Gravity Definition and 1000 Threads

I'd like to ask about a hypothetical situation. A human, wearing a jetpack, for example, accelerates forward with 200,000 m/s^2 and therefore, experiencing extreme g-force of roughly 20,408 g. If there will be a hypothetical device that will be able to redirect the gravity force (g) to elswhere...

Physicists had success in developing a relativistic quantum mechanics, also Quantum Field theory. I wonder why it's not the same with a quantum gravity theory. I suppose this is mainly because we do not have good emphirical information from a place where Einstein's theory fails: black holes...

Preface There are lots of times in physics when we use approximations of a more accurate or fundamental physics theory because it is easier to work with. For example, in quantum chromodynamics (QCD) lots of calculations are done using the Schwinger-Dyson equations rather than the actual...

Homework Statement 1. Homework Statement The Earth turns once around its axis in 24.0 hours. We will assume that it is perfectly spherical, with radius 6400 km. The mass of the Earth is taken to be 6.00 × 1024 kg. The gravitational acceleration on the surface is taken to be g = 9.80 m/s2 . a)...

Using special relativistic calculation it can be showed that magnetism is a result of electric charges in motion. using the same argument, why can't we find a magnetic force like thing for gravity?

Can someone comment on https://arxiv.org/abs/1705.00626 ? It looks quite technical, but potentially very important.

Please see the below image, it is a closed and well sealed circulated pipe structure, fully filled with water and no air inside. The density of that green object is greater than water (say 1.2 while water is 1). In this situation, will the green object be sunk? Better with some explanations...

I've seen a little bit about the gravity light. I think it works in a simple way, a weight at a certain height has gravitational potential energy depending on how far the weight will fall, this quantity represents the total energy we have at our disposal to power a light. Now we normally think...

Can someone please tell me how the energy field created by warped space (gravity) and centred at the Earth's core dissipates? Is it the pressure/compression of this force/energy that makes the core so volatile? Whilst time slows at altitude, do we become lighter, as we are further away from...

I know two essential points where General Relativity plays a central role in String Theory: i) definition of the theory using a target spacetime with some Riemannian background metric in the Polyakov action and ii) recovery of the Einstein field equations as conditions regarding conformal...

Hi, I am seeking to understand better how this well accepted idea: "...according to general relativity, gravity is a manifestation of the geometry of spacetime." (https://en.wikipedia.org/wiki/Loop_quantum_gravity) is compatible with the equally well accepted idea that gravity travels at the...

The mainstream interpretation of GRT equations is, that additional double amount of angle of bending of light (Newton vs GRT) is caused by gravity (which is interpreted as curvature of spacetime). But when looking on the equations, it seems that this additional amount of bending is caused by...

I'd be extremely grateful if anyone could help me with this ... its mainly part iv) that I'm stuck on but the other parts build up to it! Thanks very much! 1. Homework Statement I have a wheel shaped space station of radius 100m rotating about its symmetry axis (defined to be the z axis) at...

If I understand space time correctly Gravity is not a force acting on a body but rather the effect of a mass on space time causing a distortion which effects the movement of another mass through that space time. If Gravity is not an actual force then there are only three forces left to be...

If we were to able to detect gravitons then is it not that the basic assumption over which the general theory of relativity is flawed ?

Okay, I know there are many other discussions regarding this exact topic, but I might (probably not) have found an easier way to think of gravity being a force or not a force. Just like light can be a particle or a wave from how you measure it, to my understanding so can gravity. As I am told...

If an object was to lose its gravity for any reason, would it lose its reference frame to the planet and sun. Therefore keep going in a straight line? Or is there some other force that would keep it pinned to the planet. Also does this have any application to sci-fi anti gravity would it also...

As I understand, under Newtonian Gravity, there are no limits for the length of the gravitational influence of an object, except the speed of causality and the age of that object. So, considering the Sun as an example, which is roughly 4.6 billion years old, its gravitational influence would...

Hello! Can you tell me how to calculate the gravitational force between two extended inhomogeneous bodies? (In the general case, we don't know anything about the shapes, we only know the density of masses)

The measurement of g appears to be somewhat limited in extent. You either have simple pendulum experiments that yield something like 10 +- 0.5 or so m/s^2 or - at the other extreme - very expensive gravimeters which will measure to a few ppb. Not much in between. However an educationally useful...

I understand the goldilocks zone but would like to know if there are similar limits with respect to supporting life as we know it for a planets gravitational force (min/max) and atmosphere pressure (min/max.) I understand gravity can affect pressure but so can the amount of atmosphere and do not...

I would like to know the difference between this two concepts, specially the difference between the geometry deformations of space-time that they descript. As far as I know the Schawrzschild metric can be represent by Flamm’s paraboloid, but this shape is not the same that the deformation of...

Homework Statement Two small spheres of 15 g each are suspended from a common point by threads of length 35 cm. Each thread makes an angle with the vertical of 20 degrees. Each sphere carries the same charge. Find the magnitude of this charge. (The correct answer is: 0.58 μC)Homework Equations...

Homework Statement A satellite is orbiting the Earth around an orbit of radius R=2.5R0, where R0 is Earth's radius. What additional velocity is needs to be directed along the radius of the orbit so that satellite escapes Earth's gravity? Homework Equations Total Energy= K + U Conservation of...

Can anyone give a good overview of Horava gravity for a layman. I have only read one thing on it in the Scientific American going back to 2009. Where does it stand today ? How is it understood? Wha are its strengths and weaknesses?

I am trying to understand something. Let me pitch a scenario: You have two asteroids in a vacuum. Each is large enough to be round by gravity. They are separated by roughly the distance from the Earth to the moon. Relative to each other, they are moving at 0 in all directions (aka, they are...

One way to get the universe to expand is with dark energy that pulls at the matter of the galaxy separating it or equivalently for space-time to not be perfectly flat. An alternative, in principle, would be for the gravitational pull between objects like galaxies and galactic clusters to be...

I want to determine the acceleration due to gravity at a place using a helical spring. For this, I've first calculated the extension in length of the spring (##x##) for a particular load (##L##) on the pan. Then I've plotted a graph for ##L## vs ##x## for different values of L and corresponding...

Pardon me if this seems like an incredibly naive question. Perhaps the question could also be rephrased as such: "Why do the laws of classical mechanics hold true with Earth as a frame of reference?" A quick google search turned up the usual answer: the Earth rotates at a constant speed...

From the eqn of motion deduced, I can say that two body, one of 50 kg, and one of 50 g if allowed to freely fall from same height, they will reach the ground the exact same time?? Practically is it possible? How ? They are largely different but same distance in same time?

I recently read an interesting article published in Physical Review Letters in October 2014 - "Identification of a Gravitational Arrow of Time." There were also other articles in several general interest science magazines...

Hi there. I was wondering that if mini or micro black holes could theoretically exist, and if not all black holes need to "devour' matter, then could it be possible that all things we perceive to have gravity could possibly be caused by a mini or micro black hole at the center of massive objects...

Hi all,my second question is this.Why don't galaxies obey gravity? In our solar system the closer to our sun the planet is the faster it rotates.So the outer planet takes much longer for a solar year. When we look at galaxies this gravitational law doesn't apply.The outside stars spin at the...

Suppose I fell from a mountain, which would hurt less: A) Falling on a very huge pile of powder snow or B) Falling on water It's a serious questions! Thanks!

Thanks for visiting and reading this imaginary thread. So, recently I tried to write a novel. It is an ongoing project, and very far from completition. I've read so many Sci-Fi stories before, and some do not follow general physics very well. I want to make a world that is believable, but also...

I have not posted for a while,but something has been bugging me. I would like help understanding that if mass makes a dent in the fabric of space, does it mean celestial bodies are sitting at different depths in the fabric, and does that mean the less mass in an object you are then more likely...

Good morning everybody. I have a problem with this wikipedia passage https://en.wikipedia.org/wiki/Schwarzschild_geodesics#Bending_of_light_by_gravity 'cause it says "Expanding in powers of rs/r, the leading order term in this formula gives the approximate angular deflection δφ for a massless...

Here's a question that I've been trying to solve for a while but keep on running into dead ends, and I can't seem to find any info on the internet to help me. Anyways I was wondering what the integral of torque is? For my specific example I have a rod that is not equally balanced on a fulcrum...

So I've learned that the torque on an object is just: (perpendicular force)(radius) and that has worked well for things like seesaws but it doesn't take into account the torque of the object itself! In the picture the rod has a total mass of 5kg, and by definition the torque on the right is...

This is a just for fun question. I saw the movie "Contact" and they built a machine that generated gravity by spinning rapidly. I assume this comes form general relativity. Is this correct? My question then is this. Is there a simple formula that can be used in which something moving in an orbit...

So I saw this in my physics textbook and according to the highlighted sentence, it is possible for the weight to be greater than the centripetal force when the car is at the top of the circle. But how is this possible when the weight itself is PART of the centripetal force when the car is at the...

An object approaching Earth (or any planet) experiences increasing gravity as it gets nearer. However, If the object could continue until reaching the center it would find itself again in a net zero gravity field. At what point will it experience the maximum amount of gravity?

Consider the 2 objects in the pic. They both have the same mass of 200 kg. They both have a radius of 4 meters. However, the object on the right is hollow, with the walls being 2 meters thick. For the gravity equation, and the object on the right, does one use a radius of 4 squared, or the wall...

I know that the force of gravity is (ma)=GMm/r^2 or a=GM/r^2 This makes sense and If I were to drop a bowling ball down to Earth I'd expect it to fall with 9.8m/s^2. However I can calculate that the bowling ball has its own gravity using the formula noted above. My question is what will be the...

Hi, Hopefully I am not asking to simple questions, but I am just confused from all internet information, and could need some help to shed light on a few things related to gravity, just to make it an undoubtfull fact to work with. When I am correct, gravity is a consequence ? What I have read...

Suppose there is a charged particle far enough of any mass so that there is no gravitational interaction between the particle and any other body. The trajectory of the particle in space-time would appear to us like this (we are at the origin of our coordinate system). Consider that at...

I'm trying to reproduce the results of https://arxiv.org/pdf/1205.1613.pdf where the authors determined the best fit values of the parameters (u,B,c3,c4) in the Massive Gravity action (1) Using the values they tallied for the best fit parameters as outlined in table I and equations (9), (10)...

I am trying to understand why the special relativity is not suitable for describing the gravity. Consider a counterexample assuming it is the suitable and the space-time containing a gravitational mass is flat. Then one could describe the acceleration of a test particle from his inertial frame...

Is the gravitational pull of Sun on moon greater than the gravitational pull that Earth has over moon? Thanks.

In this paper (https://arxiv.org/abs/astro-ph/0603302) the authors derive the field equations for f(R) gravity considering a spherically symmetric and static metric. Now the Ricci scalar only depends on r so you could write f(R(r)) = g(r) for some g. However what it seems the authors have done...