Questions tagged [planets]
Celestial body that orbits following an elliptical path around a star or stellar remnant.
790
questions
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2answers
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Should larger rocky planets eventually crack due to temperature differences between their inner and outer layers?
Should larger rocky planets eventually crack due to temperature difference between their layers? When a tick piece of glass is left to cool down it would eventually crack...but this is caused ...
2
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1answer
69 views
What's the minimum possible size of a round astronomical body?
What's the minimum possible size of a spherical shaped rocky planet or satellite? Is it possible to occur a spherical shaped planet without having a molten core?
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0answers
37 views
Proving nearby planets are not antimatter [duplicate]
Observations of the universe make us think matter is much more common than
antimatter, and I believe no "probably-antimatter planets" have been found.
But, if Pluto, for example, somehow ...
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0answers
20 views
How do Kepler's law help in calculation of distances and masses? [closed]
Now we consider the use of Kepler's laws in stellar and galactic astronomy. The equation for Kepler's third law has allowed masses to be determined for double stars for which "P" and "a&...
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0answers
23 views
Saturn's moons - getting a stable harmonic model for Mimas and Encyladus
I have built a HTML/Javascript solar system model. It is working well with real time animation.
https://abetz-rouse.com.au/planetarium
I don't want to get into the deficiencies of my choice of ...
0
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0answers
28 views
Doubt regarding elliptical orbits and eccentricity relation with masses
I was working with Roche's Limit , You can visit the wikipedia page on Roche's Limit and Hill's Sphere (not important here). A query raised in my mind about the elliptical orbit in which the moon is ...
2
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1answer
40 views
What is the meaning of grain opacity and why does it affect the formation time of gas giants?
While doing research for my presentation on the formation of gas giants, more specifically the "core-accretion model", I have been stumbling across the term "grain opacity" and don'...
2
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2answers
74 views
Why doesn't the Earth's temperature increase in the perihelion?
I know that what causes seasons in earth is the tilt of the earth and the fact that sun rays reach the earth from different angles during winter and summer, but why doesn't the temperature of the ...
22
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8answers
4k views
For Newton's gravitation equation, how do you account for planet size?
My daughter was doing a physics problem where she had to calculate the gravitational force of an object that was 250 km above the earth... She used the equation:
$$F=\frac{G\cdot m_1 \cdot m_2}{r^2}$$...
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2answers
96 views
Which force provides the centripetal acceleration that makes objects on earth's surface rotate about Earth's axis of rotation?
Let's say an object is at rest in Earth's reference frame. We know that Earth's reference frame is non inertial. If we were to observe that object from an inertial frame, we would see three forces ...
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0answers
27 views
What would happen if a tungsten rod massing 1000kg slammed into the surface of Callisto at 15% of the speed of light? [closed]
I am writing a sci fi story and I want to know what would happen if a tungsten rod massing 1000kg slammed into the surface of Callisto at 15% of the speed of light? Given that there is a subsurface ...
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2answers
129 views
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Is drinking water an important feature for finding habitable exoplanets? Has it been found?
We need drinking water to live on other planets. Has drinking water been found on other exoplanets? Is drinking water an important feature for finding habitable exoplanets?
I want to (self) study in ...
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1answer
33 views
In a 2-dimensional sense, how do the perihelions of the planets in our solar system line up?
A bit of background, I'm currently making a 2d graphical representation of the planets orbits around the sun with Python for a university project which currently looks like the picture below (not ...
1
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1answer
15 views
Looking for a formula or model for planetary equilibrium temperature which takes into account the greenhouse effect
For a project I'm working on, I have made a bunch of hypothetical random planets orbiting random stars. I have come across the Stefan–Boltzmann law, which works nicely for any planet without an ...
0
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4answers
107 views
Is there any evidence that atoms behave differently on other planets? [closed]
I know gravity, atmosphere density and other values would be different on other planets, but is there any evidence that intrinsic atomic properties (i.e. melting point) are different on other planets?
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2answers
72 views
Claims of detection of gravitational waves with an accelerometer
Is this claim:
https://earthscience.stackexchange.com/q/21236/
of detection of gravitational waves with accelerometers legitimate?
I do not know much about this, but given how gravitational waves form ...
0
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2answers
23 views
Is there a gas present in the Martian atmosphere similar to hydrogen?
is there a gas present in the Martian atmosphere which could be extracted to inflate a balloon with sufficient lift to support an instrument platform for low altitude reconnaissance.
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2answers
103 views
Have Einstein's field equations ever been solved for Earth? [closed]
If not, what remains unknown that prevents a solution?
3
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3answers
189 views
What determines the magnitude of the atmospheric scale height of a planet?
What determines the magnitude of the atmospheric scale height of a planet?
https://en.wikipedia.org/wiki/Scale_height says that:
"Approximate atmospheric scale heights for selected Solar System ...
0
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0answers
10 views
Could the hypothetic water bodies on Mars be 'stable' only if they were large like Earth's oceans?
Could the hypothetic water bodies on Mars be 'stable' only if they were large like Earth's oceans which needs macroscopic basins? Are possible rivers and lakes enough to ,mantain all the water.As ...
1
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3answers
100 views
What would happen if the Earth was hollow and somebody rode on the “inside shell”?
I'm having a difficult time understanding basic centripetal force, forgive me. On the earth as it currently is, if you fall off a cliff you will fall closer to the core. However on a cylindrical ...
2
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3answers
40 views
Had the centrifugal force of the rotation of Earth in the past forced liquid, hot Pangea to be positioned near the Equator?
Had the centrifugal force of the rotation of Earth in the past forced liquid, hot Pangea to be positioned near the Equator? Maybe also a question for 'GSE' but if we deal with centrifugal forces and ...
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2answers
73 views
Did we adapt to Earth or Earth to us? [closed]
I often hear that Earth is a unique planet because it has life and it has its own inhabitance. We also see a proper balance between plants and humans and other animals. Why life is not possible on ...
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4answers
2k views
Our sky is blue. Would a planet that has 1% of earth's atmospheric density have the same colour sky assuming the sun is exactly the same as ours?
If not then which colour would the sky be and why?
Could you determine which elements the atmosphere is made of just by looking at the colour of the sky?
Is it possible to know the density of a planet ...
0
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1answer
55 views
What adjustments are needed to use Newton's Law of Universal Gravity to calculate the force between me and Earth?
Background
Say I weigh $80 \mathrm{kg}$, and I happen to fall to the ground with an acceleration of roughly $9.81 \frac m{s^2}$, I would, using Newton's second law of motion, $F = ma$, come to the ...
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6answers
6k views
Does bottle water rise a little bit on full moon days?
High tides and low tides are caused by the Moon. The Moon's
gravitational pull generates something called the tidal force. The
tidal force causes Earth—and its water—to bulge out on the side
closest ...
0
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1answer
28 views
How bright would the surface of each planet be?
At night when there is no moon in the sky, it is dark, you can not see your surroundings. If I were to stand on Pluto, could I see my surroundings? Would being on pluto at day be like night on earth ...
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2answers
83 views
Where from is the distance calculated in Newton's law of universal gravitation?
In the equation for universal gravitation $(1)$ between two objects, where from is $r$ calculated? From the surface, from the center? Also, are the objects assumed to be particles in this equation or ...
1
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3answers
40 views
Why can gravitational potential energy be expressed both as $mgh$ and $-GMm/r$? [duplicate]
In these two different equations for the same (?) thing, not only is one directly proportional to height and one is inversely proportional to height, but they contain completely different variables, ...
0
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1answer
28 views
Will the weight further increase while going inside the Earth? [duplicate]
Our weight is more at the pole than at the equator (because it is closer to the center).
Does that mean if we go down into the earth (some kind of bore), will our weight increase further?
I remember ...
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1answer
82 views
Is General Relativity (GR) compatible with the expanding Earth hypothesis? [closed]
There is a lot of convincing evidence that the Earth and all the other planets and their moons are expanding with time.
Prof. Samuel Warren Carey's summary of the evidence:
https://www.youtube.com/...
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2answers
48 views
How to track orbit of an exoplanet?
I was wondering if there is an established method to keep track of the orbit of an exoplanet assuming we know $a$ - the semi-major axis of the orbit, $e$ - the eccentricity of the orbit, and $i$ - the ...
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2answers
70 views
Direction of acceleration in elliptical path
The $x$ and $y$ coordinates of a particle moving in a plane are given by x(t)=acos(pt) and y(t)=bsin(pt) where a, b(<a) and p are positive constants of appropriate dimensions and t is time. I know ...
4
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2answers
105 views
How does Jupiter have two magnetic South poles and one magnetic North pole? Magnetic tripole?
Generation of magnetic field of Earth is relatively well-understood
The magnetic field is generated by electric currents due to the motion of convection currents of a mixture of molten iron and ...
0
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3answers
52 views
Is the point mass assumption valid for non-spherical objects?
In case of a shell or a solid sphere we can assume it to act as a point mass to calculate the potential and field for any object as long as it lies outside the shell/sphere.
I have learnt the proof ...
2
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2answers
79 views
Time spent by a comet inside the Earth's orbital (Kepler problem re-visit)
I come across this interesting problem comet-x-earth. It was an exam problem asking the time that a comet will be spent inside the Earth's orbital. I make an illustration for the problem:
The comet ...
0
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1answer
25 views
Conservation of energy for a planet [duplicate]
I was reading Lectures by Feynman (which are soo good at any qualification!) and he talks about how energy of a particular planet in our solar system is constant at all times $ i.e, KE+PE= constant.$
...
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2answers
41 views
How are the locations of solar system planets expressed in their orbits?
and where can I find the data about the locations of the solar system planets during their entire year?
I would like to find the data on the orbits of solar system plantes. Also I would like to know ...
3
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0answers
32 views
Are planets without large moons getting weaker magnetic fields?
Recently I read a study according to which in order for a terrestrial planet to have a magnetic field, a sufficiently large satellite is needed, since the satellite's gravitational influence melts the ...
0
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2answers
58 views
Bulging of Earth
Earth is bulged out due to the outward radial push of the centrifugal force.
For an inertial observer, there must be some force causing this outward push other than the centrifugal force (since ...
1
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5answers
142 views
How is the Earth pushing “up”/“outwards” at $9.8\text{ m/s}^2$ in general relativity? [duplicate]
So I've been trying to wrap my head around GR for a bit now, but one thing that keeps me down is the idea that while earth bends spacetime around us, the earth is also accelerating towards us at $9.8\...
4
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3answers
947 views
Would there be any gravity inside a hollow planet made of a spherical shell of basalt crust? [duplicate]
I am writing a science-fiction story, which contains a 'crazy' planet. I would like some input into the consequences of this physics according to standard physics.
The planet in question is Earth-...
1
vote
1answer
39 views
Gravitational Binding energy of a sphere of 2 uniform densities
So I know that the gravitational binding energy of a sphere of uniform density can be given by:
$$U=-\frac{16}{3}G\pi^2\rho^2\int_0^Rr^4dr$$
Which if integrated gives:
$$U=-\frac{3GM^2}{5R}$$
As ...
0
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3answers
75 views
Photon trajectories affected by gravity [duplicate]
If the gravity of a star can change the trajectory of a photon, is the speed of the photon reduced at the moment of departure from the stellar's surface? Can modern science calculate the measure of ...
0
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2answers
71 views
How fast can the Earth rotate without people on the equater falling off and how long would the day last with this speed? [duplicate]
This is the radius that was given to us
r= 6400km
What I've tried is figuring out what is the force that would push the people off the equator,and what is the force that would "pull" people ...
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3answers
25 views
Is the compass direction of a planet recorded by two different observers separated by some distance the same?
I have a basic doubt. Say I am viewing Mars from my window and I used the compass app to get an approximate 2D direction. If at the same instant another person also observes Mars from their window. ...
2
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1answer
496 views
Gravitational Field Strength of a point in between Two Planets
In my textbook, under the topic of gravitation, it states that if the centres of 2 planets, each of mass $M$ and separated by a distance $r$ and you have a point halfway between the centres of the ...
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0answers
22 views
Would the Earth have cracked differently than 'pole to pole' at Atlantic ridge if had been rotating slower?
When a thick hot peace of glass is left to cool down it will break on the surface. Have the same happened to Earth and did the fast rotation provoked the crack at the middle Atlantic to gain this pole ...
0
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1answer
65 views
Why do objects weigh less the further from Earth's center?
I just finished watching a video on gravity. It stated that an object weighs less the further it is from the center of the earth. Example being on a mountain top or at the equator being that the earth ...
0
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4answers
75 views
Doubt when calculating the gravity force excerted by a planet to an object on its surface
I have been thinking about why when you want to calculate the gravity force/acceleration that a planet exert on a obect, it is considered that all the planet's mass contributes to create a vertical ...
