Questions tagged [moon]

A smaller body orbiting a larger, primary body, where the primary body is not a star.

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2answers
70 views

What good is The Moon? [closed]

In the 2009 anime "Avatar: The Last Airbender" some guy kills a fish, which makes The Moon disappear, in order to win a war with some Eskimos. That got me wondering "What good is The ...
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Measuring Sun and Moon distances to the Earth ratio just by observing angles of elevation if upper 50 percent of Moon's surface is bright?

When the next type of calculation was possibly used for the first time? If 50% i.e. upper half of Moon were bright would the Sun-Earth to Moon-Earth distances ratio be calculated from just ...
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THE LINE OFTHE MOONLIGHT IS NOT STRAIGHT ANYMORE [closed]

I am from the USA, just a retired soldier who looks at the sky a lot. This morning 26 SEP 2020 at 1am, the Moon was approximately a quarter Moon. It was bright, the line/shadow on the moon was not ...
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How much the Earth atmosphere oscillates due to Moon tidal force and does this produces winds?

As there is the tidal force of the Moon exerted on the Ocean water I supose there must be some force acting to the Earth's atmosphere. So when the atmosphere starts falling down as the Moon is ...
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If the moon had always been a black hole (with the same mass) when and how would we have realised? [closed]

Inspired by this recent question. If, sometime shortly before writing was invented, some passing alien turned the moon into a tiny black hole (xkcd) when/how/would we have figured out it was there, ...
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If the moon became a black hole, how much would it eat in a day?

I have been thinking about the moon becoming a black hole. I was thinking about how much it would eat a day. How much mass would it suck in in 24 hours on average? I am writing a story where the moon ...
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1answer
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Can tidal locking increase rotational kinetic energy? Where does the energy come from then?

I was thinking about the explanation for how the Moon gets tidally locked with the Earth. We are working in the non-rotating reference frame of the Earth, and assume it is inertial (to an approximate ...
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How much does $g$ vary according to the position of the moon?

The gravity of the earth or more specifically the gravitational acceleration, $g$, is the acceleration objects with mass experience toward the earth due to gravity. How much does this vary according ...
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1answer
38 views

Why does the moon sometimes look reddish yellow?

So the question is clear from the title itself. Only sometimes does the moon when it just rises above the horizon, looks reddish in colour. This mostly as I have seen occurs when the moon rises when ...
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1answer
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If Saturn's rings cannot coalesce into a moon because of tidal forces, then how are shepherd moons able to exist?

From Wikipedia: In celestial mechanics, the Roche limit, also called Roche radius, is the distance within which a celestial body, held together only by its own force of gravity, will disintegrate due ...
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What's the UV index on the Moon

What would the UV index be on the moon compared to the Earth? I'm pretty sure it would be ridiculously high but I'm not sure how high.
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How big a coincidence is the Sun and Moon having almost equal apparent sizes?

It's consensus that the very similar apparent sizes of the Moon and the Sun as seen from Earth is a coincidence (as already answered in this site). This provides us with almost exact total solar ...
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What will be the absolute gravity of Io moon if Jupiter's gravity not in effect? Can GR explain it?

It is noted that the distance between Io moon to Jupiter planet and our Moon to Earth is nearly same. However, the ratio of gravity Earth/Moon is 80.4 times vs ratio of gravity Jupiter/Io is 20276.7. ...
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I want to know about the synodic and sidereal months. Why is there a difference between the two? [closed]

I want to know about the synodic and sidereal months. Why is there a difference between the two?
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1answer
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Could a planets magnetic field magnetise the core of its own moon?

Could a planet with a magnetic field make the core of its moon (or another celestial body), if it was made of iron say, into a giant permanent magnet?
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Why do we use $F=GMm/r^2$ when calculating the centripetal force of the moon around the Earth and not $g=GM/r^2$? [closed]

When we calculate the centripetal force of a satellite orbiting earth, we use $g=GM/r^2$, implying that gravitational force and centripetal force are the same. However, when calculating the ...
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What is a simple argument to prove that the stars in the sky are further away from the Earth than the Moon?

How do we know, without using modern equipment, that the stars are further away than the moon in the night sky? Further, is there a simple and actionable argument to prove that this is indeed the case?...
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What is the reason for assuming angular momentum is conserved for a moon-planet system where the moon is in an elliptical orbit around the planet?

I came across a question in the Princeton Review book for AP Physics 1 and then found the same question in the Collegeboard AP Physics course guide. Both have different answers. (See the questions ...
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Harvesting energy from Moon's orbit without water [closed]

We use the gravitational interaction between the Sun, Moon, and Earth to harvest energy from the motion of the oceans, the tidal "bulge", along coastlines. This uses the changing sea level to ...
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What is the interplay between the “spinning tennis racket” effect on a planet with three principle axis of rotation and its moon?

Suppose I have a tennis racket spinning on its second axis of rotation such that it is subject to periodically flipping over on its spinning axis, as per the Dzhanibekov effect (explained in ...
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1answer
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How does our Moon stay in orbit around Earth? A question about gravitational field strength [duplicate]

Calculating the gravitational field strength felt by our Moon, caused by our Earth and Sun, I found that the magnitude of the Sun's gravitational field is felt as greater by the Moon than the Earth's. ...
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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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1answer
116 views

Lunar surface brightness

If the Moon is visible against a clear blue sky with a lux value of around 30,000 does it stand to reason that the lunar surface must be brighter than that?
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How was the mass of the moon first calculated?

How was the mass of the moon first calculated? How do we measure it now?
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Why is the moon so bright when it is really dark

The moon is bright, and if you were 50 times closer it would be 25 degrees across with the same surface brightness, which would be pretty dazzling. Looking at the moon through a telescope (which ...
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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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3answers
131 views

What exactly is the energy source of tides?

Tides happen due to the gravitational interactions between the Earth and the Moon. We can say that the tides are pulled by the Moon's gravitational field and so it keeps on changing as it moves out of ...
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Moon is receding from Earth approximately 4cm per year [closed]

According to the theory of relativity the universe is styled as a fabric which is depressed by a large mass and a moon, still following a straight path ever 'curves inward' toward the large mass. Now ...
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110 views

Would the moon eventually hit the Earth?

The moon is rotating around the earth in elliptic or approximately circular orbit with speed $v$. Its acceleration have two components tangential and radial one. It is the radial acceleration ...
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Is gravitational energy usable and could it be depleted?

Let's take for example a tidal stream generator. We know that tides are a consequence of the Moon gravity, we know that mass is connected with gravity, so is this mean that (1) we use Gravitational ...
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Implication of Earnshaw theorem to the orbit of the moon

Can we apply Earnshaw theorem in circular/elliptical/hyperbolic orbits? I was wondering how did the moon stop at its current stationary orbit. It seems to me the fragments that gave origin to the moon ...
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1answer
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Free return trajectory versus burning rocket

It is said that Apollo was set to the free return trajectory while leaving earths gravity, heading to moon.Now the Free return trajectory is the one in which satellite uses moon gravity to return back ...
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Moon causing tides violates conservation of energy?

It is a simple fact that the moon causes tides in the earth. But these tides seem to be a violation of the conservation of energy. Why exactly would this be? Well think of it the way I am thinking ...
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Is the Moon's rotation affected by Earth's?

There is a lot written on the moon affecting the Earth's rotation but not so much the other way around. I know that moon has its own rotation: Tidal locking is the phenomenon by which a body has ...
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How to interpret doppler curve images of Chandrayaan-2 lander?

The frequency transmission data for Vikram, lander of Chandrayaan-2, received by 25 meter Dwingeloo radio telescope is plotted and tweeted by Cees Bassa. Kinks in the Doppler curve are interpreted as ...
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1answer
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Astronauts in spacecraft, they have to circle the earth many times a day, do they also have the illusion of the moon?

Astronauts in spacecraft, they have to circle the earth many times a day, do they also have the illusion of the moon? I don't think they have, because according to the theory, the illusion of the moon ...
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1answer
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How do we know the Moon has a 0.50 angular degree from us?

Before we knew the distance to the moon, how can you get the exact angular degree of it without knowing the distance to it? Obviously you can just guess or assume but how was it first calculated?
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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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Could the moon move balls on perfectly flat and level surface?

I've been looking into the concepts of highly flat surfaces and highly round objects, and I'm wondering if an experiment like this would work / has been done: Take a perfectly flat surface Level it ...
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3answers
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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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Can Hydraulic System work on a Moon Robot?

Since the Moon has no atmosphere and the temperatures reach maximum 123 C and min minus 153 C, how feasible is it to use hydraulic actuators to move the Robot legs? Since my assistant Professor ...
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1answer
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Can we build a superconductor on the Moon and beam energy where needed? [closed]

Should we not build a superconductor facility on the moon ? We find a spot where the rays of the sun don’t provide heat. This should enable a superconductivity facility to operate due to the low ...
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3answers
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Why is a gibbous moon possible?

This could be a silly question to ask, but I would like to know why is a gibbous moon shape possible. From the few cases I've drawn here, I could not think of a configuration where the Earth's shadow ...
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1answer
200 views

Conservation of Angular Momentum — Earth-Moon System — Earth spin backwards?

I am developing an exhibit for a museum. We want to show how the Earth's spin rate changes as the Moon drifts farther and farther out from the Earth. The visitor has a slider they can move to set ...
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1answer
37 views

Amount of Time the Moon remains overhead at Night?

I was wondering, as the Moon moves across the night sky, at midnight, when the Moon is overhead, how long does it technically stay over head before moving to the other side of the night sky? I was ...
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Calculating Inital Velocity required to stablize an orbit of a moon

I am currently attempting to create a little solar system simulation and I was curious if there's a decent way to calculate what a moon or planet's initial velocity would need to be to remain in orbit ...
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230 views

How is it possible to see a full moon at midday? [closed]

I’m currently doing an observational study of the moon that’s been a passion of mine for the last few years. I’ve found I can see the moon all the way to almost full at about midday). Added I can see ...
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77 views

At what velocity will the moon be able to escape the earth's orbit?

I haven't found an answer to this question online so correct me if I am wrong. This is the escape velocity equation: $v_{esc} = \sqrt{\frac{2GM}{r}}$ and by plugging the known values, this is the ...
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1answer
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Why does the red light from Sun bend towards the moon during the total lunar eclipse?

During the total lunar eclipse the earth, moon and the sun are in perfect alignment so that the moon is within the umbral shadow of the earth. However, instead of turning invisible the moon actually ...

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