I was recently pointed to this thought experiment, claiming an apparent 'contradiction' involving the various predictions of the observers.

Now, this has been discussed on PF quite recently, but I found the discussion...

Frauchiger & Renner: There's a Mistake, Right?]]>

My wife just drew this

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Construct the four lowest-energy configurations for particles of spin-##\frac{1}{2}## in the infinite square well, and specify their energies and their degeneracies. Suggestion: use the notation ##\psi_{n_1,n_2}(x_1, x_2)...

Spin-##\frac{1}{2}## particles in infinite square well]]>

Karen Uhlenbeck wins Abel Prize]]>

I learned that all or at least majority DC voltage regulators such as step down module work by interrupting DC at some intervals. However, if I am interested in continuous DC, is it possible to make such voltage regulator that doesn't interrupt voltage at given intervals? Or what would...

How to regulate a DC voltage without interruptions?]]>

What is the reason we can only measure energy "changes" and not the actual energy value associated with a system? Absolute energies and enthalpy cannot be determined but I am not...

Why can we only measure energy (enthalpy) change?]]>

I'd just like to check a some points concerning the two kinds of singularities that Penrose and Hawking describe in this paper. https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.1970.0021 The Singularities of Gravitational Collapse and Cosmology.

1.

According to the...

The singularities of gravitational collapse and cosmology]]>

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And I understand this:

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And I understand this:

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But I need to...

Maxwell's calculations on electromagnetism's speed = light speed]]>

Intro to my interests]]>

But they have me a little confused with regard to the origins of magnetic fields generated by an electric current...

Origins of magnetic fields from permanent static magnets versus current]]>

I have a question regarding the tragic crash of the latest 737 Max.

Is it not a huge error in the flight laws and the MCAS software to execute a nose down maneuver at any altitude? Should the system not have a rule to prohibit such a maneuver below a minimum altitude threshold?

I'm also...

Boeing 737 Max MCAS System]]>

Space-time curvature and the fabric of space]]>

Fluid Mechanics, Particle size, Bouyouncy Force]]>

I have no ability to perform anything more than addition, subtraction, multiplication or division. Yet, since my teenage years I have been fascinated, enthralled and intrigued by the skies. Astronomy and cosmology have been a decades-long interests of mine. I've read Hawking's 'A...

Is there any way forward for me?]]>

Relation between spectral radiance and density of cavity]]>

The charge of uniform density 50 nC/m3 is distributed throughout the inside of a long nonconducting

cylindrical rod (radius = 5.0 cm). Determine the magnitude of the potential difference of point A (2.0 cm from the axis of the...

Volume charge density and potential difference in sphere]]>

Aside from salt what other solutes would cause this to happen? Would a solute have to have very polar...

Reduction in gas concentration of water with solutes]]>

The scenario I'm considering is a solid sphere (of uniform density) rotating with constant angular velocity when it abruptly splits into two hemispheres along a cut which contains the rotation axis. The hemispheres will begin to separate; if, for example, we consider the rotation to be...

Rotating sphere which separates into hemispheres]]>

it may look like a homework but believe me that it's not. Castigliano's method was omitted when I was attending mechanics of materials course at my university and now I'm catching up. Another reason why I want to solve this is that I'm just curious what's the formula for the deflection of...

Castigliano's method for the deflection of cantilever]]>

I mean, it does make sense, if I plot f(x)= x^2 and f(x-1) = (x-1)^2 and find where they intersect the x/y axis, it does make sense. But the book I'm reading (Stewarts) confuses me with the following:

"Likewise, if g(x) =...

Am I understanding horizontal shift properly?]]>

Suppose the iterative root of ##2^x## :

##\phi(\phi(x))=2^x## (I suppose the Kneser calculation should work, it affirms that there is a real analytic solution)

Then how to compute ##\phi(\aleph_0)## ? (We know that ##2^{\aleph_0}=\aleph_1##).

Could this be...

Question about CH (continuum hypothesis)]]>

Maybe we are setting standards far too low for students even under (US) high school age?

I know there are programs in the US where you can...

University Subjects At Middle School]]>

How about plasma?]]>

I'm accepted as a PhD student. Interview for funding/RA -- Any Advice?]]>

Two particles of identical mass m interact with each other via central potential energy

Vcentral(r) = -V0(1-|r|/a), if 0 <= |r| <= a

0, if a...

Expression for effective potential energy]]>

Hi,

I am looking for an example to solve a larger Matrix by dividing into Quadrant. Is it possible for Gauss Elimination or Matrix Multiplication.

No equation possible

Example Required: Matrix Solution By Dividing into Quadrants]]>

The problem is in the image attached below

View attachment 240537

2. Relevant equations

In the working below (although I think I have misunderstood a concept)

My attempt is in...

Dynamics: Relative Acceleration]]>

Interviewing for a job with a PhD]]>

The thermal interpretation of quantum physics]]>

The following may appear to be a rather strange question but I have no access to a lab to conduct experiments so I have to rely on my imagination, and questions from textbooks, to contrive questions that will hopefully improve...

Error analysis: propagation of error]]>

Can someone help me understand the notation here (I've looked everywhere but can't find it): given a function ##f:G\to \mathbb R## I'd like to know what ##C(G),C(\bar G),L_2(G),W_2^1(G),\dot W_1^2(G)##. I think ##C(G)## implies ##f## is continuous on ##G## and that ##C(\bar G)## implies...

Functional Analysis Notation]]>

We've had many threads about Air Con and Air Coolers but these things are not widely used in the UK and it's too late to contemplate AC because they've all been sold!! There are other ways,...

Tips to keep your house cool in summer]]>

integrate:

##-v(du/dy) = κ(d^2(u)/dy^2) ##

to obtain:

## (-v/κ)y = ln(du/dy) + c##

and finally:

##u = d + w*e^(-vy/κ)##

##-v(du/dy) = κ(d^2(u)/dy^2) ##

## (-v/κ)y = ln(du/dy) + c##

How do I solve this differential eqn?]]>

t= Bx

x=...

Lorentz Transformations]]>

This is what I know: a confidence interval is a a continuous interval of values with a lower bound and an upper bound centered around a sample mean.For example given a certain population, we are interested in the...

Correct understanding of confidence intervals...]]>

Vertical line debunking]]>

Going back to school at age 40 to study engineering]]>

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I understand how the integral is solved using cartesian...

Trying to find an alternative for solving an integral]]>

Given a Hilbert space $$V = \left\{ f\in L_2[0,1] | \int_0^1 f(x)\, dx = 0\right\},B(f,g) = \langle f,g\rangle,l(f) = \int_0^1 x f(x) \, dx$$ find the minimum of $$B(u,u)+2l(u)$$.

In my text I found...

Minimization Operator Problem]]>

Given the ODE system ##x'(t) = A(t) x(t)## where ##x## is a vector and ##A## a square matrix periodic, so that ##A(t) = A(T+t)##, would the following be a good way to solve the system's stability: fix ##t^*##. Then

$$

\int \frac{1}{x} \, dx = \int A(t^*) \, dt \implies\\

x(t) =...

ODE System solution technique]]>

Consider a polymer formed by connecting N disc-shaped molecules into a onedimensional chain. Each molecule can align either its long axis (of length ##l_1## and energy ##E_1##) or short axis (of length ##l_2## and energy...

One-dimensional polymer (Statistical Physics)]]>

Love eggs? Maybe you should consider this]]>

A couple of questions about planets around Red Dwarf Stars:

I'm imagining a planet around a Red Dwarf Star...think Trappist-1...and want to know how I can prevent tidal locking for an Earth-sized terrestrial planet in such a star's habitable zone....say, 1/50th to 1/20th of an AU from the...

Question about Preventing Tidal Locking around Red Dwarf Stars]]>

Is addiction really genetic?]]>

I am carrying out a regression for diameter of a part

Diameter = -0.0531052 + 0.0443237 * exp (-0.0103633 * 'Time elapsed')

if diameter is -0.052

then can some one please calculate the value for...

Regression for a first order system]]>

But first i just want to understand the movement of fluid in a vertical pipe without worrying about viscosity or...

Understanding the movement of a fluid in a vertical pipe]]>

Wealthy parents, actresses, coaches, among those charged in massive...

US university admissions scandal]]>

What minor compliments a physics major?]]>

How much does your PhD constrain your research opportunities]]>

Convection in stars]]>

My basic understanding:

when astronauts go to the International Space Station, due to the speed at which it is travelling, time passes ever-so-slightly slower for them. This...

Effect of time dilation on a satellite]]>

The goal of the project is to improve the human-machine interface as it is a very old machine, it is a JJ LOYD T20K, my problem is that the machine no longer works(it...

Repair of an old JJ LlOYD T20K tensile machine]]>

Imagine an infinite straight wire pointing at you (thus, the magnetic field curls counterclockwise from your perspective). Such a magnetic field equals to:

$$B = \frac{\mu I}{2 \pi s} \hat{\phi}$$

I want to calculate the line...

Why the magnetic field doesn't have to describe a circle?]]>

My question is, it is the same treatment in degenerated Fermi Gas?]]>

Squaring light]]>

An experiment demonstrating the curious results is shown in the video below:

This has made me curious about the linear version of the Faraday paradox.

A conductor placed atop a...

Request about experiments on the linear-motion Faraday paradox]]>

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The solution to this problem is known. I want to use this exercise as a model to understand how to...

Understanding why we compute surface area as we do]]>

https://www.schaeffler.com/remoteme...effler_2/symposia_1/downloads_11/4_DMFW_1.pdf

http://www.partinfo.co.uk/docs/140

My primary interest was to understand why and how...

Dual mass flywheel clutch - How does it make a difference?]]>

For substances that are liquid at room temperature there is a freezing point (point that it becomes a solid) lower than the average temperature of a room. For the...

Question about the term "frozen"]]>

I'm a computer scientist (not a physicist), so I will ask a computer scientist's question.

In all the descriptions I found of Grover's algorithm, there is an element that is puzzling the computer scientist in me: it seems that you need to tell the Oracle about the position of the...

"Basic" question about Grover's Quantum Computing algorithm]]>

I need to solve a system of two equations for T and θ algebraic and with all the other parameters known.

φ is equal to: View attachment 240235

The relevant equations are the two equations left...

Solving a system of two simultaneous trigonometric equations]]>

I'm currently self-educating in maths and physics and was hoping, from time to time, to ask questions on topics or concepts that I'm struggling with. I am not studying towards any specific qualification; I just have a...

Hello Everyone]]>

Couldn't fit the entire phrase for this week's theme in the title, but there it is. Let's see what you can come up with with a theme like that!

1. Any digital photo or digitally-scanned...

PF Photo Contest - On A Clear Day... (3/16-3/22)]]>

No-Nonsense Quantum Mechanics: The Ultimate No Holds Barred Guide To The Quantum World]]>

A charge Q is uniformly distributed along the x axis from x = a to x = b. If Q = 45 nC,

a = –3.0 m, and b = 2.0 m, what is the electric potential (relative to zero at infinity) at the point, x = 8.0 m, on the x axis?

a . 71 V...

Uniform charge density and electric potential]]>

Where ##p(r)## is the probability that a neutron is absorbed in the interval ##dr## near ##r##. And what...

Neutron's crow flight distance & 2° moment of a distribution]]>

Neutron vs electron degeneracy pressure]]>

The ball has X and Y momentum. On the collision, the cushion absorbs and then return all the -X momentum to...

Mechanics of a car turning left]]>

I also have Port Redirection set up in the DrayTek 2926AC.

When I disable the primary WAN, the failover WAN activates and the internet is...

Draytek 2926AC Port Redirection lost when Failover activates]]>

so I get...

Tractor power transmission]]>

i just joined this forum because i am feeling difficulty in solving Fluid Mechanics Problem And i am hoping i will get help from experts and seniors in solving that]]>

I'm a writer who is currently working on a Sci-fi novel that deals heavily with military combat. During one scene in this novel there's squad leader who sustains a sever chest injury which causes several parts of her rib cage to break. Now, this squad leader insists on...

How would Physical Exertion Affect a Flail Chest?]]>

I'm trying to find all the valid surfaces that go through a vector field so that the normal of the surface at any point is equal with the vector from the vector field at the same point.

The vector field is defined by the function:

$$ \hat N(p) = \hat L(p) \cos \theta + \hat R(p)...

Finding all valid surfaces that go through a vector field]]>

How to Create a Universe - Instructions for an Apprentice God

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...

How to Create a Universe - Instructions for an Apprentice God - Comments]]>

Doubling I, what happens to v_d and n?]]>

- a = b = L/2
- Ay = R1
- By =...

Deflection of Prismatic Beam With Fixed Ends and Single Load]]>

Confusion about index notation and operations of GR]]>

A charge q is kept at distance d from center of grounded conducting sphere of radius R. Find V everywhere outside.

V = k*q/r

Cosine Law.

View attachment 240483 ...

Sphere image charge problem]]>

I need to find the time it takes a load to reach the end of a distance. Velocity and acceleration are also given.

I was thinking of using t=vf-vi/(a) but this does not incorporate distance which I...

How do you solve for time if a, v, and s are given]]>

A charge of +3.0 μC is distributed uniformly along the circumference of a circle with a

radius of 20 cm. How much external energy is required to bring a charge of 25μC from infinity to the centre of the circle?

a . 5.4 J

b....

Uniform distribution of charge and work needed]]>

Will quantum computation lower energy requirements?]]>

I'm a bit confused on when a force creates a moment about a point, and when it does not. In particular, in the attached diagram, would F be able to produce a moment about point A? I initially thought that wouldn't be possible...

Moment of a Force About a Point]]>

How do new technologies get developed and brought to market?]]>

the original device was flat topped, with the incoming primary water...

I am having a problem with vortices]]>