Questions tagged [moon]
A smaller body orbiting a larger, primary body, where the primary body is not a star.
314
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How can you show that the Moon's gravity is one sixth of the Earth's? [closed]
I've tried using
\begin{equation}
F_s = \frac{GMm}{d^2}
\end{equation}
but I got this answer: $1.8704 \times 10^{20} $
I'm not sure what I'm doing wrong?
13
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4answers
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Would Foucault's pendulum work on the moon?
I am taking a course in introductory general relativity and came up on this question, which a google search didn't answer.
The rotation of the Earth can be measured using a Foucault pendulum.
The moon ...
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2answers
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Is there a correlation between the Earth's spin, the moon, and temperature?
Based on NASA's arcticle, changes to land, ice sheet, ocean, and mantle flow affect Earth's spin.
Does the moon's elliptical orbit around Earth also affect Earth's spin? What effect does distance play?...
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2answers
45 views
Will a satellite orbiting the moon have a tidal locked orbit?
Suppose an artificial satellite is launched to orbit the moon. Ignore 3-body problem issues, just assume it follows a roughly titled elliptical orbit relative to the plane cutting through earth's ...
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1answer
51 views
Why are the Earth and Moon so different?
The suggestion was made that the Earth and the Moon are two parts of a once whole object. If that is true then they must share the same basic composition. They also receive fairly similar amounts of ...
25
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7answers
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Why didn't the debris collapse back into the Earth at the time of Moon's formation?
The most accurate theory for the formation of our moon is the Giant impact hypothesis, which says that a Mars sized body collided with our early Earth and after this collision all the debris got ...
0
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2answers
52 views
The role of the Sun in spring and neap tides
I am trying to understand how the Sun affects tides on the Earth's oceans and seas.
It is quite clear that when the Moon is in the first and in the third quarter, the Sun's and the Moon's ...
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1answer
33 views
Rate of potential vs. rate of kinetic energy on the moon
If I was on the moon and threw a tennis ball upwards, how would the ball's rate of potential energy $U$ compare to its rate of kinetic energy $K$? I understand the concept when it's on the earth, but ...
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1answer
64 views
If the moon became a black hole, how much lower would the temperature be on Earth's surface?
I read that if the Sun became a black hole the Earth would become colder, but the effect would be negligible because the mass of the hole is still there so there would still be tides.
But, how much ...
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2answers
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In the difference between the sun and moon's tidal effects on earth, is density or distance a larger factor?
This question is inspired by the (now looking at it, improper use of, my bad) comments section here in Physics SE. I'm not sure I could explain better than our short discussion does below:
No, the ...
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0answers
25 views
Venus light rainbow
I have recently been quite amazed to learn that rainbows produced by moonlight (or moonbows) can sometimes be bright enough to be seen (not with the naked eye though). Now I wonder, would there be any ...
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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 ...
0
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1answer
31 views
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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2answers
78 views
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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1answer
32 views
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 ...
2
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0answers
64 views
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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6answers
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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 ...
4
votes
1answer
78 views
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 ...
0
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0answers
41 views
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 ...
0
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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 ...
3
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1answer
50 views
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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0answers
150 views
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.
2
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1answer
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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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1answer
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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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1answer
26 views
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?
2
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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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1answer
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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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7answers
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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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1answer
88 views
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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0answers
45 views
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
43 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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1answer
136 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
33 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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1answer
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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
185 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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1answer
261 views
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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2answers
69 views
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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2answers
63 views
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 ...
2
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3answers
143 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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2answers
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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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1answer
115 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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2answers
96 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
48 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 ...
0
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1answer
65 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
273 views
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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2answers
223 views
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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0answers
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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
67 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 ...
