Gravity is an attractive force that affects and is effected by all mass and - in general relativity - energy, pressure and stress. Prefer newtonian-gravity or general-relativity if sensible.

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Single photon's gravitational field: “where” is it?

When a photon passes through a hole in a screen, the photon's energy is pretty localized, namely a the hole. Now let the photon "fly" for a minute into the open void. The field representing ...
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36 views

How does time stoppage inside a blackhole affect physics? [duplicate]

From the gravitational time dilation theory we know that at event horizon of a black hole the time should stop completely. However all the physics phenomenon we know (at macro level) e.g laws of ...
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Is the curvature formed due to mass/volume of spactime convex or concave?

I am really confused about the curvature of space-time. Does it bends in a concave shape in presence of mass/volume as shown by the example of rubber sheet and ball or does it bends in a convex shape? ...
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Gravitational force and potential in infite slab

Let's say that we have an infinite slab of height $2h$ and mass density $\rho$. Let's define $x,y$ as the axis parallel to the slab and $z$ as the perpendicular one, with $z=0$ at the middle of the ...
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Weight difference on full moon and no moon day [duplicate]

Since Moon has an impact of gravity, would same piece of mass be heavier on a no moon day (since moon is at opposite side, thus pulling downwards) and lighter on full moon day (since the moon is at ...
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76 views

How general relativity shows that gravity decreases as we go inside the Earth [duplicate]

Why is it that gravity decreases as we go deeper inside Earth? Can anyone explain theoretically with reference to general relativity?
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If a metric has off diagonal terms, how can I calculate the tetrads?

If a metric has off diagonal terms, how can I calculate the tetrads? I need to calculate the Dirac gamma matrices in BTZ blackhole spacetime... $e^\mu_{(a)} e^\nu_{(b)} \eta^{ab} = g^{\mu\nu}$ ...
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Evidence of possible tidal effects close to a gravitational wave emitting system

Currently we are attempting to detect gravitational wave emissions using the LIGO gravitational wave detection system (and similiar systems), by attempting to detect very weak gravitational waves ...
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The distance between the two packages [closed]

A package is dropped form an airplane travelling horizontally at constant speed. Friction is negligible. One second later a second package is dropped. a) THe distance between the two packages will ...
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79 views

3D-representation of space-time

When I read something about GR, I nearly always see some pictures that look like trampolines, like this one. I know that the curvature of space-time is described by the Riemann-Tensor $R$. I was ...
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Can Ultrasound and or Microwaves actually lock mass in place trapping it in standing wave nodes

Ultrasound Standing waves trap small particles and manipulate their velocities and direction and cause them to defy gravity. Source : https://www.youtube.com/watch?v=odJxJRAxdFU Does current physics ...
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Where does the kinetic energy come from if galaxys are moving apart due to the expansion of the universe?

We know the universe is expanding because of the red shift of far away galaxies, the further away the galaxies are the faster they recede. We also know that the energy in the universe (mass and other ...
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41 views

Is there any such thing as gravity? [duplicate]

So I was seeing this documentary and ended up knowing that there is no such thing as gravity. It said that we are not being pulled by Earth but being pushed by the space time curvature acc. to general ...
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82 views

Is it possible to focus gravitational force to a point?

I'm new to these kind of discussions and i don't have broad knowledge in physics, and I don't know whether its proper question or not. While in a discussion with my friend, a question has raised ...
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33 views

Explanation for Spiral galaxies [duplicate]

Can anyone explain to me why our galaxy is spiral and not irregular or spherical? Please be specific and if maths is required to state what you mean precisely, use it. I will understand it much better ...
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114 views

How are gravity and the strong nuclear force related?

Nature is replete with examples of apparently different physical behavior as manifestations of the same phenomenon. So, we can say that we understand something better when this apparent complexity is ...
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54 views

Calculating and modifying trajectory

I am busy working on a programming puzzle which is rather fun. The help I'm looking for is not with the coding as such but the physics behind it so I thought I'd turn to the Physics stack. The ...
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103 views

How to calculate photons/light trajectory under gravity

I'm aware many questions are out there asking similar questions about photons and gravity and I got the basic concept by searching through them. I will just call it light although it may not be the ...
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185 views

Force on side of pool from water

Given a pool with dimensions $$\ell \times w \times h \, ,$$ I am trying to derive an equation that will yield the force by the water on the sides of the pool, namely $$\ell\times h \quad \mathrm{or} ...
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108 views

Are all forces explained in terms of curved spacetime? [duplicate]

Gravity is explained in general relativity as curved spacetime. Can the other forces (electromagnetic and weak/strong nuclear) also be explained by this?
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Can the curvature of space be measured using a swimming pool?

I read somewhere that if the center of mass of two twelve ton elephants was one meter apart then the space they curve would be one nanometer longer. (Though I doubt elephants come that dense) This ...
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How do I find the energy difference between two points of a gravitational gradient?

What I'm ultimately trying to figure out is how to calculate only the potential energy attributed to the differences in the force of gravity at two distances from the Earth's center of gravity.
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Would a fast moving (approaching $c$) stream of particles be affected by the gravitational pull of a gas giant?

I was inspired by this SE question. Would the gravitational field of a gas giant (such as Yavin IV) have an effect on the super laser (i.e. slow it down, change the direction), or is the mass so ...
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139 views

Gravity and centre of mass

Does gravity act entirely as if on the centre of mass? Often I have heard this, but it seems more realistic (even if less practical) if it acts on individual bits of matter, therefore weaker further ...
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82 views

Expanding Electric Field, Magnetic Field in post-Newtonian Gravitational Potential

I've cross-posted this question from Mathematics since Physics is probably better suited for the nature of the question. I've ...
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49 views

Gravitational intensity [closed]

I calculated the gravitational intensity and potential at a point P due to a horizontal linear mass distribution of length '$L$', mass '$M$' and uniform linear density at a distance '$R$' apart from ...
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Books on Spin-2 Gravity / Fierz-Pauli theory

I am trying to find a good pedagogical book/set of notes on Gravity as a spin-2 particle. I have been reading through Gravity & Strings by Ortin but it's very brief and offers little ...
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36 views

Singular isothermal density distribution

Does anyone know where the Singular isothermal density distribution $$ \rho(r)=\frac{\sigma_{V}^{2}}{2\pi\,G\,r^{2}} $$ or how it was derived. Are there any good references on how this equation was ...
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699 views

2D space-time curvature [closed]

Actually, why is the space-time curvature considered 2D plane. As 2-D dimensional space-time curve is used to explain why moon revolves around the earth stating because the massive objects wraps the ...
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If a spaceship accelerates enough can it overcome spaghettification?

If a spaceship accelerates at the right amount would that counteract the spaghettification caused by falling into a black hole?
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23 views

How does space-time behaves between opposite gravitational pulls? [duplicate]

this is my first question in physics.stackexchange. I'll try to be more specific. I have a very basic understanding that time flows (is there a better word?) differently depending on the gravity ...
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43 views

Problems of General Relativity on small and large scales [duplicate]

As far as I know, the most important problem of GR on large scales is the cosmological constant problem which in some manner can be thought of as a dark energy problem (please correct me if I am ...
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83 views

Can you use the force of gravity (ie. surface of Earth = 9.8m/s^2) to calculate gravitational time dilation?

I am having trouble tying the Schwarzschild radius to gravitational force as I believe it is not fixed when considering different masses. I am getting results that show a different time dilation for ...
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26 views

Gravitational boson violating relativity [duplicate]

Currently doing a introductory degree level physics course, they were talking about how changes in gravity/gravitational field cause changes so quickly that if you assigned it the "graviton" said ...
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81 views

Is it possible to directly test whether of not the vacuum gravitates?

According to GR, all sources of stress-energy (e.g. everything on the $T_{\mu\nu}$ side of the EFE) should gravitate (e.g. affect the curvature/$G_{\mu\nu}$ side of the EFE). We observe the expansion ...
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85 views

Vibrating water container problem

I am struggling with visualising and understanding the phrasing of this question - cross posted from Math stack exchange since this forum is more appropriate: "A water-filled container is ...
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124 views

What force causes massive objects to bend space? [duplicate]

The visualization of gravity as shown by this video is pretty good at explaining how massive objects bend space, and such bending causes objects around it to fall towards it (a.k.a: gravity). ...
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31 views

Scalar gravity coupled to matter

I am reading Ortin's Gravity and Strings and trying to understand the generalisation of Newtonian Gravity to a relativistic field theory. On page 47 (link above) he motivates the study of the Poisson ...
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45 views

Calculating initial velocity to achieve orbital motion using verlet integration

I'm attempting to build a simple computer programme which models bodies orbiting other bodies. I've implemented a Verlet integrator (https://en.wikipedia.org/wiki/Verlet_integration) and I can ...
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103 views

Unruh radiation and conservation of energy

Consider the Minkowski spacetime filled by some fields in their Minkowskian vaccum state. Now consider a Rindler observer carrying with him, say, one liter of water. According to Unruh formula, the ...
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104 views

How does a Black hole attract light? [duplicate]

Please no hate for lack of knowledge: I am somewhat fascinated with the subject of black holes. However, I do not understand a concept which is constantly attributed with black holes: that a black ...
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global transformations in 3d gravity

I am currently working on proper and improper gauge transformations in 3d gravity and btz black holes. (because I have seen it defined with many different ways I will just say that with "proper"and ...
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61 views

Gravitomagnetic railgun

Would a gravitomagnetic analogue of a railgun work as expected, in theory? Consider replacing the electric currents on each rail with mass currents. Then place a mass between the rails, moving with ...
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115 views

Kater's pendulum graph

I was told that the graph of position vs period must be a straight line in Kater's pendulum, but my findings are more curved, also after searching in google graphs are like parabolas, my question is ...
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1answer
108 views

Is 0.1 bar (hydrostatic pressure) equivalent to 0.1 bar vacuum pressure (absolute pressure)?

Suppose we would like to test the ability of an objec to withstand the pressure under 1 meter of whater. I would like to understand how to simulate this situation using vacuum. Is the 0.1 bar (for 1 ...
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140 views

Lenghthwise center of gravity of a boat based on flotation angle

I am trying to determine the center of gravity horizontally along the length of a pontoon boat so I can properly position the load on my lift. Approximate will do. It seems like an impossible question ...
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50 views

What fills the space between the galaxies, stars and planets? [duplicate]

What fills the space between the galaxies, stars and planets with the exception of gas clouds, dust, atoms, elementary particles and electromagnetic radiation? What the authoritative opinions exist on ...
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81 views

About spin 2, graviton, in the context of attractive force.

excerpt from Introduction to Black hole physics, Valeri P. Frolov and Andrei Zelnikov In this textbook, there is comment about spin of gravitons as follows For gravitating bodies the gravitational ...
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82 views

The age of black holes

I have a very small understanding of space-time however I have been watching some interviews and reading articles featuring theoretical physicist Kip Thorne and I have a few questions that I hope can ...
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97 views

Capillary effect to pump water up to cool water

Chinese scientists demonstrated anti-gravity pump, which uses capillary effect and super-hydrophobic screen to flow water upward by 1cm using internal energy of water. How much water will be cooled ...