Questions tagged [planets]

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

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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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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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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
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1 answer
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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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How would the volume of a drop of water 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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What is the gravity in the center of Earth?

Let's suppose the earth is 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 wouldn'...
matej's user avatar
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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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6 answers
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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
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3 answers
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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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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
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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 ...
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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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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
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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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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
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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
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3 answers
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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
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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
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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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3 answers
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If the Earth rotated slower about its axis, would your apparent weight increase or decrease?

The title above was a question on an exam that was marked wrong for me. I answered that if the Earth rotated slower (i.e. longer days), my apparent weight would increase. I based this on the ...
a3dur4n's user avatar
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On the tidal heating of a moon. What is the second Love number?

Years ago it was asked here how to calculate the tidal heating of a moon orbiting another body with a simple equation. The answer is very detailed. They explain the equation, its shortcomings, the ...
1 vote
1 answer
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Earth surface acceleration and inertial geodesics

I hope this is an appropriate question for this forum. It is one I have struggled with for a while. I read that in GR gravity is not a force, and that the apparent force we feel and can measure (eg ...
Jeff Roberts's user avatar
2 votes
2 answers
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Is $F=mg$ derived from Newton's law of universal gravitation $F=Gm_1m_2/r^2$?

If so, that means gravity is only 9.8 m/s^2 at the surface of the earth?
meaningless's user avatar
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Gravitational field intensity

These are the two types of graphs between gravitational field strength $E$ and distance from the centre of the earth $r$. I found these two different graphs in two different books and I'm confused ...
Phy14's user avatar
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Change in $g$ effective due to rotation

$g$ effective at any latitude changes due to rotation of earth. Does it also change due to rotation when the body is at height or at depth or does it change only at the surface? Edit: I am referring ...
Phy14's user avatar
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2 answers
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Correct explanation of tides [duplicate]

In the explanation of tides on earth there seem to be different versions for the second water bulge on the side opposite to the moon, while everybody seems to agree that the bulge on the moon side is ...
user1583209's user avatar
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14 votes
9 answers
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Is Earth really flattened at the poles because of centrifugal force?

My question is pretty much all in the title. I was always told that our planet is flattened at its poles due to the centrifugal force generated by its own rotation. However I don’t see how centrifugal ...
Federico's user avatar
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How does a gas giant planet hold it's spherical shape when it has tidally locked rotation in it's orbit around the Sun?

How does a gas giant planet hold its spherical shape when it has a tidally locked rotation in its orbit around its Sun? Wouldn't it fall apart without its gravitational pull from the rotation? How ...
Adventures of an Amateur Astro's user avatar
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How the calculate the radiance of a planet?

In the last weeks I got interested in the topic of the irradiance of different planets in relation to their distance. Today I asked myself how could I calculate the radiance of a planet or moon if I ...
dark_ursus's user avatar
6 votes
2 answers
2k views

Possible non-negligible physical effects that relate planetary/lunar geometry and seismic activity such as earthquakes?

Could any forces from the moon, the planets or the sun in orbit hypothetically influence seismic events on earth? And if yes how to approximately calculate and compare the magnitude of the forces? ...
Hjan's user avatar
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What are the Equations for Climate modeling of alien planet?

I am studying complex dynamic system and I would like to analyze the climating formation of a possible alien planet considering climate as a complex system . For this I do not want to use a whole ...
1 vote
1 answer
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What would the nucleus of a water planet be like?

If we have a planet made out of water, would it be all solid? What about the nucleus? Would it depend on the size of the planet?
Pablo's user avatar
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1 answer
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Falling at the centre of the Earth

Let’s assume to drill a hole at Earth surface at the point P1. The hole passes throughout the centre of the Earth and finishes at the opposite side at the point P2. Let’s assume then that 1) Earth ...
gryphys's user avatar
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Solid surface of the gas giants [closed]

Given the gravities of gas giants and other similar celestial obejcts, I find it hard to believe that their centers aren't crushed to solid states. If the gas giants and other similar objects have a ...
AbduSami bin Khurram's user avatar
3 votes
1 answer
41 views

Tholins color and scattering

One of the prevailing explanations for the reddish color of certain asteroids surfaces and planetary atmospheres, such as Jupiter's and Titan's, is the presence of complex polymeric molecules called ...
Redirectk's user avatar
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1 vote
0 answers
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Did Newton derive Titius-Bode Law of the planets in his Principia? [closed]

In college I was taught that no one knows why the planetary orbits conform to the Titius-Bode Law. Recently I read that Newton HAD figured that out in his Principia. Right Now I can’t even find a ...
ktrimbach's user avatar
-5 votes
2 answers
283 views

Why is mercury the closest planet to the Sun? [closed]

I just want a solid reasoning that why Mercury is the first planet away from the Sun, then Venus, then Earth, then Mars and so on.
Safi Mohammad's user avatar
3 votes
2 answers
178 views

Calculating the excess radius of Earth in curved 3D space

This question is not a duplicate of Experimental measurement of the radial excess or How to derive exterior and/or interior Schwarzschild solution using Feynman excess radius equation?. The linked ...
Shirish Kulhari's user avatar
1 vote
0 answers
15 views

If the rock boundary exists, how did the planet Theia manage to collide with Earth? [closed]

Because it wasn't orbiting it, but in an errant orbit, but coinciding with that of the earth. Much of its matter was absorbed by the Earth, and part was thrown into space, grouping together and ...
rirakib's user avatar
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1 vote
0 answers
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High school thesis project about Jupiter's moon Europa [closed]

So basically, I have to write a thesis paper because I'm in the last year of high school. It is an independent research project and the culminating work of my studies in school, so it represents my ...
Gabriel's user avatar
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Avarage velocity of a planet in a parabolic orbit

How the average velocity of a planet (over the entire time; $t = 0$ to $\infty$) orbiting a star in a parabolic orbit can be calculated? If it's instantaneous velocity is $v$ (at distance '$r$' from ...
SCh's user avatar
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How to calculate visible light part of black body spetrum?

So I was thinking about the formation of the Moon and currently the most accepted Giant Impact Hypothesis where the Moon formed as a result of a collision of proto-Earth and a Mars-sized protoplanet. ...
NotAName's user avatar
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2 votes
1 answer
173 views

Moist adiabatic lapse rate

Wikipedia gives the following equation to calculate the moist adiabatic lapse rate $\Gamma_w$, assuming that there is only one condensible gas (water vapour) mixed in the "dry air": $\...
Redirectk's user avatar
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0 votes
3 answers
238 views

Are moons always smaller than the planets they orbit?

I'm not a physicist, asking for knowledge. Is there any moon orbiting a planet, but bigger than that planet? If not, is it mathematically possible for a bigger object to orbit around a smaller object ...
Peyman's user avatar
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12 votes
4 answers
2k views

How can I calculate gravitational time dilation between two planets? [duplicate]

I am writing a school paper and chose to do it about gravitational time dilation. I wanted to calculate the time that passed on Mars when 1000 years on Earth went by. (probably a tiny difference). I ...
Mateo Loral's user avatar
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1 answer
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Physics of a falling body within a spherically uniform system [duplicate]

I was reading The First Three Minutes and in the book it talked about how if a stone fell in a cave deep in the Earth we could calculate it's motion as if the surface of the Earth is the surface of ...
user1070280's user avatar
2 votes
0 answers
63 views

Most stable shape if Newtonian gravity was proportional to $r^\alpha$

Consider lots of mass in isolated 3D space, close to each other. Consider that only the gravitational force (Newtonian) exists. Also consider that there is no rotational motion. It is evident that a ...
whoisit's user avatar
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1 vote
2 answers
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How can the cooling of Venus near the surface be explained during the time that the specific heat capacity of $\rm CO_2$ quadruples from 60 - 40⁰ C?

Imagine that a planet like Venus with an $\rm CO_2$ atmosphere of 92 bar near the surface could be cooled by shading it from the Sun. The total heat content of the atmosphere with the initial 464⁰ C ...
Cornelis's user avatar
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