I appreciate Sabine Hossenfelder's latest video, and thought I would assemble some references. There's a mix of particle physics and cosmology topics. In general, the coincidences mentioned are ...
I am trying to understand the proof given in Ethan Bloch's book "The real numbers and real analysis". I am posting snapshot of the proof in the book. I am also posting theorem 1.2.9 given in t...
https://www.physicsforums.com/threads/proving-well-ordering-principle-from-peano-axioms.1061662/
Lamest joke you know ... :zzz:
https://www.physicsforums.com/threads/collection-of-lame-jokes.25301/
Hey! 40 years on PCs and now I'm a Mac guy, YAY! I'm onboarding at my new job, and there's a lot of content to cover on my own recognizance. I can't be asking my boss or coworker every time I n...
https://www.physicsforums.com/threads/help-old-pc-dog-has-to-learn-new-mac-tricks.1062351/
I came across a youtube video that discusses some aspects of depth of field in photography/videography. Some things that have been said collided with my understanding of DOF. I then had a long di...
https://www.physicsforums.com/threads/factors-that-influence-depth-of-field.1061650/
The tallest building in the world is Burj Khalifa in Dubai, United Arab Emirates, at 2717 feet and 160 floors.The observation deck is 1450 feet above ground level. How far can a person standing o...
https://www.physicsforums.com/threads/how-far-can-a-person-see.1062361/
Hello, this is my attempt for #19 for 11.6 of Stewart's “Multivariable Calculus”. The question is to determine whether the series is absolutely convergent, conditionally convergent, or dive...
Should be a simple test to see how much vacuum can be created by the pump but it is lifting the water in the manometer over 40 inches on one side. From what I’ve seen when reading a manometer y...
https://www.physicsforums.com/threads/calculating-vacuum-these-numbers-do-not-make-sense.1062274/
See attachment. For 37 Area of circle - Area of square Is this right? For 38 Area of square - Area of circle Is this right?
https://www.physicsforums.com/threads/find-area-of-shaded-region.1062363/
I've created a macro program used by a CNC milling machine to cut threads in a hole. I like to use macro programs because it allows me to use the same macro for any different size of feature just...
https://www.physicsforums.com/threads/cnc-thread-mill-macro-programming.1062343/
I am nobody important, and don't have any relevant training. I do what I enjoy, and learn whatever my curiosity demands. Lately, that has involved taking a close look at the properties of fundame...
https://www.physicsforums.com/threads/i-like-listening-when-nature-speaks-on-its-own-terms.1062366/
Here is my sketch: The triangle ##abc## is arbitrary, the triangles ##acp##, ##abq##, and ##bcr## are equilateral with centroids ##m##, ##n##, and ##k##. I suspect that the triangle ##mnk## is ...
https://www.physicsforums.com/threads/triangle-of-centroids.1062365/
A Christmas tree ornament is in the shape of a semicircle on top of a triangle. How many square centimeters (cm^2) of copper is required to make the ornament if the height of the triangle is 6 cm...
https://www.physicsforums.com/threads/find-number-of-square-centimeters-of-copper.1062362/
I'm trying to brush up on my Calc 1-3, and Physics 1-2. I got up to integration in Thomas' Calculus book no problem. The integration part of it is a bit convoluted to me though. So, I'm trying to...
https://www.physicsforums.com/threads/good-site-for-opencourseware-at-your-own-pace.1062360/
TL;DR SUMMARY: This is an astronomy application. MENTOR NOTE: MOVED FROM A TECHNICAL FORUM SECTION, SO THE HOMEWORK TEMPLATE IS MISSING. How long does it take a beam of light to reach Earth fro...
https://www.physicsforums.com/threads/how-long-for-a-beam-of-light-to-reach-earth.1062322/
For California Community Colleges the minimum requirement for Physics instructor is: MASTER'S IN PHYSICS, astronomy or astrophysics OR Bachelor's in physics or astronomy AND Master's or above i...
Hello! I considered number line and I couldn't take random points that correspond to hyperreal numbers on the hyperreal line. Instead it was points A, B, C that correspond to real numbers. Ho...
I am currently in the beginning of my Junior year as a physics major. This semester I am taking Electromagnetic Theory A, Mathematical Physics A, Mathematical Physics B and a special topics cours...
https://www.physicsforums.com/threads/should-i-withdraw-from-a-class.1062331/
Which songs were performed, arranged or produced better in a cover than the original version? Which songs should have been left well alone? Also, I think restricting the covers just to releas...
How does one roughly predict the mean free path for electrical conduction in a nanostructure at different temperatures and under different electrical conditions such as different voltages and amp...
Sometimes you see a news article that grabs your attention mainly because it makes a statement where you say wait, what? “I don’t get it.” Much of these are political, but luckily, there ar...
https://www.physicsforums.com/threads/i-dont-get-it.1062352/
QUESTION 1: DETERMINE THE NUMBER OF POSSIBLE MICROSTATES FOR THE COMBINED SYSTEM. My answer: 12 microstates. QUESTION 2: SUPPOSE WE HAVE A SYSTEM COMPOSED OF TWO SUBSYSTEMS THAT HAVE REACHED TH...
https://www.physicsforums.com/threads/find-number-of-microstates-of-combined-system.1062309/
I’m not at all sure I’m posting this in the right forum. If not, please forgive me. Also, I have no background in physics. That said, here goes: If 2bar of helium flowing through a 9.0mm in...
This thread is for documenting the setup of my new telescope. It's not completely new, I'll be using some peripherals from the old telescope, such as the camera, filter wheel, off-axis guider (...
https://www.physicsforums.com/threads/documenting-the-setup-of-my-new-telescope.1059921/
Is it possible to get an interference pattern if the original laser beam is not splitted before reunited? Can I use 2 mirrors which will be separated 2 cm from each other and they reflect the lig...
https://www.physicsforums.com/threads/questions-about-a-laser-interferometer-pattern.1062356/
Greetings fellow forum goers, I am MoreRight or by full pen name ProfessorMoreRight. I came here to further my knowledge in the realm of physics and in particular with a focus on figuring out ho...
https://www.physicsforums.com/threads/greetings-and-introductions-for-myself.1062357/
Hi Everyone. I hope someone can point me in right direction. I am struggling to work this out . If it was 1d confinement the calculated n number would be the energy level. So for example n= 3, m...
https://www.physicsforums.com/threads/particle-confined-in-3d-box-quantum-states.1062337/
TL;DR SUMMARY: This is an astronomy application. One light-year is defined by astronomers to be the distance that a beam of light will travel in 1 year (365 days). If the speed of light is 186...
https://www.physicsforums.com/threads/number-of-miles-in-one-light-year.1062321/
I am trying to find solutions for the Klien-Gordon equations in 1-d particle in a box. The difference here is the box itself oscillating and has boundary conditions that are time dependent, somet...
https://www.physicsforums.com/threads/klein-gordon-equation-with-boundary-conditions.1062358/
This is the general suggested approach given in a textbook. My question is why can I not directly write it in vector form? E1 vector + E2 vector =0 should be valid no? Why are they choosing t...
I tried to start by assuming that we need to integrate something over 1 period (2pi). Therefore, we need i(t)^2 R integrated over something. From there, I recognized that this is an underdamped m...
HOW DID YOU FIND PF?: Google I am working on a project that requires us to protect components from high heat. We were thinking on using sodium bicarbonate, but our module needs to be exposed F...
From the few interpretations of quantum mechanics that I know, let's say: Copenhagen Many Worlds (MWI) Bohmian mechanics Superdeterminism Retrocausality/transactional Objective-collapse Qbism* C...
Old thread: https://www.physicsforums.com/threads/science-jokes.4463/page-44 My wife just drew this
https://www.physicsforums.com/threads/collection-of-science-jokes-p2.847743/
I need to pass the value of a variable from one FORTRAN program to another. The main program carries out calculations with some numerical inputs A,B , I want to enter numerical values of variable...
https://www.physicsforums.com/threads/passing-variables-in-fortran.1062082/
we can express theta as a product of the angular velocity and time thus plugging this in space of theta in the above equations we can express r hat and theta hat as a function of time. But i am h...
https://www.physicsforums.com/threads/unit-vectors-as-a-function-of-time.1062338/
Due to the constant never ending supply of "cool stuff" happening in Aerospace these days I'm creating this thread to consolidate posts every time something new comes along. Please feel free to a...
https://www.physicsforums.com/threads/space-stuff-and-launch-info.879196/
Sometimes I see a line (or maybe a brief multiline) post or part of a post in the Physics Forums that I think is pithy, witty, and maybe acerbically funny. I invite other members to post accordin...
https://www.physicsforums.com/threads/great-one-liners-from-pf-members.992032/
This thread is for all who like the daily Wordle game of the New York Times as much as I do. The rules: 1) https://www.nytimes.com/games/wordle/index.html 2) Post your result. 3) Do not sp...
https://www.physicsforums.com/threads/wordle-lovers-play-the-nyt-daily-game.1016903/
Good evening, unfortunately I can't get to the solution of my task I wrote for the system: ## frac{dz}{dt} = nabla_p H ; \ frac{dp}{dt} = - nabla_z H ## Then the solution would be (as ## ...
https://www.physicsforums.com/threads/solve-this-hamiltonian-system-in-several-ways.1062345/
I am reading these notes on measure theory. On page 27, in chapter 2 on the construction of the Lebesgue measure, in section 2.8 on linear transformations, the author presents a lemma which is n...
https://www.physicsforums.com/threads/parallel-rectangles-contained-in-oblique-rectangle.1061487/
Post your favorite animal pictures here!
https://www.physicsforums.com/threads/share-animal-pictures-for-animal-lovers.583729/
Have lot of questions which find good answers here. Still many unanswered.
https://www.physicsforums.com/threads/spirituality-lead-to-cosmology-lead-to-here.1062347/
I am picking this up as a continuation and extension of the idea laid out e.g. in @davenn 's thread "The Sun today - 9 July 2017 - nice spot group" https://www.physicsforums.com/threads/the-sun-...
https://www.physicsforums.com/threads/solar-activity-and-space-weather-update-thread.923468/
I know nothing, yet I have ideas. I like coming up with thought experiments, but without a strong foundation in physics or math, they could just be musings of my imagination without any grounding...
Hi, I'm a Machinist from Canada. I enjoy challenging myself by learning and creating custom macro programs for different manufacturing processes on my CNC machine. I'm hoping to get some insight ...
https://www.physicsforums.com/threads/cnc-machinist.1062339/
Is there a way to trace all the reactions I have had to others' posts in various threads of this forum? Like an index? If only to retrieve all the useful information I've learned from them, but...
(Edit: since the thread title was changed, this first sentence is too cryptic: the original title referred to a Tool song....) Besides being a favorite song by a favorite band, the thread title...
https://www.physicsforums.com/threads/the-secrets-of-prof-verschures-rosetta-stones.1054432/
BITCOIN, “HEISTS, THEFTS, HACKS, SCAMS, AND LOSSES.” http://www.npr.org/blogs/thetwo-way...-exchange-mt-gox-goes-dark-after-theft-report > "The website of major bitcoin exchange Mt...
https://www.physicsforums.com/threads/bitcoin-heists-thefts-hacks-scams-and-losses.740560/
I am writing a saga of multiple stories set at different time periods in a fictional version of our real world. At a certain point in the worlds timeline, in the next thousand or so years of the ...
https://www.physicsforums.com/threads/extinction-event-in-my-story-is-it-believable.1062097/
Dirac ("GTR" p. 47) makes an interesting observation immediately after obtaining Einstein's field equations with the simple energy-momentum tensor ##T^{munu}=rho v^mu v^nu##. (##v^mu## is the fou...
https://www.physicsforums.com/threads/variation-of-cmfr-mass-density-rho-along-a-world-line.1062305/
I am talking about university level. There is lots of genius physicist/engineers who were bad in math. If mathematics is the language of physics how this is even possible? Do math and physics...
https://www.physicsforums.com/threads/bad-at-math-and-great-at-physics-explain-this-paradox.1062225/
positron g-factor positron--positron moller scattering antiproton g-factor antihydrogen atom gravity antihydrogen atom spectroscopy antihydrogen anion (hydride) spectroscopy antihyhelium at...
https://www.physicsforums.com/threads/testing-antimatter-fundamentals.1062328/
I decided to go through @psie 's measure theory notes to refresh myself since it's been a while. I got to the theorem on page 60 which I will attempt to summarize my confusion as just this statem...
https://www.physicsforums.com/threads/are-slices-of-measurable-functions-measurable.1062316/
Hi Pfs, I would like to know if it would be possible for our known theories to derive conservation laws if space time was really granular. I think that entanglement is the only process which ...
https://www.physicsforums.com/threads/repeated-measurements-and-granular-space-time.1062327/
My name is Feliz. I am doing a self-study of college algebra. I am not a classroom student. My student days ended in December 1993. I've always enjoyed mathematics and decided to conduct a review...
https://www.physicsforums.com/threads/hello-from-nyc.1062320/
I understand that the "spiral" converges to 1+i-1/2-i/3!+1/4!+i/5!-1/6!-i/7!... . It splits into two: one for Re, 1-1/2+1/4!-1/6!..., and the other for Im, 1-1/3!+1/5!-1/7!... . Any hints on ho...
https://www.physicsforums.com/threads/a-spiral-in-the-complex-plane.1062332/
What in physics (or some other topic) would you memorize if you could? Yeah I know memorization doesn't usually have a point, just asking, if you could just do it without effort, what would it be...
https://www.physicsforums.com/threads/what-would-you-memorize-if-you-could.1062298/
In my line i have, ##dfrac{∂r}{du} = vec{i} +dfrac{1}{2}u vec{k} = vec{i} +1.5 vec{k}## ##dfrac{∂r}{dv} = vec{j} -dfrac{1}{2}v vec{k} = vec{j} -0.5vec{k}## The normal to plane is given...
How Can I add bar Legend for g in the following code in mathematica? Thanks in advance? f := t + 1 g := t^3 + 3*t + 12 ParametricPlot*Cos], f*Sin]}, {t, 0, 1}, {, 0, 2*Pi}, ColorFunction ->...
https://www.physicsforums.com/threads/bar-legend-for-a-different-function-in-mathematica.1062326/
My set-up is the following: i have an iron bolt suspended on a string next to an electromagnet, of which I steadily increase the voltage and thereby the magnetic field. Supposing the force is li...
Well, that sounds spectacular and terrifying.
https://www.physicsforums.com/threads/large-eruption-at-ruang-volcano-indonesia.1061910/
Φ = 𝜑S (dQ/dt) = k*S*dT avec dT = (1500 + 273.15) - (40 + 273.15) = 1460 avec dQ = - 0.24 * 440 * 1460 = - 154176 donc, -(154176)/dt = 40 * 0.0062 * 1460 = 362.08
##arg((b-a)/(c-a))## is an angle between ##ab## and ##ac##. ##arg((a-c)/(b-c))## is an angle between ##ca## and ##cb##. For them to be equal, ##b## has to be equidistant from ##a## and ##c##, i...
https://www.physicsforums.com/threads/three-points-on-the-complex-plane.1062306/
https://www.npr.org/2024/05/01/1248565614/duane-eddy-rock-guitarist-obituary Rebel Rouser by Duane Eddy
https://www.physicsforums.com/threads/r-i-p-duane-eddy-rebel-rouser.1062324/
Hi,
I have problem to prove that the following inequality holds
I thought of the following, since it is a convex function and ##x_1 <
x_2 https://www.physicsforums.com/threads/prove-inequality-of-a-convex-function.1062310/
I know it is a simple problem, but I am confused by the fact that we can look at the problem from two points of view. In general, we differentiate between the balls of the same colour, I mean w...
https://www.physicsforums.com/threads/probability-two-possible-points-of-view.1062311/
Background: In my opinion the next decade has great potential for difficult circumstances for worldwide. I have been obsessed with coming up with a small electrical power generation system (minim...
https://www.physicsforums.com/threads/on-demand-steam-engine-idea.1062054/
This answer shows an extended version of Pascal's Triangle that works for negative numbers too. In This video, Sal shows how to interpret the members of Pascal's Triangle as the SUM OF ALL T...
TL;DR SUMMARY: Review/Rating of “Gravity … … “ by James B. Hartle Thoughts regarding prerequisites for reading this book I would be really grateful if someone would rate/evaluate/rev...
Let's assume that a player has a probability ##p## of winning a point on the opponent's serve. 1) What is the probability (##P##) of a break of serve - i.e. winning the game? 2) What is the e...
https://www.physicsforums.com/threads/tennis-probabilities-challenge.1059978/
What I mean is on a coordinate plane like below we take the positive x axis measure a certain distance x on it and take the infinitesmally small quantity dx next to it in the positive direction: ...
So basically i am vary green when it comes to equations/formula Well to the point i don't even know if proper name for what i'm looking for is called equation or formula but let's stick to equat...
Following the above statement my teacher was trying to prove something and it started with suppose q1 and q2 are charges placed in a medium (k) of infinite expanse. The distance between them bein...
Locomotives are a complex combination of mechanical and electrical systems. The video shows different parts of a locomotive and their function. A standard mainline freight locomotive develops 440...
https://www.physicsforums.com/threads/modern-us-locomotive-design-and-operation.1048539/
Let ##D_rsubset mathbb{R}^2## be the disk of radius ##r## centered at the origin. If ##f : mathbb{R}^2 to [0,infty)## is uniformly continuous such that ##sup_{0 < r< infty} iint_{D_r} f(x,y), dx,...
https://www.physicsforums.com/threads/limit-of-a-nonnegative-continuous-function.1058512/
Every day we learn new things. Sometimes it's just a small fact or realization. No matter how trivial or random, let's start recording our daily lessons. Please start off with "Today I learned"....
https://www.physicsforums.com/threads/today-i-learned.783257/
Let ##0 < alpha < 1##. Find a necessary and sufficient condition for the function ##f : to mathbb{R}##, ##f(x) = sqrt{x}##, to belong to the class ##C^{0,alpha}()##.
https://www.physicsforums.com/threads/a-function-in-the-continuous-hoelder-class.1056668/
compare 2 situations When a person stands inside a boat and blows air on the sail will the boat move or not and second case human blowing but outside of the boat , thought of something along t...
https://www.physicsforums.com/threads/action-reaction-of-a-sailing-boat-and-wind.1062256/
After 5 months of sending a repeating loop of meaningless bits, the 46 year old Voyager 1 is back to sending actual data. https://www.cnn.com/2024/04/22/world/voyager-1-communication-issue-cause...
https://www.physicsforums.com/threads/46-year-old-voyager-1-once-again-sending-real-data.1062075/
I know that to prove the total coriolis torque from the coriolis torque on a point mass is to express dm as a function of ##dtheta## and integrate from 0 to ##2pi## and then the x component disap...
https://www.physicsforums.com/threads/gyroscope-coriolis-torque-and-force.995231/
Question A WHEEL OF RADIUS R AND MOMENT OF INERTIA I ABOUT ITS AXIS IS FIXED AT THE TOP OF AN INCLINED PLANE OF INCLINATION Θ AS SHOWN IN THE FIGURE. A STRING IS WRAPPED ROUND THE WHEEL AND ITS...
Find, with proof, the sum of the alternating series $$sum_{n = 0}^infty frac{(-1)^n}{(2n+1)^3}$$
https://www.physicsforums.com/threads/sum-of-an-alternating-series.1062237/
From posts like this I get that the color of the sky is explained by Rayleigh scattering, but needs density fluctuations. However as atoms are not uniform and are localized, the density is $$rh...
https://www.physicsforums.com/threads/density-fluctuations-and-the-color-of-the-sky.1062313/
How many particles (approximately) from the solar wind reach deep into the Earth's magnetic field every second. Possibly measured in mass?
The (i) is straightforward: take the second derivative to 0. The (iii) is obvious: after the substitution, ##x^2## comes from the ##X^3## with the coefficient ##-3A/3## and from the ##AX^2## wit...
https://www.physicsforums.com/threads/to-deduce-geometrically.1062292/
references _ Paved Track Stock Car Technology by Steve Smith Tune to Win by Carroll Smith Software - Suspension Analyzer by Performance Trends In order to understand the complexity of a Formul...
https://www.physicsforums.com/threads/race-car-suspension-class.326355/
Wolfram gave the solution and a hint: i want to understand the hands on approach steps... In my approach (following Wolfram's equation) i have, ##(x-3)^2(2+12(x-3)+(x-3)^2=-25## ##(x-3)^2((...
https://www.physicsforums.com/threads/solve-the-equation-x-4-12x-3-2x-2-25-0.1057248/
from what I understand, work is the integral of the force with respect to displacement along the path of displacement $$Delta w=f*Delta r$$ and is defined so that the change in kinetic energy is...
Hello All. I looked at a question "A noisy machine in a factory produces sound with a level of 80 dB. How many identical machines could you add to the factory without exceeding the 90-dB limit?"...
Just wondering if anyone here is familiar with the Cass Report, which was recently published in the UK? I've been reading a lot of different stuff on it, including criticisms of it's methodolog...
https://www.physicsforums.com/threads/the-cass-report-uk.1061974/
The context is going down a hill in rollerblades: when people fall and they come to a quick stop (due to not having protective gear and there being lots of friction), they always end up with majo...
I'm always finding weird things in the news and thought it might be fun if we all shared odd stories we came across. Please feel free to post odd, funny or unusual stories in this thread. Turns...
https://www.physicsforums.com/threads/weird-news-compilation.878428/
A topic for random photos: Ko-Larn island 7 km West of Pattaya
Show that $$frac{pi}{4} = 1 - frac{1}{3} + frac{1}{5} - frac{1}{7} + cdots$$
https://www.physicsforums.com/threads/does-the-taylor-series-for-arctan-converge-at-x-1.1054705/
Let us try to promote some physics history in this sub. What are some anecdotes in the history of physics that you want to share? Be it a true story or a popular myth. I'll start: I recentl...
https://www.physicsforums.com/threads/interesting-anecdotes-in-the-history-of-physics.1059261/
Maybe this is more general discussion, but I am excited / nervous about the upcoming launch of the JWST. https://jwst.nasa.gov/content/webbLaunch/countdown.html I can't wait to see the observ...
https://www.physicsforums.com/threads/the-james-webb-space-telescope.1010264/
Let's say I have the following situation $$I = dfrac{partial}{partial x^{alpha}}int e^{k_{mu}x^{mu}} ;d^4k$$ Would I be able to commute the integral and the partial derivative? If so, why is ...
Hi guys Please refer to the attached image. It is really easy to derive a set of differential equations which present a spring on a mass system, however how can one consider a system where ...
https://www.physicsforums.com/threads/decoupling-of-a-spring-mass-system.1062283/
(i) and (ii) makes sense to me but the answer key says (iv) is correct too, but shouldn't the answer be 2 significant figures for (iv). 2 and the first zero are significant if the lc is 100 kg as...
https://www.physicsforums.com/threads/significant-figures-doubt.1062297/