Questions tagged [gravity]

Questions regarding the attractive force which exists between any two bodies of matter.

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Light/Dark energy/Dark matter

So I have been working on my comic book project that takes place on another planet. But in my story, there will be warp gates and there will be other civs that can travel between stars. I am ...
Kul Tigin's user avatar
3 votes
2 answers
188 views

Black hole explosion due to rotation

I am not an expert, I was just thinking about this scenario: A black hole that, for some reason, will start spinning faster and faster. Is it theoretically possible that the rotation becomes so fast ...
Nicola Lepetit's user avatar
2 votes
2 answers
227 views

Fractal structure of the universe

I decided to return to the question first written here after some time, since a short and succinct phrase had formed in my head that described the phenomenon that I was trying to understand. What are ...
dtn's user avatar
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6 votes
1 answer
160 views

Gravity is inversely proportional to the distance squared, and tidal forces to the distance cubed. Is there any phenomenon inv/prop to the distance^4?

Kinda ran out of characters for the title so had to improvise. Gravity decreases with the square of the distance due to the inverse-square law, and tides are inversely proportional to the cube of the ...
user267545's user avatar
-3 votes
1 answer
180 views

Shouldn't the Friedmann equation take into account the massive extra distance traveled during the time for gravity to travel across the universe? [closed]

I’ve got a question that has been bothering me for the past few years that of the few sources that are only somewhat related to this, none of them say anything about this should be wrong so I can’t ...
Gref's user avatar
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8 votes
6 answers
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At what velocity would an object have to fall in order to become weightless? [closed]

Assume an object is falling toward the earth then at what velocity would the object be weightless? Taking the air resistance into account might be a factor here so lets assume no air resistance to ...
Sedumjoy's user avatar
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1 vote
0 answers
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How long could a world like the Moon survive with an Earth mass black hole in the center?

I asked that question at the worldbuilding stack exchange. https://worldbuilding.stackexchange.com/questions/202273/how-long-could-a-planet-or-moon-survive-if-it-had-an-earth-mass-black-hole-withi ...
M. A. Golding's user avatar
3 votes
3 answers
1k views

Celestial "orbits"

I heard that we're losing our moon, its slipping away from us in such tiny imperceptible steps that we don't notice any significant change even over kiloyears. The same must apply to planets, inching ...
Agent Smith's user avatar
1 vote
0 answers
67 views

Does dark energy increase eccentricity in orbits of galaxies?

I came across this thesis dissertation which indicates that if a pair of orbiting galaxies are sufficiently far apart (with a sufficiently large orbital radius) then their orbits would change from ...
vengaq's user avatar
  • 827
6 votes
6 answers
465 views

Gravitational waves vs. "normal gravity"

Imagine you have a super sensitive 3D accelerometer/gravimeter alongside the Virgo interferometer. A gravitational wave passes by and Virgo detects a variation in the length of the 3000m long arms. ...
Peter's user avatar
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4 votes
5 answers
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Could the human body feel the sudden disappearance or end of a gravitational force?

For example, if the Sun suddenly disappeared, would we physically feel it 8 minutes later (not counting light/temperature), since propagates moves at the speed of light. And if so, would the effect be ...
Parrotmaster's user avatar
3 votes
2 answers
505 views

Spiral Galaxies

I only have a very, very, basic understanding of linear motion, much less so of circular motion. What I can recall is my book telling me if you spin a stone tied to the end of a string and the string ...
Agent Smith's user avatar
-2 votes
3 answers
243 views

Can black holes even exist [if mass cannot be retained near the collapse threshold]?

A black hole happens because enough material mass exists in an area to create a gravitational field strong enough that nothing escapes (including light). This gravity also exceeds the strength of ...
hamstar's user avatar
  • 113
3 votes
1 answer
519 views

If you are in a deep gravity well, where time goes by more slowly, do you see the unfolding of a cosmic event at a different rate?

If you were on one of those planets orbiting a super massive black hole (ala Interstellar), where time is moving more slowly, would you time astronomical events differently or even the age of the ...
Jack R. Woods's user avatar
8 votes
5 answers
2k views

Does the escape velocity formula take into account how a gravitationally bound object's distance to its primary increases before coming back down?

Confusing title, I know. Imagine a perfect, homogenous sphere with an exact radius of $1,000 \text{km}$ and an exact mass of $8 \times 10^{15} \text{kg} $. If you use the formula for escape velocity $...
user177107's user avatar
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2 votes
1 answer
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Hierarchy of gravitational interactions of astronomical objects: from single to large-scale structures

Hierarchical structure is clearly visible in the Universe. The "observable universe" includes almost empty voids, between which lie large cosmic filaments. The filaments consist of galactic ...
dtn's user avatar
  • 705
12 votes
3 answers
5k views

If the Earth had another moon would it be better protected from asteroids?

Would the moons get struck by asteroids instead of the Earth or would the moons attract more asteroids and make it more likely the planet gets hit?
user avatar
5 votes
3 answers
265 views

Are there really confined Globular Clusters?

I am trying to find real physical examples of (self-gravitating) astrophysical systems that are appropriately confined and can thus be seen as in equilibrium. Modelling-wise, you can theoretically put ...
FriedBarking's user avatar
0 votes
1 answer
135 views

What is everything wrong with this theory of dark matter?

So I had a hypothesis about why dark matter exists, but seeing as I've just barely begun studying astrophysics its most likely chock full of misconceptions and oversights. Here's a diagram of the ...
Aryaman Rtunjay's user avatar
1 vote
0 answers
35 views

Dark energy affecting the ejection and infall of material in galaxies?

Some galaxies have active outflows of material (mostly gas) that would eventually stop at some distance and then fall again into the galaxy due to gravitational attraction. However, can dark energy ...
vengaq's user avatar
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4 votes
1 answer
303 views

Dark Matter's effect on galaxy structure

One "fun fact" that's always been, well fun. Is despite what most assume, our sun does not orbit a supermassive black hole or any object at the center of our galaxy. Recently I read an ...
Troy Dube''s user avatar
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0 answers
59 views

Question about how it's possible for black holes to have gravity and a possible resolution [duplicate]

1. Assumptions 1.a: gravity propagates at c (maximum) 1.b: gravitational fields cause time dilation 1.c: escape velocity at the event horizon is c 1.d: gravity "warps" space-time, but in ...
P Varga's user avatar
  • 190
1 vote
1 answer
84 views

How to turn find velocity dispersion from radial velocity

In the above given picture Vi is the velocity of the i-th galaxy in the cluster while Vm is the mean velocity of a galaxy in the cluster. and V i,r is the radial velocity of the i-th galaxy and V m,r ...
Moiz khokhar's user avatar
6 votes
3 answers
1k views

Concerning a binary system of stars/planets/black holes could one of them be ejected before eventually merging or colliding?

I was having a discussion with an undergraduate student of physics about binaries and their interactions with external celestial bodies (which could cause the ejection of one of the members in the ...
vengaq's user avatar
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3 votes
0 answers
66 views

Gravitational recoil with stars/planets...?

When two black holes are merging, the resulting merge can be ejected if one of the black holes had less mass than the other one, so the gravitational waves emitted by both of them is unbalanced, and ...
vengaq's user avatar
  • 827
4 votes
2 answers
173 views

Is it possible to detect gravitational lensing of both light and gravitational waves originating from the same event?

Is it theoretically possible to detect gravitational lensing of both light and gravitational waves, when both originate from the same source/event (merger of two stellar black holes or merger of two ...
Alex's user avatar
  • 681
17 votes
4 answers
4k views

What is the shape of orbit assuming gravity does not depend on distance?

We know that the orbit of the earth is elliptical considering the force of gravity is inversely proportional to the square of the distance. But assume that, gravity does not depend on distance. ...
Arafat's user avatar
  • 171
0 votes
1 answer
97 views

How do primordial black holes are able to have an event horizon?

How do primordial black holes have an event horizon? Sorry for the stupid question, but I know primordial black holes have just a handful of mass in a cosmic scale compressed in a singularity. But if ...
Artur Carneiro Barroso's user avatar
1 vote
0 answers
22 views

How can Aggregation of Gravitational Fields of subplanetary solar objects improve our understanding of the motion of the planets?

If we imagine magnets on a table as a simplified analogy in regards to gravitational attraction between objects, then it may be demonstrated that when three objects are placed in a row labeled in ...
Darren's user avatar
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1 vote
0 answers
33 views

Modelling dark energy as a potential?

Dark energy is the cosmological constant.However can we model dark energy as some form of field with a corresponding potential?
Volpina's user avatar
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1 vote
0 answers
60 views

Can the gravity of objects entering the observable universe be detected?

As time passes, we will be able to see objects that are further away, as their light eventually reaches us. Since gravity also travels at the speed of light, would we be able to detect when a super ...
Colin's user avatar
  • 79
1 vote
1 answer
122 views

How does superfluid dark matter keep stars orbiting at high speeds in galaxies?

According to A paper on Ultra-Light Dark Matter, Superfluid dark matter is a kind of Bose-Einstein condensate. But how does it help stars keep their high or velocities in galaxies. Can somebody ...
user avatar
0 votes
0 answers
37 views

Lagrange points and Laplace equation boundary condition

I have been reading about Lagrange points and Lagrange regions and how we can apply Laplace's equation for these regions however which are the boundary conditions of the Laplace equation at these ...
Volpina's user avatar
  • 111
3 votes
2 answers
328 views

Gravitational-Wave Strain and Power (watt/square metre)

If we detect a gravitational wave with a strain of, for example, $h=10^{-20}$, what is the flux of power carried by this wave, in SI units, $W/m^2$ ? How can flux of power be calculated for a given ...
Hamidreza Abdollahi's user avatar
1 vote
0 answers
52 views

Are short-period comets more stable (in their orbits) than long-period ones?

Why the sharp distinction between short-period (P) comets of less-than-200-year orbits and those (C) with even slightly longer ones? To explore the possibility that it has to do with stability, I will ...
Kurt Hikes's user avatar
  • 4,927
1 vote
1 answer
131 views

Eccentricity with a law of gravity different from the classical one

How can I calculate the eccentricity of the orbit of a planet (with mass equal to that of the Earth) around a star (with mass equal to that of the Sun) assuming that the force of gravity is given by ...
LOGIC's user avatar
  • 29
2 votes
0 answers
84 views

Velocity of the object in Binary system

how to i can calculate the velocity of the object? If i know the distance of the object from the center of mass, and i know distance between the two (identical) ellipse center... (the two object has ...
Domahidi Péter's user avatar
3 votes
4 answers
8k views

Does the Earth constantly lose mass?

The Moon is orbiting the Earth in a circular motion. To keep any object in a circular motion we need energy. Hence, does the Earth lose energy by pulling the Moon? In that case, does the Earth's ...
Prajwal D M's user avatar
13 votes
1 answer
2k views

How would "dark matter", subject only to gravity, behave?

If we were to hypothesise that the Universe contained a significant mass of "dark matter" particles subject only to gravity, presumably general relativity would give us a good idea of how ...
mikado's user avatar
  • 233
2 votes
2 answers
258 views

At what point above Jupiter is the gravity Earth-like?

Jupiter is a massive planet. We get it. However, we have also heard that, since it has such a huge radius, at different elevations it is possible to experience different levels of gravity. We hear ...
user98816's user avatar
  • 469
8 votes
1 answer
120 views

How light could the lightest objects able to exist in a stable orbit be?

Below a certain M1M2, gravity would get so weak that the masses wouldn't be able to orbit each other with stability, as other factors would overwhelm them, even in the quietest, stillest places in the ...
Rabbi Kaii's user avatar
2 votes
1 answer
468 views

Does a planets mass affect its gravitational pull? Let's say earth increased or decreased in mass could that theoretically affect gravity?

This was a random thought I had, and I can't seem to find any answers. I was thinking that if the Earth shrunk that could possibly cause an increase in ...
KaydPepto's user avatar
2 votes
2 answers
79 views

Can a satellite at lagrange point be stabilized with gravity gradient?

Assuming that the satellite is big enough and the it is at the Lagrange point between the Earth and the Sun, can this satellite be stabilized with gravity gradient? (which means, can this satellite ...
Cho's user avatar
  • 23
1 vote
0 answers
65 views

What would happen if all water on earth including the oceans was placed evenly over the atmosphere of Earth? [closed]

Would that massive water body sit on top of the atmospheric bubble or would it fall to the ground? Would it rain water or fire instead? Would we see the skyes red instead of blue? What would be the ...
Lerian Acosenossa's user avatar
1 vote
0 answers
53 views

How to call the fear of no gravity? [closed]

In opposite to barophobia I can't google out a fear of the case, when a man is taken out of the ship and he must go through the spaceship's docks and he can't get the direction of gravity - in the ...
Peter.k's user avatar
  • 119
3 votes
0 answers
90 views

Kinetic energy in cosmology?

Spacetime expands at an accelerated rate due to the Hubble flow. In many papers that I've read, objects coupled to the Hubble flow are treated as if they have some velocity and kinetic energy ...
vengaq's user avatar
  • 827
2 votes
2 answers
1k views

What kind of effects would two moons have on an earthlike planet?

On Earth our moon has several effects: it generates two high and two low tides a day; it slows down the spin of the planet and stabilizes its wobble, etc. So, what possible effects could two moons, ...
CuriousExplorer's user avatar
6 votes
1 answer
278 views

Is the speed of time much slower on sun surface?

The gravity forces on Earth and Sun is different and in Interstellar, they said something like high gravity slows time. So if we say Sun is N billion years old, that must be earth time but on Sun's ...
thevikas's user avatar
  • 171
2 votes
0 answers
45 views

Is frame dragging expected to be quantized in a theory of quantum gravity?

Protons and electrons have angular momentum which is quantized. Would the angular momentum of black holes be quantized in quantum gravity? Would this then affect Hawking radiation?
user avatar
2 votes
1 answer
67 views

The path of a particle in planet's magnetic field doesn't not seem to change with the charge of the particle. Can someone please check what is wrong?

I am trying to plot the path of a charged particle in a planet's magnetic field. For positive and negative charge (β=charge/mass) different solutions/paths are expected. But,I got the same solution (...
Lunthang Peter's user avatar

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