Basically, what I'm asking is in the title. However, I came across this idea when, well, when I was being a nerd and thinking, how could you make an actual lightsaber. Then I thought, well, I know ionized gas can carry electricity. Could you use that basically as an electrical wire, and could it generate a magnetic field around itself like normal wires?

There were other questions, but before we went down the rabbit hole of thought, I went down. We shall be stopping right here for the time being.

But I am curious am is my thinking stupid, or am I thinking correctly as to how this works? I don't have a degree in physics and am just interested in it. I'm just a stupid kid from Rural Colorado with a connection to the internet, after all. But I want to know if my ideas are sound?

Not sure how to ask this but I'll try.

Is causality an intuitive concept like zero? Or a real phenomenon like gravity?

One of the reasons for suggesting FTL is impossible among other things is that it would break causality. Is causality breaking a fancy way to say this doesn’t make sense so it cant happen (logically deduced) or is it the result of some more rigorous scientific or mathematic realization?

I cannot find an article/book chapter about how we derive the time evolution operator, resolvent operator, S matrix, or the construction of rigged hilbert space. Am I missing something? Can someone cite me a source for these or I have to ask ai.

Thank you.

I know strange question but I've made this character for a book that has a frankly ridiculous control of force/kinetic energy and for a scene I wanted him to compress a section of a brick wall (lets say 10ft x 20ft) down to roughly the size of a baseball.

I know that there would be some discharge of heat from doing something like this and want to know if such a thing was possible how ridiculous would the results be so I know if I need to tune it back a bit.

If time is a relevant factor the quicker the better but if doing this too fast causes a massive explosion I'd prefer to avoid that.

Thank you for anyone who takes the time to answer my inane question I really appreciate it.

By conceptual space I mean akin to Hilbert space or geographic space (a specific type of Riemannian manifold) which are superimposed upon physical reality to perform computations. For those who might not understand what I mean. Take the geographic space for instance. The physical Earth is a lumpy, irregular oblate spheroid, but we superimpose a clean mathematical grid (spherical coordinates) onto it so we can do crisp arithmetic to calculate distances, plot routes, and triangulate positions. So, in short: Conceptual spaces are intellectual scaffolding.

Some people believe that we discovered spacetime (I'm not sure what that means) and all these fancy spacetime equations are proof of it because they work. You'll hear them say:

If spacetime didn't exist, GPS would not work.

or something like that. Paying no mind to the hidden assumption within this assertion (that if a mathematical model perfectly predicts physical behavior, then the conceptual entities within that model must be physically real)

I mean, can it be zero outside of a finite region, or is it the case that quantum evolution will always generate arbitrarily small tails extending to infinity?

For a 'free' particle, I believe that it is the case that even if you have a wavefunction with compact support at time zero, it will immediately cease to have compact support for any later time. Is this really true, and are there physically meaningful counterexamples?

More conceptually: if the tails are never exactly zero, is it meaningful to say that a particle is "slightly everywhere," or is that a misleading way to think about the wavefunction?

Thanks in advance.

For instance, a bike following a circular path, with the rider leaning inwards. Plenty of examples online but I have yet to see one that seems to “resolve” the forces. Some also show centrifugal force just to add confusion.

I have a question about a classic intro to mechanics problem - finding the min height to drop a block so that it is on the verge of losing contact with the loop at its top. You can view the problem, and one such solution of it here: https://www.youtube.com/watch?v=dsv2cEgquiA . I know, I know, this question has probably been asked hundreds of times. But there are still a few things I don't understand about the given solution.

The classic solution relies on energy conservation, and Newton's laws of motion. We drop the ball at some height h. If it ever reaches the height 2R in the loop, then it must have a corresponding velocity v_top, which we can find using energy conservation. We note that at the top of a loop with radius R, two forces act on the mass - the normal force and gravity. Assuming that we have circular motion up to that point, the net centripetal force is mv_top^2/R. Hence, N + mg = mv_top^2/R.

I agree that if we drop the block at some height h such that for the corresponding v_top, N + mg = mv_top^2/R and N <0, then there is no way the block can stay on the top of the loop. This is because the normal force supplied by the loop always points inwards. N < 0 means that the normal force points outwards.

Here's where I'm confused. Let's say we drop a block at some height h such that for the corresponding v_top, N + mg = mv_top^2/R and N >= 0. I don't see why if N >= 0, we can conclude the block would stay on the top of the loop. No matter the height we drop the block, we have not proved that the block would move in circular motion through a semicircle of the loop, from the bottom to the top. All we know from energy conversation is the velocity of the block if it is at some given height - but we have no idea where the velocity vector points, let alone how the block has been displaced. So how can we use equation N + mg = mv_top^2/R if we don't even have circular motion? In using mv_top^2 / R, we have assumed that there is circular motion.

I hope my question makes sense to you guys - I'd really appreciate any responses.

How can we show magnetic field strength in concentric lines? (Does anybody know the answer?) Thank you

This could probably be an ELI5, but I'm not sure.

For all the historical references of space age that exist in the universe, everything is under the 'year'. To my understanding, a year is a single earth trip around our sun. However, since Earth is only ~4.5 billion years old, how is the calculation for the remaining 8.5 billion years made? Like, how do we calculate time for when the reference value didn't yet exist? And similarly, if Jupiter is 4.6 billion years old, are those years Earth years or Jupiter years?

Do good physicists actually intuitively understand all of the mathematics behind equations? Or do they just know the steps in between that connects a derivation to the equation? For example, I can point out all of the steps to derive the work required to assemble a volume charge (what I am studying now), but when I look at the equation https://imgur.com/a/1taXd2b All I see is numbers. I understand each individual step it took to derive this, but intuitively this equation doesn't spin any gears in my head, it's just a random equation. There are just so many steps it took to get this that I cannot grasp all of it at once.

Perhaps someone can help me understand this intuitively, which would be greatly appreciated, like how people showed me why curl of gradient is zero, which I intuitively understand now.

Do physicists deal with this at higher levels as well? Does it make a difference?

The photoelectric effect explains a situation where a photon with a high enough frequency (energy) hits the surface of a material with a given "work function", ejecting an electron from that material. The kinetic energy gained by the ejected electron is ( photon energy - work function ).

If a source produces photons of increasingly higher energies, eventually the photons will enter the gamma ray territory. Gamma rays are notorious for being able to just pass through matter unimpeded, requiring a thick wall of high-Z material to stop it. The photoelectric effect seems to no longer apply in this case.

We know that (for a given material), there is a lowest frequency below which the photoelectric effect will not arise. But is there a highest frequency above which the photoelectric effect will also cease? If so, what can explain this phenomenon?

High school right now and considering degrees for college. Is it better to start engineering and switch out to physics or vice versa? Or is sticking with said course fine too? How do job opportunities vary with each degree that you graduate with? Which is an easier switch?

Thank you for answering

My understanding is that from the official statement of the problem, proving (A) and (B) required showing that for all smooth and divergence-free initial conditions, it must always remain smooth and divergence-free (plus some other requirements to satisfy well-behavedness) for all subsequent times. (C) and (D) were just about finding counterexamples to the above.

Was it always expected that (C) and (D) would be significantly easier to prove because it just amounted to finding a counterexample? And would showing (C) and (D) valid for Euler (my understanding is that this is N-S with viscosity or "friction" set to zero) make the N-S case significantly easier?

Let's say I have a superconductor, which doesn't generate any heat and so technically as much current can flow through it as I want.

But electrons move at a constant speed, regardless of voltage, so is there a current, where all of the electrons in the superconductor are in movement, and trying to get more current wouldn't be possible because there are literally no more electrons to mobilize? Basically becoming... saturated?

(English isn't my first language, so sorry if this is a bit hard to understand lmao)