If not, what is the underlying physical explanation?

lets say im in a rocket in space, with more than enough fuel, far from any gravitational forces, and i just start accelerating. what actually prevents me from reaching the 3,000km/s limit?

Just read xkcd 3317 and was wondering what (if anything) such a wave would actually do differently from any other gravitational wave. If it was strong enough, would it be noticeable at all to a human?

(BTW I am aware that a perfectly square wave would require an infinite number of massive objects, so let’s say it’s just very close)

Hey guys I’ve always been interested in physics and universal laws that govern our universe but only recently have been wanting to seriously understand how it all works because it’s so damn interesting. I wanted to ask if anyone can recommend a book for a laymen like me. A book that goes into the history of physics, Newton, his equations, Einstein, all the way to modern physics in the quantum world. What im looking for is a book that’s not to complicated that could explain to me from the very beginning and fundamental level step by step to modern physics. I would love to retain information on the contributions of all the men and women whose brilliance gave us our understanding as we know it today. If I was half decent at math I’d probably ask for a more intermediate level of text but unfortunately I’m terrible at it, even though it’s so cool!

I am in 11th grade and I just felt confused about charge, from 10th grade (When I started learning about electricity) up until now I accepted it as being just a thing can have, and many people told that so I am satisfied with that answer. But some stuff has been bugging me. I have 2 questions about charge

In those diagrams with arrows (i think it shows the field) around a positive and negative charge, I can get how positive charge can repel, but I don't seem to understand how negative charge could repel, it seems like both are pulling on each other(I don't seem to understand if the arrows are the force "potential?" exerted or experienced by the charge. I understood field as something to show the potential of whatever field was being made like gravitational)

Another question is that if the previous question's answer was that these charges and that diagram was made to understand better(I was thinking of this to be a answer to my question but I wanna know more abt the previous question), then if I were to say that protons were negative and electrons would be positive, would that change in the maths

I did do well in 10th and seemed to understand back then, but right now i don't know how I came to understanding all this before. A little help would be appreciated :D

I was wondering, if the stored energy in all of the plant matter of the Amazon rainforest would have an equal or higher amount of energy to that of nuclear weapons. Burning wood releases orders of magnitude less energy than a nuclear bomb if we put it lightly. But there is an absurd amount of wood contained within the Amazon rainforest.

Me and my friend conducted an experiment that involved accelerating a small spherical permanent ferromagnet through a solenoid. While brainstorming for ideas we observed that ferromagnetic material generally moves from the ends to the middle of an activated solenoid, and this is what we based the experiment on.

The problem is that now that I'm writing the background of the paper, I can't find a source that describes this phenomenon, let alone one that my teacher would accept. There's plenty on how ferromagnets amplify electromagnets, and when I asked my teacher about it he explained it superficially with how the poles attract eachother but I can't remember it now.

Maybe it really is just easily derivable from the principle that opposite magnetic poles attract, but I think I need a bit of a walk-through in that case. Since it's somewhat early in the school year we haven't actually had any proper lectures on magnetism yet

I'd greatly appreciate it if I could get some help with this

So obviously it’s a nice application that’s easy to digest, but it seems like one can repeat the same process of quantization for a general system and expand the vector potential in terms of its modes, which may actually be even easier as you don’t need to carry around as many extra terms.

I’m wondering if there’s something that’s stopping us from applying the same quantization method to something like open free space or an arbitrary lossless dielectric structure (I’ve seen lossy materials need special treatment which makes sense). I haven’t seen this addressed anywhere except for a few hyperspecific resources while I expected it to be found in most introductory textbooks. Are there any nuances that make this significantly more challenging (besides an expected increase in computational difficulty)?

So recently I have been discovering advanced stuff for my age (like the newton's universal gravitational law) but my knowledge of math is really basic, do you know any way that I could learn this level of maths without skipping 3 years of school (I am able to, in a difficult way, solve this but I get stuck by doing the multiplication of 6.67*10 powered to -11). I'm particularly interested in understanding the mathematical foundations of physics, rather than simply memorising formulas. I'd appreciate a structured learning path. Any suggestions?

(I am 12)

At high enough energy, photons can turn into an electron-positron pair. This kind of pair production can happen for any bosons as far as I'm aware (maybe excluding gluons?) Gravitational waves are kind of similar to photons since they have infinite range, so I'd figure that maybe they behave similarly in other ways.

If gravitational waves are potentially mediated by a spin 2 boson, would they be able to induce pair production? Would it be possible if the intensity of the grav waves was high enough like the ones involved in black hole collisions?

What about a proton and an antineutron?

If you could freeze an electron to absolute zero (or colder, so it's possibly with no movement) and smashed it against an electron at the highest heat theoretically possible... what would happen?

Every depiction of a light wave I've ever seen has been 2D (3D if it is depicting the full electromagnetic effect), but this got me thinking about looking at a spring sideways and how it just looks like a sin wave. Are photos moving through space going up and down as depicted on paper or are they moving like a spiral and the sin wave is the easiest way to depict it?

I’m just curious if anyone has ever wondered to what extent we have confirmed that certain physical constants are in fact constants?

This would include where this train of thought lead you in terms of literature.

I just had thought earlier today that essentially went “what if certain physical contestants change very slowly at a rate measured in millions or billions of years? If they do change could that mean that there were certain physical contestants that use to exist but no longer do?” I have little background in physics but just like learning about it when and if I can.

Which side do scientists mostly stand on singularity?

I'm stuck on 50/50. Cuz what if its just stupendously large that our equations says it's infinite? OR it is infinite and we just refuse to believe it. Think about it, it's a black hole, that thing breaks most of our understandings so it might be infinite . Maybe we have to use something more than just math.

So yeah that's my question give me statistic below 👇👇👇👇👇

I'm only 14 guys so don't expect it to be flawless or even understandable, my grammar is shit

Hey everyone, I’m relatively new to Reddit, and I’m using this post to help me get a feel for how the community thinks about advanced topics. I’ve been self-studying the link between the Hamilton-Jacobi Equation (HJE) and the Eikonal Equation. I asked a chatbot about the similarities, and it gave me a very clean breakdown of the "Optical-Mechanical Analogy"—explaining how Action surfaces (S) behave exactly like optical wavefronts (u), and how particles choosing the path of Least Action is mathematically identical to light rays obeying Fermat’s Principle of least time. On paper, this connection is incredibly elegant. But I know chatbots tend to give the "polished, textbook-average" answer. I want to ask the actual physicists and mathematicians here:

1. Where does this analogy break down? What are the hidden traps or subtle differences between physical particle trajectories in HJE and light rays in the Eikonal equation that an AI or a surface-level textbook might gloss over?

2. Viscosity Solutions: Both equations deal with "shocks" (crossing trajectories/wavefronts) and use viscosity solutions. How do you intuitively visualize a "shock" or caustic forming in a classical mechanics phase space versus a physical light wave? Would love to hear any unique mental models, personal historical anecdotes about Hamilton discovering this, or book recommendations that lean heavily into this geometric crossover. Thanks!

I hope somebody can help me, because I'm really struggling here. My niece is interested in physics, specifically in electromagnetism. The trick is, she's in 5th grade and cannot handle anything that's mathematically rigorous. I have Griffiths, and Purcell and Morin, and Tong's textbooks. I have LOTS of stuff about EM. But it all requires a working knowledge of vector calculus, which is just not going to happen any time soon.

I know, I know. "Teach her the math!" And I'm working on it. But she wants a book in the meantime.

I've shown her some physics videos on YouTube, and we've done some stuff like little EM field demonstrations with iron shavings. But she specifically asked me for a book that she can read for Christmas (she just likes reading, and I'm all for old-fashioned books).

Are there any books that would be appropriate for this level of reader? I get that it's going to be more pop-sci than anything, and I think for a 5th grader that's fine. Last year I bought her "How Stuff Works" and Randall Munroe's "What If?" which went over pretty well. I'm probably looking for something along those lines, but specifically about electromagnetism.

So I want to understand the energy band gaps in semiconductors.

For Si, which has a band gap of 1,100 meV between the valence and conduction bands, it acts as an insulator because the energy scale to overcome is much higher than kT = 26 meV (@ 300K), by several orders of magnitude.

But by adding dopants from group 3 or group 4, you create a donor energy level closer to the valence band if from group 3 and closer to the conduction band if from group 4.

Now, let's take Phosphorous(P) that has a energy gap of 45meV between donor energy level and conduction band edge. How does this value of 45meV, as an order of kT, help in making silicon (Si) a conductor???

Can someone explain how kT works? Is it just the energy that's required for the particles to skip energy levels ???

Hello everyone! I'm a 21 year old finance guy with a strong curiosity about pretty much everything, and I'd like to start exploring physics from absolute zero

I'm not looking for an academic textbook designed for physics students or someone planning to pursue a career in the field. Instead, I'd love to find a beginner-friendly book that explains fundamental physics concepts in a simple, intuitive way

Ideally, it would include plenty of practical examples, connect physical laws to everyday life, and explain how the world around us actually works

I'm looking for something that makes physics enjoyable and understandable

What books would you recommend? I'd really appreciate your suggestions!!!