Gravity Definition and 1000 Threads

Hello there.My question is:can Newtonian gravity be generalised to include not only bodies with mass but energy also?Thank you.Can my thread be moved to classical physics?

It seems a gravitational field does not alter the electromagnetic field strength. Is this correct? My reasoning: With no gravity, field strength is: F_{\mu\nu} = \partial_\mu A_\nu - \partial_\nu A_\mu Introduce gravity: \partial_\mu A_\nu \rightarrow \nabla_\mu A_\nu = \partial_\mu A_\nu +...

https://phys.org/news/2018-04-dark-interactive.html "Observations using the Hubble Space Telescope appeared to show that a galaxy in the Abell 3827 cluster - approximately 1.3 billion light years from Earth - had become separated from the dark matter surrounding it. Such an offset is predicted...

I'm watching the Stanford University Lecture series: Einsten's General Theory of Relativity presented by Leonard Susskind (who incidentally has to be one of the greatest educators I've ever watched). Whilst deriving the basic divergence equations relating acceleration, mass density, and...

Before I attempt to delve into the math of tensors and curved spacetime, I'm hoping to get a more general intuitive grasp of things. As such, I'm parsing through a lot of lower level articles on these topics, and several that I've come across have argued that Newtonian gravity can be thought of...

It has been hypothesized by quantum field theory that the vacuum is not empty due to the energy time uncertainity relationship. Instead it is filled with a sea of virtual particles popping in and out of existence and renormalized to the observed value we see today in experiments like the casimir...

Normalizing respect m, M, R and k then the normalized force for the case of the bar bell body aligned with the direction of R become Fn = 1/(1+x)^2 + (1-x)^2 is a vectorial sum but in this case the vectors are aligned We can assume x<<1 but is not really material to the problem For...

Hi, I have a question about a hanging rope - how do you find it's mass? I've been searching a long time, stumbled across some advanced calculus involving catenary functions and equations, but couldn't quite figure it out.

If I shine a white light out into space from Earth, and it bends around a black hole and comes straight back to me so I can see it in my telescope, is the light red or blue shifted, or neither? For sake of the thought experiment, let’s leave out cosmic expansion that would stretch it on it’s...

I think Physics should not be weird, there have to be explanations or it might mean we don't understand enough.

Summary:: i) Set up a differential equation that describes how the pressure ##p## varies with the distance r from the center of the planet. Hint: You can base your reasoning on static equilibrium and Archimedes' principle. ii)Calculate how the atmospheric pressure p and the density of the...

https://phys.org/news/2020-09-function-collapse-gravity.html An interesting article I saw yesterday. However, both Nature articles (the summary [https://www.nature.com/articles/s41567-020-1026-2] and the actual technical paper [https://www.nature.com/articles/s41567-020-1008-4]) are behind a...

The only plausible solution for this is rotation (maintain 1g acceleration for long time requires insane amount of energy). What kind of problems caused by this? If living habitats rotate, the whole ship will rotate unless the habitats are detached somehow. It affects manuevering. Is this a very...

So I am working on a project where I am attempting to accelerate an object upward Against Gravity but I am having trouble figuring out the math behind the force needed to do this here is what I have come up with so far,my apologies I am not very good with math I found this equation W=m(a+g)y...

Seeking an equation for gravity where gravitational force goes to zero at large distances I realize the Newtonian formula has trouble with this. And I've heard gravity never goes to zero in relativity. So, maybe a quantum gravity one, that isn't too complicated? Thanks!

Hey everyone, lately I read a german newspaper article about an Asteroid which passed Earth in a very small distance (asteroid 2020 QG, distance of closest approach was about 2950 km). Here is another link about this event written in English: Article about 2020 QG (Businessinsider.com). As far...

There are anti-protons and anti-electrons (anti-neutrons, too?), and "Dark Matter" and "Dark Energy" and, presumably, a "mirror version" of everything in our universe. I don't know a GREAT deal on this subject and I wondered: Is there a "Dark Gravity" that is throwing off our calculations with...

Hi everyone:) I have spend a couple of days trying to teach myself the math of orbital mechanics and have been able to generate a model of the orbital path of Haley's Comet, incorporating realistic distances and periods using Kepler's second law & ellipsoid functions. This is a GIF of the motion...

How does mass determine the bending of space from inside a black hole?REPLY

Hi all, I am looking for a pedagogical (or maybe also historical) paper that describes the attempts of quantizing gravity and the problems that appear along the lines. It is quite interesting to hear from public talks that "when we try to canonically quantize gravity as we did EM we get...

While deriving the formula for the position vector of the center of mass of a system of ##n## particles, we assume some external force ##\vec{F_i}## on each particle and internal forces ##\vec{f_{ij}}## between any two particles. In the derivation, we come to the conclusion that the position...

It takes infinite amount of time to cross the event horizon from an outsider's perspective. But black holes eventually decay from Hawking radiation. So if you wait long enough a black hole won't exist anymore, as it would have decayed into nothing. The in-falling observer witnesses infinite...

Apologies in advance if this has been touched before. If the Earth has 81 times the mass of the Moon, why the Moon has 1/6 of the gravity of the Earth?

Hello all, My second hypothetical question for the day (and last). Suppose you drilled a hole from the surface of the earth, through the Earth's core, and out the other side. The sides of the hole are reinforced preventing any of the hot stuff from escaping the Earth's core, in fact this hole...

Hello all, Suppose you created a 20x20 foot hollow sphere at the most central point of the earth’s core. This sphere is protected from the heat and oxygenated, in fact it’s a perfect 22 degree C inhabitable environment for a human. What kind of gravitational forces would one experience in this...

These are the solution, I'm not understanding something: In the absence of gravity, the total kinetic energy and vertical momentum are conserved). So we have ## \frac{1}{2} m v_0 = \frac{1}{2} M \dot{Y}^2 + \frac{1}{2} m \dot{y}^2 ## ## 0 = m \dot{y} + M \dot{y} ## Ok. But, if the ball goes...

A new preprint establishes that almost all models implementing loop quantum gravity violate the principle of general covariance, and can only satisfy a more limited condition. Is this the huge problem for loop quantum gravity theory that it appears to be? Or is the less strict condition that can...

At the core of the earth, or sun, there is no net force of gravity...every direction is up...does this mean that space is not curved, or more generally, becomes less curved from the surface of an object towards its center?

I am trying to design/build a large self-filling drinking station, aka water bowl, for my goats and cow (see design attached). It's a takeoff of a dog's self-filling water bowl, i.e., uses gravity and vacuum to automatically refill the bowl as the water in the bowl is drank. The rain barrel is...

Is it possible to derive laws of Newtonian gravity from some symmetries?

Why is it that all of the planets in our solar system (to our knowledge) orbit the sun in such a way that they all go around the sun in roughly similar orbital planes? Why don’t we have planets with orbital planes at significantly different angles?

Is the above statement accurate? I am just wondering, aren’t tidal forces also produced by the centrifugal force of a rotating frame? So then what really distinguishes gravity from fictitious forces? (I don’t know any general relativity so if you reference things like the Riemann curvature...

Hi, I don't know if I am in the right part of this forum to ask so if not please move my thread to the appropriate area. I do understand how gravity works on a very basic laymen level like the old Newton apple tree example but beyond that, nothing more.

I have a fundamental question about the pressure and I am not sure if my reasoning is correct. Let's take an example of 7 stones shown below. They don't fall because the center of mass of each stone is falling right under the stone below. If I replace the same thing with a liquid, and we know...

I have started reading about Claudia de Rham's theory of massive gravity (https://www.imperial.ac.uk/people/c.de-rham) and how it can explain the mechanism of the expansion of the universe, among other thing. Lots of infos available on the above link. Has anyone found flaws in the theory or...

I don't know what the general opinion will be of this presentation. It seems ok to me but are there any enormous bloopers in it? (If there are, then the level is wrong and I apologise)

In the solutions (page 6, points ii) and iii)), https://ocw.mit.edu/courses/physics/8-04-quantum-physics-i-spring-2013/assignments/MIT8_04S13_ps1_sol.pdf, it is mentioned that given that the Planck mass is about 20 orders of magnitude larger than a proton and that the Planck length is about 20...

My solutions (attempts) : a> w=v/r | r=6.35x10^6m | therefore V=7.04x10^-5 m/s b> speed of rotation is faster at the equator than the pole as w=v/r. As w remains constant, as r increases towards the pole V has to decrease. c> F = W - R d> Stuck here. I presume that I have to use the equation...

I remember, a few weeks ago, when looking for homework problems I could help with, seeing one as described in the title. I couldn't think of an easy solution and was busy at the time so i made a mental note to think about it later. I finally got around to doing that yesterday, and brushed up on...

Why I think gravity *is* the only force doing work on the rider: 1) The only forces acting on the rider are gravity and the normal force. Broken down into their component vectors, we have: -> The component of the force of gravity moving parallel to the rider's direction of motion -> The normal...

Hi! I'm curious what your take on this is. I'm taking an introduction to U.S. Government course and my professor was discussing the inefficiencies of the public sector; the discussion on politics isn't relevant here but he did make an interesting point about space travel. He argued that the...

A thought occurred to me. According to Einsteins general theory of relativity gravity is not a force. How then does it cause a spring to stretch?

We feel that Earth pull as to the ground but is Earth accelaritng up "in some way" so gravity is also inertial force?? I read that we still don't understand what is gravity...

Hi ... air resistance is the reason that objects of different mass fall to Earth at different speeds. In a vacuum all objects fall to Earth at the same rate regardless of mass. OK - I get it but all the experiments that illustrate this tend to rely on tall buildings or massive vacuum chambers...

The Penrose interpretation postulates that the wave function is real and that there is objective collapse without departing from reality as we know it. It does not make any assumptions; the observations of quantum mechanics and classical mechanics are exactly what they appear to us. "Accepting...

Hi On the Earth , apparent gravity comes from the vector addition of the gravitational force directed towards the centre and the outward centrifugal force. It means that for a pendulum at rest , the direction the bob hangs downwards is not directly towards the centre of the Earth but there is a...

Apologies in advance if this is a naive question. From what I've understood, it's not particularly meaningful to talk about gravity as a force, since it induces the same acceleration (classically speaking) in everything. Whatever device or accelerometer we use, every component of that too will...

I´ ve seen that Newtons law of gravity is considered and used very accurate to predict planet and satellites motion ( eclipses, etc..), but if space time is actually warped as Einstein told, how come Newtons law be accurate when it only depends on the mass and distance of to planets or stars...

HI all! Clearly a noob here. The title says it all. I can't seem to find anything. Thanks for any help, folks.

German V2 rocket engine burn was 70 seconds. Rocket speed about 4000 ft per second. Rocket launched straight up for 3 seconds then turned to a 42 degree angle. There is a lot of counterdicting information online about how high up V2 want and how far it flew but that is not the point. Engine...