Gravity Definition and 1000 Threads

Usually we hear about people working on a theory of quantum gravity, in order to avoid the singularity in the center of a black hole for example. But what if it's the other way around to some extent as well? What if it's gravity keeping quantum objects from doing their greatest reality-defying...

Just wondering if anyone here finds these video/picture leaks about UAP's (Unidentified Aerial Phenomenon) interesting and inspiring enough to try and figure out how they work? Pretty big game changer of technology and would be fun to discuss. I'm hoping at least someone agrees.

"If the Earth were not spinning, you would be heavier as you would feel the full force of gravity."so how does this apply to the moon? the moon does not rotate and therefore you would experience the full force of gravity as stated above,yes,,yet the appolo missions film footage showed...

hello according to GR gravitational force is not a real force rather a space time curvature ok a body in motion follows a sort of invisible rails why doesn't a body at rest remain at rest, then ?

Hi everybody. I recently started to learn GR from a very begginer level. I would like to share with you some lines of discussion, to understand your approach to some specific topics which for me are key to better understand the whole story. If a put an accelerometer on the floor it reads 9.8...

I wonder if someone please could explain what the relationship between a spectral line strength and gravity is? Does the equivalent width of e.g. Ca II decrease with increasing gravity? what kind of processes affects the strength of a line if we change the gravity of a star? Hope you can help me

It is know that Coulomb"s law is similar to Newton"s law of universal gravitational and that gravity is always attraction, and electricity is both attraction, and repulsion. Why is gravity only attraction? I have such an idea that electric forces are gradually inferior in strength to...

Is the Earth getting closer to the sun from gravity?

Calculated maximum range of arrow at 45 degrees with initial velocity measured horizontally is of course reduced by air resistance. BUT initial velocity at 45 is reduced because propulsive force is constant and gravity reduces velocity by about 3m/sec. So not all distance loss is drag. Authors...

So for the work done by the kinetic friction, the displacement along the incline is ##s## as given. What I canNOT understand is why the displacement in the y-direction is used for the work done by gravity i.e. ##W = -mgh## where ##h## is the displacement in het y-direction. This instead of the...

Hello guys, I was wondering if someone could provide me some help on this problem. for (c), I know that it will be 0 as the amount of word done from A to B = the am of work done from B to C. But, What I receive as seen in the picture is 2.11N Which is not correct.. In the first try I used a...

So I have 2 Points P1 and P2. P2 is the center of mass which has an X and Y coordinate. P1 is where I think that it will fall over from and only has an X location. Now what I want is to find a way to get how far the angle at P1 will change in relation to where these points are within a given...

Hi All I was wondering if anyone can assist with a task of calculating whether an MDF unit will tip over if fixed only to the wall behind it with mechanical fixings as shown below. And what force will be required to do so. I've given it a try. Let me know your thoughts, would be much...

So we are finding the L2 Lagrange point, specifically the distance from the earth, or d in this instance. I have used the equation above and I have come out with 1.5 * 10^9 meters as d, or L2's distance from the earth. Can anyone verify this, is the equation correct and is my final distance...

Hello everyone, I know that GR equations are complicated and beyond my scope. But does GR give a simple gravitational equation: Force (as we know it) as a function of distance? (without any complicated tensors). - If yes. What is the equation? Does it give us something similar to Newtons...

Many years I read a lay person friendly article on Horava Lifshitz gravity. https://www.scientificamerican.com/article/splitting-time-from-space-evidence/ Im curious to know how has this theory developed? Is it taken seriously? What are the outstanding problems ? Have there been any impressive...

Could they generate enough lift for 1/11th the weight of a human? Was picturing a giant warehouse and curious if it would work!

Hi everyone. I am new here and have a question that has been bothering me for a few days. Maybe you guys can help me out. Suppose a band gives a 60 minute concert on a planet with extremely strong gravity. This concert is recorded on site on a cassette, which has space for 60 minutes. Then a...

I know passive diffusion rates behave differently on the International Space Station relative to Earth (video of a contained flame experiment burning up there.) However, does the random walk of pollen particles etc. have slowed velocity in comparison to that on Earth? Has been bugging me for a...

When the Webb is at a point on its L2 orbit, (not at L2), what direction is the centrifugal force vector compared to the direction of the combined earth-sun gravity vector on the opposite side? Is the direction of this centrifugal vector ALWAYS parallel to the sun-earth plane? or is it always...

Will there be a compression of matter that the planet is made out of due to gravity when we are talking about planets? If so I would like to know what the effect would be in the example given in the summary.

If a person was rotating on a verticle axis from head to toe like the Earth or quasar. If nothing can go faster than light, from the person's perspective looking at the stars traveling across the night sky, if you increase the rotation of the earth, stars further than a certain critical distance...

I was just wondering how much work is being done in the field of quantum gravity nowdays. Is there still a huge volume of research published on the topic? Are we closer to a "solution" nowdays than we were a few years ago? And also, what exactly would constitute a solution to such problem?

Firstly I would like to start with solving the problem with energy conservation principle which most solutions to the question show. -Gmm/r= 1/2 mv^2 +1/2mv^2 -Gmm/2R Where m= mass of planet r= initial seperation v= final velocity. R=...

Wanted to check with you guys that I'm not going crazy... Exercise 19: Let ##\phi : \mathbf{R}^2 \rightarrow \mathbf{R}^2## be a counterclockwise rotation by angle ##\theta##. Let ##\partial_x, \partial_y## be the coordinate vector fields on ##\mathbf{R}^2##. Show, at any point of...

I understand that string theory has almost no testable predictions, however loop quantum gravity is an enticing candidate for only quantum gravity and it doesn't explain much of symmetry, constants, mixing angles etc in Standard model. There is obviously not enough evidence to create a full...

Hello! I had a random question while playing around with a garbage can that I hoped y'all could help me walk through: Let's say that I have a hinge on a table, rotating with gravity acting perpendicular to it. Energy is provided into the hinge, let's say by a spring, like so: I want to know the...

It's a well known fact that acceleration due to gravity is independent of the mass of the accelerating body, and only depends on the mass of the body it is accelerating towards and the distance from it. One can prove this mathematically very easily. F=GMm/r^2 (equation 1) but also F=ma...

Could I please ask for a help on how to attack this question? A heavy rod AB of length L can be made to balance across a small smooth peg C when a weight of 2W is suspended from A. Alternatively, it can be made to balance across the peg with a weight of 3W suspended from B. If the distance AC...

I have been seeing quite a bit of news on Gravity Batteries, and am curious about the actual energy generated from the stored GPE ? I know GPE = mass x height x gravity h = 50 ft m = 6000 lbs g = 32.2 ft/sec^2 GPE = 9,660,660 joules = 2.68 KWh But what is the actual energy output from this ...

"why size matters in animal behaviour? How can a hamster survive falling from the top of a skyscraper, ants carry over 100 times their own body weight and geckos climb across the ceiling? In the first of this year's Christmas lectures, Dr Mark Miodownik investigates . He reveals how the science...

Hello everyone, I have researched about dinosaurs and pterosaurs and a theory by various authors claiming the only way to explain their great size is with ancient lower Earth gravity . If this is supported theory among scientists then the next question is: How could the Earth have lower...

If the center of gravity changes on a die, how do the odds on each of the eyes change?

If gravity is the affect of time dilation because of the distance from the bottom of an object to the top then wouldn’t that mean that gravity doesn’t exist at the quantum level?

Having re-read "Dragon's Egg" recently, I recall that the cheela, being composed of degenerate matter, would explode if removed from their high-gravity environment and placed in freefall.* (For those who haven't read the story, the environment here is a half-solar mass neutron star with a...

I hope this is okay to ask here. I'm working on a sci-fi short story, and for the purposes of the story I want to have a small ship that maintains its position over a specific location on the Earth's surface. Originally, I thought this would be easy. After all, that's what geostationary...

(I am not sure which forum this post belongs to. Hope someone kindly helps me move it to a proper forum.) In papers, for example, here, here, and here, the authors start from the Lagrangian for matters and gravitational fields, then Dirac's constrained canonical quantization is used. They...

What would be the consequences of such thing? How it will affect physics theories and the world?

Hi, there. I am interested in quantum gravity. But I am not sure how to find review papers about its recent developments. I tried "quantum gravity" on google scholar. But I could not find a suitable review other than that about loop quantum gravity. I am not sure what are the other approaches to...

Rovelli points to three pieces of existing observational evidence that should guide future quantum gravity research. Bottom line: * abandon Lorentz invariance violating quantum gravity theories, * abandon supergravity and string theory, and * stop working on the anti-deSitter/conformal field...

I think you would do force of gravity= mass x acceleration acceleration of gravity= 9.8 m/s mass 75 kg 75kg x 9.8 m/s =735 N i don't know if that's right but i have no idea how to calculate it after he lands, any help would be greatly appreciated!

Suppose I have an object consisting of a hemisphere of radius r and a cone of radius r and height h. The shapes are glued to each other on their faces and the object is set standing on its hemisphere side. Depending on the value of h, the center of gravity for the system will change. I have...

Based on the photo electric effect. Maybe its perception that is the problem? Charge doesn't travel through a vaccuum. Electro magntic waves alway carry photons. Photons can make charge. Charge creates magnetism? Would explain why Coulumbs equation is the same as the one for gravity but on a...

In Zee's Gravity in a Nutshell P107, 13 lines from the bottom, for a sphere of radius a, should the curvature G be 1/(a^2) instead of a^2?

A question to physicists: What sort of real world scenario / image would *best* depict the increase in gravitational potential energy in a radial field? Would a rocket traveling through the Earth's atmosphere suffice or are there better alternatives? This image would have to be relevant to the...

Moderator's note: Spin off from previous thread due to advanced nature of topic. There is classical field theory too, and GR is a relativistic classical field theory of the gravitational interaction. It's ironic that you fight for a geometrical-interpretation-only point of view and at the same...

I have just met linearized gravity where we decompose the metric into a flat Minkowski plus a small perturbation$$g_{\mu\nu}=\eta_{\mu\nu}+h_{\mu\nu},\ \ \left|h_{\mu\nu}\ll1\right|$$from which we 'immediately' obtain $$g^{\mu\nu}=\eta^{\mu\nu}-h^{\mu\nu}$$I don't obtain that. In my rule book...

Im trying to obtain regularized (and triangulated) version of Hamiltonian constraint in the LQG. However, one step remains unclear to me. I am starting with the Euclidean Hamiltonian:$$H_E=\frac{2}{\kappa} \int_\Sigma d^3 x N(x)\epsilon^{abc} \text{Tr}(F_{ab},\{A_c,V\}) $$ Now i have to...

I’ve watched a few videos recently that explained that gravity is not a force rather it is caused by time dilation because clocks tick slower closer to mass. Objects will follow a geodesic through spacetime and require a force to move them away from a geodesic - so the surface of the Earth is...