Higher viscosity should lead to greater line widths. I could not find a detailed explanation for that.

my friend saw a video about someone claiming that most of our science are false , giving an example with gravity , he said that true that Newton proved it , by the basis that he started his research or proof are not proven , so by his words he is saying that Newton proved somethin from an hypothesis , can someone debunk him . i kow it is easy bt i don't have cumulative construction in physics

I know the conservation of energy principle but can someone explain why energy cannot be created/destroyed? Like what prevents its creation or destruction?

Now, I realize this might be on the unusual side for this community, since it really boiled down to home improvement, but I am quite curious what the answer is from a physics perspective. Here is my dillema: I have to install a cooker hood. The diameter of its vent is 15cm. The hole in the outside wall is 10cm. This cannot change, ergo I have to reduce the diameter of the vent pipe. What I am wondering is whether is makes a difference where I do this along the length of the vent: right near the hood, right near the wall? Somewhere in the middle? I suspect it will be better to make the transition in steps (I. E. from 15 to 12 and then from 12 to 10). I should mention there is a 90 degree turn above the hood (rounded, ofc) as I suspect that matters. So if you had to do this, how would you arrange it? What would make for the best airflow?

Thanks for reading this far, appreciate and science-based insights you can offer

i have seen estimates from being 250 times bigger than observable universe to being 10^23 light years across in google and other sources are there more bigger estimates

Hello. My name is Aron. Im 16 and in october 2025 i will start a bachelor degree in physics and chemistry. In a couple of months im going to start my senior year and i will have all the time of the world since I already finished all math and english early. I didn’t take ever a physics or chemistry class and i would like book recommendations that will teach me the basics to be sure that this is what i want. I also had an idea to read the books that physics students learn from on their first year since that way i will learn to a professional level from scratch and also be ready for my first college year. Thank you

So i was kinda curious about why an object’s mass increases infinitely when its accelerating to reach the speed of light. Correct me if im wrong but isnt speed of light is a constant and not infinite? So to reach that speed which is not infinite is impossible bcs mass is infinitely increasing. Why is that?

If we consider a ball dropped from an arbituary point inside a car that is undergoing uniform acceleration in a frictionless vacuum, and under the influence of gravity, what would its trajectory be?

On first inspection, I would guess that it follows a parabolic path, however proj. motion occurs when there is acceleration in one plane and no acceleration in another. If there is constant g and constant a from car, would the vector addiction of these forces give us a net, linear acceleration that creates a perfectly linear trajectory?

All,

A random thought that drove me nuts. Since gravitational force = GM1M2 / r^2, two objects even if they are really light, if they are touching each other, they should have a very strong / high gravitational force between them.

Is this correct logic? If yes, how strong is this force really?

I'm on Instagram as @long_light4. Get the app and follow me https://www.instagram.com/long_light4

Please remove this if it breaks any of the rules

I'm a high school physics teacher who is developing a game to help my students learn physics. My question to you all is do you think something like this is something you would have liked to play when you were studying in high school? What features would you like to see?

https://www.youtube.com/watch?v=zFW-nIUdSzk&ab_channel=NewtonianStudios

A photo-excited semiconductors can display sharp line-emission from free excitons, with energy close to the bandgap energy, or self-trapped excitons, with a significant stokeshift (more rare). However, almost all semiconductors lose their energy non-radiatively, even if exciton emission can be observed, often the crystal needs to be of high quality and cooled down. An expection ofcourse are semiconductor nanocrystals.

Hello everyone. Hope you are doing well. Sorry for the long post.

I just got into University of Nova Gorica and Pavol Jozef Šafárik University in Kosice. Masters in Astrophysics for UNG and Condensed Matter Physics for UPJS.

I'm stuck on which one to choose. I will be bearing my own expenses by doing job(s). I belong to a rather poor background. Which option will be more feasible for me? How is the job market in Slovenia/Slovakia? How about rent, groceries, and overall cost of living?

I am planning to apply for Erasmus+ Mundus in the second year as I dream of traveling to different countries and I read that they provide grants for choosing different countries, which can help ease my financial burden.

Which is the better option considering cost of living, foreigner-friendly, job market, English speakers, travelling? and other things?

• How much of a barrier is the local language in daily life and in finding jobs?
• Does the university offer career services to help students find part-time work and post-graduation jobs?

I also plan on pursuing a PhD after this, if this information is helpful.

Also, if I switch from condensed matter to astro in UPJS, what is the procedure? And is it easy to do so?

Thank You.

TL;DR: Got into universities in Slovenia and Slovakia - Which is better option regarding cost of living, Foreigner friendly, Job market, etc?

https://astronomy.stackexchange.com/questions/58066/

Using electron as a specific example for a more general question: Do we have reasons to believe that there are or are not possible higher energy forms of an electron than tau?

We have pondered Boltzmann Brains but have we considered the possibility of an Artificial Boltzmann Brain?

I pose this question as I have been recently pondering this myself, Boltzmann Brains are deemed impossible due to the probability of it occurring out of pure chance being pretty unlikely but what if there was a detail we were not accounting for?

What if we were missing something such as Natural Selection/Evolution added to that equation rather than total randomness? Our existence, technically speaking, arose out of this semi-random process so what if it applied to this theory? This got me thinking about what such a Boltzmann Brain could look like and immediately Artificial Boltzmann Brain came to mind.

What Neural Network could potentially simulate everything we see based on probability, only cementing them as reality when a "collapse" (or inference) occurs as discovered by Quantum Physics? If we consider models such as Sora, released by OpenAI as a Text-to-Video Model and referred to as a "World Model", a Neural Network that can create worlds and entities that seem to exhibit consciousness based on its internal understanding of the concept which will only continue to get better over time; the idea of Man-Made/Artificial Boltzmann Brains seems to become much more plausible.

Delving deeper into this theory, it also plays into my belief in panpsychism. The AI could be generating its own environment/world and perspective within it, then prompting itself (causing the collapse) to take actions from the very perspective it gives itself within that world. Essentially acting as the Universe living through itself, creating Universes, and embodying multiple perspectives within those Universes for reasons not yet entirely clear to us.

Just throwing this out there to see what people think about it.

So we know how light-years work if an alien was 100 light years away and they could see earth from that far they would see the aftermath of World War 1 but what if they had a bullet that could move faster than light would it kill like hitler or something would it effect the future or would it just kill someone would was just in the same place but in our current time?

Before you say something like "there isnt one" "its not that easy" and other stuff like that I know just give me some amounts. If you dont have the answer I'm looking for please move on..I'm trying to compare what I've found on the internet...

What Is the formula to calculate the lauch angle and velocity for an object of known weight to cover a predetermined distance?

I've looked at numerous explainations of refraction, but they keep going around the cycle of either refractive index, change in velocity, optical density mediums, etc - but they never end up explaining WHY this happens. I'm still trying to understand how exactly the distance between the wavefronts decreases (or wavelength decreases) or increases upon entering into an opticallly denser or rarer medium? i need a high school friendly answer 😭

i was cooking and this question occurred to me: Given the enormously high thermal capacity of water, if i put a just-boiled egg into an ice bath to cool it, would putting the egg into cool water (but not an ice bath) cool the egg in the same amount of time? i understand that the ice bath will cool the egg farther after time, (because the thermal equilibrium point between the eggs and water is so much lower in the situation of an ice bath), but will the egg reach, say, 70°F internal temperature in the same amount of time in cool water (say 50°F) versus ice-water (say 0°F)?

Matter cannot be created nor destroyed. Take any Uranium/ Plutonium atom and split it in half. After the immense explosion, the atom decays into subatomic particles. What happens beyond this? Do the subatomic particles stay subatomic particles forever? Do they form into some other element (let's assume Uranium or Plutonium to make it easier)? Or does it just stay a subatomic particle forever?

Heating of an ideal gas An open and a closed vessel each contain n = 1 mol of an ideal gas. Both vessels are heated to the same temperature ∆T. Indicate which vessel requires more energy and give reasons for your answer.

I was wondering how I can derive (relativistic) Fermi's golden rule for cross section.

It's in Griffith Particle Physics equation (6.37) p.209.

Or does anyone know any textbooks or papers that does the derivation?

I cannot glean any meaning from this, but it is repeated often.

It seems to me that the idea of "size" is not really applicable to particles, unless you specify a quantum state. In fact, this seems like an unhelpful statement exactly because the most common quantum states we look at are single-particle plane waves, which have infinite "size," if you were to claim the idea of a "size" is applicable.

I know that most results online say "yes it is a basic, physical law" because it is outlined as a law in thermodynamics but I don't feel like it answers whether or not it is a physical law itself or some emergent thing. I was listening to "Why This Universe" podcast, which is hosted by some people at Fermilab, and they were discussing it briefly and ultimately like (paraphrasing) "I don't know if it's an actual physical law or just an emergent one" but also expressed it was something they hadn't discussed or been asked about much before, before moving on.

Could the physical laws we know of have parameters in such a way that would result in a universe without any entropy? Or could it seem to always be there?

I'm learning about Langmuir probes and I'm confused about the difference between the plasma potential and the floating potential. 

So if my plasma is placed in a grounded metallic vacuum vessel, the bulk of the plasma will be at a positive potential with respect to the vacuum vessel, correct? This potential is the “plasma potential” (Vp). It acquires this potential due to the (initially) higher flux of electrons out of the plasma (compared to the ions) to the walls. This magnitude of this potential is such that the currents of ions and electrons out of the plasma to the vessel are forced to be equal. Do I have the right idea here?

When it comes to Langmuir probe theory, the floating potential is described as being a distinct quantity from the plasma potential. Assuming the probe is being biased with respect to the same grounded chamber, the floating potential is defined as the bias voltage "at which the electron and ion currents to it are equal". So in this case, is the floating potential of the probe simply just ground? It seems like in general, this is not the case, hence my confusion.

I have also seen the floating potential described as the "potential an electrically isolated surface acquires with respect to the plasma". By electrically isolated surface, do we mean some conductor that is isolated from any other conductors (like, hypothetically, a metal surface just floating in space in the plasma)?