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

learn more… | top users | synonyms

0
votes
1answer
12 views

Is it accurate to say that we have a gravitational attraction towards all objects in the known universe?

Its probably small, but is there a theoretical gravitational attraction between all objects in the universe? Light can move pretty far, so does that mean gravity can as well, and is the gravity ...
9
votes
3answers
386 views

How do we know that the speed of the influence of gravity is instant?

When I was in college, I posed to my astronomy professor a thought experiment that had been puzzling my mind for some time: "If the sun magically disappeared, instantly, along with all its influences, ...
2
votes
3answers
104 views

How much would you weigh if Earth stopped orbiting the Sun?

I have a curious question. The reason why astronauts are weightless in space is because they are orbiting Earth. If they suddenly stopped orbiting they would fall directly into Earth. Earth is doing ...
4
votes
1answer
115 views

What is the difference between Sphere of Influence and Hill sphere?

Wikipedia's definition of Hill sphere is: An astronomical body's Hill sphere is the region in which it dominates the attraction of satellites. To be retained by a planet, a moon must have an orbit ...
1
vote
4answers
139 views

What happens if gravity shuts down for only one second?

Question has it all.What happens if total gravitational force in the universe shuts down for only one second?
2
votes
5answers
199 views

Could light be dark matter?

Is it possible that light itself is dark matter? I am speaking of photons (e.g. visible light, infrared, ultraviolet, etc...). I realize light is understood to be massless, but it is obvious it at ...
7
votes
1answer
119 views

Dark Flow: statistical limits on existence

Dark Flow has been thrown around as a term a lot lately, especially with the latest Planck results. New Scientist reported last year that it was now statistically improbable, but the paper by Atrio ...
1
vote
1answer
57 views

Is there any way a meteor can hit at less than escape velocity?

Note: I have figured out one case: The meteor is splash from an impact on a close-in moon. I'm looking for any path from deep space. My understanding is that anything from deep space will ...
0
votes
1answer
41 views

Apocalypse on earth

What would it feel like on Earth if the Earth accelerated due to sudden changes in the solar system like ejection of another planet? Would there be giant tidal waves and other cataclysmic events?
-3
votes
2answers
45 views

Brain vs galaxy [closed]

The number of neurons in the human brain is equated with the number of stars in the Milky Way. Could the Milky Way act as a consciousness of its own, with the gravitational strength between the stars ...
4
votes
1answer
92 views

Maximum Amplitude of a Lissajous Orbiting Object in a L4 or L5 Position

I stumbled on The Lagrangian points during some wikipedia reading. After looking at the gravity contours, I naturally come to the conclusion that the L4 & L5 should have a wave pattern and then ...
2
votes
3answers
203 views

Why isn't the star that created the black hole a black hole?

If the mass of a black hole is creating so much gravity that light cannot escape, why isn't the mass of the star that created the black hole (before it went supernova) trapping light as well? By all ...
0
votes
3answers
115 views

Earth's gravitational pull on ISS

How do they make International space station to orbit the earth beyond earth's gravity acting on it? We all know that ISS is rotating at an altitude of just 350km away.How could ISS escape earth's ...
5
votes
3answers
82 views

Can you explain the pattern of Hill sphere sizes of the objects of the Solar system?

I found this image on calculations of Hill sphere for planets/dwarf planets of the Solar system. From http://en.wikipedia.org/wiki/File:Hill_sphere_of_the_planets.png I found it interesting that ...
8
votes
1answer
285 views

Determining effect of small variable force on planetary perihelion precession

Is there an analytical technique for determining the effect of a small variable transverse acceleration upon the rate of aspides precession (strictly not a precession but rotation of the line of ...
1
vote
2answers
79 views

any unique phenomenon when the cores of two planets are aligned with their star's core?

Imagine a line passing through the cores of two planets (in the same planetary system) and their star. Have we ever witnessed this - either with both planets on the same side of the star or on ...
1
vote
0answers
30 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 ...
1
vote
1answer
40 views

Under Earth's gravitational pull, how dense would an object have to be to reach its Schwarzschild Radius?

The Schwarzschild Radius is a theoretical radius, that if the mass of the object was compressed into that certain radius, the escape speed from the surface of the compressed object would equal the ...
1
vote
1answer
40 views

Electron Degeneracy Pressure and the Pauli Exclusion Principle

I have read that what keeps white dwarfs from gravitational collapse is electron degeneracy pressure. How does this pressure prevent further collapse, and how is it related to the Pauli Exclusion ...
3
votes
2answers
172 views

What is gravity really?

What is gravity? I want to know more than it being simply the "mysterious force" that attracts things to earth. Is it a particle, a wave, or something else entirely?
6
votes
3answers
381 views

How does a gravity slingshot actually work?

From what I know of elliptical orbits, an object speeds up near the periapsis and slows down at the apoapsis, much like we learned in high school physics how a sphere would roll down and back up a ...
3
votes
1answer
51 views

How massive does a planet need to be to create gravitational lensing?

Is it ever possible for starlight to be distorted in a noticeable way from something as small as a planet? I'm guessing that the chances of this working are better on a dense terrestrial planet than ...
2
votes
1answer
53 views

What is the time/size/rigidity ratio for a space object to become mostly round?

In the answer here multiple comets are identified that do not form a single round body. A drop of water will form a round shape in the time it takes to free fall a couple of feet. All of the ...
1
vote
1answer
35 views

Is there a radius inside of which objects are (doppler) blue shifted?

The Andromeda galaxy is about 600,000 light years away and is doppler blue-shifted. Are there objects closer to us than Andromeda which are red-shifted? Are there objects farther than Andromeda that ...
1
vote
1answer
40 views

Finding the radius of an eccentric orbit at any point

Knowing the apoapsis, periapsis and therefore period of an orbit, how can I find the radius of an object in an orbit at a given angle or time, whichever is needed. For example, if I have an object m ...
5
votes
4answers
146 views

Using the Sun as a Gravitational Lens

Can the Sun be used as a gravitational lens to achieve better telescopic viewing? Can this effect be practically used to view celestial objects?
1
vote
1answer
51 views

What is the physics of a gas mass subject to gravity in space?

There are many formulas for atmospheric pressure on earth, but how does gas behave in free space? I am thinking about why stars form. I am guessing that the gas density will influence pressure, as ...
7
votes
4answers
679 views

What is the difference between our time and space time?

I am trying to understand the phenomenon of space-time. But, everything on internet seems to be too complicated for me since I do not have a background in physics. Can anyone give me simple ...
8
votes
1answer
127 views

Parking a telescope at a Lagrange point: is this a good idea from a debris point of view?

The James Webb space telescope is supposed to be located at the Earth-Sun L2 Lagrange point. Do we expect the region around that point to have a higher concentration of space debris, asteroids, ...
3
votes
1answer
65 views

Dark Energy Expansion

The new Cosmos extra features mentions that at about 6,771,500,000 years ago the universe began an accelerated expansion. How do we know this? What evidence do we have for this renewed and accelerated ...
1
vote
1answer
68 views

Could dark energy be negative gravity?

Main question: Could dark energy (the mysterious accelerating expansion of the universe) be explained by "negative gravity"? "Spin off" questions: Does antimatter have negative gravity? If ...
3
votes
1answer
168 views

Would time go by infinitely fast when crossing the event horizon of a black hole?

If you were to fall into a black hole, my understanding is that from your reference point, time would speed up (looking out to the rest of the universe), approaching infinity when approaching the ...
7
votes
1answer
99 views

Is it safer to be near a star or a black hole?

If a star or black hole neared the solar system, which would do the least damage? For the sake of a good comparison, lets assume the candidate star is an "average" 5 solar mass star, and the black ...
2
votes
1answer
63 views

If Mars orbited the Earth how distant would it have to be to cause the same tides?

If it were possible to replace the Moon with Mars, how distant would it have to be to essentially create the same oceanic tides as the Moon currently does? Mars seems to be roughly 3 times the mass of ...
3
votes
1answer
73 views

What is the optimal escape trajectory from near a black hole?

Consider a space ship that is being drawn closer to a black hole. The crew begins to notice the effects, and discovers that they are nearing the black hole. They then manage to halt their ...
2
votes
2answers
72 views

Where is a Hollow Object's Center of Gravity? [closed]

Let's imagine that the Earth's moon is hollow. Given this scenario, where would its center of gravity be? What would the conditions be like at the center? Also would one still be able to stand on the ...
1
vote
1answer
98 views

A day in earth, a thousand years somewhere else

By followig the laws of physics, is it possible, that in a place far far away that one day (at that place), is counted as 1000 years in the earth. I am familiar with black holes having impact on ...
5
votes
2answers
147 views

Why do we have the cosmological constant?

Since the cosmological constant is not required to explain that the universe seem to be expanding, why do we have it? What other factors cause us to have that constant? Background: Without the ...
1
vote
0answers
62 views

Faster Earth spinning speed to overcome gravity, possible? [closed]

As far as I know we stick to the surface of the Earth as its gravity is pulling us and Earth rotation is in a way reducing the gravity. At what speed should Earth be spinning so that we all get ...
1
vote
2answers
108 views

Will a new planet form if Jupiter's influence on asteroid belt will diminish in a few billion years?

I know that tidal forces are pushing Jupiter farther from the Sun, but I couldn't find exactly the yearly amount. In a few billion years would this effect (and subsequent decrease in gravity pull) ...
3
votes
2answers
68 views

If the moon still had a magnetic field how long would have been possible to keep an atmosphere?

Let's assume the Moon had a considerable magnetic field to prevent the atmosphere dispersion caused by solar wind. Given the low gravity of the Moon, how many years would pass before all the gases (of ...
5
votes
2answers
131 views

Has someone looked the other way?

I learned that gravity always pulls, it is always attractive. There is no antigravity, no "negative" mass. I also learned that most matter is dark, invisible. We know that because we see visible ...
3
votes
4answers
280 views

Why don't we feel the speed of earth moving

When we move our vehicle, we "feel" the speed of it. However, when stationary, we still are moving,but moving by quiet a speed. We know that earth moves with X ...
7
votes
2answers
360 views

What was the length of year 1 million years back?

We know that the universe is gradually expanding and this indirectly means that the gravitational force between sun, earth, planets and other stars (roughly anything in the universe) is gradually ...
2
votes
1answer
223 views

What would happen if Jupiter and Earth were at the same distance as the Moon is from Earth?

If Spock came with a super machine capable of moving planets, and placed Earth so close to Jupiter as the Earth's moon, the gravity of Jupiter would make us fall into it?
1
vote
2answers
98 views

How would water waves behave in partial gravity?

Would an "indoor" pool of water on the Moon or on Mars behave differently than on Earth? Would the waves caused by a splash be higher or lower? Would they propagate faster or slower? Would boyance be ...
2
votes
1answer
108 views

What is the minimum mass required so that objects become spherical due to its own gravity?

Is this minimum mass known? or maybe, is it given in terms of density? If so, how much density is the minimum to have an spherical object due to its own gravity?
12
votes
4answers
415 views

Doesn't gravity attract objects in space until they collide?

If the formula to calculate the force of gravity of two objects is: $$F1 = F2 = G * (M1 * M2/r^2)$$ Why do planets stay in orbit? Or is there another formula at work?
1
vote
1answer
99 views

Why is every year the same number of days despite the gravity in the solar system?

I was just watching a Geoff Marcy talk on YouTube showing how they infer the presence of planets transiting distant stars. The supposed periodicity wasn't always quite regular from what I could see, ...
5
votes
4answers
323 views

Does the gravity of the planets affect the orbit of other planets in our solar system?

When one planet passes near another during its trip around the sun, does their gravitational pull is strong enough to disrupt noticeably each other's orbit ?