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Questions tagged [planets]

Celestial body that orbits following an elliptical path around a star or stellar remnant.

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Numerical Solution of the circular restricted three body problem [closed]

I am trying to numerically solve the differential equations in the planar circular restricted three-body problem. In the rotating frame, the differential equations are given by \begin{equation} \...
Markus Hamre's user avatar
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Why does a moon's orbit get more circular with time?

I understand that there is a transfer of energy between a moon and a planet depending on whether the moon is orbiting faster or slower than the spin rate of the planet. This would obviously change the ...
Jack R. Woods's user avatar
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4 answers
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What is the relationship between gravitation, centripetal and centrifugal force on the Earth?

I'm trying to analyze a situation wherein a ship is moving across the surface of the earth. I am trying to analyze this situation in a reference frame that is rotating with the earth (NED frame). I am ...
john morrison's user avatar
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2 answers
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The topology of planets [duplicate]

Just a curiosity: Let $g \in \mathbb{Z}_{>0}$. Is it possible for a planet of topological genus $g$ to exist? For example, is there any contradiction (from the point of view of physics) in assuming ...
numberwat's user avatar
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Why are planets denser as you approach the center?

Gauss' law says that the net electric force inside a hollow, uniform, not rotating sphere is zero. Since gravity is also proportional to the inverse square of the distance, I assume this should apply ...
Joseph Hirsch's user avatar
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Gravitational attraction between two bodies

While the gravitational force between two bodies is directly proportional to their masses, and inversely proportional to the distance between them is understandable / seems logical, how did Newton ...
Niranjan's user avatar
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Can we treat the entire mass of the spheroid as being concentrated at its center?

I know that to find the gravitational force between two objects, if either of them is a sphere, we can assume its mass to be concentrated at its center and use the formula for gravitational forces for ...
Peter swift's user avatar
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Despite tides the Moon, as far as I know, doesn't slow down. Where does the energy come from? [duplicate]

Hy, I don't have anything to do with physics, so please forgive me if I explain my question in a weird way ;) As the Moon rotates around the earth it is creating tides and waves on the earth. IE it's ...
Jakob S.'s user avatar
19 votes
6 answers
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If gravity is not a force, what makes massive objects spheroid?

For most of my life, the explanation given for why celestial bodies like stars, planets, etc. are round is due to gravitational force. Simply put, if an object has enough mass, it will, in turn, have ...
Quantum Wonder's user avatar
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2 answers
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Why are planets cold?

Excuse me for me ignorance, I'm just fiddling around this question for quite a while. The question of course is not limited to planets. Boiling down to, why isn't the universe heated up by now to ...
jAndy's user avatar
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How symmetric do we know the gravitation field to be?

Currently, the only ways to measure gravity is on quite large scale. So these experiments measure gravity averaged between vast systems of particles. Of course, such an averaging results¹⁾ in a ...
Ilya Zakharevich's user avatar
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Minimum size for a planet to have a molten core

What would be the minimum size for a planet or moon so that it would have a molten core? Gravity and density would play a part but how could this be worked out?
Michael Mcgarry's user avatar
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Magnetic compass working on the Moon and the Mars planet

Mars planet Moon Magnetic compass Theoretically and practically, will a magnetic compass work on the Moon and the Mars planet?
Prashant Akerkar's user avatar
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What regulates the size of our atmosphere?

Our atmosphere is only about 100km thick before the official start of space. That is a mere 1.57307% of the radius of Earth (6,357km). The difference between the gratitational force at sea level and ...
Peter R. McMahon's user avatar
4 votes
1 answer
384 views

What are the odds of a rogue planet that enters into a galaxy reaching the black hole at the center of the galaxy?

I am wondering if anybody has ever calculated the odds of a rogue planet, which has been traveling through interstellar space and then enters into a galaxy, being able to travel all the way to the ...
user57467's user avatar
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Helium in Uranus atmosphere

I read that in 1986 Voyager 2 measured the composition of Uranus' atmosphere, which turned out to be composed of $85 \%$ hydrogen and $15 \%$ helium. It's not clear to me how this relevant amount of ...
gryphys's user avatar
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How to calculate equilibrium height of tidal bulge?

I am trying to model the shape of the tidal bulge caused by the moon. I asked GPT for a formula and it gave me equilibrium tidal bulge height as $$\frac{2 R_{earth} G M_{moon}}{3 r^3 \Delta g}$$ and ...
spraff's user avatar
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What is the real shape of Earth? [duplicate]

As it now widely dicussed and accepted that Earth is not a 'perfectly round sphere/ball but more a 'oblate spheroid' why then do NASA have 'photographs' of a ROUND Earth?
T Ruth's user avatar
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1 answer
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Angular momentum of the Moon (or any body orbiting another orbiting body)

Let the Moon have angular velocity $\omega$ around the Earth. The Earth itself revolves with velocity $V$ around the Sun. The radius vectors are $r_i$ from Sun to a point on the Moon, $r_i'$ from ...
sasssu's user avatar
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4 votes
2 answers
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Exact analytical solution for the surface gravity of an oblate spheroid

I would like to know if an exact solution for the surface gravity force components of an oblate spheroid has been published and if not can anyone derive it here? Assume an ideal rigid oblate sphere of ...
KDP's user avatar
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Why is Earth a sphere? [duplicate]

Physicists and Physics enthusiasts . I am new to this platform. And I wanted to post a question . Since I have nothing in my mind. I wanted to ask , Why is the earth a sphere and not other shape? ...
rasulus's user avatar
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What is the hydrostatic shape of an ideal rotating planet? [duplicate]

It is a well-known fact that rotating planets have a flattened spheroidal shape. However, the NASA site says about Haumea: The fast spin distorts Haumea's shape, making this dwarf planet look like a ...
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Is either Geocentrism/Heliocentrism more "correct" than the other? [duplicate]

Yesterday there was a casual discussion of the findings of the scientist Galileo in my German class. It was mentioned that his breakthrough was that, he found a convincing explanation that earth ...
Cathartic Encephalopathy's user avatar
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Why does a total solar eclipse happen every 18 Months?

What is the math involved in calculating how often a total solar eclipse happens. Can you predict it by just looking at the period of the moon around the earth and the period of the earth around the ...
244529's user avatar
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Holsapple simple scaling law [closed]

Could someone explain Holsapple's simple scaling law? Furthermore, is Holsapple simple scaling law able to be used on Earth in the context of dropping an object and measuring the impact crater size? ...
Imstrugglingomd's user avatar
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1 answer
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Estimate Saturn's mass [closed]

How can you estimate Saturn's mass using data from Cassini's final moments in September 2017 (apoapsis on September 12 at 1:27 a.m. EDT Saturn time at a distance of about $1.3*10^6$ km from Saturn, ...
Enkt Enktson's user avatar
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Gravity formula inside a planetary core

I am trying to work through this problem so that I can understand how to convert from pressure values to radius values inside a planetary core in a code. The core has variable density depending on ...
Priya Bose's user avatar
1 vote
1 answer
117 views

Atmosphere of a hypothetical planet

A hypothetical planet is 2/3 the radius of earth but has 1g surface gravity. Given the planet has the same surface gravity as earth, the atmospheric pressure would be the same. This would also mean ...
Adrean Mainhart's user avatar
3 votes
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61 views

Why is sunset in mars blue?

This is the Martian sunset, as captured by the Spirit rover of NASA. Notice the colors are inverted, i.e. the direct rays blue and diffused rays red, which is exactly the opposite of what you would ...
AlphaLife's user avatar
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Issue while understanding gravity/radius of earth graph [closed]

I have following question. What are my opinions? 1. Option 1 - This is incorrect. I think dotted line in option 1 from bottom to peak represents center to surface of earth. After the peak, line ...
Pankaj's user avatar
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2 answers
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How to measure the ratio of a planet's radius to a star?

I was reading a physics problem related to astronomy, and upon re-reading it, I realized that it could be really indicated to extrapolate some really interesting physics-related information. One of ...
Bml's user avatar
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Potential energy with different heights [duplicate]

If system consists of earth and ball and ball is dropped from height $h_i$ to $h_f$, then: $\Delta U = -(W_{earth} + W_{ball})$ ($W_{ball}$ can be neglected since it's small) $\Delta U = -(-mg(h_f - ...
Dimitri's user avatar
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0 answers
69 views

Dynamic equilibrium of planets

We can describe statical equilibrium ( forces, moments ) in a cuboid $$ \Sigma F_x=0,\Sigma F_y=0,\Sigma F_z=0~$$ In dynamics can we describe similar dynamic equilibrium within an inertial ...
Narasimham's user avatar
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Can gravity of planets besides Sun and Moon affect tides on Earth?

The tides in some places on Earth are over 50 feet. If the gravity from Venus had a ten thousandth the affect of the Sun and Moon on a 50 foot tide it would make a difference of one twentieth of an ...
JohnTrainor's user avatar
2 votes
1 answer
1k views

What does Newton's Theorem XXXIII in his book "Principia" mean?

If to the several points of a given sphere there tend equal centripetal forces decreasing in a duplicate ratio of the distances from the points; I say, that a corpuscle placed within the sphere is ...
Livid's user avatar
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8 votes
2 answers
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How would the volume of a drop of water (from a dropper) on the Moon and other bodies compare to one on Earth? (indoors of course!)

Searching for "volume of a drop of water from an eyedropper", I ran across this answer on Quora: It depends on the size of the dispensing tip, but generally for a Pasteur pipette it is ...
uhoh's user avatar
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8 votes
5 answers
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What is the gravity in the center of Earth?

Let's suppose the earth is a perfect sphere and let's ignore its rotation and movement. What would happen if I would be in the center of the earth? Would the gravity be zero in any direction so I ...
matej's user avatar
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1 vote
1 answer
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Very Basic Question about Kepler's Second Law of Planetary Motion

In order to derive Kepler's $2$nd law, in the lectures we have used the conservation of angular momentum, where we defined the trajectory of a planet in a two dimensional plane (the plane where the ...
gluon's user avatar
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16 votes
6 answers
4k views

If another planet was opposite Earth, would we be able to observe it?

Imagine another Earth-sized planet, in the exact same orbit as Earth, but 180 degrees out-of-phase. In this arrangement, at all times, you would be able to draw a single straight line through space ...
ConnieMnemonic's user avatar
3 votes
3 answers
183 views

Why do the planets tend to spin in the same direction as they orbit the center sun?

I mean, why do the spin angular momentum and the orbit angular momentum of a planet tend to have the same direction? As we all know, a planetesimal $m$ orbiting a sun with mass $M_{sun}$ at $r$ will ...
Harry's user avatar
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4 votes
1 answer
103 views

Will Hawking radiation violate baryon number conservation around gravitating bodies other than black holes?

Numberous articles discussing a recent research paper suggest that even stars and planets will eventually radiate away their mass like hawking radiation. My question is will this violate baryon ...
Keith Reynolds's user avatar
3 votes
1 answer
53 views

Does a planet's "equatorial bulge" induce any kind of motions or currents in the atmosphere?

Rotating planets, like the Earth, are not perfect spheres but are instead oblates. This affects both the crust and the atmosphere, creating a bulge in the equator 1. I was wondering if there are ...
vengaq's user avatar
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0 votes
2 answers
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Does air in the atmosphere get friction as a planet rotates?

Does air in the atmosphere suffer friction in some way due solely to the planet's rotation? I mean, if you took a rotating planet with an atmosphere (not being influenced or heated by its star, its ...
vengaq's user avatar
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0 votes
1 answer
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Do only gas planets have discs or even rocky planets may have them orbiting around?

Do only gas planets have discs or even rocky planets may have them orbiting around? If rocky planets are great in volume is then a higher chance for an orbiting disc to exist in the planetary orbit?
Krešimir Bradvica's user avatar
1 vote
2 answers
47 views

Is it possible to determine if a planet can have a moon based on its mass and gravitational pull?

I'm curious, if based on what we know with Newton's law, can we determine if a random planet, knowing it's mass and gravitational pull, can hold a moon in it's orbit. Or to phrase it another way, is ...
Oneiros's user avatar
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1 vote
1 answer
60 views

Could rogue planets with cold nucleus have winds or water currents/waves due to the planet's rotation?

Are there any types of wind or waves caused and produced only and exclusively by a planet's rotation? Not influenced by the planet's rotation, but produced solely by it? In the case of waves, are ...
vengaq's user avatar
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6 votes
5 answers
3k views

Does the Earth experience air resistance?

Consider the earth body excluding the atmosphere, undergoing circular motion around the sun. Does it experience air resistance due to the atmosphere?
bluesky's user avatar
  • 303
2 votes
3 answers
579 views

Why are distant planets illuminated like stars, but when approached closely (by a space telescope for example) it’s not illuminated? [closed]

when I look up into the night sky I see planets, not twinkling like the other stars, but still illuminated. However, when the Hubble or James Webb telescopes approach planets we see the local features ...
Franklin Montez's user avatar
1 vote
0 answers
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What percentage of Mars' surface would be under the water if we dropped all of the water from moon Enceladus on it? [closed]

Enceladus, one of the Saturn's moons that is known for water geysers, is estimated to contain a body of water as big as a ball $220 ~\mathrm{km}$ in radius. That's about $\sim 4.46 \times 10^{7} ~\...
Kusavil's user avatar
  • 343
0 votes
2 answers
292 views

How does Kepler's Second Law show that a planet further from the sun will move slower?

This is probably a very stupid question. We are told that due to Kepler's Second Law, which according to this very straightforward explanation: "Kepler's second law of planetary motion describes ...
Gordon's user avatar
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