Questions tagged [planets]

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

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2
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1answer
72 views

What is the second $r$ in this equation for the Two Body Problem?

$$r=\frac{r^2\frac{\mathrm d\theta^2}{\mathrm dt}}{\frac{Gm_2^3}{\left(m_1+m_2\right)^2}\left(1+e\cos\theta\right)}$$ I have this equation for the radial distance of a planet from the barycenter. But ...
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1answer
79 views

Bad value for sphere of influence with Venus [closed]

I would like to get value of sphere of influence than Wikipedia for Venus: on https://en.wikipedia.org/wiki/Sphere_of_influence_%28astrodynamics%29 It is indicated for Venus: $S_{\text{OI}}=0.616\,\...
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1answer
515 views

How do we know the Earth's core is Molten with Seismology?

My current knowledge about how the core of the earth was discovered is the observation made from non returning/reflecting sonar signal when sent to deeper depths through the earth's crust/mantle. How ...
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1answer
499 views

How did Mars lose all its surface water?

A lot of geological evidence suggests that Mars once had quite a bit of surface water. I assume it wasn't whisked away into space, so where did it all go? What processes caused the water to go there? ...
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2answers
358 views

Accurate Equation for Earth's Gravitational Binding Energy

This is a relatively important question for anyone who can answer it. I am trying to find the equation that accurately solves for Earth's Gravitational Binding Energy. The information below is from ...
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1answer
52 views

Earth bulge and axis precession

We know that earth is not spherical because it spins. Does every object that spins bulge? for example a rotating wheel bulges? Also how moon and sun create the torque that shifts the axis of rotation (...
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3answers
598 views

Why do gas giants have similarly coloured stripes?

After looking at Jupiter and searching 'exoplanets gas giants' on google I found that many had stripes on them. I found that pretty peculiar. So why do they have stripes. I think it has something to ...
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1answer
71 views

Digging a hole in the moon across its diameter [duplicate]

What will occur if one digs a hole in some moon/dead-planet without an atmosphere (and without a Lava Core), such that this hole shall have a 1 meter diameter and will be so deep that shall go through ...
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0answers
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How severe would the consequences be if the earth's moon were wrenched from orbit?

The old TV series Space 1999 from the early 1970s seems to have resurfaced on Youtube reminding me of something I watched as a child. It is one of those obviously ridiculous SciFi series (from the ...
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3answers
952 views

Gravitational advantage of outer planets in war

The Expanse books cover a lot of aspects of war in a situation where humans inhabit many planets and moons of the solar system. The author makes the point that, in a war situation, the outer planets ...
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3answers
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The acceleration in Earth's gravity

The acceleration in earth's gravity is $9.807 m/s^2$ at my location. But is this value uniform in the entire earth? For example in the inner core or outer core. What is the acceleration in the center ...
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3answers
167 views

Relativistic space rocks. Are they possible?

I was thinking that the Universe is full of extreme events. Colliding galaxies, exploding stars, colliding planets (like in one of models of our Moon formation), colliding black holes... Can it be ...
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12answers
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If gravity disappeared, would Newton's third law make everything that was pressed to the ground by gravity get pushed upwards? [closed]

If gravity disappeared, would Newton's third law make everything that was pressed to the ground by gravity get pushed upwards?
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2answers
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How can you calculate the atmospheric layers on another planet?

I'm working on a program that procedurally generates planets, and I'd like to make a realistic atmosphere with realistic pressures at different altitudes. I know that for earth we have 7 layers to our ...
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3answers
969 views

Why is Mars so cold when it has so much atmospheric $CO_2$?

Mars has 1/10 of Earth's atmosphere but that atmosphere is 95% CO2. Why is Mars so cold when it has so much atmospheric CO2?
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1answer
31 views

Gravitational/electromagnetic effect of planets on solar activity?

Does the gravitational and/or electromagnetic influence of planets have any effect or correspondence to solar activities (e.g. solar flares/CMEs) - and if so, does the planetary position (where they ...
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1answer
44 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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1answer
52 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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0answers
71 views

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. Is ...
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2answers
130 views

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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1answer
130 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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2answers
324 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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3answers
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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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1answer
488 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
189 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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1answer
104 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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2answers
362 views

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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3answers
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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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1answer
199 views

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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4answers
5k views

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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1answer
529 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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0answers
86 views

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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2answers
270 views

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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1answer
133 views

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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1answer
53 views

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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1answer
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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
247 views

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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2answers
854 views

Does the Earth emit gravitational waves?

We know about Bohr's model and his vague postulate challenging Rutherford regarding discrete orbits and not emitting electromagnetic waves during this. Extending this idea to our solar system, does ...
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1answer
50 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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2answers
71 views

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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1answer
60 views

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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4answers
8k views

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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1answer
258 views

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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1answer
676 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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1answer
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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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1answer
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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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2answers
90 views

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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1answer
46 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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0answers
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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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1answer
190 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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