Questions tagged [planets]

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

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1answer
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Will a body as big as the moon collapse inwards if it was partially hollow?

Take a hypothetical scenario where the moon is hollow upto R=R/2 So will the moon collapse inwards as there is nothing to balance the gravitational force from outside?
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Is it physically possible the existence of moons or planets where objects float permanently above the surface?

I found the following exercise while studying gravitation: A small moon of mass $m$ and radius orbits a planet of mass M, keeping the same face towards the planet. Show that, if the moon approaches ...
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Why do we weigh less on equator when centrifugal force isn't a force at all? [duplicate]

Why would we weigh less on equator as the weighing machine measures the force by which we push ground and that should not change if are on equator or poles?
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How Can I Calculate the Speed Required for an Orbiting Planet to Pass Through a Given Point in Space?

I've been trying to derive an equation for this for a while now, but I haven't had much success. Let us set up the equation. There is a star with mass $M$ and a planet that is distance $d$ from the ...
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If Earth is mostly fluid, why does it not stretch as it rotates? [duplicate]

Discs are naturally occurring shapes in the world, because any soft object experiencing rotation on a single axis will stretch itself into a disc shape such as pizzas and galaxies due to centrifugal ...
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Range of Earth's gravitational field

We know that the acceleration due to gravity acting on a body situated h meter away from the surface of the earth is given by, $$g' = (1 - 2h/r)g,$$ where $\,r$ = Radius of the earth ($R$) + $h$. Now ...
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How the moon takes energy from Earth (if at all)?

At least twice (on the comments of this answer, and mentioned in passing on this book), I have read that the moon takes energy from Earth due to tidal drag. The notion seems that: a) energy must ...
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Orbital distances of planets [duplicate]

So is the exponential pattern in the planetary distances related to Johann Kepler's discovery in 1596 that the ratios of the orbits of the six planets known in his day were the same as the ratios ...
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Why temperature of planets decreases as we move far from Sun?

Is there a friction in the space? If yes, then does that affect speed, wavelength and amplitude of an EM wave? And i also want to know, why temperature of planets decreases as we move far from Sun?
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How could I calculate the exact amount of force I need to apply to a mass to get it to orbit around another mass?

I am currently taking AP Physics, and we are learning about gravitational forces in planets. We know the equation for gravity: $$F_g=\frac {Gm_1 m_2} {r^2}$$ But, with this equation alongside the ...
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Tidal forces between Moon and Earth

I started studying about gravitation recently and I came across the fact that when finding the gravitational force between the earth and some point mass in space, we can consider the mass of the earth ...
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Can the centre of a rocky planet ever freeze?

When a rocky planet like the Earth or Mars forms the gravitational potential energy is converted to heat energy within the planet. Planets lose heat energy over time by emitting radiation. But is ...
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What are Love numbers and what is the Moon-Earth tidal quality factor?

I need to find the quality factor (ie. $Q = \frac{\text{energy stored}}{\text{energy dissipated per cycle}}$) associated to the Moon orbiting around the Earth. Looking around for this, lead me to the ...
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Why are planet's maximal/minimal angular speed ratio harmonic?

See this Wikipedia page for Harmonices Mundi, a book by Kepler (yes, he was the one to discover the three Kepler's laws). The author writes: He found that the difference between the maximum and ...
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Theoretical lower limit to the density of a planet

If a celestial body is too dense, hydrogen fusion will ignite and it will become a star. As such, there is an upper limit on the density a planet can have. But is there a lower bound on the density ...
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Motions of planets from a non-rotating earth frame

Suppose you are hovering just above the earth at a fixed distance such that you are not rotating with it (the earth is obviously rotating about its own diametrical axis) but you are orbiting the sun ...
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What would the chemical and atomic effects of an antimatter star be upon a normal matter artificial planetoid? (Thought experiment)

Setting aside all the challenges of actually achieving such a thing, and as a thought experiment, what would the chemical and atomic effects of an antimatter star be upon a normal matter artificial ...
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What would the effect of an antimatter star be upon a normal matter planet? (Thought experiment)

Based on the answers from this question: Would the solar wind from an antimatter star be any different from a non-antimatter star?, it seems that an antimatter Sol type star would conduct fusion ...
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What is the difference between the nutation of the Earth and the Chandler woble?

I have been trying to understand the different things about the earth's rotation and revolution. But the terms Chandler wobble and nutation seem alike yet have different time periods.
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Could a planet experiencing tidal locking have a habitable area?

I wonder if it would be possible that, on a planet that always shows the same face towards the sun, there is a habitable area for some life-form similar to that of the Earth. I guess, since one face ...
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Where does the radial velocity component come from?

Any object under the influence of a central force will have two components of velocities: Radial and rotational I understand that the rotational velocity is there due to the centripetal force. But ...
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Can we rule out life swimming in the oceans of Europa and Enceladus on the basis of a lack of available energy?

Jupiter's moon Europa and Saturn's moon Enceladus (and several other moons too) have large subsurface oceans of liquid water, an ingredient considered essential for life. These two moons occasionally ...
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Why is Jupiter's ring system so faint?

Planetary ring systems are formed when asteroids, comets, or any other large objects pass too close to the planet and are torn apart by the planet's gravity [1]. Jupiter is often called the "punching ...
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How deep must Earth's ocean be to form Ice VII on bottom?

Is there way to tell how deep must Earth's ocean be to form Ice VII on bottom? Or is it impossible because of our planet is too small? As I know, in 11.5km Mariana Trench there is 108 MPa and to form ...
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Can dark matter explain the unusual orbit of transnettunian objects? [closed]

While we are struggling to find an hypothetical planet 9 to explain the unusual orbit of transnettunian objects, I was wondering if it could be just dark matter. We know that the universe is mostly ...
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Is space-time fabric around Uranus tilted?

I am completely new in this field, so please pardon me if I am asking something which makes no sense at all :) The Situation: According to Einstein's theory of relativity, there is a 4th dimension ...
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Weight at Poles and Equator Wrong?

Recently, I was thinking about the acceleration due to gravity on Earth when I remembered that I was taught that you weigh less at the equator because a fictitious centrifugal force "throws" you off ...
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Recent/More accurate rotation velocity measurement?

I've been researching for papers for hours and can't seem to find this. Where can I find the most accurate equatorial rotational velocity measurement for Mars?
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Do all the planets in our solar system orbit the sun in the same direction and in the same plane?

Do all the planets in our solar system orbit the sun in the same direction and in the same plane? (as in a flat orbit if you are looking from "above")
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Ever looming shadow

If I'm not mistaken the reason the moon eclipses the sun is because the ratio of distance to size, in regards to the moon and sun, is 1:1. And is it not also true that the reason we only ever see one ...
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Does frame-dragging affect planets?

The question has come up many times as to why the planets in our solar system lie in essentially the same plane. The most common answer is that they started out that way due to the accretion disk ...
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Equator water pipeline flow at sea level?

If a water pipeline was built at sea level eg. Gulf of Mexico and the other end was at sea level in southern Chile, then the pipeline was primed with pumps, would the water then gravity feed and flow ...
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Is the notion of 'weight of Earth' meaningless?

I am not talking about the distinction between mass and weight, just the concept of 'weight'. In University physics (book by Young & Freedman, 14th Ed.) it is given that the weight of an object ...
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On a planet with winds faster than sound, what would it sound like?

I'm watching a Youtube video of the strangest planets and some of them have atmospheres/winds that constantly go at like 20x the speed of sound, ex: HD 189733-b .On earth, fast winds is actually ...
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Confusion about a claim in the “Brief History of Time” by Hawking

In the first chapter, while talking about how Aristotle was able to conclude that the Earth is spherical, Hawking says that had the Earth been a flat disk the shadow of the on the Earth on the moon ...
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Why Earth’s crust is max 100 kms wheras Moon and Mars have much thicker ones?

We know that the Earth’ mantle and core are hot, whereas the crust has cooled down. The cooling process of the 4,5 billion years of the Earth’ exisence resulted a crust of between 50 and 100 kms. ...
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Ptolemaic system parameters

I recently learned about the Ptolemaic system, which seems pretty accurate. There is even a simulator on the Internet: https://astro.unl.edu/naap/ssm/animations/ptolemaic.html You can see that there ...
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Why doesn't Venus have a magnetic field? How does the speed of rotation affect the magnetic field of a planet?

Why doesn't Venus have a magnetic field? How does the speed of rotation affect the magnetic field of a planet?
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Can a planemo turn into a star?

I read this question Why is planet CFBDSIR2149-0403 hot? and wonder what will happen to this "planemo". Will it attract more mass as it flows around in the gas clouds in space and eventually light ...
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How hot can the surface of a planet be?

I just read this article https://edition.cnn.com/2018/07/02/world/newborn-planet-image-study/index.html and noticed that the astronomers estimates the surface temperature of the planet to 1000 °C. ...
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Mars longitude reference?

Platforms like NASA's JPL HORIZONS web-interface for solar system dynamics often have obtainable parameters like sub-solar or sub-terrestrial longitude for a given time and celestial object. (example: ...
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Uranus: The Spin

In his prog. , on the outer planets, Brian Cox stated that Uranus spins on its side because it once endured an interplanetary collision. Such a cataclysm would normally be devastating for both ...
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Is there a maximum distance from a planet that a moon can orbit?

Given a planet that orbits a star, and a moon that orbits that planet, is it possible to define a maximum orbital radius of that moon, beyond which the moon would no longer orbit the planet, but the ...
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If the mass of the Earth is decreasing by sending debris in space, does its angular momentum also decrease? [duplicate]

We are sending huge amount of debris into space from earth, and also very heavy satellites and rockets, then the mass of earth must be decreasing over time. If the mass will decrease, then ...
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Jupiter & Saturn

In his prog. on Jupiter, Brian Cox stated that the complex gravitational interplay, between Jupiter & Saturn, prevented Jupiter from drifting through the Asteroid Belt, and approaching our part of ...
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How does the Earth remain in its shape?

I know only stars do nuclear fusion to keeps its shape from gravity. Then what about the Earth? Earth doesn't do nuclear fusion. How does the Earth keep its shape even though the gravity keeps pushing ...
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1answer
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How to integrate acceleration due to gravity with height? [duplicate]

If I project a body at a very large velocity such that it reaches a height h which is comparable to Earth's radius, then how to derive an equation for 'h' in terms of initial velocity 'u' and other ...
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How does the gravitational acceleration on a surface of planet change, if its radius shrinks while retaining the same mass? [closed]

If the radius of the earth were to shrink by $1$% while its mass remained the same, then how would the acceleration due to gravity on the earth's surface increase by $2$%?
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Do planets in elliptical orbits exhibit constant magnitudes of acceleration in their orbits?

I'm trying to reason through a problem. Consider Jupiter, which orbits the sun in an elliptical path. Is the magnitude of its acceleration constant throughout its orbit? My reasoning leads me to ...
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1answer
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How is sound affected by gravity?

How would sound be different on a planet with a stronger gravitational field? My reasoning leads to sounds of the same wavelength having higher frequencies - is this correct?