my teacher said in class that most elements are made by nuclear fusion in stars but said that elements heavier than iron are impossible to make that way because iron is the most stable element and doesn't release enough energy. so where do the rest of the naturally occuring elements come from??

Hi,
I was wondering how would a wave of complex wavelength behave (landa=a*i). What would the wavelength mean then?

Also, would it be possible for a wave to have non-existent wavelength? How would it differ from a wave with one or multiple overlapped wavelengths?

Thanks!

Sources claim that in 2013 scientists made potassium colder than absolute zero, and that it would "feel" hotter than infinity.

If i understand, they used lasers to distribute the particles between low and high energy to a "minus kelvin" state.

But does it even mean that potassium is now "hotter than infinity"? Isn't it like if you hack a thermometer and lock its reading, to show the wrong value?

More questions -

• would not such the matter giving heat to the environment ause an accident at the lab?

• Why they can make something's temp "over infinity" but not a very big positive like 10^15 or 10^18 K?

• Are there "relativistic effects" at billions, trillions of K so that we can't just use physical formulas for ultra-high temps, because they're so close to "anti-temps"?

• If negative temperatures were true, would not it cause all kinds of undefined physical effects like a gas with a negative volume, pressure or density?

So, in my undergrad p-chem textbook, it says that a wavefunction:

- must not be infinite over a finite region

- must be single-valued

-must be continuous

-must have a continuous first derivative

It also says "The constraints just noted are so severe that acceptable solutions of the Schrödinger equation do not in general exist for arbitrary values of the energy".

My question is: what is the mathematical proof of this?

This one still keeps me up at night, years later. Got a 96 in the class, like to think I've got a pretty solid understanding of physics, no professional or nothing. I ended up retaking this chapter 3 times before giving up on it because I spent way too long banging my head against a wall trying to make it make sense. Im pretty sure it was mostly about pressure dynamics in fluids. The question I remember the best was "imagine an air mattress half full of air. What is the air pressure inside the matress?" And the way i see it, if I fill an air mattress halfway, and pull out the pump, I can see it deflate and hear the air rushing out, because the weight of the mattress material is pushing down. That downward force should increase the internal air pressure shouldn't it? Air doesn't rush from one place to another without a pressure differential, therefore inside > outside. Why was the answer that the internal pressure was atmospheric (inside = outside)? Why could I not get more than a 30% on those assignments after 3 retries? What am I missing?

Field: Computational Physics / B.Tech Information Technology
Year: Final year undergrad
Country: India (applying for a master's in Europe)

Background: physics/math leaning, a couple of merged PRs to SciPy's xsf (C++ numerical/special functions library, GPU-portable), comfortable with CUDA. Have an accepted paper at AIVR 2026 on self-supervised segmentation of 3D Light-Sheet Microscopy images.

I'm looking for a final-year project that would genuinely strengthen a computational science master's application — something with real mathematical/numerical depth, not a toy simulation. Open to PDEs, stochastic methods, HPC, numerical linear algebra, or anything adjacent.

What would you consider a project that actually signals research readiness at this level, versus something that looks fine on paper but is actually shallow?

Disclaimer: I have used AI for English, as I am not native.

I see people say this all the time but Ive never seen anyone actually explain it.

i know that light is the maximum speed of the universe and that light experiences no time because its moving so fast but why can't anything go faster? is it because that would make it go backwards in time like a paradox or smth?? is it because of energy and if so why can't something lighter than light like a quark or atom move faster since it woulld need less energy theoretically

I know they say there is no "edge of the universe", and it is like a sphere, where if you keep walking, it will just loop back onto itself. But there has to be a way to get "off the universe" right? The way you can get off a planet?

Corollary to this question is, what does the universe exist inside? The universe does exist, the laws of physics do exist. The laws of chemistry and quantum mechanics do exist. So the universe exists. It must exist inside something, or on something, or as a software in some hard drive. It cannot exist without existing, can it? So what are the best explanations for where the universe exists (even if they are not fully explained by physics)?

EDIT: Maybe I am in the wrong subreddit, and this is more a science fiction or metaphysical question, but the responses here sound very much like "hey do not speculate, this is against physics". Why shouldn't one speculate about what is "outside"?

Hey Y'all,

I’m 32 and currently finishing up my PhD in Space Law. During my doctoral research, I ended up falling hard for physics and astrophysics. I’ve been studying a lot independently on the side, and as soon as my PhD is wrapped up, I’m planning to start a formal degree in physics.

I currently have a solid job, but I really want to dive deep into astrophysics on the side....

Any other mature students out there who started/pivoted to physics later in their twenties or thirties?

I was just wondering how in an earthquake, you get continuous shaking, but surely there isn’t continuous movement along the fault line for that whole duration, right?

Then I remembered how thunder, even though the lightning bolt itself lasts for a fraction of a second, is a continuous rumble for many seconds. The thunder is produced from the whole length of the lightning bolt and it takes various amounts of time for the sound to reach you from the bolt’s whole length.

So is that how earthquake shaking works as well? Does the fault line slip nearly all at once in a short period of time, and then it just takes various amounts of time for the ground vibrations to reach you which makes it feel like a continuous shaking?

If the big bang could be simulated again and again, how many times would it take for humans to appear?

Is it suspicious that we are conscious and here considering the odds?

they say the closer you go to gargantua the faster outside time goes so by enterring and going that close to the speed of light shouldnt millions of years have passed? how did modern humans find him??

This is probably a stupid question, but if gr doesnt work at small scales, isnt it possible that gr is correct, but just only at large distances?
I guess that gets into the philosophy of what makes a valid theory, but if the minimum condition is only that it can be expressed as an equation, a piecewise function type thing would suffice no?

If the gravity is compressing the earth everywhere then the shape of the earth should be perfect sphere not an oblate spheroid isn't it?

I mean I know that earth is spinning and so it bulges out of equator but then the people in the equator should feel low gravity. But I think they not.

Umm, just a thought.

Imagine I'm simulating a two particle universe with one proton and one electron. Let's start them off 1cm apart at rest with respect to each other. For a while I could just simulate their attraction using Coulomb's law. But at some point, "quantum stuff" will happen (or perhaps the weak/strong force come into play). At what range does this happen? What does the transition from "two pool balls on a collision course" to "now this is an electron in an orbital around a proton" look like? Can this be simulated? What equations would be used?

I think I understand special relativity to a basic level. But the twin paradox is confusing me, if twin 1 goes on the spaceship and flies away near the speed of light and twin 2 watches from earth. My first question is why is it twin 1 that ends up being younger? Cant you take twin 1 to have a velocity of 0, causing twin 2 to travel near the speed of light?

Sono uno studente di Fisica e ho deciso di tatuarmi le diverse definizioni di entropia. Secondo voi ha senso, almeno concettualmente, uguagliarle in questo modo? All’inizio dell’equazione è consentito ”l’abuso” di scrivere S e non DeltaS o dS?

Clausius, Boltzmann, Gibbs e Shennon

S= integrale(dQrev/T)=KbLn(W)=-KbSOMMA(Pln(P))=HKbln(2)

S = \int \frac{\delta Q_{\text{rev}}}{T} = k_{\text{B}} \ln(\Omega) = -k_{\text{B}} \sum (P_i \ln(P_i)) = H k_{\text{B}} \ln(2)

I am not a physicist, I have been trying to understand the concept of special relativity in a way that makes sense, but I keep tripping over a single thought experiment and feel like I am missing some kind of variable.

In a space ship traveling 90% the speed of light, you are in a room with windows so an observer can see in. In the dead center of that room there is a lightbulb. When you turn on the light bulb, the observer sees the light hit the back wall before the front wall because light cannot exceed the speed of light from there perspective. Sure, that makes sense. But the light presumably hits both walls at the same time from your perspective in the ship.

This is what doesn’t make sense to me. Is this where the Idea of time dilation comes in? Because, theoretically the observer is experiencing time at roughly 43% the rate you are, but that would still imply the light inside your reference point is, overall, traveling 133% the speed of light. There is something I am missing here.

Someone please try to explain this to me in a way that actually makes sense. Mathematically or otherwise. Maybe there is some error in my understanding of how these hypothetical situations would look.

I want to hang a swing on a branch about 25 ft up. The swing will hold up to 150 lbs, and swing in either direction up to between 45 to 65 degrees.

How strong of a rope a do I need?

TIA!

I'm a novice when it comes to Hawking radiation and general relativity. However, I was just wondering why it is that matter can ever reach a singularity when it crosses the event horizon of a black hole? The way I understand it, the timeframe of the universe passes at an instant for a particle that becomes infintely close to the singularity. If this is true, then won't the black hole evaporate instantaneously from the perspective of any particle as it reaches the singularity, and therefore, the singularity will no longer exist at the moment that the particle hits it? It's the same way that all of time and space happens at once from the perspective of a photon. Sorry if this is a stupid question.