Questions tagged [gravity]

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

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8
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2answers
309 views

Is it possible for a moon to continuously have a side facing its star whilst orbiting a planet?

For example; is there any possibility for the moon to always have a side facing the Sun whilst orbiting Earth? And if so then what would the day cycle be like?
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1answer
122 views

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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1answer
95 views

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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447 views

Estimating the Rate at which Moon is Moving Away from the Earth

Here it has been discussed why the moon is moving away from earth at a rate of 1.5 inches per year. Is there any way we can estimate the value (e.g, 1.5 inches per year) mathematically?
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1answer
51 views

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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1answer
81 views

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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3answers
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Why don't we orbit the center of our galaxy?

At the center of the milky way, there must be some giant mass that keeps the galaxy from just floating away from itself. So, obviously, we feel the immense gravitational pull of whatever this is. But, ...
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3answers
554 views

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 ...
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5answers
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Is the influence of gravity instantaneous?

When I was in college, I posed to my astronomy professor a thought experiment that had been puzzling my mind for some time: "If all the matter in the Sun magically disappeared instantly, how long ...
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1answer
681 views

Are the planets in our solar system in free fall?

If I’m correct, the International Space Station is in free fall, but is moving fast enough to keep it’s position. Assuming that is true, does that mean that some/all planets orbiting the Sun are in ...
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1answer
242 views

How far out can the sun keep celestial objects revolving?

Astronomers define the Solar System as the distance under the influence of gravity from the Sun. I read that the Oort cloud is probably the farthest object that surrounds the sun. The sphere of this ...
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2answers
124 views

Do unattached objects contribute to a planet's gravity?

If you could measure Earth's gravity with infinite precision, and did so both with Earth and its full population, and Earth with no people, would there be a direct difference in gravity? Is this even ...
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2answers
267 views

When the asteroid hit the earth 65 mya did the earth's gravity pull change? By how much?

When the asteroid hit the earth 65 million years ago, did the earth's gravity pull change? By how much?
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0answers
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Does center of gravity of Solar system influence intensity of space rays reaching earth, space dust, speed of earth rotation?

I found an interesting article, claiming very interesting things. But I cannot find any trust-worty sources confirming such bold claims. Maybe someone came across some solid proof? 1) Center of ...
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0answers
172 views

Great attractor is doing the big crunch? [closed]

Laniakea and other super clusters are moving towards shapely super cluster . Even the Great Attractor is moving towards it. Isn't it all about the Big Crunch?
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1answer
879 views

Can a star eat a black hole?

I know there are stars much larger than the sun and that we've discovered "small" black holes, so, let's say that the Pistol Star, which is at least 80x the mass of the sun, and the smallest known ...
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1answer
180 views

Are there sufficient observational data to measure non-Newtonian perihelion advances of any Asteroid and Comet orbits?

Anomalous (i.e. not predicted from Newtonian theory) advances of the perihelion direction have been observed for many solar system planet orbits and have been accounted for by Einstein's General ...
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2answers
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The size of the radius of the event horizon of a black hole created by the merger of a black hole binary system

Let's assume that you had a black hole binary system and everything said here is possible. Their large masses would lead to a large emission of gravitational waves. The loss of orbital energy and ...
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2answers
365 views

Roche limit - calculation with centrifugal forces

Let's assume there is a small natural satellite oribiting a massive planet. The satellite rotates synchronously (revolution period = orbital period) on a circular orbit, both bodies are homogenous and ...
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2answers
3k views

Does every object in the Universe have gravity? Space has no gravity, why?

My science teacher told me that every object in Universe has gravity but space is a part of Universe too, so, why does the space have no gravity?
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0answers
718 views

Gravity on a right rectangular prism? [closed]

Let's assume there is a right rectangular prism floating about in space, what would the gravity be like across its 6 flat surfaces? What gravity would you experience if you set foot on the rectangular ...
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2answers
728 views

Spacetime curvature illustration accuracy

When a particle travels through spacetime, this is sometimes illustrated moving in flat grid with various depths. How accurate is this way of imagining gravity? Can the gravity well be infinitely ...
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6answers
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Are black holes really singularities?

Can't black holes just be super dense objects? They could still be black (having the color of black never really required special physics, after all) and have a really strong gravitational field. If ...
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0answers
219 views

If Earth had rings, how long would it take for the rings to loose orbit? [closed]

If Earth had rings, how long would it take for the rings to loose orbit? One of the answers in this question https://physics.stackexchange.com/questions/281828/if-earth-had-rings said we did at one ...
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1answer
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Can Earth be spun like a magnet?

Could an asteroid or a rogue planet have enough magnetism and/or gravity to spin the Earth near the speed in which they are passing by Earth?
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2answers
71 views

Are there currently any planned or proposed missions to measure the gravitational fields of other planets in our solar system?

I just recently found out about the GRACE Nasa mission which basically mapped out the gravitational anomalies of earth as well as serving extensively in the study of earths geology and the movement of ...
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1answer
713 views

How does space time differ between galaxies? [duplicate]

Does the gravity wells differ enough between galaxies to have different speeds in space time? How much slower in space time would the biggest galaxy have compared to the Milky Way?
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1answer
191 views

How would you relate the respective solar gravitational pulls of two planets?

I was asked this question: How much weaker is the gravitational pull of the Sun on Neptune at 30 AU, than it is on Earth at 1 AU? How would I even begin to determine this?
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Does Uranus have a stronger gravitational pull on its moons than Earth does?

I've read that Uranus has a lower surface gravity due to its lower density than Earth. However, does this mean Uranus has a weaker pull on its moons than Earth does for the same reason?
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4answers
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What happens if gravity shuts down for only one second? [closed]

What would happen if gravity completely stopped for 1 second?
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4answers
3k views

Why is gravity only an attractive force?

As per the universal law of attraction, any two bodies (having some mass) experience a force of 'attraction' which is proportionate to ...and ...inverse proportionate .... Then comes my question: Why ...
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2answers
358 views

Is the Roche limit used this way?

Has the Roche limit affect been observed having an effect on an constructed object gravitational wise to cause damage? Could the Roche limit be used to slow an object?
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3answers
244 views

Where do rocks come from?

Consider a loose pile of rocks in an early solar system, say a tiny asteroid. As it accretes more and more material, the pressure at its center eventually becomes great enough to collapse the gaps ...
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2answers
365 views

Does gravity repel when dark energy is involved?

So I am currently reading the book We have no idea by Jorge Cham and Daniel Whiteson. In one of their chapters they talk about how gravity is a force that only attracts and doesn't repel, most of the ...
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1answer
160 views

Behaviour of black holes

This question could be strictly linked to my another question related to black holes. It’s known that the horizon event is a place where dust,star components are ready to be incorporated to the ...
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1answer
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Is it correct to assume that the relationship between an objects mass and size, is what decides if it’s a black hole or not?

I’m asking this question in reference to a scenario I saw posted a couple of days ago, where it’s stated that if you would shrink earth to the size of a cherry, it would become a black hole. Is it ...
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2answers
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Will Earth lose the Moon before the Sun goes into supernova?

Ive read on some sites and saw on youtube videos that the moon is getting away from earth by 1-3 cm a year. Is this enough to make the Earth lose the Moon before the Sun goes into Supernova? Im ...
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5answers
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What's the fastest moving object in the universe?

We know that nothing can have proper velocities larger than the speed of light in vacuum. But are there any objects in space that get close to it? Any comets, or other objects thrown by gravity or ...
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1answer
10k views

How can I calculate the orbital periods in a binary star system?

I have two stars, with known masses and known orbital radius. How do I calculate the orbital periods of both stars?
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2answers
144 views

What defines stationary vs spinning in space?

To produce artificial gravity on a space station, we simply spin it around some central point, and the acceleration makes objects "fall" outwards. If our space station is so far in deep space that it ...
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1answer
330 views

How much time does it take for a meteor (shooting star) to touch the ground after its combustion? [closed]

I know that meteors that We see as shooting stars travel tens of thousands of kilometers per hour and are tiny as a grain of sand, but after hitting the atmosphere and burn I suppose that its ashes ...
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1answer
73 views

Maximum disturbance to space time of gravitational waves, and will this affect humans? [duplicate]

Do we have a theory that can tell us how much change gravitational waves can make to space time. If it is infinite then I think any time we can see biggest change in space time and how much could it ...
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2answers
778 views

Why don't small stars end up as a black holes?

I have recently done some research into black holes, and realized that big stars form black holes, whilst smaller ones don't. Is this because the gravity isn't strong enough for it to fall in on ...
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3answers
413 views

Explaining gravity assist to a 6-year old

We've been talking about Cassini with my 6-year old daughter recently and I've mentioned that it picked up more speed by passing close to Venus (twice), Earth and Jupiter. But then, I've struggled to ...
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2answers
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Where is a Hollow Object's Center of Gravity? [closed]

Let's imagine that the Earth's moon is hollow and the remaining mass is structurally strong enough to retain its spherical shape (like a really big tennis ball). Given this scenario, where would its ...
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3answers
6k views

Is a perfectly circular orbit possible?

Let's assume that there is a perfectly spherical planet and there is a moon which is also perfectly spherical. Let's assume that there is no atmospheric drag and no other gravitational pull. If the ...
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1answer
13k views

Is the moon moving further away from Earth and closer to the Sun? Why?

According to The NASA Moon Facts page: The moon is actually moving away from earth at a rate of 1.5 inches per year. Why is the moon moving further away from the Earth? Is this a result of the ...
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3answers
2k views

Does gravity slow or speed light up?

The speed of light in a vacuum is presumably the fastest speed possible. if gravity bends the course of light, does this imply that gravity the retards light so it is moving at a slower speed? If ...
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1answer
207 views

Is there something wrong about the gravity formula? [closed]

Help needed, please. I need the input of the experts here. I have always been troubled by the formula ..F = G * m1 * m2 / r^2.. , which appears to be counter-intuitive. It should be ...F = G ( m1 + m2 ...
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2answers
203 views

How strong would gravity need to be to prevent star formation

This question got me thinking. In another universe, with a different value for the gravitational constant G, how much bigger would G need to be for star formation to be prevented? In other words in ...

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