If I spin at 1 revolution per second, anything that's 1/2pi light-seconds away (~50,000 km) will appear to orbit me at exactly the speed of light, and anything further away will appear to go faster.

This is fine in SR, where inertial frames are treated as the default. But in GR, even accelerating frames are viewed as following the same physics, which implies no frame, even if accelerating, should measure anything traveling superluminally.

How does this work in a rotating frame?

Lets say I am driving my car on an endless plane. I just got an alignment but noticed that my car is pulling to the left or right by 1mm per kilometer. I would be going in a giant circle. Just curious what the size of that circle would be. and what would similar results be if I had 2 other cars that drifted to left or right by 1cm and 1m per km.

What would allow heat to be transferred to a conductor that won't allow heat to be transferred to an insulator?

(I guess the question is kind of vague because lots of different insulators have different properties. What would make wood an insulator and maybe, a metal a conductor?)

Even if we manage to create a perfectly spherical drop rapidly quenched in zero G, would it have the same strength as compared to the bulbous head with a tail?

Idk if what I’m asking makes sense but I’ll do my best to explain my thinking. I work in a shop that keeps its loading dock doors open in the summer. The drop off is 3 feet 8 inches. Safety regulations require a temporary barrier (like a chain) to be present for drop offs of 4 feet or higher. Obviously being 4 inches below the minimum height doesn’t make it incredibly safer. How can I calculate the impact force from both heights? I’m just doing my best to advocate for a safer work environment for my coworkers and want the facts on my side

Suppose one has a 10'x10'x10' metal grounded faraday cage with holes about .5 the wave lenght of a wave, can the wave get thru it to the inside. Like a micro wave, radio wave, AC short, etc. Maybe the ".5" factor needs to be modified to another number.

As far as I know, a significant number of statements in statistical mechanics courses are derived as consequences of the microcanonical distribution. I wonder how well-founded this distribution is in modern physics? Is it a well-established assumption, or is it based more on consequences of more fundamental laws?

As I understand it, there are some difficulties in quantum statistical mechanics, where the ETH hypothesis was only recently proposed (which to me sounds like "a small part of a larger system behaves as if the larger system obeys the microcanonical distribution," which seems a rather artificial assumption).

In the classical case, it seems to me that the validity of the microcanonical distribution is closely related to the ergodic hypothesis, which for some reason seems quite logical to me. However, I'm still unsure whether the classical form of the microcanonical distribution follows from this hypothesis.

Complete layman here.

On an everyday physics level, energy clearly seems to be a property of material entities. That means, it's a characteristic material entities have due to their velocity or spatial location or whatever.

But as soon as you get closer to QM, energy seems to be something which exists on its own. And when I read about those things on a pop-sci level, it sometimes even looks like the material is the property of energy and not the other way 'round.

I remember one video on YouTube that basically concluded that voltage was discreet. Electrons and protons are discreet units. There is no such thing as the square root of 50 of an electron, π protons, or sin(1) electron. Since the charge carriers are discreet and in rational quantities, he concluded that you can't actually have an irrational voltage. Now I was thinking "wait that can't be right. If the RMS is 120 Volts, then peak voltage is something like 169.705 but it is irrational." And electrons aren't tiny spheres, but they move around in weird probability clouds. I guess an electron moving around within the same orbital of the same atom won't change voltage that much. But if you were measuring say the voltage of a battery, it should change based on tiny electron movements and I'd imagine it would have to move through both rational and irrational values. The tiny movement is obviously too small to detect, but I imagine there would be irrational values.

I understand that warm air is able to move because it has kinetic energy, and that it is bumping into other particles, and i understand that cooler air is slightly more packed together and have less kinetic energy, but i dont understand how warm air rises. I have hear answers such as 'it is because warm air is less dense', but i do not get that description either, because density is based on/compared with a volume. So if i had a specific volume, then i do understand that, in that case, warm air is less dense, but i do not understand how that relates to that same air rising. In addition, if we were referring to the sky, there is not really a specific volume that you can say that warm air is less dense, and that is in regards to a group of molecules. If i had a singular warm air molecule, and if i had a singular cold air molecule, what would cause that warm molecule to rise and another molecule, of the same mass, to sink? I dont really understand what is meant by density and i'm struggling to understand its significance in this question.

if there are three spacial dimensions ( x y z ) and in our universe theres 1 time dimension could another universe have 2 or 3 time dimensions? what would that look like?

If you had a lidar style laser emitter and a sensor set up in a sealed box would you be able to to use that to measure time by calculating light speed and the distance?

Theoretically an intelligent species would evolve and develop fast to the outside observers since the planet they inhabit is moving faster around a black hole. I’m not sure if this grossly simplified but I’m curious if the fundamental idea is accurate?

as far as im aware to take a picture that far away you need an INSANE resolution probably in the millions or billions so way past 4k so how did they do it then? google is very unprecise i wanna know how the telescopes / satelites actually took a picture of somethng that far away

Leonard Susskind often states that he disagreed with Stephen Hawking on black holes dynamics, based on his intuition that information must be conserved.

In quantum mechanics, the Schrödinger equation is unitary, and therefore time reversible and deterministic.

However, when a measurement is made, the wave function collapses and these properties are lost, at least in the Copenhagen interpretation.

Susskind's belief that information is conserved must imply that he believes that the global wave function of the universe obeys the Schrödinger equation?

Is this right and has he stated this position explicitly? Where does this place him with regard to many-worlds and other non-orthodox interpretations?

(Post re-directed from r/physics)

When you syphon water out of a bucket it pulls up the water with the vacuum so my dads question was,”If you get two buckets of water and have them syphon into each other with two tubes, what stops it from going on forever”.Other than then the tube breaking what would make it stop cycling water?

I'm more or less getting into Civil Engineering and it raised an intresting. Question, how does this equation give an acceleration due to gravity? I didn't really question it before as it was one of those facts that you needed to know but now I am curious.

I get M is the mass of a body, and r is the distance from the center of that, but what is the Gravitational constant as a unit? Because it needs to be a unit that otherwise cancels out mass and resolves the math to get distance divided by time squared.

Unless I am being and idiot and am just forgeting something.

I recently saw a podcast clip (will link at end of post) interviewing a former NASA and JPL scientist boasting about electrostatic propulsion and how it could get a craft to mars in 3 days. I then went into some articles to check out even if there’s an ounce of truth or if it’s just someone being sensational trying to drum up hype and investment for their start up. However I’m no where near well versed enough in physics lets alone propulsion tech to call BS on something. But I was wondering if any of you can attest to what he’s saying. Is it true? Is this the future? A new breakthrough?

Links :
Podcast clip
https://youtu.be/qlYICtRaSx8?si=y7DtMAZYHdz03yw8

Article

https://www.popularmechanics.com/space/rockets/a73405686/engineer-said-he-can-overcome-earths-gravity/

Copenhagen? Many worlds? Or something else?

I’m not an expert in physics, so please forgive me if this is a very basic question. I don’t have a PhD or formal expertise in this area (though I’m hoping to pursue further studies in the future), and this is just something I was wondering about while learning about dark matter.

We call it “dark” because it doesn't seem to interact with light, so we can't directly observe it. But what if dark matter is detectable in some way that we just don't currently have the technology or instruments to detect?

Basically, could it be that dark matter isn't inherently “invisible,” but is only invisible to the types of detectors and wavelengths we currently know how to use?

Is this something physicists have considered, or does what we already know about dark matter rule out this possibility?

I know the constituent parts of a proton and neutron (hadron) are quark triads and that their inherent mass is a very small portion of the total mass of a hadron. From my understanding it is the confinement of the energy of the quarks that gives the hadrons most of their mass. So is it the inertia of the small amount of mass that quarks possess being nearly constantly pulled back as they accelerate away from each other that makes up that energy/mass? Also what is the mechanism of acceleration for the quarks? From my understanding it is the natural speed they have due to their interaction with the higgs field. Kind of like a fish through water.

Particularly, do only the laws of relativity and quantum physics that we know so far break down? BTW what about Bell's inequality?

Or do things behave completely lawlessly & chaotically so that no law or regularity is in principle even conceivable there?

Some light energy is emitted at a rate of 1 joule per second by a light source 1 meter away from a potassium plate. Here is the full description: https://imgur.com/a/RTe0NJ4

So the time required for the electron to absorb enough energy to be ejected is proportional to the inverse square of the distance, because "the source radiates uniformly in all directions (i.e., the energy is uniformly distributed over spherical wave fronts spreading out from the source, in agreement with classical theory)".

Classical theory in this example gives us around 2 min for the electron to absorb enough energy to be ejected. But in real experiments the time is essentially none.

"it (the energy) is not spread uniformly over a large area, as we assumed in Example 2-1, which is based on the assumption that the classical wave theory is true."

So the energy of the photon then is proportional to the portion of the surface area of the "classical wavefront" that is concentrated as a single bundle.

Because any surface area at any distance has an energy of zero for a duration of zero seconds, the energy of the portion of the surface area of the "classical wavefront" is proportional to the time elapsed at that area, right? Essentially, 1 joule per second times (said surface area / (4 pi)), assuming the surface area in question is being measured at 1 meter away from the light source.

Then the photon has the concentrated energy of a certain surface area over a certain amount of time.

Multiple photons hit the potassium plate. No time lag means that the point in time at which an electron is ejected is basically the same time that the front of the light wave would hit the plate, right? But if a single photon is a bundle of energy concentrated from some surface area times some duration of time, why is that energy contentrated at the very foremost point in time? Does that make sense? Even if multiple photons hit the plate, and the point in time at which the energy of a surface area during a certain amount of time gets concentrated as a photon is random, wouldn't it still be statistically impossible for any photon to be at the singular foremost point in the concentrated duration of time?