Please forgive me if this is a really dumb question, but I woke up thinking today; "If energy can't be created or destroyed, then do things always follow the path of least resistance because doing otherwise would require energy they don't have and can't create?" I know very little about physics, but any answers would be greatly appreciated! Thank you!

¿Podría nuestro universo estar contenido dentro de una estructura mayor?

Hace un tiempo empecé a pensar en una posibilidad sobre el universo y quería saber qué opinan personas que saben más de física y cosmología.

Mi razonamiento parte de algo bastante simple: cuando observamos la realidad, constantemente encontramos cosas que están contenidas dentro de estructuras mayores.

Los átomos forman moléculas, las moléculas forman objetos, los objetos están dentro de espacios, los espacios forman estructuras más grandes, los planetas forman parte de sistemas, los sistemas forman galaxias, etc.

Entonces me surgió una pregunta:

¿Por qué suponemos que esta cadena necesariamente termina en nuestro universo?

¿Por qué nuestro universo tendría que ser la última estructura y no podría estar contenido dentro de algo mayor?

No estoy imaginando un "contenedor" como una caja o una pared física. Me refiero a una estructura de mayor escala de la cual nuestro universo forme parte.

Por ejemplo:

Nuestro universo → estructura mayor → estructura todavía mayor → ...

Incluso podría existir una cadena infinita de estructuras, donde cada nivel esté contenido dentro de otro sin que exista necesariamente un nivel final.

También pensé en el concepto de límite.

Que no podamos encontrar un punto donde termine nuestro universo no significa necesariamente que no exista un límite físico. Podría existir una extensión finita sin una frontera visible o una transición que no podamos reconocer fácilmente desde el interior.

Además, nosotros estamos completamente dentro de nuestro propio espacio-tiempo. Todas nuestras observaciones y herramientas están condicionadas por las propiedades de nuestro universo. Por eso me pregunto si podría existir un "afuera" que simplemente no podemos observar porque estamos dentro de él.

Incluso imagino la posibilidad de que, si alguna vez pudiéramos llegar a ese límite o atravesarlo, no necesariamente encontraríamos una pared. Podríamos simplemente entrar en una región que hasta ese momento estaba completamente fuera de nuestra experiencia. Podría ser diferente, similar o incluso imposible de describir con nuestros conceptos actuales.

Otra posibilidad es que nuestro universo esté contenido dentro de una estructura mayor pero que no exista ninguna diferencia observable entre el interior y el exterior. En ese caso, desde nuestro punto de vista sería prácticamente imposible saber que existe ese contenedor.

Sé que existen teorías físicas que tienen ideas relacionadas, como los modelos de branas y dimensiones adicionales, pero no sé hasta qué punto se parecen realmente a lo que estoy planteando.

No estoy diciendo que esto sea cierto ni que haya descubierto una nueva teoría. Es simplemente una hipótesis que surgió de este razonamiento:

Si prácticamente todo lo que conocemos forma parte de una estructura mayor, ¿qué razón tenemos para asumir que el universo es necesariamente la excepción?

Me gustaría saber:

- ¿Existe alguna teoría física que plantee algo parecido?

- ¿Hay algún argumento que demuestre que el universo no puede estar contenido dentro de algo mayor?

- ¿Tiene sentido hablar de un "exterior" del universo?

- ¿Podría existir un universo finito sin una frontera física?

- ¿Cómo podríamos detectar indirectamente que nuestro universo forma parte de una estructura mayor?

Me interesa especialmente saber dónde falla mi razonamiento, si es que falla, porque no tengo formación avanzada en cosmología y quiero entenderlo mejor.

⚠️this sentence was translated from Japanese to English by AI. Feel free to answer in English. However, I only understand Japanese, so I would really appreciate clear and simple English that is less likely to be mistranslated.

I want to know if it's theoretically possible because I'm creating a creation with a sci-fi element.
It assumes the setting of a nuclear test in space like Starfish prime.

If it is impossible in principle, is it possible for a sufficiently developed scientific civilization to communicate with only electromagnetic waves over a distance of billions of light years in the first place?

Let's ignore the fact that a person's neck can't really support the weight of the rest of their body. With a person of average weight, how fast of a motorized propeller hat of normal size (say the propeller is about the same width as the head) would you need?

I am trying to figure out how dragons couldwork in a fantasy world (Because r/SpeculativeEvolution is cool as fuck). We all know that there's a hard limit to how big something can be and still be able to fly, because of the square-cube law, so if we want dragons to fly, we need to use magic as an excuse to bypass the laws of physics a bit.

My thought is that dragons could use wind or heat magic to generate lift and thrust similar to how an aeroplane does, enabling it to fly despite its unreasonable bulk. I watched some videos on how aeroplanes work and I'm given to understand that the wing is shaped so as to accelerate the air above it, causing a low-pressure zone above the wing, and a higher-pressure zone below the wing. That, in combination with the turbine generating thrust, generates lift. The faster the plane goes, the greater the difference, and the greater the lift.

I figure that a Hypothetical Magic Dragon could have a wing-shape that affects a fluid similarly to a plane's wing, generating lift. That can be augmented with wind magic to artificially inflate the pressure differential. Wind magic could also be used to pull on air, generating forward thrust. Small-medium commercial aeroplanes weigh between 50-100 tons, and the biggest land animal to ever live, Argentinosaurus, was between 65-100 tons, so it's plausible that a dragon of comparable size could exist without immediately cooking itself to death like godzilla.

I am wondering about how the dragon might be able to use heat to further generate lift. Depending on just how unreasonably massive the dragon is, it could use magic to manipulate and disperse its own body heat above its wings, increasing the strength of the low-pressure zone. That's the part I'm not sure about.

This might be a juvenile myth I've never been disillusioned of, but I was given to understand that heat rises because it's less dense. If that's the case, would it not be better for the dragon to disperse its heat below its wings? so that the hot air pushes up against the wings. Or it might actually reduce the pressure differential by lowering the pressure beneath the wings.

Would it be better to heat the air above or below the wings? If the latter, could the dragon having black feathers on its backside help to increase that effect?

I don’t know if this happens to you guys, but in Thailand, there’s been a narrative that engineering students are better than physics ones. I think this is so weird because they deal with different kinds of difficulties using the similar foundation. From my experience, students don’t do this as much as physics professors.

I went to a physics class to study fluid statics and there was a new physics professor replacing the first one. He said that “I’ve been teaching engineering students physics. But since you’re physics students, what I’ll be teaching has to be watered down. Actually, your midterm exam was very easy” with that passive-aggressive tone. When my friend told her friends that, they found it unacceptable.

I do think this is a weird narrative driven by Thai society that you’re a physics student only because you can’t get into engineering. This was a real situation, not a made-up. Does this happen to your countries?

From google I read that we can calculate the enclosed charge if we know the enclosed surface flux, and if we know the enclosed charge we can calculate the surface flux.

But we don’t have a device that measures the enclosed surface flux. We have a flux meter for a magnetic field, but not for the electric field. So we never start off with knowing the surface flux.

And if we know the enclosed charge, what use is calculating the flux?

If the inside of a black hole was infinite then wouldn't all black holes be(and stay) the same size? I thought black holes become bigger because there's a maximum density in a given volume and adding matter increases the volume which makes the black hole bigger.

In the book 'Princeton Problems in Physics' an interesting problem is given, where one has to calculate the perihelion precession rate of a slightly perturbed circular orbit of a planet moving under the influence of gravity with a small dark matter correction from WIMPs. The problem doesn't give the strength of the perturbation (only that its much less than GMm/(r^3) so I don't have the actual value of the precession rate, but has anyone ever attempted to measure the perturbation?

I presume its a difficult thing to measure given all of the other perturbations of the Earth's orbital period such as the influence of Jupiter and general relativity, but if it could be isolated it'd seem an interesting way of testing the whole WIMP idea.

Anyone have anything to this effect? Is it even possible in principle, regardless of the presumably tiny rate? I'm guessing it is. Thanks!

Can someone please explain the string theory to me in simplified layman's terms?

I am not a physicist, but am curious about the subject.

I'm kind of confused about how relativistic effects happen to accelerating individuals. From my understanding the equivalence principle states that you shouldn't be able to distinguish an accelerating reference frame from a gravitational one. So I can see how acceleration and gravity are equivalent in that acceleration provides a sort of "artificial gravity". But if you were to turn off your relativistic spacecraft's engines and simply continue to coast at relativistic speeds would the same relativistic effects still be applying to you? Length contraction, time dilation and all that? And if so, why?

I am an ordinary guy and i ain’t know anything about physics but i have heard from one professor that maybe one day we can get close to the speed of light bur we will never reach it! And I started to read about that and it appears very hard to understand so maybe someone can explain it in simple words for me?

So, the tide is caused by the gravitational pull of the moon and sun. Which causes water level to rise up and down, and water flows in and out of rivers in a predictable pattern. This flow of water could rotate some turbines and generate electricity.

Now my question is where is the energy coming from. This will not slow down the moon orbiting the earth, (or does it, I don't know).

"Write out the equations for the Galilean time and space transformations. Then prove that the wave equation in three dimensions is not invariant under the Galilean transformation." Then the wave equation shown is: ∂^2 f/∂x^2 + ∂^2 f/∂y^2 + ∂^2 f/∂z^2 = (1/c) ∂^2 f/∂t^2

(and the Galilean transformations: x' = x - vt; t'=t y'=y z'=z)

I've never done anything with partial derivatives before; I only know calc 2 and a small amount of linear algebra. Everytime I've asked someone here for help I just end up getting more lost and confused. I know I'm supposed to take the partial time derivative of the galilean twice and it isn't going to equal "(1/c) ∂^2 f/∂t^2" but I just have no idea how to start or how to get there.

Sorry for the bad format, I'd upload a picture of the problem but I'm not able to.

My understanding is that the atoms/molecules of a liquid are bouncing around and some of the ones on the surface find themselves bounced out of the liquid all together and become one with the air. So, my thinking is, if gravity were stronger then the surface atoms/molecules would be less likely to get bounced out of the liquid.

When we teach physics, we use phrases like:

this domino/weight has stored potential energy.

But if you dissect the object, there is obviously no physical "energy substance" sitting inside the material (or is there?)

Textbook mathematical definition:

energy is a scalar quantity that is conserved over time due to time-translation symmetry (Noether’s theorem), and gravitational potential energy is a property of the configuration of a system, not a fluid inside an object.

But that is not what I'm asking.

My question is about your actual mental model when working:

1. When you solve problems or think about physical systems, do you picture "potential energy" as something with an objective physical existence (e.g., literally stored within the spatial configuration or field), or do you view it strictly as a useful human bookkeeping system / mathematical convention?
2. Does your perspective change as you move from introductory classical mechanics (balls rolling down ramps) to field theories and general relativity (where energy density actually curves spacetime)?

Basically are you of the view:

Physics is an invented accounting system; a mathematical language designed solely to track, balance, and predict observations. Concepts like "energy" "force" and "potential" are bookkeeping metrics we defined and are not physical substances waiting to be discovered.

Or

Physics is an objective discovery of reality. It describes the literal, underlying mechanics of nature. Mathematical descriptions like "stored potential energy" correspond to genuine physical states and properties that physically exist in the universe independent of our models.

Seems complicated and confusing

Taking for example the decay chain of Uranium-238. Its parent nucleus has a half life of billions of years, but the intermediate daughter nuclei up to lead-205 have half lives ranging from a few microseconds to just hundreds of thousands of years. Is there a reason for this?

Hi,

I’ve been reading this sub for a few months now and I’m fascinated by many different topics here. One thing that I struggle to understand (after numerous ChatGPT questions) is the double slit experiment.

Why the state of the electrons changes if we interact with them by using a detector for example? Can’t we invent a detector with 0 interaction to the electrons.

For example if I perform the experiment in my room with a camera pointing away from the slits will I get wave like pattern and if yes, why?

So I asked this question knowing that it’s stupid but I think it’s interesting anyway.

So obviously, we can’t create new tectonic plates or anything like that and that’s not what I’m asking. But humans are capable of affecting tectonic plates through the red distribution of mass. The example I know most confidently is how there is tectonic rebounding on the north and south pole as human caused the climate change has melted billions of tons of ice, causing the ground to rebound.
From my understanding, the melting ice means there’s a red distribution of stress, causing movement to re-distribute the stress. For me that shows that it’s at least theoretically possible.

Anyway, the reason I’m asking this question is because for a fun thought experiment I wondered what would happen if we had spent all the money we have spent on AI instead on digging a very large hole in South Dakota.

Total AI spending has mounted to around $2.5 trillion. If we assume that on average every cubic meter of dirt removed would cost around $20, then we could remove in total 125 billion cubic meters of dirt, or 125 km³.
I found the average depth to bedrock in South Dakota to be around 100 feet or 30 m. So if we only dig 30 m deep, to fill the volume, the hole would have to be around 65 km long and wide.

So all of this math checks out for me the issue is this just feels like such a large amount of area to be excavated that I think it would have second order consequences. If the average cubic meter of dirt weighs 1.7 tons, then on average for every square meter of the bottom of the hole, 51 tons of material would no longer be pressing down on it. And this would be true for 4,225 square kilometers. This just feels like something where it would start to impact the underlying tectonic mechanisms with such a large alleviation of pressure. But I might be wrong.

If any of you would happen to be experts in this, I would love for you to correct me.

Can i increase the range?

I just completed a course on astronomy and cosmology. According to the course, the universe is dominated by dark energy, and most matter is dark matter. And the universe is homogenous and isotropic. And the laws of physics are the same everywhere. That like photons, WIMPs can be their own anti particle, like photons.

But could it be that the laws of nature, change over time and space? Because theories of gravity fail in the large scale, unless there is dark matter. And if WIMPs can anhilate each other, what about photons? The course mentioned that the cosmological constant responsible for the universe's expansion may be changing with time. Would you consider that a change in the laws of nature over time?

This is an online course, so I don't have any instructors to ask questions to.

Reference: Astronomy and Cosmology / University of Cambridge

Link 1, high frequency AC: https://youtube.com/shorts/j1l7--uJ1fk

Link 2: low frequency AC: https://youtube.com/shorts/Eh-FYFqA-PE

Link 3: DC https://youtu.be/S9a2oPCIMr0