Questions tagged [moon]
A smaller body orbiting a larger, primary body, where the primary body is not a star.
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Could earth's axial tilt shift due to an asteroid hitting the moon? [closed]
Earth's obliquity is around 23,5°, a value that is known to shift over secular timescales (cf. Milankovich cycles). However, I've been wondering if a change of axial tilt could occur rapidly (without ...
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The true cause of the Moon illusion? [closed]
As shown in the figure, the blue line is the lens, $w$ is the height of the object, $x$ is the height of the image, $v$ is the image distance, $u$ is the object distance, and $f$ is the focal distance....
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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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1answer
33 views
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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53 views
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
30 views
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
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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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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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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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2answers
73 views
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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1answer
40 views
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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Y the relation among centripetal, centrifugal and gravitational force exerred on the moon is different from an object on the earth surface?
I read that since the earth vid rotating on its axis ,an object on the earth surface experiences a centrifugal force because the object is also moving around the earth's axis.So,that centrifugal force ...
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1answer
47 views
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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4answers
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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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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
66 views
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
99 views
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
118 views
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
169 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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36 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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172 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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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
73 views
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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47 views
How fast would an object at cruising altitude (around 10,600 m) need to travel to stay on the opposite side of the Earth to the Moon? [closed]
I am trying to figure out how fast an object will have to travel (at a height around 10,600 m) to never be in the presence of the moon. Meaning the object will always be on the opposite side of the ...
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Why is the Moon's Centre of gravity different to its centre of mass? [duplicate]
All the places that I've seen an answer to this question simply state that it's because there is a stronger gravitational pull on the near side of the moon, facing the earth. But I'm wondering how ...
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Show me how the sky is like in Jupiter (but not mars)
Assuming someone is "standing" on the "surface" of Jupiter (ok, in a stable position deep inside the gas giant's gravity field analog to standing on the surface of a rock planet) where the moons can ...
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If the Earth would change into a ball of water, how wil its form develop, considering only the Sun's and Moon's influence? [duplicate]
Let's fantasize that the Earth changes in a non-rotating ball of water. And let's assume the only gravitational influences on it are those of the Sun and Moon.
What will happen to the form of the ...
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2answers
125 views
What happens to the water on the surface of the Earth if the Earth is not rotating about its axis in the Earth-Moon system?
Suppose the Earth is not rotating. As usual, the Moon follows its normal path around the Earth. Let's assume it's a circular motion and that there are no other gravitational influences.
A test ...
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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
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Confusion about angular momentum of earth-moon system
My assumed definition of angular momentum is the sum over $i$ of $L_i =r_i\times{\omega_i}\times{r_i}$ for each particle about some origin.
We have two spheres rotating about the centre of orbit. For ...
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Can amateurs use the retroreflector on the moon? [duplicate]
There is a retroreflector on the moon, placed there, I believe, by astronauts in the 1970s. I think there is at least one station (in France?) that continuously beams a laser at it to measure the ...
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2answers
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How to tell if the moon is waxing or waning?
Imagine you are placed in an unknown location in the middle of the ocean. You see the moon at its half.
Which are the different "sets of information" which, if provided to you, would allow you to ...
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1answer
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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101 views
What would happen to the Earth, if the moon was a black hole? [closed]
Would it be a feasible scenario?
I have read this question:
What would happen to the Moon if Earth is turned into a black hole?
Where Lubos Motl says:
The extremal Kerr J=GM2/c∼RbhMc. Now, the ...
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1answer
96 views
How did the Moon get into orbit?
It's the accepted theory that Moon was formed when an object collided with Earth, throwing off a lump of matter which became the Moon.
But also, an object cannot be launched into orbit from a planet ...
