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Questions tagged [gravity]

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

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How to determine the mass of a galaxy?

I am having a slight disagreement with my professor. We can measure the mass of a distant star cluster from: A.Its color B.Its radius C.Its metallicity D.Smearing of lines in ...
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Can't pulsars and stars be used for gravitational wave measurement?

Suppose that we collected photons from a distant star, and they arrive regularly at 15 photons every microsecond onto a CCD, when a gravity wave bends space time, wouldn't the regular 15 photons graph ...
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Why do astronauts move so slowly in zero gravity? [closed]

When astronauts are floating about in a spaceship or space station, they nearly always move very slowly. After doing a bit of research I can't see why being in zero gravity would restrict movement to ...
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Looking at the Expanding Universe through the lens of relativity [closed]

The basis and most observable metric for how the universe is understood to be expanding at an accelerating rate is the red shift in observable light. I am assuming it has been thought about or maybe ...
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Why does gravity make time go slower and warp light?

I know that objects with lots of gravity are capable of warping light or slowing time (an example being a black hole). I also know this is because of the theory of relativity, but I need someone to ...
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A neutron star without a flat surface and an atmosphere?

In the Kurzgesagt video Atoms As Big As Mountains — Neutron Stars Explained they state that neutron stars have an atmosphere that reaches about 10 centimeters above the surface. How is this possible?...
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Mini disk of a blackhole meaning

What is meant by the "mini disk" of a blackhole? Is it the same as accretion disk? If not, whats the difference? Eg: In the abstract of this paper https://arxiv.org/abs/1806.05697 it is mentioned "...
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Is the moon inside earth’s atmosphere? If so, what are the consequences?

Recently, a paper was published claiming that the Earth’s atmosphere extends far beyond the Moon. This has been reported on by a number of news sources and websites, including the ESA, Business ...
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Can the moon's gravity influence be observed on the space station's orbit?

In browsing through Astronomy Stack Exchange, I came across this question about orbiting the moon (Is it possible to achieve a stable "lunarstationary" orbit around the moon?). In further ...
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First observation that the movement of a planet or asteroid in its orbit was affected by another planet?

Answers to the question How did Kepler determine the orbital period of Mars? describing careful observations centuries ago got me thinking. Question: What was the first analysis of observations that ...
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How to separate binary and optical stellar pairs?

I have list of stellar pairs from The Washington Double Star Catalog (WDS), i.e. I have next parameters: angular separations position angles stellar magnitudes of both components Additionally I have ...
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Is gravitational lensing a good way to search for negative mass?

Is it possible to verify negative mass with gravitational lensing? The following video proposes an idea that galaxies are surrounded by negative mass: https://youtu.be/MZtS7cBMIc4 Could this be ...
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Why do sun spots appear near the equator of the Sun?

I noticed on many examples sun spots are near the equator of the Sun. Why are there no sun spots closer to the poles of the Sun?
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Can two planets in an empty universe meet/be pulled together?

For this question assume that the entire universe is completely empty. The universe is not expanding or contracting, it is completely motionless since time immemorial and has never moved before. Only ...
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What would happen to the solar system if Earth's mass was removed?

This question is inspired by the "Stargate SG-1" episode "The Road Not Taken". In that story a device is used to shift the entire Earth to another dimension to defend against an attack. I'm not ...
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Is an elliptical orbit around a black hole, or an orbit consisting of three bodies (including the black hole) possible?

If this is possible, would it then lead to an object undergoing varying time dilation (predictable variation with elliptical and random variation with three body)?
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Can light be curved due to heavy gravitational force?

Lets suppose there is a huge planet having large amount of gravitational pull, then will the light passing through the planet get attracted towards it.
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Do falling bodies ever slow down?

I've had some discussions recently about black holes, and the issue of infalling bodies taking forever to reach the event horizon. That's essentially what Einstein said in his 1939 paper on a ...
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Change in axis of the Earth if the Moon would dissappear [closed]

I read that, if the moon would not be there or if it would dissapear or be destroyed it could cause the earth to rotate into a possible axis of 45° degrees. Because it would be missing the ...
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Are other planets' gravity measurable on Earth?

I understand that we can calculate the gravitational force other planets exert on Earth, but can it be measured?
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Why doesn't the vertical light beam get out of a black hole?

I'm asking this question as a follow-up to if light has no mass why is it affected by gravity? Imagine you’re standing on a gedanken planet, shining a laser beam straight up into space. The light ...
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Why do nebulae turn into accretion disks but planets do not?

What are the factors that prevent planets from also turning into disks, like the stellar dust in a nebula does? The Earth is not a perfect sphere, but rather it's squished at the poles and it bulges ...
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1answer
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Largest non-hot gas giants

Excluding 'fluffy' or 'puffy' gas giants that are 'inflated by heat from their stars, what is the maximum radius of a gas giant planet. I keep reading things like "...Jupiter is 'about' as big as ...
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Gravitational acceleration inside a planet

The gravitational acceleration, g, inside the Earth generally decreases with decreasing distance to the center: However, apparently for Jupiter, the gravitational acceleration only increases with ...
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Can eternal inflation and gravity explain dark energy?

First of all, I have absolutely no background in astronomy and physics. I just watch a lot of "i-hope-scientific" youtube channels talking about physics and astrophysics and I can kind of follow the ...
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How would humans with appropriate equipment navigate the surface of Saturn's moon Titan on foot?

Taking into account the physical characteristics of Titan (e.g. surface gravity, atmospheric pressure), what would be the most efficient method of motion for an astronaut to navigate the surface of ...
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How does gravity affect pressure under water?

How different would being under water in Europa differ from being under water on Earth? Would it be possible to dive deeper on Europa with a submarine than on Earth and by how much?
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Why don’t we feel the Earth rotating beneath us?

I’m not sure all of the details in the experiment but basically it went as follows. Someone marked their location of take off in a hot air balloon and went straight up in the air. They stayed ...
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Black hole, escape velocity, going up?

I do know nothing can escape a black hole, and I understand popsci explanation of geodesics of space-time around and inside the event horizon. I however have some trouble with following thought ...
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Could a moon be passed from one planet's orbit to another?

Like if you had two planets that had a close orbital path could the moon be pulled away from the first planet?
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1answer
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What is the smallest possible planet with same sea level atmospheric pressure as Earth? [closed]

Suppose there is a planet made of pure tungsten (a quite common and heavy element), with perfect spherical shape. Which should be its radius so that the air pressure and ground/sea level is the same ...
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1answer
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The specifics of two Earth-like worlds orbiting each other? [closed]

I'm currently looking into writing a story or two set on twin worlds, which I came to find out in my research is apparently not a new idea (Double planets? Rocheworlds? Am I close?). But I want it ...
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Since gravity is like an indent on a piece of paper (the space/time matrix) to a marble, can the black hole eventually suck in the matrix?

Can a black hole suck in time? People claim that if you were to put a bowling ball on a trampoline and rolled much smaller balls through the deppression, some would stay in "orbit", some would roll ...
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2answers
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Is there a limit to how fast spacetime can bend/warp around an accelerating object?

If in the future a spaceship can accelerate to nearly the speed of light, will it encounter any kind of resistance/drag from the spacetime in front of it not being able to bend/warp fast enough around ...
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Could the Moon sit on the Earth?

Let say that the Earth's Moon was knocked out of orbit and landed on the Earth with some damage but not world ending. Would Earth's atmosphere envelop to include the Moon? Would the moon sink into the ...
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1answer
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How dependent is Earth is with the other Planets' gravity? [duplicate]

How would the Earth be affected if the Moon was destroyed as far as our orbit around the Sun? What if Mars or Jupiter was destroyed?
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1answer
72 views

Does time dilation increase within overlapping gravitational fields?

If a spaceship was to travel to the barycenter of a binary star (the stars having identical size and mass) and come to a stop there, would the people on board this spaceship find that time is moving ...
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1answer
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Expansion ofthe Universe [duplicate]

If the universe is expanding how come Andromeda is heading for us? In isolated spatial areas does gravity overcome universal expansion? What is the gravitational force between us and Andromeda?
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Astrophysical Jet Size?

I am wondering about what is the estimated size of astrophysical jet that shoots out from a black hole, I don’t know if it is determined by the size of a black hole. What would classify a black hole ...
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Space curvature and its rotation

As I learn, the gravity is caused by the spacetime curvature. Is there any gravitational/magnetic field that really exists around the Earth, or any other planets? Since the planets/stars rotate, does ...
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Why does earth not collide with the sun? [duplicate]

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 the curvature of ...
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1answer
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Could dark matter be wrong? [duplicate]

As I understand, the evidence for dark matter is the observation of the gravitational dynamics of objects around the size of galaxies and above. They move in a way such that the equations imply there ...
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Is there any orbit at which the Roche limit can be “felt”?

Do any of the planets have a Roche limit that is strong enough to be felt by an astronaut whilst in orbit?
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How come moon's difference in thickness between sides does not create an unbalance on its mass?

I've just found out that moon's dark side is 30 miles thicker then the closer side to the Earth. So I'm wondering about moon's mass. How come it's still balanced? Supposing the far side is indeed ...
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Can gravity be amplified by other celestial bodies in its vicinity?

I`m wondering if the gravitational pull from earth that should be constant around the planet, will get amplified by a celestial body like the moon orbiting the earth?
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Universe Sandbox 2 accurate representation of gravity

I've been playing Universe Sandbox for a while now and I have never been able to make a near Earth asteroid collide with it. By "make" I mean, simulating billions of years of known, near Earth objects ...
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How does the gravity of one planet affect the velocity of other planets?

If there was a massive enough planet outside of earth's orbit to affect it, how would the earth's velocity change? I know it would be small, but would the velocity increase or decrease?
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Could two planetesimals orbit a dense object and share an atmosphere?

Could two objects be caught into an orbit around some kind of dense object, perhaps a rogue planet. Could they share an atmosphere.
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Physical measurements and celerity of black hole mergers?

LIGO detected a black hole merger for bh's of about 30 solar masses, with a schwartzchild radii of about 20km. Were the gravity waves generated by masses distanced by a few microns or a few ...
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Why do neutron stars collide instead of just revolving around each other like planets revolve around the Sun?

We know about events like two neutron star colliding and resulting in a black hole, also collision of black holes, and collision of galaxies. But we never see a satellite such as a moon colliding with ...