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.
Hi,
If we are standing on the ground, the Earth applies a force equal to our weight to us, but why do we feel a greater force when we fall to the ground from a certain height? Our weight is the same along this small height because our mass and acceleration are the same and, even so, the normal...
Good day,
If I consider my system to be an object and the earth, and the object is on the surface of the earth, then the system will have gravitational potential energy. Why couldn't I say that only the object (considering it as my system) has gravitational potential energy?
Thanks
weight/mass = gravitational field strength.
my working is ->
weight = 150kgx10m/s² = 1500N
mass = 150kg
gravitational field strength= 10N/kg.
is this correct?
A massless scalar field in a curved spacetime propagates as $$(-g)^{-1/2}\partial_\mu(-g)^{1/2}g^{\mu\nu}\partial_\nu \psi=0 .$$
Suppose the gravitational field is weak, and ##g_{\mu\nu}=\eta_{\mu\nu}+\epsilon \gamma_{\mu\nu}## where ##\epsilon## is the perturbation parameter. And let the field...
This question is very confusing since I don't see two distinct particles that are exerting a gravitational force on each other. Also to complicate matters, a gas is made of many individual particles and I don't know how to determine the gravitational force on a single particle from so many other...
First, in section 20.4, after listing all the things gravitational potential energy does not do, they say the equivalence principle forbids it being localized. I thought I understood the equivalence principle, but maybe I don’t. Any comments explaining that would be appreciated.
Second, they...
Regarding this paper:
https://iopscience.iop.org/article/10.3847/1538-4357/abbb96
In the opening sentence of the Abstract the following is stated:
"The strong equivalence principle (SEP) distinguishes general relativity (GR) from other viable theories of gravity. The SEP demands that the...
If we compare 2 scenarios... A) 2 solar mass black hole hyperbolic flyby of Earth at 5000km/s far enough not to cause a tidal disruption event vs B) an extremely close binary pair of 1 solar mass black holes whose barycenter hyperbolically travels past Earth at 5000km/s, also far enough not to...
I am thinking of the mechanism that causes mass-energy to curve spacetime
We have the Wheeler (was it ?)description, viz approx "mass tells spacetime how to curve and spacetime tells matter how to move...".
Are there any analogous circumstances in other areas of physics where all (or a...
Hello everyone.
Probably this question is trivial, but nevertheless I am confused about Newtons law of motion:
$$F=G\frac{m_1m_2}{r^2}$$
Now, some sources say, that F is the force between the two masses m1 and m2. Other sources say, that F is the force that m1 exhibits on m2. But isn’t this a...
With regard to relativity of simultaneity and the "block" universe and reflecting on the notion of skewed time slices associated with frames moving relative to each other, one observer sees one event a distance away (parallel to the direction of motion) occurring before another event a distance...
I don't know if this is the ideal sub-forum for this but I'd like to know more about this very recent activity I first saw here >>>>>'
It looks like this could be some actually testable, actual breakthrough advances in Physics and the evolution of our Universe. Any comments appreciated.
In https://physicsworld.com/a/physicists-measure-smallest-gravitational-field-yet/ the gravitational constant was measured by the smallest object until now, this is a small golden ball, with a radius of one mm. The intention is to measure some quantum gravitational effects in the future.
But, I...
In Box 2.4 of the book "Black Holes & Time Warps" by Kip S. Thorne, he explains gravitational time dilation using the equivalence principle. For this he uses an experiment thought analogous to the one used by Einstein in 1911 to postulate the existence of a gravitational Doppler shift, but...
Suppose some aliens travel to our solar system after seeing our radio broadcasts using an Alcubierre drive. Would it not create a notable gravitational disturbance? Or does it leave spacetime undisturbed around it?
Spacecraft heading to Uranus and Neptune in the next decade could be used to investigate gravitational waves as they venture into the outer Solar System. That is according to a new study by a team of Swiss and Danish researchers, who say that examination of the radio signals from far-flung...
Off the back of a recently closed thread where there was some discussion about the gravitational field of an infinite flat slab, I decided to have a play at investigating that. I've found a few interesting things.
It's fairly straightforward to solve for this situation. You use Cartesian-esque...
first to find the force by gravity, it would be
4 kg * 9.8 m/s = 39.2 N
then solve for work using W= F*d*cos(theta)
W = 39.2 N * 3 m * cos 28
= 103.83 J
My confusion is do I use sine or cosine and what angle do I use, the actual angle of the incline or the angle between the mass and the...
Let's assume a binary system with an inclination angle ##i## (angle between the orbital plane and line of sight). Then, according to this source - equations (128) and (129) - for the amplitudes of the tensor polarization modes ("plus": ##+## and "cross": ##\times## polarization) I could write...
It even gives a hint, it says "consider two horizontal surfaces z1 and z2 and think about what thermodynamic equilibrium means for particles traveling from one surface to the other". This really trips me up because I am not sure what to do with this. Obviously in equilibrium the number of...
The faster the relative speed or the more intense the gravitational field, the slower time passes. Does it make sense to ask what both have in common that affects time? Or does the question possibly only make sense in the context of certain theories, for example the LQG, where space and time...
Hi,
When regarding Gravitational Potential Energy, I know the formula is U=mgh. However, when the object is on an incline (say at an angle of 52 degrees) would it still be mgh or something else? (This isn't homework I simply was just curious).
hi guys
i was reading a book on astrodynamics and was trying to understand the mathematical treatment of the Earth gravitational potential . i kinda understand the main idea , after reaching the following equation of the potential in terms of the Legendre polynomials :
##\alpha = r_{Q}/r##...
The equation of motion for a particle in a gravitational field is
ai = -Γijk vj vk
In inertial coordinates the Lorentz force is
mai = qFij vk
So it seems like F corresponds to Γ. Just like F is expressed in terms of the derivatives of A, the christoffel symbols are expressed in terms of...
I'm trying to think of a how the double slit experiment can detect a photon without interacting with it in theory. In principal (not reality of course) does a photon have a gravitational signature which could be used to detect which slit it traveled through during the double slit experiment...
In gravitational lensing, the image magnification is defined as the image area over the source area. But many texts also give it as the inverse of the determinant of the jacobian, A, of the of the lens equation. My question is how these are equivalent.
The lens equation is...
https://www.physicsforums.com/threads/what-are-the-best-parameters-for-lcdm.831858/
Hello.
In the above linked thread from 2015 Science Advisor Chalnoth replies to Earnest Guest.
First, the cosmological constant has been a component of General Relativity pretty much from the start. The way...
I understand that under the GTR space and time are curved and movement takes place along that curved surface. Setting aside for the moment the additional consideration that the space curvature is in three dimensions, I do not understand the impetus for acceleration. If an object is just sitting...
Usually spacetime curvature is localized/proximal to what is "causing" it, right? I'm wondering whether there is a term for the situation seen with gravitational waves where there is some relatively flat space between observable gravitational effects and the mass(es) that "caused" them? I'm...
Hi,
I am confused about the negative aspect of these quantities. The definition in my book for gravitational potential is:
"The work done to move a unit mass from infinity to a point in a gravitational field"
I understand that the work done is negative because gravity is doing the work if you...
Would using gravitational waves to measure (it's obviously a gedankenexperiment!) position and momentum of, say, an electron in a specific state, disprove HUP since the quantum of energy of grav. waves does not exist? Would it be possibile to have an arbitrarily small uncertainty in position...
When a gravitational wave passes through a location in space, what is the magnitude of equivalent gravity that it produces at that location?
Or rather, is it correct to say that gravity can influence gravitational waves but gravitational waves can't influence gravity?
1. I believe that the gravitational field strength would decrease because it is inversely proportional to the square of the distance from the centre of the Earth, g∝1/r^2.
Gravitational potential energy at large distances is directly proportional to the masses and inversely proportional to the...
1. The centripetal force is equal to F= mv^2/r.
The velocity of the Earth can be found by:
V=2πr/T
T=1 day = 24 hr*60min*60sec=86400 s
v=2π*6.4 x 10^6/86400 s
v=465.4211 ... ~465 ms^-1 to 3.s.f
Therefore, F=1*465/6.4 x 10^6
F=98/1280000=7.265626 *10^-5 ~7.3 *10^-5 N
Would this be correct since...
1. Newton's Second Law states F=ma and the formula for centripetal acceleration is v^2/r
Therefore, F= mv^2/r
Would this be complete, I just feel that I should need to do something further but I am not sure what?
2.F=mv^2/r
Gravitational force = GMm/r^2
Gravity is the cause of centripetal...
1. Since the gravitaional field strength is 1/6 of that on Earth:
W=mg
W=90*9.81/6
W=90*1.635
W=147.15 ~ 147 N
2. ∆Ep=mg∆h
∆Ep=90*1.635*50
∆Ep=7357.5 J
I do not now whether this method would be suitable and if I should have instead used the formula for gravitaional Potential, V grav=-Gm/r?
3...
Would it be correct to say, that gravitational waves of the magnitude that is currently detected by LIGO and similar detectors, are prevalent to the extent that there is no single location in the known universe, that such magnitude of gravitational waves, don't pass through at least several...
An elevator in outer space where there is negligible gravity, accelerates at the most precise constant acceleration that current technology enables.
Inside that elevator, resides an accelerometer that is the most precise accelerometer that current technology enables, but not more precise than...
Here is a video i have watched:
It made me think of the following questions:
A. Gravitational waves at the scale that emanate from earth:
1. It is doubtful if they exist at all.
2. They are predicted to exist, but at an extremely small magnitude.
B. In case the answer is A2:
1. These...
hello I would like some help with the first part of this homework.
for the moment i have done this:
E initial=m*g*h
Efinal= 1/2 m*v ^ 2+1/2I*ω ^ 2
Ei=m*g*h+1/2I*ω ^ 2
Ef=1/2*m*v ^ 2
my doubt is with the potential energy since it confuses me when there is or not...
Hello everyone! I was listening to a podcast that featured a cosmologist and she mentioned that if the universe was positively curved (and therefore a sphere overall), light would travel around the universe and then end up where it started. I wondered, would a gravitational wave do the same?
I'm reading Schutz's A First Course In General Relativity and in chapter 5 he discusses an idealized experiment in which an object is dropped from a tower, then turned into a photon and sent back up to its original height.
In classical mechanics we would say that as the object falls it loses...
In my new novel, Handwavium, renowned genius physics Professor Samuel Clements Silver has created a prototype gravitational wave radio. For plot purposes, the protagonist needs to use the signal to triangulate his location.
I know LIGO has three detectors and have seen reports of sources like...
When I did this the first time I didn't really think too much about it, so I just wrote$$p = \frac{nRT}{V} \implies W = \Delta U - Q = - Q = -\int_{\frac{4}{3}\pi r_0^3}^{\frac{4}{3}\pi r^3} \frac{nRT}{V} dV$$That turned out to be correct, but when I thought about it I didn't understand why this...
the gravitational potential energy of a body at any point is defined to be negative of the work done by the conservative force(gravity in this case) from bringing it to that point from a given reference point. if the reference point is taken to be at infinity and the potential energy at this...
Is it theoretically possible that one day a gravitational wave detector will be developed, that is sensitive enough to detect gravitation at the order of magnitude that an Earth like planet has?