What is Gravitational: Definition and 1000 Discussions
Gravity (from Latin gravitas 'weight'), or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light—are attracted to (or gravitate toward) one another. On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the ocean tides. The gravitational attraction of the original gaseous matter present in the Universe caused it to begin coalescing and forming stars and caused the stars to group together into galaxies, so gravity is responsible for many of the large-scale structures in the Universe. Gravity has an infinite range, although its effects become weaker as objects get further away.
Gravity is most accurately described by the general theory of relativity (proposed by Albert Einstein in 1915), which describes gravity not as a force, but as a consequence of masses moving along geodesic lines in a curved spacetime caused by the uneven distribution of mass. The most extreme example of this curvature of spacetime is a black hole, from which nothing—not even light—can escape once past the black hole's event horizon. However, for most applications, gravity is well approximated by Newton's law of universal gravitation, which describes gravity as a force causing any two bodies to be attracted toward each other, with magnitude proportional to the product of their masses and inversely proportional to the square of the distance between them.
Gravity is the weakest of the four fundamental interactions of physics, approximately 1038 times weaker than the strong interaction, 1036 times weaker than the electromagnetic force and 1029 times weaker than the weak interaction. As a consequence, it has no significant influence at the level of subatomic particles. In contrast, it is the dominant interaction at the macroscopic scale, and is the cause of the formation, shape and trajectory (orbit) of astronomical bodies.
Current models of particle physics imply that the earliest instance of gravity in the Universe, possibly in the form of quantum gravity, supergravity or a gravitational singularity, along with ordinary space and time, developed during the Planck epoch (up to 10−43 seconds after the birth of the Universe), possibly from a primeval state, such as a false vacuum, quantum vacuum or virtual particle, in a currently unknown manner. Attempts to develop a theory of gravity consistent with quantum mechanics, a quantum gravity theory, which would allow gravity to be united in a common mathematical framework (a theory of everything) with the other three fundamental interactions of physics, are a current area of research.
Following the new discovery of gravitational waves by LIGO, I just want to make sure I understand the concept of these waves. I believe I currently have a novice understanding of gravitational waves: when a large, fairly sudden change happens to the position of a particle (acceleration or its...
The LIGO paper https://dcc.ligo.org/LIGO-P150914/public puts limits on the dispersion of gravitational waves, which can be interpreted as an upper limit of 10^-22 eV on the mass of the graviton. We all know that low-amplitude gravitational waves are supposed to propagate at c according to the...
Hello,
I have read some of the posts which discuss the meaning and mistakes involving the equation:
## m_0 = \frac{h f }{c^2}.##
My question has to do with gravitation. I would like to know if it is correct to associate to a photon with frequency f, crossing a region near a mass M, a...
There are rumours that scientists at Advanced LIGO have detected gravitational waves ... it is about 100 years after Einstein predicted they were there in his mathematical theory of general relativity ...
Anyone know more about this rumour ...?
Peter
Homework Statement
A person lived 75 years in a city located 3.1km above sea level. How much longer could they have lived at sea level? (Times are measured by an observer at infinite distance).
Homework Equations
tr/t∞ = {1 - [ (2GM) / (r(c^2)) ]}^(1/2)
Rc (Radius at city) = Rearth + 3.1km...
Homework Statement
Two small objects of equal mass 3.0g are placed a certain distance apart. How many electrons must be transferred from one to the other so that the electric force between them is equal to the gravitational force between them?
Homework Equations
Coulomb's Law: F = K...
I am aware that the greater a body's velocity the greater its relativistic mass. As a result, I assume that the faster a galaxy is receeding from us, the greater its gravitational lensing affect is. My question is this: does the extent of a galaxies gravitational lensing continue to increase at...
https://www.sciencenews.org/blog/science-ticker/first-run-gravitational-wave-search-winds-down-rumors-abound?tgt=nr
May be i was wrong and there is GR's, but this article is speculative.
How come that, in the context of discussing the search for gravitational waves, I never see the cosmological constant mentioned ? We know that ##\Lambda \neq 0##, so this seems strange to me; in the presence of a non-vanishing constant, the background is not Ricci flat in the vacuum case, so...
OK, I could probably find the answer of this simple question somewhere, but...
If an astronaut stays on space station, in a weightless state, for 30 years, how much older does he/she become compared to a person who stays on the Earth all the time?
I think it is about one second. Am I...
Note: I know this question has been asked before, but I wasn't allowed to ask my question on that thread
1. Homework Statement
The gravitational self potential energy of a solid ball of mass density ρ and radius R is E. What is the gravitational self potential energy of a ball of mass density...
Homework Statement
I'm reading the book Relativity, Gravitation, Cosmology by Ta-Pei Cheng. I'm in the part where he derived the gravitational time dilation formula for static gravitational field,
τ1=[1+(Φ1-Φ2)/c2]τ2.
This implies that clocks at a higher gravitational potential will run...
In section 4.4 of gravitational radiation chapter in Wald's general relativity, eq.4.4.49 shows the far-field generated by a variable mass quadrupole:
\gamma_{\mu \nu}(t,r)=\frac{2}{3R} \frac{d^2 q_{\mu \nu}}{dt^2} \bigg|_{t'=t-R/c}
I have the following field from a rotating binary...
I am doing an Astronomy GCSE. I have to work out the orbital period for a satellite. I have got quite far with it, but I am really stuck. I have spent hours at it! This is the question:-
A space laboratory is in circular orbit around the Earth at a distance of 6000km from the Earth's centre; its...
I know that this question has been asked many times before on this forum, but on every existing thread either the question or the answers, or both, were too vague. I understand that inertial mass is defined as the property of an object to resist change of its velocity, that is the mass that...
Orbiting bodies are often stressed and twisted by the tidal forces of the larger body. My question is, if these stresses cause the planet to heat up then what system provides the energy to do this? Does the larger body lose energy? Can the gravitational field act as a medium for energy exchange?
Hi everyone I'm kinda new here, your support will really be appreciated ! :D
1. Homework Statement
Let's say the cylinder has radius R, and height T.
Homework Equations
U = ∫GmdM/x
The Attempt at a Solution
My attempt is shown in the picture, I took a tiny element of the cylinder with...
Can gravitational waves be treated like light or water waves? E.g. what would happen if two waves intersected at their max amplitude? Or what would happen if they intersected at a peak and trough?
Homework Statement
A large sphere exists in space, which has a mass of 1 * 10^28 kg
The sphere has a radius of 100,000 km
What will be its gravitational pull (aka: "relative gravity") on its surface in terms of gs (1 "g" being equal to the gravitational pull of the Earth which is 9.807 m/s^2)...
For example if there were two objects orbiting each other and one was much heavier than the other, for instance a dwarf star and a neutron star. Would the lighter object have a greater gravitational pull than it's mass would say it should because it's pull was operating longer on the heavier...
Here is a gravitational slingshot figure from some homework exercise :
##m_1## is a small mass, say, a space probe, and ##m_s## is Saturn. The direction of ##m_1##'s velocity completely reverse direction due to Saturn's pull. ##m_1## come from very far away and end up very far away as well at...
Homework Statement
Three uniform spheres are fixed at positions shown in the figure.
i) What is the magnitude of the force on a 0.0150-kg particle placed at P?
ii) What is the direction of this force?
iii) If the spheres are in deep outer space and a 0.0150-kg particle is released from rest...
To note this is not for any piece of homework. Anyway, what possible masses and a distance between them are required for there to be a gravitational field strength of 1 Newtons per kilograms, when these figures are put into Newton's equation of
F= G (m1 * m2 / r sqaured)
Many thanks!
Here is the question with two parts
The fastest that a human has run is about 12 m/s.
a) If a pole vaulter could run this fast and convert all of his or her kinetic energy into gravitational potential energy, how high would he or she go? 7pts
b) Using the 1990 pole vault world record of 20...
Hello,
in nuclear physics we have a mass defect by the binding energy of the nuclides.
A similar effect appears in the theory of gravitation induced by the gravitational binding energy, which reduces the mass.
But for example at the ISCO of an Kerr black hole we have binding energys about...
My understanding of electromagnetic radiation is this:
When a charged particle accelerates, there is a change in its associated electric field at all points in space, though not instantaneously. The "electric field wave" is basically the propagation of the disturbance that occurs when the...
Hello all,
I could be looking at this the wrong way but here it goes:
From what I understand, if a star collapses into itself to form a neutron star, it would become more compact, denser and heavier with a larger gravitational attraction.
Now, if I understand correctly, the size of...
Question:
There is a large parallel beam of incoming particles with mass m and uniform velocity v0 (v0≪c) in the presence of a gravitational field of a (spherical) planet with mass M and radius R. (without GR) The question is what fraction of the particles will eventually arrive at the planet...
Hi,
I have often read that at large enough distances, the gravitational effect of a black hole is no different than the gravitational effect of a star or other body of the same mass.
But that at close distances the difference shows up, for example the notion of the photon sphere at 1.5 times...
Hello PF members,
Source of the gravitational field in the Einstein field equations is energy–momentum tensor and the curvature of space-time is directly related to the energy and momentum of whatever matter and radiation are present.
Suppose a electron at rest .
1- Can this electron be...
Homework Statement
Suppose an object of length “l” is located a distance “r” from a gravitating object of mass “M.” From physics you will learn that the gravitational acceleration is GM/r^2. Derive the difference in gravitational acceleration between distance “r” and distance “r+l” from the...
I'm trying to write a class for the gravitational field of any planet (I tested it with values for Earth though), and it gives completely the wrong answer! I suspect this is either a mathematical error, or an issue with my declarations of stuff as public, private, static etc. Compiles, just...
What happens to a body experiencing a gravitational wave?
Suppose I put a ball in the path of a GR wave. As the wave passes through it, the space will expand and contract. This means that the space between every point in the ball should expand and contract. But what will be the reference point I...
Hey guys, take a look at this question if you may
Suppose the moon, instead of a sphere, is a disc orbitating the Earth ( the moon's total mass is equal to the disc's total mass), the intern radius of the disc is equal to half the distnce between moon and Earth's center of mass and the external...
Hey guys!
What would be the gravitational effect of Earth on it's surface, if somehow the density of mass was uniform and equal to 2/5 of the real value? Assuming that the size e shape os the planet doesn't change.
If gravitational lens can "focus" light, is it possible with gravitation, so that the resulting gravitation would be strangely unhomogenous?
(If it is a dumb/noob question just tell we pls.)
Acceleration due to gravity is used as a constant throughout the massive body,but it varies due to height and depth & also varies from equator to pole,so it affect the rotational speed of planet from equator to pole.So, why would it takes as a constant.
Hi all,
Thanks for taking your time to help me. It means a lot!
For some context: I'm a physics student taking an analytical chemistry course and am a bit confused by the concept of electrical potential.
Gravitational potential is the potential energy per unit mass, V(gravitational) = U/m. (I...
I know once the escape velocity is reached, the object will continuous to move away from the Earth. But the Earth's gravity can still act on the object no matter how far it goes, so what keeps the object from stopping or even returning back to Earth?
Thanks in advance!
Homework Statement
Two basketballs, each of mass 0.58 kg and radius0.12 m, are placed on a floor so that they touch each other. Two golf balls, each of mass 0.045 kg and radius 22 mm, are placed on a table so that they touch each other.
What is the ratio of the gravitational force exerted by...
I think I have a layman's understanding of time and length contraction. However, I don't really understand gravitational time delay or distance contraction. If we were to put two clocks at the front and end of a rocket, the one on the top would experience time more quickly than would the one on...