

From my reading of several quantum optics textbooks and spectroscopy texbooks, the emission and absorption spectrum of an atom or molecule are always given in terms of the time-correlation function, for example the emission spectrum of a two level atom is given by: $$...

Hello, I am currently studying about entanglement on spin-1/2 chains and I was able to find some information about the mathematical point of view of concurrence but I can't understand the physical meaning of it . Can somebody help me, please?

Hello guys, I am using the book 'university physics with modern physics by freedman'(just started chapter 6: energy). I was wondering if someone could point out what is needed to be known to continue with electricity. 2nd semester just began and I haven't had previous physics encounters besides...

I am studying Tunable couplers with Programmable Integrated photonics by Jose Capmany. In this textbook, what is the physical meaning of signal s1 and s2? Is it an electric field intensity or the phase of electromagnetic wave? And what is the physical dimension of transduction coefficient here?

I am comic fan There are several fiction character with electricity ability. Like Sasuke and Kakashi from Naruto , and Killua Zoldyck from Hunter X Hunter, they use membrane concept of electricity to cover their bodies, which helps the electric nerve pulses to run at the electrical membrane...

hello, i have a question about the forces that act on a rod at it's pivot point. the rod is free to rotate about the pivot point at the edge and it starts from rest parallel to the ground.the question is : when it reach to angle theta find the a] the angular velocity b] angular acceleration c]...

Is there anything we know of in this physical world that is less than 3 spatial and 1 time dimension? Or is that pretty much everything, no more, no less?

Given the usual raising & lowering operators ##A^{\dagger}## & ##A## for a quantum harmonic oscillator, consider a coherent state ##|\alpha\rangle \equiv e^{\alpha A^{\dagger} - \bar{\alpha} A} |0\rangle##. I first check that ##|\alpha\rangle## is an eigenvector of ##A##. I already proved that...

Standard formula for final velocities ##v_1##, ##v_2## in elastic collision with masses ##m_1##, ##m_2## and initial velocities ##u_1##, ##u_2## is given by $$v_1 = \frac{m_1-m_2}{m_1+m_2}u_1+\frac{2m_2}{m_1+m_2}u_2$$$$v_2 = \frac{2m_1}{m_1+m_2}u_1+\frac{m_2-m_1}{m_1+m_2}u_2$$. By rearranging...

What is the physical explanation behind the pedrail wheel (a.k.a the walking wheel). Someone said it "makes it's own road", but how does it allow a vehicle to climb stairs, navigate rough terrain etc.? I have looked all over the Internet and even visited a university library, but information on...

The above article gives lots of evidence to support the claim we are living in a simulation. I know this is usually considered hypothetical, but in the article they give physical explanations that fit topics discussed in this forum. Please read and give your opinion

I want to code up a (physical) model of an aircraft or car, and I want to create an automated integrated test to check that the code produces reasonable and realistic results. For example, I want to check that the path taken by the aircraft or car is physical and reasonable. However, I don't...

What does Gödel’s theorem say about physical reality? Does Gödel’s theorem imply that no finite mathematical model can capture physical reality? Does the nondeterminism found in quantum and chaos physics - it’s impossible to predict (prove) the future from the present and the laws of physics -...

It appears that many texts on astrophotography and telescopes for amateurs tend to avoid mathematical formulas, as such, they are of little use to do some practical calculations. What I am interested in is: Magnification Image scale Focal length Focal plane and sensor plane! (CCDs!) Focal-ratio...

I think this is Information Theory but I'm not sure what forum that might belong in. (Note: this is a thought experiment not a practical suggestion for copying things.) The other day I was examining a 3D printed widget I designed, and I wondered if I could ever recreate it should I lose the...

This is the picture of the problem. My solution is: I'm not sure if the limit is 0 to 2 or 0 to 4...

Hello all, So I've been working through the solutions to some simple introductory problems for the Schrodinger Equation like the infinite square well, and I'm trying to make sense of how to think about the phase component. For simplicity's sake, let's start off by assuming we've measured an...

I tried to solve it and I got the following is it correct? and 2 My solution... is a negative distance?

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This is the image of the problem: I tried to solve it and I got the following is it correct? derive and equal to 0 because it is between an angle of 0 and 180° is this statement correct?

This is the image of the problem I tried to solve it and I got the following is it correct?

I have read some documents on the subject, but until now, unfortunately, I still do not have a good understanding of them, most likely due to personal shortcomings that start from physics. In this regard, I would like to try here to expose some doubts that will almost certainly appear very...