Graviity Definition and 30 Threads

hobbyist, passionate studing of issues such as the nature of gravity, the LamdaCDM model, the dark matter, the dark energy, and the prevalence of ordinary matter over antimatter (baryogenesis)

What is the minimum velocity (theoretically) of an object located at the CENTER of the Earth to move it outside its gravitational field?

I'm trying to make a 2D game on Unity similar to Universe Sandbox 2. I currently am working with a star and planet, both with roughly the masses of the sun and earth respectively for comparison and at a distance of 31,000,000km. My current model uses Newton's formula for gravitational force (F...

Please could someone explain this to me? GRAVITY IS A MYTH (59 sec) Summary; in slow-mo a man drops a virtually extended free hanging slinky; the lower part appears to hang in the air for a moment. In the comments: Rob; “..the overall mass of the slinky is falling but the bottom part is being...

Question: Suppose that two bodies of masses m1 and m2 are a fixed distance d apart, and that both of them act on a third body of mass m. Find the position of the third body such that the two forces are in equilibrium. I have solved this question and obtained the answer listed in the back of the...

This might sound as a dumb and silly question but if you think about it, it makes sense. If we wrongly assume that gravity is a force just like any other, and given the fact that time is closely related to gravity and that gravitational time dilation is a thing, wouldn't reverse time travel...

Picture below. Both bodies are made of same material but the body placed in water had 2.4 times greater mass. What is the relationship between buoyancy Force and gravitational force between body in water and body in air?I have no clue how to solve this. I know that body with greater mass has 2.4...

My high school physics days are long ago ;) This is not homework, well, other than it is work, at home. For a real application: Very space constrained "workshop", got a bench drill press, and want to build a table on wheels for it, to be able to move it into a corner when not needed. Those...

Can the effects of gravity possibly extend through time? Is there a natural law that forbids this? Could this be a possible explanation for dark matter?

Gravity batteries intrigue me. We are starting to develop them now. We currently are able to drop cement blocks and harness the energy that the kinetic energy releases. We are considering them as an alternative energy source to help the environment. Here’s a link for those unfamiliar with it...

First of all, sorry for my naive question here which likely doesn't make sense. The universe is currently expanding with galaxies receding from each other at increasingly faster pace. Is it possible that the universe is a closed hypersphere system, where galaxies are actually not actively...

The Wikipedia page on gravitational time dilation (https://en.wikipedia.org/wiki/Gravitational_time_dilation) states: "Relative to Earth's age in billions of years, Earth's core is effectively 2.5 years younger than its surface." A clock subjected to less acceleration (gravitational or...

Homework Statement A spigot pours beans onto a scale platform. At a time t = 0.0 sec, the spigot is opened and beans begins to pour out (with initial velocity 0) at a rate of 1.00 kg/sec onto the platform from a height of 10.0 m above. (a) At t = 10.0 sec, what is the weight of beans on the...

I am trying to answer a question about projectile motion were the change in height is that significant that the gravity cannot be assumed constant.

If we have two objects A and B appear on the opposite sides of the equator of a planet like Earth with the same mass as Earth. Object A is a neutron star with the mass of the sun and object B is a iron cube with the mass of one gram. Will A or B hit the Earth at the same time or will one hit...

How do the components of the stress-energy tensor act on gravity regarding a) the FRW-universe? b) a solid ball? In a FRW-universe ##\rho + 3P## determines the second derivative of the scale factor. So, there are no non-diagonal components. Just theoretically, if the perfect fluid was...

I am trying to compare an experiment on spinal changes due to zero-g in astronauts. Researchers simulated zero-g spinal elongation by suspending human subjects so that no part of their body touched the ground. This figure shows the % change in disc thickness for each subject compared to data...

I know that n-body problem can be complicated, but that's for the dynamics. What about a static case: e.g. if I have the distances of several bodies A, B and C etc. and their distance to a reference mass m, can I just use the vector addition of the Newton's gravitational force to add up all of...

would a gravity well resemble a angle food cake pan well traveling through a sphere? being you start outside the well. travel inward towards the core then outwards to the edge of the well again. wouldn't this also mean gravity wells would be replaced with pressure wells at the core?

Homework Statement I need help getting started with this problem At what altitude above the surface of the Moon must a lunar module orbit in order to complete each orbit in 1 h 49 min 39 s? Homework Equations g= Gm/r^2 ? The Attempt at a Solution Not quite sure how to start or anything , any...

according to einstein the mass go straight in the curved space because the sun makes the space curved and so the Earth circle the sun. but i don't understand why this "geometrical" explanation is a replacement for the gravity. how does the mass (of the sun for example) makes the space curved...

Could someone please provide a diagram of all the forces acting on the plane, and explain why the answer is E? This is from the 2014 F=MA exam. Thanks, blueblast

Homework Statement The problem is stated in the picture. Homework Equations Fg=Gm.1m.2/r^2 The Attempt at a Solution I found a similar question where someone wanted to find how high will the weight be half the weight on the surface. Here is one of the answers: F =G.m1.m2/r^2 F´ =G.m1.m2/r´^2...

I am working on a story where superheroes have started to appear. Their powers are all based on manipulation of spacetime and mass, and not on electromagnetism. One character is a speedster who can compress time. He can experience many seconds while everything around him experiences one...

Hi, I'm trying to make a physics based game to teach my progeny about the universe. My first step will be to show how bodies gravitate around other bodies, and then model a solar system, a galaxy... simple things. I could do it using Newton's laws, but I want to include things like black holes...

Homework Statement I know that potential gravitational energy is relative to the reference point that I decide to choose (like in the picture below). But then if, for instance, I set my reference point in the ceiling and my vertically down y-axis to be positive. What would the potential...

Verlinde sought to reproduce the successes of other modified gravity theories in a variant of his entropy based gravity theories called "emergent gravity". Unfortunately, it doesn't reproduce the observed data. Federico Lelli, Stacy S. McGaugh, and James M. Schombert "Testing Verlinde's...

Gravity tends to make ordered structures of free particles. Does this mean that gravity is decreasing the entropy of these particles, or is there some compensating mechanisms in order to let the entropy increase (for example the emergence of gravity waves, though I doubt that's enough to compensate.

Dear Forum, I am filmmaker from Berlin and despite physics focus back in high school I am really bad at it. I am trying to get my head around some ideas I am working on and would kindly ask you for some tiny calculations. I hope this is OK and maybe even fun for someone here? So my questions...

arXiv:1212.3687 (cross-list from gr-qc) [pdf, ps, other] Time delays across saddles as a test of modified gravity Joao Magueijo, Ali Mozaffari Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Extragalactic Astrophysics (astro-ph.CO); Earth and Planetary Astrophysics...