Gravity Definition and 1000 Threads

You have a rope hanging over a fixed support with a heavy weight at one end and a lighter weight at the other end. You set the end of the rope with the lighter weight spinning in a circle and let the heavy weight end fall under gravity. As the heavy end falls the length of the rope that is...

The existence of dark matter was initially proposed to address discrepancies between observed galaxy rotation curves and the expected behavior dictated by our current understanding of gravity. Typically, it's argued that stars at the edges of galaxies rotate faster than expected, leading to...

Black holes accrete mass around them and it falls gradually up to the even horizon where mass is trapped by the black hole forever. However, the rate of mass falling from the accretion disk to the black hole ranges from being very fast to very long-lived, depending on various conditions...

2 recent gains on loop quantum gravity theory arXiv:2403.18606 (gr-qc) [Submitted on 27 Mar 2024] Test the Loop Quantum Gravity Theory via the Lensing Effect Lai Zhao, Meirong Tang, Zhaoyi Xu https://doi.org/10.48550/arXiv.2403.18606 and [Submitted on 7 Dec 2023 (v1), last revised 28 Dec...

from ... www.physicsclassroom.com/class/1DKin/Lesson-5/The-Big-Misconception "Free-fall is the motion of objects that move under the sole influence of gravity; free-falling objects do not encounter air resistance. Huh ?? of course it encounters air resistance, doesnt it ? An object...

shouldn't it be a sort of partially GR and partially QM? I mean in a sort of superposition of both theories such that in the specific limit becomes GR and another limit QM, and in the between both regions it's something entirely else, not QM and not GR. Is this possible? I haven't yet done the...

This question is mainly for @A. Neumaier, but I post it in public in case others are interested. The usual reason given for needing to quantize gravity is, heuristically, that, in the presence of quantized stress-energy where there can be a superposition of different stress-energy tensors...

In discussions about simulating gravity in a spaceship by the use of tethered masses revolving around a common centre, the assumption appears to be that these masses must be equal. Would instabilities occur were this not the case? Or would the problem go away simply by placing the hub at an...

https://www.science.org/doi/10.1126/sciadv.adk2949

Can the force of gravity overcome the Planck force? I remember that a long time ago I read that in the universe the Planck force was the maximum force that could be reached. But when Sagittarius A and the black hole at the center of the Andomeda galaxy approach, I have made the calculation that...

I don't know complex mathematics about general theory of relativity but i tried to understand it from internet. Somewhere i heard that in GTR gravity is explained as curvature of space-time not as force as in Newton's laws. If GTR doesn't explains gravity as force then why G which is constant of...

I've never had any physics class before so please bare with me on my lack of understanding. I've been thinking about gravity and its relation to entropy lately and was wondering if my thinking is correct. Entropy seems to be an opposing force to gravity. where gravity is creating gradients...

The Wikipedia article on Quantum Gravity reads: "The observation that all fundamental forces except gravity have one or more known messenger particles leads researchers to believe that at least one must exist for gravity. This hypothetical particle is known as the graviton" To which... yikes...

Stars have mass. This mass has a gravitational pull. The nuclear fission of the star pushes against the effects of gravity. Why doesn't the gravity reduce as the star burns more and more of the hydrogen/helium/carbon that it's made up of? In other words, how can a black hole be created when the...

I want to emphasize that I am not familiar with general relativity. Consider a system of particles with masses ##m_i## in gravitational field of another body ##A##. Total gravitational force exerted on ##A## will not be $$\sum G \frac{m_i m_A}{r^2}$$ where ##r## is distance between system and...

Hi Pfs, I read somewhere that if the graviton had a spin 1, then gravity would be repelling. Is there a formula showing that the attract-repel depends on the parity of the carrier's spin? thanks

Hey there, I just want to know if objects with small mass have their own gravity. To think of it they must have gravity as all matter with mass have gravity. When such a small mass is dropped one meter above the surface of earth would the earths and the small mass gravity combine? If so...

I started by calculating the energy at the Earths surface, which is just -G(150)(6 x 10^24)/(6400 x 10^3) = -0.9 x 10^10, and calculating the energy at the orbit radius, E = -G(150)(6 x 10^24)/(18000 x 10^3) = -3.4 x 10^9, then doing some subtraction we have -3.4 x 10^9 - (-0.9 x 10^10) = 5600 x...

I had a question about this paper (https://arxiv.org/abs/1401.3742) There, the authors indicate that dark energy competes against gravity in oversdensities and can slow down or even prevent their collapse. I have a simple question about this: Galaxies will in principle evaporate their outer...

Is it possible that MOND might be standard gravity plus an additional force that is inversely proportional to distance. One that is also a property of matter? I ask, because viewing this way begs the questions: If two, then why not more, and if more then perhaps a series with a hope of...

To do this apparently, you need to use the work-energy theorem. You can calculate work done by gravity easily. However it was said that work done by the reaction forces from the hinge is zero, I don't get why. Reaction Force from the hinge is an external force on the rod, and all external...

The given answer is g/4. But when I substituted R/4 into the radius, I get 16GM. Am I just using the wrong equation altogether? He also said that you also got g/4 if the distance was 2R.

It is believed that gravity interacts with itself. I assume that gravity between stars increases. Does gravitational self-interaction change the galaxy's shape or increase the rotation curves of stars?

While not exactly correct, we will continue to use Newtonian gravitational force and tension force in the lab frame. We will not concern ourselves with GR, besides the approximation is reasonable for low velocity and small mass. In the lab frame, the forces acting on the pendulum is weight and...

Hi everyone! Not sure if this is the right place, but here we go: I am layman when it comes to physics, so I might be overthinking this completely, but I need to make sure that the physics stack up before I do the actual pipes etc. I have a 1000-litre water tank and below it I have a smaller...

people say that gravity is not a force, that it's rather a distortion of space-time so objets that go to a gravitational center are actually just moving through space in linear direction but there is a problem in this theory shouldn't objects go to the center in constant speed? why are they...

We learned that normal force equal in magnitude as mg and opposite direction, it is reaction force to gravity. 1.If normal force is not equal gravity, isnt this violate newton 3. law action=reaction? 2. If gravity is higher than normal force , this system has net Force non zero,it means...

Hello everyone! I joined this forum to reach out to people much smarter than me. After searching the matter, i realize this subject has been beaten to death for a VERY long time. But, as of yet, I have not stumbled upon a definitive answer to my question. Flipping through my news feed...

Just a quick question, are we attracted by a hydrogen atom billions of light years away by gravity or is my gravity completely masked by earth's gravity and so I am not attracted by the hydrogen atom? I am talking on a very very very small and incomprehensible scale.

I have found some papers (like this one: https://www.aanda.org/articles/aa/full_html/2009/45/aa12762-09/aa12762-09.html) which say that dark energy increases the potential energy in a system of a quasi-stationary gravitationally bound many-body system. It also says that because of this, the...

The Alpha Experiment at CERN has finally produced a paper on whether antimatter falls towards the earth under gravity. The research confirms that antimatter acts identically to regular matter in regards to gravity. Observation of the effect of gravity on the motion of antimatter. Anderson...

Took longer than expected, but now we have a result. Observation of the effect of gravity on the motion of antimatter Antimatter falls down with (0.75 ± 0.13 (statistical + systematic) ± 0.16 (simulation)) g, compatible with the expected 1 g and ruling out -1 g.

Hi, Fairly new to the forum, but trying to post some ideas on new ways to look at gravity, but not sure where the correct place is. Where is the best place to discuss new ideas please? John.

Dear all, currently I'm reading the Dutch translation of Heino Falcke's "Light in the Darkness: black holes, the universe and us" as a preparation on a course on black hole I'm giving later this year. In part 1 it contains a remark about space telescopes, and the author imagines us to travel...

As our sun and the other stars evolved from gravitationally led aggregations of hydrogen gas which permeated our early universe then that is an example of a high entropy system becoming a low entropy system and the so-called "arrow of time etc." was reversed?

Hi! I am trying to understand the physics behind the gyroscopic phenomenon called spin drift. Spin drift occurs to bullets that are spin-stabilized over the course of their flight. Spin drift starts with an induced rotation in a spin stabilized bullet. As a bullet flies through the air...

Data and graphs here (the time is measured every 1/30 of a second, but for some reason, Google Sheets thought 1/30 wasn't a number so its in decimals!!! very confusing!!! so sorry about that!). why is the slope only 4.68, should it not be 9.81m/s^2? is the slope of m/s^2 not supposed to be...

Movement isn't required to achieve gravity, even the artificial kind. Standing on a rotating body requires you to be actually physically standing on it. How is this achieved? Well, by gravity of course. Unless you are tied/stuck to the rotating body, but in that case there is no gravity pushing...

Does gravity cause quantum decoherence? In the microscopic world, gravity seems to act weakly, but in the macroscopic world, it seems to act strongly. Is this the boundary between the microscopic world and the macroscopic world? So a phenomenon like quantum tunneling can occur in the microscopic...

The acceleration near the earth, due to the force of gravity is g. Now every particle when moving in a curve trajectory had a centripetal acceleration towards the center (say the sun) a=(v^2)/R. If this is true why we measure weight only with the account of g? I guess when R is big it might be...

Gravity in the very center of the planet must be zero because all other atoms are pulling evenly around the center. We have a deap gold mine in South Africa and uranium waste storage Norway. Has the force of gravity shown change at these depths. Even at the bottom of the Pacific ocean gravity...

I stumbled upon gravitational variations that do not coincide with altitude, latitude or lunar interference. The only logical explanation I have for this would be the geology or makeup of the earth below those locations. But what is the variation of the Earths makeup below the crust? From my...

I know to break it down into its x and y components and then use Pythagorean: Acceleration in the x direction is Fx/m ---> (7.50 x 10^6*cos55) / (4.50 x 10^5 kg) = 9.56 m/s^2 Acceleration in the y direction is: (Fy - mg)/m ---> ((7.50 x 10^6*sin55) - (4.5 x 10^5* 9.8 m/s^2)) / (4.5 x 10^5 kg)...

It is widely known that the more massive a main sequence star, the higher its luminosity, which is called the mass-luminosity relation. This relation is so important, many authors and educators cannot resist the temptation to include an explanation for it. While I applaud that sentiment...

My studies relate with construction engineering and environment improvements and I have a passion about combinatorics and exact sciences. I'm always in touch with the novel things that pop out in science related media. I don't like when people start make politics upon science findings. I'm the...

Some evidence (Bekenstein, Hawking, Jacobson, Verlinde, ...) points to the idea that gravity is really a thermodynamic theory in disguise. Other evidence (Susskind, Maldacena, Witten, ...) points to the idea that gravity is dual to a lower dimensional conformal field theory (CFT). Are these two...

I have no expertise in this area, other than rudimentary concepts. The following might apply if the visualization of space, as depicted below, represents actual reality, but I don't know for sure. Please help me understand better, you guys! 2-dimensional space The curvatures deform into the...

The Wikipedia section below says that gravity is the earliest to appear out of the fundamental interactions, but wasn't high energy in every area already curving its local spacetime surroundings? https://en.m.wikipedia.org/wiki/Chronology_of_the_universe#The_very_early_universe

all i could accomplish was calculating the distance between P and the ceiling in a horizontal line(6)

Inverse square law would reduce the gravity from the parts of Earth that are farthest from our feet. It'll also reduce the gravity from Earth's center by a lesser amount, but would that be lesser enough so the gravity 20 kilometers under our feet is stronger than the core's gravity or even the...