Gravity Definition and 1000 Threads

The charge associated with gravitational interactions is the mass. In the Standard Model, charge conjugation is the "flippin" of all kinds of charges (electric, color, etc). So, if we were to, say, incorporate quantum gravity in a beyond the Standard Model theory, what would the full charge...

It came to my attention yesterday this, from my ignorant point of view, amazing paper that describes what it looks as another Theory of Everything: https://arxiv.org/abs/2110.02062 If I didnt understand incorrectly, from first principles / a pre quantum theory (Trace Dynamics, 8D octonionic...

Floating inside a closed spaceship, no windows, not knowing if I'm free falling near a gravity source or far away from any gravity source, are there any experiments that can be made, to determine if there is a gravity source near and if there is such an experiment, to determine the gravity...

I am looking for first articles of quantum gravity in the history which before Matyevei. What is earliest articles of quantum gravity and how can ı find them?

$$\begin{aligned}v=u+at\\ \Rightarrow v=gt\\ \Rightarrow g=\dfrac{v}{t} \cdots (1)\end{aligned}$$ $$\begin{aligned}s=ut+\dfrac{1}{2}at^{2}\\ \Rightarrow s=\dfrac{1}{2}gt^{2}\\ \Rightarrow g=\dfrac{2s}{t^{2}}\cdots (2)\end{aligned}$$ $$\begin{aligned}s=vt-\dfrac{1}{2}at^{2}\\ \Rightarrow...

If: Gravity propagates via "particles" of gravity, and The particles of gravity are massless and so move at the speed of light then how can the gravity particles escape from a black hole? Aren't they as trapped as the photons? It seems as if black holes should present no gravitational field...

i have tried V=Vi - (g*t) with an answer equals to 4 as well as d=Vi(t) + 1/2 a t^2 with an answer equals to 19 my final asnwer was 1.43 and it was still wrong i used formula a=v/t v=14 t=10 i divided 14/10 to get 1.4

When I stand and relax my hand without lifting it. It's very relaxed. Within few minutes, I feel my hands become heavy. Why is this so.

I’m writing a 3DOF sim for a rocket. I’m having a hard time visualizing centrifugal effects from the Earth's rotation on the rocket while it is moving along the rail (acceleration > 0). I know that once it has left the rail I no longer need to account for it since it’s in the ECI frame and...

In this 1965 paper by Weinberg, https://journals.aps.org/pr/abstract/10.1103/PhysRev.138.B988, he describes a quantum field theory of the graviton in a Coulomb-like fixed gauge, where the free graviton has only space-space components and is traceless. This of course makes the field dynamics...

~ Shower Thoughts ~ Twin A is in a spaceship, Twin B is in a spaceship. Both in 'deep space'. B follows a highly elliptical geodesic which goes around a planet (or black hole) with strong gravity, very far away. When they meet again, who is younger and why? I genuinely don't know what this...

My understanding, possibly my ignorance, is that dark matter is calculated to exist from observations that there's not enough matter to fit observations if the current theory of gravity is right. Is it possible to put into a nutshell why the case for dark matter together with current...

Hello! The paper I study is related to string theory and modified gravity theories topics. As they say in page 5 “The four-dimensional effective theory now follows by substituting Eq. (13) into the original action, Eq. (4)” I wonder how did they drive a 4- dimensional effective metric...

Hi, On this link: https://physicsteacher.in/2020/07/11/the-formula-for-acceleration-due-to-gravity-at-height-h-with-derivation/ They prove the formula for acceleration due to gravity at height h, which is: g1 = g (1 – 2h/R). There are similar articles online. When they go through the last...

Hi Pf I am reading the origin of gravity written by Erik Verlinde I have the same problem with a paper written by Jacobson on the same subject. They want to deduce gravity from the holographic principle and thermodynamics. I suppose that they cannot talk about geodesic at the beginning. the...

In a textbook, which is not in Englisch language unfortunately, I found a passage saying that intrinsic curvature of spacetime is just a specific definition. The alternative definition is that spacetime is flat, whereas clocks and rods have variable lengths - which is just Feynman’s bug...

I didn't pay them much attention until I saw the PBS Space Time's one, and I went "What!? Really!? Am I missing something, here, like a brain? Have they all gone crazy"? And then I remembered where I first saw it: In Brian Greene/Horn/e's 2011 The Hidden Reality book. On P14 there is a...

I am an Engineer, so I have some knowledge about physics and calculus. I've seen relativity in university years ago but only briefly. The majority of my knowledge in SR and GR, which isn't much, are from reading, studying and searching online myself. I have seen some definitions that I am not...

It's a puzzle. I have decomposed vector v by using formulas known from physics: m*g*sin(theta) and m*g*cos(theta). I got: ##\vec v = (5, 5*\sqrt{3})## But it has been marked as wrong. Consequently, the rest of my calculations is not correct. Could you tell me, why?

Does anyone have any good laypersons reads to get a good summary the dark matter versus modified gravity? Thanks

Hi, I need to prove that the tension for artificial satellite consists of two points of mass m/2 connected by a light rigid rod of length , the tension in the rod is - $$ T=\frac{3}{4}\frac{Gmm'l}{a^3}-\frac{1}{4}\frac{Gm^2}{l^2} $$ the satellite is placed in a circular orbit of radius a>>l...

As per the summary I don't understand why physicists talk as if gravitons are inevitable, when gravity is just curved spacetime? Why would curved spacetime have a particle?

The equivalence principle states that a person stood on Earth would experience “gravity” the same as if he was in an elevator in space traveling at 1g. I get this. but when Einstein was first exploring this, I read he came to the realisation that a person free falling on Earth (if in a vacuum)...

Can time dilation vary without a gravity well or accelerating a viewer towards light speed? Are there other variables that affect the flow of time?

I was reading Einstein's 1911 paper named "On the Influence of Gravitation on the Propagation of Light" when stated the formula for frequencies measured by observers at different fixed positions (heights) on Earth surface. One observer is at the origin of some coordinate system and measures a...

I imagined all possible quantum gravity theories in one set, of which only one is correct, and further divide these theories into testable and non-testable. Question: how do we know if the correct theory is currently testable? If it is testable, then we need to come up with new theories until...

OK. Gravity is not a force it is a contraction or curvature of space. I was free-falling and now I hit the ground. Why don't I float through the universe, or go upward instead of still trying to go downward. Because I hit the ground, and now there is no force(like gravity) and my free-falling...

Let's say an object far far away from the Earth free falls in gravitational field. At Earth's surface free falling object gains kinetic energy E_1. Let's say an electron far away from the proton free falls in electromagnetic field. At Bohr's radius free falling electron gains kinetic energy E_2...

Hello, I am very new to the concept of center of gravity and I have a question. I wanted to know if the center of gravity of an object is always in the same location in 3-D space. For example, if I was able to find the center of gravity for cylinder/rectangle when its lying flat on a horizontal...

Let's say a mass is gently laid on top of a massless spring. The spring compresses. There is a change in the height of the mass. Therefore, there is a change in the gravitational potential energy: a decrease. The compressed spring now has potential energy (it has gained energy). The change...

If I hold a ball above the ground, it has potential energy. Once gravity pulls on it, it becomes kinetic. What is gravity and how does it convert one kind of energy to another?

I had a bit of a brainwave regarding artificial gravity (outside of rotation or linear acceleration). As we know "gravity plating" is just a plot device to allow sci-fi films and shows to escape the pain of having to accurately recreate a zero-g environment. But then I thought: gravity is a...

It's one of those staples of sci-fi. Unless you're going for a hard sci-fi that uses rotation or linear acceleration to achieve simulated gravity, your starship will likely use "gravity plating". As we all know, gravity plating is just a plot device, usually for shows with more limited budgets...

Could I please ask for help with the following: Given: The centre of gravity of a uniform solid right circular cone of vertical height h and base radius a is at a distance 3h/4 from the vertex of the cone. Such a cone is joined to a uniform solid right circular cylinder of the same material...

With a pure die, all odds are equal. With a pure die, the center of gravity is exactly in the middle of the die. But what if the center of gravity is not in the center? How are the odds then. For example, how do the odds become if the center of gravity is exactly on the line that runs through...

Hi all, I've recently become transfixed with the idea of magnetism and gravity. I have two main questions I'd like to see discussed more. 1. Would it be possible to harness magnetic fields for energy on earth/for acceleration between planets? 1a. Has this been studied at all? 2. Why do we...

So far, I have found g of the foreign planet, Vf of the ball, and realize that GPEiA = KEfA (Am I right here?). Thus, since GPEiA = GPEiE, GPEiE also equals KEfE. I also understand that, since the same impulse is applied to catch the objects, both objects have the same momentum at the moment...

My name is Dilip (James) I am fascinated by physics and have written three books on the subject, which indicates my level of interest.. My latest book “The Electromagnetic Universe: A New Physics” is available on Amazon and describes in detail: a new theory on the propagation of light, a new...

The force is driving the rotation is gravity. My question is that what is the track acceleration? How do I calculate it?

I want to derive an acceleration in the case for a stationary mass in the gravity field. I found the total energy in the GR is provided by a simple equation: https://en.wikipedia.org/wiki/Schwarzschild_geodesics ## E = mc^2\sqrt{1 - rs/r} * \gamma ## So, this is easy to provide acceleration...

Could I please ask for help with the following question. Part 2 is my problem. I have no idea how to begin, any hints would be much appreciated: 1) Prove that the center of gravity of a uniform triangular lamina is the same as that of three equal particles placed at the vertices of the lamina...

At 0:51 in this simulation video there seems to be a brief moment upon merging that these singularities produce what appears to be negative gravitational "Spike?" that seems to bulge spacetime in an opposite metric compared to normal spacetime flatness. Is this a quirk of the simulation or is...

A recurring topic in particle physics, is the possibility of a "desert" above the electroweak scale: no new physics (new particles, new forces) until the grand unification scale or the Planck scale. It's important to remember that the Higgs boson mass was correctly predicted three years in...

I'm re-watching Star Trek TNG and I just started the episode where they encounter Scotty aboard a ship that's crashed into a Dyson sphere. That got me thinking. What would the mass and external surface gravity of a Dyson Sphere be? I've done the math myself, but I'd appreciate someone double...

Could I please ask for help with the following: A lamina ABCD is in the form of a trapezium in which DC is parallel to AB, AB = 2a, CD = a and AD = h and the angle BAD is 90 degrees. Find the position of the centre of gravity of the lamina from the edges AD and AB. The lamina is placed...

[Mentor Note: thread split off from a different thread] https://www.physicsforums.com/threads/heavier-objects-fall-faster.1002022/ Since seeing this thread yesterday, I have been trying to derive the time equation for the collision of two masses due to Newtonian gravity. Unfortunately, this...

Newton thought of gravity as action at a distance. Einstein showed that gravity is the curvature of space-time. Einstein's General Relativity is the best answer, but neither discusses gravity at the quantum level. I tend to think of gravitational force to be the result of matter interacting with...

I remember being told that heavier things fall at the same rate as lighter things when everything else is equal. But this guy does a demonstration of a Xenon balloon falling faster than a Neon balloon. Why? Also an overloaded plane may not be able to fly, but it has the same aero dynamics, it...

Could I please ask for help as to why I disagree with a book answer on the following question: Answer given is book is $$\frac{1}{2}(a+b)$$ Here's my proposed method: Prior to this question there is an example of a similar question: And here is the answer: So, to solve my question I...

Does intervening mass between two stars decrease the gravitational attraction between these two stars? Is gravity a local phenomenon in that local mass interacts with the surrounding gravitational field caused by the local star and distant stars?