Gravitational Definition and 1000 Threads

In weak field regime i know that it is possible to quantize the gravitational field obtaining a quantum theory of free particles, called gravitons, which is very similar to the one for the electtromagnetic field. Do you know some book in wiich i can study this theory? In anycase what is the...

What do physicists expect to do or find with lensing in the next fifteen years? Is there some specific object(s) they are looking for, or a concept?

Homework Statement Given that we know the mass of the moon and the Earth and the distance between their centers as the moon orbits the earth, if the Earth's angular velocity about its own axis is slowing down from say some initial given omega to a final omega (due to tidal friction in reality)...

To motivate the question, Andy Strominger recently put out a paper on calculating the Sagnac shift of counterrotating beams due to the angular momentum flux of a passing gravitational wave. See here: http://arxiv.org/abs/1502.06120. But consider now two nearby freely falling gyroscopes...

The slowing eras of cosmological expansion are generally justified as being due to gravity. How is gravitational slowing justified in a flat or nearly Flat universe. If the universe were closed or if our Hubble sphere were the complete universe, gravitational slowing is a logical consequence...

In attempt to describe the consequences of the Equivalence Principle, this is almost said: When there are gravitational accelerations present, as for example in the gravitational field of the earth, the space cannot be the flat Minkowski space. Indeed, in the Minkowski space we can have...

The question: Is there a gravitational attraction between two atoms if they are located at a distance of several light years of each other? Or physics does not have the answer to this question yet? ) (Sorry if this question has already been discussed on the forum. Please send a link to the topic...

Hi THere! can somebody please tell me why gravitation and electrostatic force exist? why two charges attract or repel each other, and why two masses always attract each other?

I just wonder if there were any serious (and peer reviewed published, to be in line with guidelines) theory, which had proposed some link between speed of light in vacuum constant and between gravitational constant G. For example a calculation of speed of light based on G. Tried google search...

Homework Statement Homework Equations [/B]The Attempt at a Solution

I should preface this question by saying that I am not familiar with Einstein's general relativity, so I am trying to understand the relationship between gravitational and inertial mass from a purely classical standpoint. Newton writes that the gravitational force exerted by an object is...

Homework Statement :[/B] "Calculate gravitational potential at point Z, which is 8.10 x 107m away from a planet of mass 1.08 x 1023. " (This point is between the planet and a moon, where the gravitational field strength is zero. I'm not sure if that makes a difference. The moon's mass is 4.8 x...

Homework Statement "Complete the diagram to display gravitational field lines between two objects of equal mass." Homework Equations N/A as question is descriptive.The Attempt at a Solution Okay, I know it's a bit of a mess but what I'm trying to show here is that the fields are radial and...

Homework Statement Imagine you could place 1g of electrons 1.0 m away from another 1g of electrons. calculate the electrical force and gravitational force between them. Homework Equations fe= kQ1Q2/r^2 fg=Gm1m2/r^2 The Attempt at a Solution So the number of electron is N= 0.001 /...

I was wondering if the way that light vibrates causes it to bend slightly while moving around an object with extreme mass (on top of the bend caused by relativity.) I was drawing what I thought the path of a photon should be around a massive object, but the uncertainty principal bugged me. Am...

1. Calculate the gravitational field strength at 500km above Mars' surface. Mass of Mars: 6.39 x 1023 kg Radius of Mars: 3.39 x 103 km Constant G: 6.67 x 10-11 2. I used the equation g = GM / r23. To begin with I added the 500km height above ground to the radius, giving 3.89 x 103 km. I then...

Hello again. In a double slit experiment with electrons, suppose that we have the instrumentation to measure how space-time is curved by these particles. Would it be possible to obtain the electron's position and momentum by measuring the change in the direction of photons that move nearby but...

Hello, We know that light get bent near stars (because of its gravitational force), and in fact it cannot escape the gravitational forces of black holes. We also know from Newton's laws of gravity that the gravitational attraction between any two objects is ZERO if any mass is ZERO. We also...

This is the gravitational potential energy formula $$U = -\int_\infty^r\vec{F}_\text{field}\cdot d\vec{r}$$ If r vector's direction is form infinity to r, then it means it has same direction as Gravitational Force. So cos0=1 But after multiplication there is a negative sign here: "-GMm" $$U =...

According to Wikipedia, the gravitational time dilation formula is given by t_0 = t_f \sqrt{1 - \frac{2GM}{rc^2}} = t_f \sqrt{1 - \frac{r_0}{r}} where t0 is the proper time between events A and B for a slow-ticking observer within the gravitational field, tf is the coordinate time between...

Am I correct in thinking that the force of gravity between 2 test objects at rest on a planet's surface is less than it would be for the same objects at rest in deep space? I understand that this occurs because in GR gravitational potential has a mass value which is lost on the surface, while...

Hi everybody, I have been reading about gravitational waves, but I don't get how the E modes work; in one place I read that they were created during the inflation time, but in other I read that they come from the recombination. Does it mean that they were produced almost when the Big Bang...

Just a little curious. What formula did Sir Isaac Newton used to find out the exact value of Earth's gravitational force ? Can we apply that formula to find out the gravitational force of other objects ? Let's say, calculating the gravitational force that my bottle has or our body. I know that...

I am reading a textbook about potential theory, it mentions that a uniform sphere has 'dependence' on its gravitational potential, in terms of spherical harmonics. [ite I don't understand the term dependence? What does this mean exactly? Cheers

Could we detect Earth gravity wave from Earth orbit?

Hi guys. How do astrophysicists measure the redshift of electromagnetic waves from galaxies due to gravity without the use of General Relativity? If I can be more specific, how do astrophysicists know that the gravitational redshift of light emitted from some part of a galaxy or galaxy cluster...

Hi All, Can someone tell me why gravitational waves are always decomposed in spin weighted spherical harmonics with spin weight -2 ? I'm assuming you can hand wave the answer with something to do with the 'graviton' being a spin 2 particle but this isn't very satisfying to me. Are there any...

If two masses that are separated by a distance are created from pure energy using the equation E=mc^2, where did the gravitational potential energy between them come from? Does this mean the speed of light isn't really constant, and must be changed very slightly to accommodate it? Could it be...

I have been studying the "fallen" photon experiment, in which the frequency of a photon changes as it falls through a height H. f'=f_0(1+\frac{gH}{c^2}) It is often stated that this is a huge factor in the application of GPS. However, I do not understand why. I understand that the photon will...

My friend and I were discussing this, and google didn't seem to reveal any result. Much like how Bohr's theory managed to derive the Rydberg constant without much effort, has the gravitational constant been found in terms of other quantities yet? It just seems bizarre that Newton proposed a...

Homework Statement Earth actually has an electric field of 1.0 x 10^2 N/C at its surface pointing toward the center. (b) Compare Earth's electric field and gravitational field in terms of i) direction ii) shape iii) how it changes as height increases. c) What is the largest mass that can be...

Hi! So I learned Newtons Law of Gravity and used the numbers to calculate that the acceleration due to the attraction between masses is 9.8m/s/s. Hooray! This is what I've learned is the acceleration due to gravity. However, does the rotation of the Earth and the subsequent centrifugal force...

Homework Statement A uniform cord of length .25 meters and mass .015 kg is initially stuck to a ceiling. Later, it hangs vertically from the ceiling with one end still stuck. What is the change in gravitational potential energy of the cord with this change in orientation?Homework Equations Ug...

Heisenberg's Uncertainty Principle (HUP) tells us that the standard deviation in position times the standard deviation in momentum is equal to Planck's constant divided by 4π. And HUP also causes there to be a zero point energy in the fields of QFT. This is because position and moment can not...

I have been reading up on GR and for the life of me i can not understand how GWs travel through or distort space time, do they distort ST or do they travel with space time?

Suppose I have a cylinder of gas and at time t=0 I can turn on a strong vertical gravitational force. Let the force change quickly (but a time long compared the mean free path divided by the average gas particle velocity) to reach some constant maximum value F(z,t) = F_max. (This force can be...

I'm reading T. Padmanabhans General Relativity. In section 7.6, he describes the gravitational collapse of a sphere of pressureless dust(So ## T_{\mu \nu}=\rho u_{\mu} u_{\nu} ##). I should say his argument is the same as Landau's, but reading Landau's didn't help too. At first, he assumes a...

Dirac had proposed that Gravitational constant would reduce with time.Why?

I am hoping to recover some of the knowledge of physics I gained in high school that has vanished into the mists of time. Currently, I am being abused on Facebook by a self-proclaimed authority who ridicules my contention that gravitational acceleration is a constant. I get the idea that gravity...

Homework Statement A projectile is fired vertically from Earth's surface with an initial speed of 3.1 km/s. Neglecting air drag, how far above the surface of Earth will it go? Homework Equations KF+UF=KI+UF U=-G(M1m2)/r2 K=1/2mv2 mass of Earth = 5.972E24 radius of Earth = 6371km G=6.673E-11...

Homework Statement As a moon follows it's orbit around a planet, the maximum gravitational force exerted on the moon by the planet exceeds the minimum gravitational force by 11%. Find the ratio rmax / rmin, where rmax is the moon's maximum distance from the center of the planet and rmin is...

Homework Statement The definition of gravitational potential at a point in my textbook is "the work done per kg to move a small test mass from infinity to that point" I am having difficulty grasping this concept, how is work done bringing an object closer to earth?? shouldn't work be done...

I try to find answer to quite basic question. Let's imagine neutron star and object with mass of 1 kg located far from the neutron star. Total energy of the object is ##E = U_g + mc^2##, for case when its velocity is zero and and ##U_g## is potential energy of gravitation. The neutron star have...

Homework Statement Need someone to confirm if I answered correctly. Thanks for your support :) A) Draw the pattern of the gravitational flux passing through a horizontal surface A, of area 1m² close to the Earth's surface. B) What is meant by the phrase "Gravitational potential at a point in a...

I considered a free falling object in the Schwarzschild metric at rest at infinity and found as approximation the acceleration : $$\frac{d^2 r}{dt^2}\approx -\frac{GM}{r^2}+\frac{3G^2M^2}{r^3c^2}$$ This would mean if there are no sign error in some sense that the force becomes repulsive at...

Homework Statement Jupiter has a core of liquid metallic hydrogen, with uniform density $\rho_c$, with radius $R_c$. This is surrounded by a gaseous cloud $R_g$, where $R_g>R_c$. Assume the cloud is of uniform density $\rho_g$. The problem also specifies that we are to assume both regions of...

Homework Statement Consider a satellite in circular low Mars orbit 300km above the planetary surface. R = 3396km M = 6.419 x 1023kg G = 6.674 x 10-11m3/kg/s2 Find the orbital velocity of the satellite (using the given values, I assume, as there is some inaccuracy in the real-life mass value...

Penrose wrote in the Road to Reality that gravitational clumping increases the entropy of the universe. The early universe was very low in entropy because it was very smooth, with very little clumping. So, is it accurate to say that the early universe was high in entropy except for the...

Is it possible to pulse Alcubiere drive once to catch up a gravitational wave to surf it, then pulse again to stop?

According To Einstein's Relativity. Supposing a Man Went To Another Planet That Has a Gravity More Than Earth Hundreds Of Time Which Means That Time Is Too Slower There Than Earth. If We Say That 1 Hour In That Planet Is 10 Years On Earth And He Stayed 2 Hours There Will He Comeback To Earth...