Questions tagged [gravity]
Questions regarding the attractive force which exists between any two bodies of matter.
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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
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Can a small black hole orbit a large star?
I recently read about the discovery of a tiny black hole (with only three times the mass of the sun) nicknamed ‘The unicorn’ about 1500 light years from earth. This got me thinking, can this black ...
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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.
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 $...
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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 ...
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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 ...
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Gravitational field for oblate spheroid?
Consider a planet, described as an oblate spheroid. Assume that the spheroid is uniformly dense but not a point source. Outside of the object, do all vectors in the gravity field point through a ...
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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?
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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 ...
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Time in 0 gravity points
If being close to a supermassive body like a black hole makes time pass more slowly for us than for an observer from a point of view with a weaker gravitational field, if we get to be at a point in ...
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Lack of objects between heliopause and Oort cloud?
If we take a look at a logarithmic scale of the Solar System, there appears to be a large gap between the heliopause and the Oort cloud:
Why is that? There are some objects in the gap, but why are ...
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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 ...
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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 ...
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The anomaly of spiral galaxies and the need for dark matter
Please could some explain this to me - I understand that some galaxies are rotating with a speed that the stars on the outer reaches should not be held within the spiral given the observed matter and ...
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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 ...
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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 ...
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Are gravitational waves affected by gravity?
Are gravitational waves affected by gravity? When a gravitational wave passes by objects, do their gravitational fields warp or change it?
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What are "non-Keplerian" orbits? What are some familiar examples in our solar system, and can some still be closed?
This excellent answer to Forms of stellar orbits around the galactic center invokes the following concepts:
non-Keplerian orbits
closed orbits
I have a fairly good idea what these mean and so might ...
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Spinning black hole vs non spinning black hole
Does a spinning black hole have a stronger gravity than a non spinning one.After all, a spinning black hole is stretching space-time more, so does that make a difference is gravity?
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Why do Earth and moon move apart but binary black holes move closer?
According to the accepted answer on Is the moon moving further away from Earth and closer to the Sun? Why?, the moon is receding from Earth because tidal forces and friction cause energy to be lost.
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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 ...
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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 ...
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Why does time pass faster in moon than the earth?
One of my friends said that,
time passes faster in moon than the earth
Why does time pass faster on the moon than on the earth?
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Is there a way to estimate or calculate the tidal range induced on a water-bearing planet?
Consider a system in which a central star is orbited by a planet with liquid water oceans, which is itself orbited by a moon.
Given the masses and distances between these three objects, is there some ...
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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 ...
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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 ...
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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. ...
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How large can a ball of water be without fusion starting?
How large can a ball of water be without fusion starting?
Peculiar question: some explanation might be necessary. My young son is into ‘space’ and astronomy. One of his posters says that Saturn could ...
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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 ...
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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 ...
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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 ...
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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?
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What effect does Earth losing a part of its mass have, is there an impact on the Earth's orbit around the Sun?
This is a random question that popped into my mind. I'm not a physicist or astronomist, however, I am genuinely curious. Also, this is not intended as a science fiction question, but an actual science ...
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On a log-log plot of surface gravity to planet mass, what is the meaning of the y-intercept?
I am playing around with data from exoplanets.org, and am interested in the plot of surface gravity to planet mass. I reproduced this plot:
after downloading their data and performed a non-linear ...
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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 ...
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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 ...
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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 ...
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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 ...
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If the Sun disappears right now, when the absence of its gravity affects on Earth? [duplicate]
Imagine if the Sun disappears right now. When the Earth will be affected by its absence? Does it affect immediately, or it takes almost 8 minutes? (The time that light travels from the Sun to the ...
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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 ...
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Physical Meaning of the Principal Tidal Fourier Modes and Their Integers
I'm trying to understand tides evolution of planets, and I often come across the Prinicipal Tidal Fourier Modes expressed as:
$$ \omega_{lmpq}$$
For example, see the discussion after Eq. A15 in ...
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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 ...
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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 ...
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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 ...
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Which factor most affects the accuracy of Kepler's Third Law when applied to solar system planets?
We know that Kepler's 3rd Law is not perfectly accurate due to gravitational perturbations of other planets, moons, etc., but which factors most affect the accuracy?
Is it the semi-major axis, mass of ...
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