Interesting Definition and 790 Threads

I've just found this interesting song. The lyrics are quite intriguing. :))

I was searching for a homework based on earthing. I read a conversation about it. It felt so amazing. So I thought I should sign up too.

Hi folks, 50 odd years ago I did a physics degree - wonder if anything interesting has happened since. Logged in a while ago, but seems lost. Worked in signal processing, still do the odd wee research contract. Nothing right now, thought I would have a look in here.

Check this one out about the number of hairs on a person's head, if not behind a paywall (I can't tell because I subscribe to Scientific American). Let me know if it is, and I will post a precis...

Not sure if it is meant to be a pump or a compressed air motor. Or maybe it can work as a pump or as a motor? What would be the practical problems? Does it add anything to the prior art? --- Edit : Not sure how it will make a proper seal, with that step in the back plate.

https://www.bbc.com/future/article/20230116-how-donkeys-changed-the-course-of-human-history

The lines have a slight purplish hue to them (at least reflected from leaves) and are about 2 feet apart. Here are images of the lines and the sun through the tree.

This is a good book to read, free pdf version. Don’t judge the book by it’s cover. Read section 1, and 2, see if you learn something you weren’t expecting ~.^ This is the above link’s target: https://www.gutenberg.org/files/33283/33283-pdf.pdf Enjoy!

I know there have been a number of previous threads discussing the work of Pavel Kroupa, and this work has generally been categorized as far out of mainstream because it deals with his views on alternative gravity theories and so forth. However, I have come across two of his papers that describe...

Hey All, The simulation I am currently looking at is regarding the following paper: https://iopscience.iop.org/article/10.1088/1367-2630/10/4/045030. Let us define J = C_{3}/R^{3} (equation (2) in the paper) and let T be the simulation time until the trajectories of each particle changes by at...

NOT a home-work / college question, merely wondering... Just as there are 'interesting' numbers, per primes, Pythag' triples, Euler-stuff etc, are there any 'interesting' angles between 10~~25º ?? I've had a hunt around, noticed several possibilities invoking eg transcendental fractions of...

Generally, we try to apply scientific knowledge in some manner to benefit humanity. Often the application requires some standards or precautions so that the applications will have maximum benefit and minimal risk. One such application was that of ionizing radiation. X-rays were discovered in...

Hello there, first let me say I hope this is the right section for this topic, and if not please feel free to move it! So a couple days ago I took a trip up to Mackinaw City, Michigan, and saw a few interesting and intriguing things (luckily!) in the sky that night, and was just hoping maybe...

Looking East this morning about 5:15 am. No telescope needed. But the pic is not actual - it is from Stellarium.

While working on a probability problem I accidentally found this relationship: $$\frac a b = \frac a {(b-1)} - \frac a {{(b-1)}^2} + \frac a {{(b-1)}^3} - \frac a {{(b-1)}^4} + ~...$$ I have done a bit of work on it myself, and have tried to research similar series. It seems to lead to some...

Imagine a magnet moving up and down so that its flux 'B' cuts the copper rod to produce an alternating emf, suppose if the movement is fast enough such that its frequency equals to the electron spin resonance frequency given by F = B x 2.8 Mhz per gauss, neglecting skin effect, more copper...

Veritasium on YouTube https://www.youtube.com/c/veritasium/community has posted this problem, inviting viewers to say what would happen: Is the following answer correct?

Here we go!

I found an interesting math result ("halting problem is essentially solvable") yesterday, but now I see a contradiction (it follows "halting problem is solvable"). Participate in finding my error. Here is my short yesterday article (with links to other yesterday articles): [Unacceptable...

Just saw an interesting video on youtube explaining Logical Effort very nicely. https://en.wikipedia.org/wiki/Logical_effort

A book on optics which is less mathematical maybe a similar one to physics for poets or gamow gravity classics

I recently came across the following lecture on what QM is: I was shocked by how close it is to my view. What do others think? Thanks Bill

Bostelmann, H., Fewster, C. J., & Ruep, M. H. (2021). Impossible measurements require impossible apparatus. Physical Review D, 103(2), 025017.

Bumped into this video after admiring the falling cat by @A.T. As an experimental physicist, indeed experienced a little of the 'hole in the brain' phenomenon!

I found this interesting video from Presh Talwalkar: Problem Statement. If: $$x + y + z = 1$$$$x^2 + y^2 + z^2 = 2$$$$x^3 + y^3 + z^3 = 3$$ Then, find the value of the higher powers such as $$x^5 + y^5 + z^5$$ The solution posted there uses the full Girard-Newton Identities. Here is an...

Could you point me to interesting videos about plasma ball?

Hello everybody, I hope it is the right section to post. For an exam, I should delve into a topic concerning graph theory. My work should include theoretical explanation, pseudo code, correctness analysis, complexity analysis and code implementation (C ++, python or other). Could someone...

Hi All Here is how the Aussies are making the Oxford Vaccine: https://www.abc.net.au/news/science/2021-02-12/covid-19-vaccine-oxford-astrazeneca-adenovirus-csl-manufacturing/13140104 Thanks Bill

That's pretty much it. If there is a very basic strategy that I am forgetting from ODEs, please let me know, though I don't recall any strategies for nonlinear second order equations. I've tried looking up "motion of a free falling object" with various specifications to try to get the solution...

What may have caused this bonding

On examining Maxwell's third equation which is about time varying magnetic fields (Faraday's electromagnetic induction) we find that time varying magnetic fields produce loops of electric fields in space irrespective of whether a coil is present or not, if any coil is present then these loops of...

Hi guys, As some of you may already know(😅), I'm 18 and currently attending my last year of high school in Italy, and looking forward to studying aerospace engineering abroad(UK or USA). My interest in STEMs is swiftly growing, leading me to study a lot on my own, taking part in as many cool...

https://www.scientificamerican.com/article/new-views-of-quantum-jumps-challenge-core-tenets-of-physics/?fbclid=IwAR0z2pTmGqTBkm2JzvSNe6piKPZCGbhdpyZWcHeLO_2B-w5fPxFRKgfrGvY I love quantum physics almost mystical and paradoxical nature. That seems to be ending. Especially with the advent of...

What then can happen to the radio signal sent into space? It seems to me that after a while our signal will return to us as an echo, but the return period depends on the frequency of the signal. This corollary does not have a rigorous mathematical proof; an analogy is simply drawn with rational...

Isn't entanglement just the conservation of spin, momentum, and position along with Heisenberg's uncertainty principle? I don't really see the big mystery or maybe I am just not understanding a key part of what makes entanglement so interesting. Can someone pinpoint how this receives so much...

Prove that for positive reals $a,\,b,\,c,\,d$, $\sqrt{ab}+\sqrt{cd}\le \sqrt{(a+d)(b+c)}$.

https://au.news.yahoo.com/disturbing-photo-heroic-boy-saved-sister-dog-attack-051333690.html When a six-year-old boy saw his little sister being attacked by a dog he didn’t hesitate to jump in and protect her. Bridger from from Cheyenne, Wyoming in the US has been dubbed a hero after he...

This new technology will make monitoring outside of labs possible. It requires a brain implant. Kind of reminds me of the Borg.

t is Torque I is the inertia moment P is the power c is the constant light speed r is the spot distance to the fiber p is the torsional constant theta is what we want In the equilibrium $$t = 0$$ $$ F\Delta T = \frac{E}{c} = \frac{P\Delta T}{c} => *F* = \frac{P}{c} (1) $$ This will be the...

I need to find the differential equations for each mass. ##y_1## is the equilibrium position, and ##y_2## is the second equilibrium position for each mass. I was thinking consider the next sistem: \begin{eqnarray} k\Delta y-mg&=&m\frac{d^2 y_2}{dt^2} \\ -2k\Delta y_1 -k\Delta y_2 -2mg...

I find the following facts interesting. Morocco and Algeria have been using hydroxychloroquine since the beginning, ignoring the WHO, who say that it is useless and dangerous. By contrast, Canada and France follow the WHO and forbid the use of hydroxychloroquine for covid. The numbers are...

Hi all, I have recently faced some problem about distances between two curves, and (re?)"discovered" an interesting point that I would like to share with you. In the following, we consider a function of two variables ##f(x,y)##, but it should be clear that the definitions and the result is...

I'm having trouble finding a hobby that really excites me. I've always been a big fan of science but I never really knew what I should do with it. So far I've just been programming but I haven't really found much use for it outside of building websites or apps which is a really boring task for...

No-Nonsense Quantum Field Theory: A Student-Friendly Introduction by Schwichtenberg, Will let you know how it is when I read it. More details here

Check it out: https://www.amazon.com/dp/B07PYMLZWJ/?tag=pfamazon01-20 Its available free if you have Kindle Unlimited. Many books do not get right that Einstein knew QM very well indeed and greatly admired Dirac, of whom he said: 'Dirac, to whom, in my opinion, we owe the most perfect...

The Inside-Out hypothesis, proposed in this paper (open access), explains the origin of several eukaryotic cellular structure based upon the cell geometry resulting from expansions cell protrusions becoming the cell's non-nuclear cytoplasm. Here is their summary diagram: and their caption...

This meditation is prompted by the cold I'm currently suffering. One of the products I like is a very intensely-flavored cough drop called "Fisherman's Friend". I found a mostly-full package in the house and commented to my wife that it was Mint flavor. "We must have picked that up in Germany"...

I regularly start my classes with an opener that I hope might 'spark something' in the minds of my high school physics students. This is usually the Astronomy Picture of the Day or some interesting science news article. Sometimes it is more mathematical. On the math side, so far, I've thrown up...

A theoretical astrophysicist was absentmindedly working through papers on Mossbauer spectroscopy, eventually coming to the Pound Rebka experiment, a remarkable test of GR. (Gamma rays were sent from the top of a building to a receiver, so as to measure the gravitational blueshift in such an...

Summary: I would like to know your favorite (freely accessible) resources and exercises. Preferably not ordered by topic, university (bachelor) level and requiering some creative thinking/ no overly tedious calculations. I was not sure where to put this, feel free to place this thread in...