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Questions tagged [moon]

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

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If not the conjunction moon, then what? [on hold]

It was either 2017 or 2018, I don't remember the season, I didn't really think much about it, but I was driving in the Finger Lake regions of NY, Cayuga lake to be exact, It was still dark out, I left ...
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3answers
86 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
53 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
21 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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1answer
98 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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1answer
69 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
38 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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1answer
44 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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2answers
93 views

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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40 views

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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25 views

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
72 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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2answers
94 views

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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32 views

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
107 views

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
28 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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1answer
84 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
85 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 ...
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1answer
30 views

Difference in gratitational field due to lunar apogee/perigee

I am trying to answer this Phys.SE question but got an unreasonable answer: In making laboratory measurements of $g$, how precise does one have to be to detect diurnal variations due to the moon's ...
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2answers
62 views

Delta-V of Earth to Moon mission using Moon orbit

I have read this article here and it talks about the delta-v cost of travelling to and from the Moon. Importantly it says that getting to an orbit round the Moon, and docking with a space station, and ...
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1answer
80 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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91 views

Does water height in mixed semidiurnal tide systems change in a sinusoidal pattern between peaks?

I'm writing a bit of plotting software that takes the time of high tides and low tides and interpolated what the height should be between these times. I know that diurnal tidal systems follow a ...
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1answer
28 views

Would a Lunar space elevator only be stable if it passes through Earth-Moon L1 or L2?

I understand that space elevators are extremely hypothetical (bordering on pure fiction), but they are supposed to be theoretically possible. My questions is about what longidtudes a lunar space ...
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35 views

In which direction is orbit around the moon easiest to achieve?

Suppose a conventional spacecraft is launched from Earth with the intention of establishing an orbit around the Moon. In the context of this question, the Earth/Moon system is viewed from far above ...
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1answer
73 views

Why does not the Moon escape from the Earth? [duplicate]

We know that Gravitational Force that is applied by the sun on the moon is greater than that by the earth on the moon. My Question is then why does not the moon escape from the earth and go towards ...
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1answer
81 views

What caused the curve in the Apollo transearth trajectory?

In reference to the below image, The thin black curved line is the Apollo 11 trans-lunar trajectory (outbound) The dark blue line is a tangent to the trajectory just after the TLI burn (as best as I ...
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1answer
24 views

Lunar angular frequency

I have this question from my teacher which quite confuses me. It asks to calculate lunar angular speed, when we know that the Moon circles Earth in 27.3 day. Why is number (27.3) significant here? ...
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4answers
238 views

Why doesn't the moon appear yellow?

The sky is blue (I'm told) because nitrogen in the atmosphere scatters short blue wave lengths of light from the sunlight, which is also why the sun appears somewhat yellowish rather than white, as it ...
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1answer
64 views

If the moon also fall then why can the astronaut moonwalks?

imagine astronauts inside the ISS while everything are in free fall, the astronauts are floating around. Now if the moon are also in free fall then how come astronauts can perform moonwalk on the ...
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27 views

Can the collision of asteroids form another moon?

In the lifetime of the earth, is it possible for sufficient collisions to occur in the asteroid belt to form a prototype moon?
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42 views

How big a lens would you need to light a fire with moonlight? [duplicate]

Randall Munroe posted an interesting what-if in which he claims that you can't use moonlight to light a fire, because it is impossible for reflected light to raise the temperature of an object higher ...
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7answers
7k views

Why does the full Moon appear?

I know that the full Moon appears when Sun, Moon and Earth are in a straight line, but if we consider that they are in straight line, why is the Moon illuminated? I mean to say that Earth should ...
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1answer
90 views

Does the moon rotate around the earth-moon axis?

It is well known that the moon always shows the same side to the earth. But does the orientation of this side change? I.e. does the moon rotate around the moon-earth axis?
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1answer
961 views

Buoyancy on the Moon

A body is floating partly immersed in a liquid. The body and the liquid are taken to the Moon. What will happen next? Will its immersed part come out of the liquid? Will it sink? Will it continue to ...
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3answers
223 views

Why is a bright night sky dark?

The sky in the day is colored blue because molecules in the air scatter blue light from the light of the sun. The sky during a some nights of having a full moon is very bright, as it shines the dark ...
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2answers
131 views

Increasing distance between Earth and Moon [closed]

I have a problem where a planet's rate of rotation is decreasing due to tidal effects of the moon. I know that the angular momentum of the system will be conserved. So, in order to conserve that the ...
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2answers
227 views

If gravity can be disrupted by larger forces, why does the moon orbit the Earth instead of the Sun? [duplicate]

I read an thread on this site about how a larger gravitational pull can overpower a smaller gravitational pull. I took this to mind, and I started wondering why the moon orbits the Earth instead of ...
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4answers
388 views

Does escape velocity require you to cross Moon's orbit?

Escape velocity is the velocity required to project an object from an object's (here, the Earth's) surface so that it "escapes" the gravity of that object (or in our case, the Earth's gravity). Now, ...
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1answer
212 views

why do total solar eclipses vary in length?

Quoting https://www.mnn.com/earth-matters/space/blogs/why-2024-total-solar-eclipse-may-outshine-2017, For the 2017 eclipse, the duration of totality will last between 20 seconds (over Kansas City,...
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1answer
51 views

What speed should I maintain on land or in the air in order to experience the whole path of total solar eclipse?

What speed should I maintain on land or in the air in order to experience the total path of total solar eclipse? And What other factors are taken into account for calculating that speed? For e.g. ...
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1answer
108 views

Total eclipses becoming rare soon?

Given that the moon is receding from the earth and that the average angular size of the moon is approximately equal to the angular size of the sun at the moment, what is the current rate at which ...
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3answers
5k views

How can a full moon be seen south of an observer's location?

I know this seems like a simple question, but I'm trying to debate with a flat earth theorist. I asked him to explain why can the ISS visibly be seen orbiting the Earth with the naked eye, and he put ...
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1answer
71 views

“Global” orientation of an inclined orbital plane

I'm pretty much trying to figure out, whether an inclined orbital plane rotates with its parent or not. To make my problem understandable an equivalent question would be, whether the longitude of ...
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1answer
313 views

Expanding Moon's orbit and newtonian mechanics

the 2 body problem of earth and moon is suppose to be perfectly described by Newtonian mechanics / Kepler's laws. How ever the moon's orbit is been moving away from earth in contradiction to the ...
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1answer
99 views

Someone walking on near side vs. far side of Moon - are weights different? [duplicate]

Running a thought experiment, I considered someone's weight when they were standing on the Earth with the Moon directly overhead. My initial thought was that the person weighs less because the Moon's ...
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2answers
739 views

Gravity on the surface of Io

Something about this seems a little incorrect to me but I can't quite put my finger on it. The moon closest to Jupiter is Io, with a diameter of $3650$ km and a mass of $8.93 \times 10^{22}$ kg, and ...
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1answer
248 views

Orbital pendulum (librating moon dumbell model)

Consider a moon orbiting its planet on a circular orbit. The moon is tidal locked to its planet, and has two permanent bulges, not exactly aligned with the planet. According to Newton's theory of ...
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1answer
251 views