Gravitational Definition and 1000 Threads

The man floating inside the elevator travels through space at constant velocity, and soon reaches proximity to a planet. To an outside observer, the elevator appears to change course and accelerate towards the planet, so he reasons there is a force acting on the elevator, changing its course and...

Hi all, I've been wondering: Thinking of Arthur Eddington's relativistic oriented 1919 eclipse observation, would the photon deviation due to the Sun's gravitational imposition have caused the photons to exhibit a qualitative redshift due to the time photons had spent within the Sun's...

Hi there I have been attempting the parts to this question and I'm finding some trouble on how to answer the last part which is d)iii Here is what I have done for the rest of the parts and what I think I should start off with in part d)iii Thanks!

Below, I have already solved - I assume - correctly for question 1. Question 2, I am nearing to what I believe is the solution. Question 3, I simply have no idea where I should begin considering that it is interconnected with question 2. With that said, below is the lengthy and somewhat tedious...

Is an object with escape velocity in gravitational freefall?

To begin with, I posted this thread ahead of time simply because I thought it may provide me some insight on how to solve for another problem that I have previously posted here: https://www.physicsforums.com/threads/special-relativity-test-particle-inside-suns-gravitational-field.983171/unread...

Below is an attempted solution based off of another user's work on StackExchange: Source: [https://physics.stackexchange.com/questions/525169/special-relativity-test-particle-inside-the-suns-gravitational-field/525212#525212] To begin with, I will be using the following equation mentioned in...

If there are three bodies A, B, and C arranged linearly, and B is free falling towards C, will the gravitational presence of A affect the rate of free fall of B towards C?

Is there any astronomical indication that gravitational force between dark matter might be weaker than between visible matter?

In this paper by Carlip, a comparison is made between electromagnetic and gravitational aberration. For the latter case, he takes as a study subject the Kinnersley’s “photon rocket”, an exact solution which is known to have the strange property of not producing any gravitational waves, even...

By the time the gravity wave reaches us it is very small in energy, I assume. We do not know how to make gravity waves in a laboratory but we have a place where we have a very sensitive gravity wave detector. If we had a lab set up a few blocks away we might be able to do various experiments...

In the Lagrangian (L1) point between two hypothetically massive (and close) objects , is gravitational time dilation effect summed or canceled, or something else?

Here is the most recent one:

I am trying to derive the gravitational binding energy of the cluster. Its given as $$U = -\alpha \frac{GM^2}{r}$$ Now for the derivation I started from $$dU = -\frac{GM(r)dm}{r}$$ I I tried to write ##dm = \rho(r)4 \pi r^2dr## and do it from there but I could not do much. Any ideas how can...

Hi, Gravitational energy in de Sitter has equation of state w=-1 (cosmological constant) and w=-1/3 (curvature energy in open or closed de Sitter). Is this just gravitational radiation, and how does this accord with the equation of state of photon radiation w=1/3? Does this mean that densities...

Hello! I need to do some analysis for a project with the SXS gravitational wave data: https://data.black-holes.org/waveforms/catalog.html but I am a bit confused about the initial conditions of their simulations. I read the paper they published about the data (it can be found at that website)...

Ok, so I've been on a kick trying to really understand why QM and GR are incompatible. I think I get that GR can't be realistically converted into a quantum field because it creates some infinite series that you can't use the normal tricks you would for other QM fields. Hard block, ok got it...

The is a question about gravitational time dilation and escape velocity. As others have pointed out, you may use escape velocity to calculate gravitational time dilation in a gravitational field. (Interestingly, you can't use gravity to calculate gravitational time dilation, which makes...

F=Gm1m2/r^2 2.67 = (6.67x10^-11)(m1xm2)/25000000 M1xM2 = 1 x 10^18 M2 = 1x10^18/M1 (Equation 1) From the question stem, we know M1 + M2 = 2.5x10^9 (Equation 2) So, substituting Equation 1 into Equation 2 we get: 1x10^18/m1 + m1 = 2.5 x 10^9 I'M STUCK FROM HERE ONWARDS... in the solutions...

Hello, I hope you are all very well ! Let's say a man, standing on point "0 m" throws a ball 10 m in the air. The gravitational force goes in the opposite (down (always)) of the action (up): I supposed it's -9.81 m/s². The same action but this time the man stands on the point "10 m" and the...

I am interested in knowing how to calculate the gravitational wave (GW) spectrum with inflation as a source, I have some background in inflation but I am not so familiar about calculating the GW spectrum. I am reading a paper (https://arxiv.org/abs/0804.3249) about it, however, a big part of it...

For the first part, I considered the Force acting on it by all charges as given by $$\vec {F} = \Sigma_{j} \frac{m_{i} m_{j}}{\left(r_j - r_i \right)^{1.5}} \vec{r_j} - \vec {r_i} = \Sigma_j m_i \vec {g_j} $$ Where ##\vec{g_{j}}## represents gravitational acceleration of ##m_i## due to jth mass...

I'm reading on Wikipedia about quantum field theory and read this: "Quantum field theory naturally began with the study of electromagnetic interactions, as the electromagnetic field was the only known classical field as of the 1920s". Why wasn't Newtonian gravitation regarded as a classical...

According to wikipedia, the strong equivalence principle states “the gravitational motion of a small test body depends only on its initial position in space time and velocity, and not on its constitution, and the outcome of any local experiment (gravitational or not) in a freely falling...

If the sun has a gravitational influence on Earth and on its moon then why isn't the moon revolving around the sun. If the gravitational force of sun is large enough to make planets like Jupiter revolve around it (which has a greater mass than that of the moon.) Why not moon?

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I am trying to create a simulation for a gravitational 2 body problem. But I am kind of having trouble to define the equations that can be solve numerically. From an inertial frame I defined the position of the two objects as the ##\vec{r_1}## and ##\vec{r_2}## with masses ##m_1## and ##m_2##...

I think choice B is correct because when I draw the free body diagram of each object, there are three forces acting on each of them and the resultant force is towards the center. Choice C is wrong because the net field at center is zero. I think choice D is also correct because if the...

Please, I need a good books about the meaning of "Gravitational and Capillary waves "

Seems gravity waves are longitudinal waves, similar to sound waves as it is produced by the vibrations of spacetime? So in theory, if we can produce a powerful enough gravity wave, can we hear it? G-waves are usually produced by merging binary neutron stars or black holes. These celestial...

like a shot bullet or arrow has negligibly more gravitational force than a still bullet or arrow?, this is what I'm asking, m=e/c^2 F=Gm/r^2, thus, F=Ge/(c^2*r^2) where e represents the (mass of the object + energy added to the object) thus more the energy, more the gravitational force, even...

(Throughout all my post, I will refer to “gravitational potential energy” just as “potential energy”) Hi! I have this confusion about when is potential energy positive/negative and how it is related to how we define our axes. I think it is easier to understand my confusion with the following...

I suppose we can just find the net x components and y components and then go from there. Σ Fx = F(mass 1) - Fx(mass 2) G* (m^2)./d^2) - something I'm not sure how to express the component forces of the 2nd mass

Is it fair to say that all energy from a Gravitational Wave that enters the photon sphere of a Black Hole is destine to become part of that BH? And other parts that remain just outside of the photon sphere would experience gravitational lensing? Perhaps focusing the GW to an area of much...

Gravitational energy is the potential energy a physical object with mass has in relation to another massive object due to gravity, so, does an object outside a gravitational field have no gravitational potential energy? For example, the Earth is 4.5 billion years old, so it's gravity stretches...

Summary: Gravity and ageing Hi I am new here, please may I ask, A celestial object creates gravitational pull, as the universe is expanding and accelerating, the spaces between objects unaffected by gravity, are they subject to ageing. A craft on a course towards an area would occupy those...

A quick search turned up Simaciu, Ion. (1997). Chromatic aberration of gravitational lens. 10.13140/2.1.1133.6003. The math is beyond me so I first made a basic assumption that chromatic aberration of gravitational lenses worked somewhat analogous to a prism in that red is bent less than other...

Usually when setting up an energy equation I use the general form, (Initial KE) + (Initial PE) + (Any other work done to the body) = (Final KE) + (Final PE) ... For this I said the initial GPE and KE are 0, and the work done by the field is GMm/x (derived by integrating a force of -GMm/r^2 from...

This is based on "Concept Question 10.4" in Andrew Hamilton's General Relativity, Black Holes, and Cosmology. I have modified the question somewhat in order to focus on what seem to me to be the key issues. Suppose we have a spherically symmetric ball of stress-energy surrounded by vacuum. More...

I wonder why electromagnetic waves don't escape from a black hole while gravitational waves (obviously) do. What is the difference between the two kind of waves? And between gravitons and photons? thank you for your attention

Under what circumstances are they different?

I am reading the following paper on the basic physics of a binary black hole merger: https://arxiv.org/ftp/arxiv/papers/1608/1608.01940.pdf Imagine two black holes orbiting each other until a point they merge. As you can see in Figure 1, the wave period is decreasing and thus the frequency...

Friction is commonly thought to arise from the electromagnetic forces of the atoms at the boundary between two surfaces in contact. However it occurs to me that, in addition to charge quanta, there are also mass quanta present in this system and they could very well play a role. Now, I'm just...

Gravitational waves are produced by accelerating masses. Since all space is curved -- more curved near large masses stars, less curved in intergalactic space -- all moving masses are being accelerated to some degree. Do all moving masses therefore produce gravitational waves? If they do, will...

Two black holes that are orbiting and collide give off mass in the form of gravitational waves before the collision. Do these waves get absorbed by something, or is this mass lost to the universe?

Does relativistic mass make a proportional gravitational effect on observer it flies by? Does 1 ton (resting 1 ton) of lead moving relatively observer at some speed close enough to C may appear as a micro black hole? What abort Hawking radiation in this case? Does it mean that we may convert any...

Hi, Could you please help me to clarify the following problem? In the gravitational field of a mass, the force on a body in steady state comes from the gradient of the gravitational potential - or the gradient of speed of time. But what about accelerated reference frames? I assume that there is...

In Special Relativity, you learn that invariant mass is computed by taking the difference between energy squared and momentum squared. (For simplicity, I'm saying c = 1). m^2 = E^2 - \vec{p}^2 This can also be written with the Minkowski metric as: m^2 = \eta_{\mu\nu} p^\mu p^\nu More...

Do all black holes have the same gravitational pull yes or no, and if not, is it possible that if space and time bends on itself and connects two black holes that the one with the strongest pull will continue as a black hole and the weakest will turn into a white hole considering the amount of...

Why do we use the equation ##\frac {1}{2}mv^2 = \frac {GmM}{r}## to derive potential velocity, and then put that in the Lorentz factor in order to derive gravitational time dilation? Shouldn't we be using the relativistic definition of kinetic energy -> ##mc^2(\gamma - 1)## to derive the...