Gravity Definition and 1000 Threads

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...

So the other day I saw a YouTube video on how gravity works according to general relativity. From what I understand, objects bend space_time with their mass and create a shape which is close to a cone. Since objects only move forward in time through a straight line, the bent space_time makes...

Homework Statement A safe (mass = 1.00*10^3 kg) is suspended a height (d) above the top end of the spring (spring constant = 27800 N/m). The rope holding the safe breaks and the safe falls, compressing the spring a total distance of 1.80 m. What is the initial height (d) of the safe when it...

Homework Statement Two-body problem given as $$\ddot{\textbf{r}}+\frac{GM}{r^2}\frac{\textbf{r}}{r}=0$$ $$\textbf{h}=\textbf{r}\times\dot{\textbf{r}}$$ where the moment of the momentum vector mh Homework Equations The vector solution to the above equation may be obtained by first taking the...

well since gravity waves are supposed to have mass, they are supposed to be effected by gravity itself, and :/ how are we supposed to detect gravitational waves emitted from a black hole when none can get out?

I know quantum mechanics meeting with general relativity or quantum gravity is a difficult work to do.　In order to understand the problem more, I would like to know about QM in virtual gravity, e.g. Rindler system or rotating system. Is wave function in rotation system is fully derived, for...

Besides the Feynman lectures on gravitation, I'm looking for modern and complete treatments of the topic of classical gravitation as a field theory in flat space time. Any suggestion?

As a neophyte when it comes to the relativity solutions I have been surfing the web. I came across something in Science Forums. <speculative link deleted> I have now become interested in what gravity does to light. My understanding of the post above is that the reference frame for light...

Hi everyone, First of all, I am new to this thing and I hope you guys can help me with this. So I am Ruzanna, a freshman,(I am 14 years old) and live in the Netherlands. So, I have this project for physics where I had to make my own pendulum, and use it to calculate the gravity here. Well I...

Homework Statement A complex or irregular body with some mass, m. How to determine the 3 co-ordinates of centre of gravity? Homework Equations Moment method with ∑M = 0. The Attempt at a Solution Say I have a gearbox and I need to find the COG. I can mount the gearbox at two longitudinal...

Dumb question probably -- But is there a way to measure gravity in a particular area of space, or a "measurement" .. I.E. the gravity 10 miles above Earth v.s 1000 miles above. Not force on another object, but some "unit" or measure of gravity itself.

Reading a thread in relativity I would like to know more precisely about radiation from charge. 1 I put a charge on the table of my house. Gravity and table reaction force work on the charge. They cancel so net force does not work on the charge, thus no-force no-velocity cause no radiation...

Alright, so this has been bothering me for awhile, and the more I think about it, the more it bugs me. I'm almost guaranteed wrong about what I'm going to say here, but I'm not sure why I'm wrong, so hopefully someone here can explain my wrongness to me. Unfortunately, this is going to take...

Sabine Hossenfelder recently wrote about an old theory of quantum gravity due to Weinberg: asymptotically safe quantum gravity. Is anyone familiar with this idea? What I couldn't figure out from the article is whether asymptotic safety is an approach to making consistent quantum field theories...

I n ordinary weighing scale, in left pan, there is spiral shaped coil (like that mosquito coil) or any long shaped rod. Middle point of this coil is touching the left pan. Let mass of this coil be W1. Second body of mass W2 is attached to other end of this coil. So the left pan is experiencing...

When humanity unified electricity and magnetism, that ushered in a massive technological evolution for our species, perhaps only equalled by the advent of QM and modern electronics. Is it even possible to imagine the consequences of unifying Gravity with EM? Is it possible that we will...

Homework Statement If you have an object say in a vertical pipe, which only has a gravitational force acting on it would the reaction forces only be friction forces? If this is the case how would you calculate the forces? would you calculate the friction force using the friction coefficient or...

For many, many years (don't ask), I've been running into the classic example of the local reference frame: the man in the box who can't tell if he's floating free in space, or falling into a gravity well. It occurs to me that if one is in a falling box, a mass released at the top of the box...

Hi. I am currently working on an assessed science experiment write-up. The experiment is about whether or not if mass of a pendulum bob affect the oscillation time for a simple pendulum. Obviously, the answer is no but I am struggling to write a concise and accurate explanation to why this is. I...

When we do the stretched rubbers he etc analogy of gravitational well, there are two differences 1) the ball moves into depression because of gravity of the earth. 2) stretched rubbersheet is physical and prevents ball from falling down while space would allow you to move anywhere as space...

What is the relationship of gravity to density? In black holes the cause of gravity is that the star shrinks and becomes dense. But Jupiter's gravity is more than the Earth's gravity, although its density is lower? Is the sun's gravity more than the Earth's gravity, even though the intensity of...

Homework Statement If the height of a frictionless incline is h. Determine the work done by the force due to gravity F as the crate of the mass m slides down the incline Homework Equations W=Fd cos (theta ) Force due to gravity perpendicular to incline= mg cos(theta) The Attempt at a...

In most cases, we know why things happen. Protons can stick with each other because of the strong nuclear force. There's all kinds of forces and we know mostly about why they occur and how they are transmitted. But I don't understand gravity. Why do objects with mass attract each other ? I know...

I am trying to work out the velocity of the ball in a loop in terms of theta from the horizontal (like a unit circle) as it loses contact with the track. And having a lot of trouble understanding this equation m*g*sin(theta) = m*v2/r and this explanation: The ball will leave the rail when...

Hello, I'm reviewing kinematics for an upcoming AP physics exam, but I seem to have forgotten a crucial fact. In typical rocket problems (when the rocket blasts off with an initial acceleration for example 5 m/s^2), why don't we subtract 9.8 from 5m/s^2 when using a value for acceleration? When...

I have only seen scenarios so far where the elements are all along the diagonal, but what are some known cases where there are off-diagonal elements? Thank you.

Hello, I'm new at the forum. I'm a science-fiction writer. My question then concerns an imaginary, fictional situation. I'll try to be brief but it's not easy to explain: Let's imagine that a character who lives on Earth is strongly attracted by the gravitational force of some other celestial...

Homework Statement We have the equation for gravity due to the acceleration a = -GM/r2, calculate velocity and position dependent on time and show that v/x = √2GM/r03⋅(r/r0-1) Homework Equations x(t = 0) = x0 and v(t = 0) = 0 The Attempt at a Solution v = -GM∫1/r2 dt v = dr/dt v2 = -GM∫1/r2...

If what we perceive as the force of gravity is really just the effect of curvature of spacetime, why do theorists hypothesize the graviton as the force carrier for gravity? I thought that GR does away with the notion that gravity is a "force." So, is gravity a force or is it merely an effect?

Greg Bernhardt submitted a new PF Insights post Either the Sun Is Getting Smaller or Gravity Is Getting Weaker Continue reading the Original PF Insights Post.

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?

Having seen plenty of 'vacuum in a tube' tests on youtube I am wondering how a human can work in such an environment. I'm trying to understand how a space suit can be tested before it is used 'live' in space, and how seemingly 'everyday' materials are used to protect astronauts from the harsh...

Choose any distance in the universe, a million light years. This distance creates around us a sphere that divides the universe into three parts. Universe outside the sphere, universe within the sphere and universe on the surface of the sphere. We are going to determine the gravity of the...

I know that rotation can cause there to be artificial gravity. But I was thinking of making a floor plan that is all horizontal with the generation ship having a rocket shape and with it being longer than it is wide and wider than it is tall. So I was thinking of giant centrifuges on every...

I am trying to explain to someone why there is still gravitational time dilation at the centre of the Earth. (Not to over-tax the rubber sheet analogy, but...) When we sketch a gravity well, we show a curve that starts out nearly flat, then curves away from the flat plane, until it reaches the...

This question came up at another forum. The delta-v of potential guns is limited to the range 3 km/s to 11 km/s (hydrogen gun). Assume the astronaut is either on the moon or orbiting the moon. I'm wondering if a single impulse followed by gravity assists (and ideal planet alignment) could result...

Homework Statement The Russian Mir space station had a mass of 130 tonnes and orbited Earth at an altitude of 480km with an orbital speed of 7621.4m/s. The diameter of Earth is 12 760 km. a) What centripetal force was acting on it? b) Find the value of the acceleration due to...

Hy folks, Upfront I want to apologize for my writing and my dissability to use correct symbols to ease readability of the example. Ok now that that's done I just want to start upfront. If we set a usual example of an object falling from a tower with a height of x meters and assume that the...

Homework Statement Homework Equations K = (1/2)mv2 U = mgh W=Fd Integration/Calculus The Attempt at a Solution I'm not sure what I should be doing for this question, if height changes how is it possible that velocity stays the same, according to the conservation of energy (frictionless wire)...

Would the beam of a powerful laser have any gravitational tug?

Gravity is weak - while we can study the other interactions with individual particles, for gravity we need macroscopic objects to get measurable forces. This makes it easy to measure quantum effects for the other interactions, but hard to do so with gravity. Gravitational forces are always...

I am currently solving a problem where I need to find the gravity in the ISS (distance 400km from Earth with Radius 6371km). I am using the formula g=GM/R^2 . One way to solve it would be to find GM by multiplying g(which is 9.81) and R^2 (which is known) and then to use it in GM/(R+400)^2 and...

Homework Statement What is the tension of this rope? Cosmonaut m=100kg is outside of spaceship M=5 tons on rope with length 64m. Cosmonaut along with his spaceship moves in orbit at a neglible distance. m=100kg M=5000kg L=64m Planet's mass 6*10^24 Planet's radius 6400km Homework Equations...

Homework Statement When considering a satellite in geosynchronous orbit, its speed is zero across (relative to) Earth's surface. From Kepler's third Law: T2=(4π2r3)/(GM), we can derive that v2=GM/r This would tell us that as the radius of a satellite to Earth's centre increases, its velocity...

The next questions will be in english and spanish, since my birth language is spanish I may be mistaken in a few english words. --------------------------------------------------------------------------------------------------------------------------------------------- Spanish Debo advertir que...

https://arxiv.org/abs/1803.04973

What is the difference between the gravitational force and gravity? Because I was under the impression that gravity is not a force, but one of the 4 fundamental forces of nature is the gravitational force, so I was wondering what the difference between the two is?

1Problem: Two equal satellite, A and B, of a planet of mass M, describe circular trajectories where the radious are 0,5r and r. We can afirm that: A- The intensity of gravitical force acting on B is half of the gravitical force acting on A; B- The value of centripetal aceleration of A is one...

I seem to be missing something very basic to the relationship between gravity and mass. If gravity is equivalent to acceleration, what is the basis for the acceleration that generates the gravitational force of an object such as the earth? What is accelerating? Am I even thinking about this in...

According to various sources, the Moon is separating from Earth 4 cm every year. I’ve searched for the explanation and I’ve found the following: The friction the seas and oceans from the Earth make with it’s soil causes the Earth’s rotation to slow down. This causes the Moon to speed up...