Questions tagged [planets]

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

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32 views

What's the difference between a convection and a polarization electric field?

In the ionosphere and magnetosphere communities, studies frequently refer to the "convection electric field" and the "polarization electric field". What is the relationship between them, and what are ...
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47 views

Can a planet have multiple significant sized moons?

The Earth has one moon at about 1/80 of Earth's mass. Is it possible to have two moons large enough each to subtend a >30 minute disk as viewed from the surface? I have tried with various ...
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How fast would the Earth have to spin to lose the atmosphere?

I have read these questions: How fast would the Earth need to spin for us to feel weightless? Why can't we feel the Earth (or being in any non-inertial frame) rotating? And it made me curious....
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How do astronomers explain trajectories of planets?

I'm wondering how astronomers can explain the trajectories of planets because: planets spin, so have angular kinetic energy. Thanks to the mass-energy relationship this means space-time curvature. ...
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81 views

The Earth's Equatorial Bulge [duplicate]

It is stated that the Earth is a 'squashed sphere' due to the very slight bulge at the equator. (Thought in reality it's such a small difference, it's essentially spherical) Typical values: ...
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160 views

Does the Earth emit heat?

I'm reading my first book on physics "Seven brief lessons on physics" by Carlo Rovelli, and in his chapter on "Probability, time and heat of black holes", he mentions that Stephen Hawking showed that ...
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Why should asteroid coming towards a star deflect away from star if gravity is an attractive force?

I was finding the closest approach of an asteroid (whose energy is sufficient to exit the gravitational field of the star )so that it can escape the gravitational field of the planet .The asteroid ...
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409 views

How would the rotational and orbital mechanics differ on a torus-shaped planet as compared to a spherical planet?

I am making the attempt to develop some computational models of Star systems and I was wondering how the a torus shaped planet would compare to a traditional spherical planet in the context of ...
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1answer
102 views

Is there any moon without its planet?

Is there any planet without its star? Is there any moon or any planet wandering in outer space without a definite orbit? (The name moon or planet used here serves only for size and spherical shape ...
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101 views

Could there be a minimum black hole within each moon, every planet, every star?

It's the spherical aspect of these celestials bodies that makes me think about this. Could planet Earth have started itself with a tiny black hole?
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Why do all the planets and stars in our solar system have such similar average densities?

This table lists the average density of all the planets in our solar system. We could also consider the Sun (average density 1.41 g/cm³) and Pluto (average density 1.88 g/cm³). The densest body (Earth)...
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Planetary Gravitational Pull

I have read that Jupiter and Saturn apparently have no surface. I have a hard time believing that a ball of gas can have such a strong gravitational pull without any kind of a solid surface. Can ...
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Planet Orbital locations based on year / month. (table?)

I am finalizing an Orrery that used Arduino to move planets into their respective orbital position based on the year and month from a users input. I am looking for a table or database that has the ...
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What is acceleration due to gravity at the centre of the earth? [duplicate]

When I asked my teacher that what is the acceleration at the centre of earth, he replied that it is 0 as when we move inside the earth, the effective mass decreases i.e. the mass that exerts ...
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489 views

Arbitrary Planet Spectrum

During my revision for an astrophysics quiz, I have encountered a question where I don't know where to start because I feel like I am lacking some intuition. I would appreciate any feedback! ...
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Gravity train and fastest path

As a fun exercise to kill some time, I have been thinking in the gravity train. For a point mass falling through a tunnel dug from pole to pole in an spherically symmetric planet of radius $R$, the ...
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Question about the Normal Force exerted by Planet Earth in relation to centripetal force

I have the following question based on a paragraph from my Physics textbook (I am translating, so the result might not be the most elegant): It states that due to the centripetal force resulting from ...
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Why is the Earth not an exact sphere and what makes it bulge at the equator? [duplicate]

In chapter 7 of the Feynman Lectures Volume 1, Feynman explains that the Earth is round due to gravitation as everything attracts everything else. He also says that it is not an exact sphere since it ...
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Can a tunnel through a planet be used as a power generator?

Assuming that it were possible to do so, if a tunnel from one side of a planet to the other were lined with copper wire, could dropping magnets down the hole be used to generate power?
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Earth-like atmosphere on Mars, possible?

I recently watched a TED talk by a journalist, Stephen Petranek, in which he talks about colonization of Mars. Reaching the end of the presentation he talks about terraforming the planet, making it "...
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3answers
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I don't understand why pressure should increase with depth into a sphere

Newton demonstrated that the gravitational force at a distance r from the center of a uniform sphere is "as if" all the mass was concentrated at the center. The proof I have seen starts by first ...
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1answer
37 views

Difference between solar annual and solar daily earth tides

I understand there is a semi-daily and daily solar earth tides (S1,S2) because the earth is rotating around its axis. I understand there is an annual and semi-annual solar earth tides (Sa, Ssa) ...
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Effect of Change in Mass on Planetary Motion [closed]

How would a change in the mass of a planet in the solar system affect its orbit? For example, if hypothetically the mass of Mars were doubled, would it [a] move closer to the Sun, [b] move further ...
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Is it possible for a planet or a moon to exist with absolutely zero atmosphere?

Mercury has an atmosphere, no matter how thin that might be. Scientists say that the space is not completely empty because we can always find a few hydrogen atoms per kilometer all over the outer ...
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If there is friction and everything stops on earth why does earth not stop due to friction?

Why do planets revolve around the Sun if there is a force called frictional force? Why do planets not stop rotating while the objects in motion stop after a while? Why are they continuously moving? ...
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Rotation rate of Mercury vs. a day on Mercury

In the latest episode of Last Week Tonight (June 3rd), John Oliver says a day on Mercury is 1,407 earth hours (58 days and 15 hours), which is correct. Neil D. Tyson says The time you gave is ...
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458 views

Gravitational force on object inside Earth

When we find the gravitational field on an object that lies inside Earth we simplify the problem by considering the sphere whose radius is the distance of the object from the center of Earth. We use ...
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Why do the sun and planets differ in their chemical elements composition?

The chemical elements composition of the sun changes as its nuclear furnace changes elements into heavier ones. But it is supposed to be mostly Hydrogen at the start. The planets are too cold for ...
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What will happen if rotation of Earth will get reverse? [duplicate]

Today one question pop up into my mind... What will happen if Earth spinning about its axis and around the sun will start moving in reverse direction... Whether it will affect us... What are all ...
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Is it possible that the axis of rotation of a planet also rotates?

Assume that there is a planet that rotates around a axis. Is it possible that this axis also rotates around another axis? For example, the planet is $\{(x, y, z)| x^2 + y^2 + z^2 \leq 1\}$ and this ...
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29 views

Could planetary magnetic fields repel each other?

If two planets with magnetospheres approached each other, would they repel or attract?
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Which planets would be visible from the Saturn system using the Naked Eye?

I was wondering which planets would be visible using the Naked Eye from Saturn? Would these planets always be visible or disappear as they got further from Saturn? Plus which planets wouldn't visible ...
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118 views

Is Gravity Cumulative

This is to tie in with a previous question >The Sun's Orbit - Is it What We Think? Are gravitational waves cumulative? and if so how does this affect our galaxy and other astronomical bodies? Now ...
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Is there a skip ahead formula for simulating planetary motion using time step increments?

Is there a formula that would allow me to skip to a particular time step in a simulation involving planetary motion without having the simulation pass through every time step before? For instance if ...
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1answer
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Thought experiment regarding a posible preferential configuration of tectonic plates

Oceanic and continental tectonic plates have different densities, and their relative position have a very important effect on the evolution of Earth's climate on geologic time scales. There are many ...
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102 views

Zero-level of combination of $1/r$ and $r^2$ potential

I am solving a problem which involves a central big mass $M$ and around it a spherically symmetrically distributed mass of constant density $\rho$. The force on a mass a distance $r$ from the centre ...
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46 views

How much time will it take for an object to fall to the center of the Earth? [duplicate]

The reason I want to know is because many years ago in Sunday school I learned a story that in probably 600 AD some sinner was swallowed up by a hole, and that he's still falling as of today. I can't ...
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Estimation of Equatorial Bulge of the Earth [duplicate]

My dynamics lecture notes repeat the Earth's equatorial bulge can be approximated as: $$ \approx \frac{\Omega^2R}{g} \approx \frac{1}{300} $$ (Do they mean R/300?) They also include statements like: ...
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What will be the nature of motion? [duplicate]

If a piece of matter is released along the tunnel extended between one end to the opposite end through the diameter of the earth, what will be the nature of motion?
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What do the planets in our solar system smell like? [closed]

For example, if Jupiter is mostly hydrogen and and helium, but has ammonia clouds, does that mean it smells like a cat's litterbox? Does Mars smell like iron? Asking in order to give kids a more "...
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63 views

How dense could an Earth-sized planet be before beginning to undergo fusion?

I'm trying to figure out the maximum possible density for an earth-sized planet before it would become an earth-sized star. To try to figure this out, I found a reference star, VB 10, known for being ...
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Are the high tides always more unequal when the centre of gravity is within a planet?

In case of our high tides at both sides of the Earth it seems that they are almost equal. But is there a slight difference because the center of gravity is about 1,700 km below the surface of the ...
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1answer
143 views

Making a tunnel in the Earth through its center [duplicate]

If I make a tunnel in the earth through its center from one place to the antipode place and throw a ball into the hole, what will happen? So far I can think, the ball will oscillate with SHM motion ...
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1answer
138 views

How Literal is Mass-Energy Equivalence in Gravitation?

Does, for instance, energy emit gravitational force on nearby masses, or energies, and thereby increase the overall energy of the system? (I am ignorant of field theory and would appreciate being ...
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What's the earliest a planet could have been formed? [duplicate]

From what I know the Earth is ~4 billion years old and the universe is ~14 billion years old. Are there factors that prevented the Earth from forming for that first ~10 billion years? Perhaps ...
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Gravity Time Dilation interior to a planet

Regarding Gravity Time Dilation: We know that, in a stronger gravitational field, time passes more slowly. As one descends below the Earth's surface, how does the intensity of gravitational pull ...
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is it mathematically accurate to simply objects to point masses when calculating gravitational forces between them? or is it just an approximation?

i tried searching for the exact mathematical proof that validates this assumption, but couldn't find any. also, is this assumption still accurate if the density of the object resembles a planet (...
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Force on moon & what will happen next?

The moon is rotating around the earth. It is feeling a force by earth due to gravity. So if I some how manage to exert some force into moon, what is be the scenerio? I can think of: The moon will go ...
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Why is the value of $g$ 0 in Earth's center? [duplicate]

We know that the value of g in the center of earth is zero(0). But applying the classical formula for calculating g: We find g=(GM)/0 which is undefined. So how can this be zero. I don't understand.
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Speed at the perihelion [closed]

Hale Bopp has a period of 2400 days, with a mean distance from the sun at 174 AU and 1AU away in perihelion and 357 AU away in aphelion, what is its speed at the perihelion? what formulas do you need ...

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