# Questions tagged [gravity]

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

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0 votes
2 answers
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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 ...
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 ...
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 ...
• 705
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 ...
• 958
-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 ...
• 11
8 votes
6 answers
4k views

### 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 ...
• 1,161
1 vote
0 answers
98 views

### 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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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 ...
• 313
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 ...
• 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. ...
• 381
4 votes
5 answers
3k views

### 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 ...
• 186
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 ...
• 313
-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 ...
• 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 ...
• 2,932
8 votes
5 answers
2k views

1 vote
0 answers
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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 ...
• 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 ...
• 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 ...
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 ...
• 121
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 ...
• 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 ...
• 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 ...
• 758
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 ...
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 ...
• 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 ...
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 ...
• 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 ...
• 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, ...
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 ...
• 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?
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 (...