Questions tagged [the-moon]

Questions regarding Earth's only natural satellite. For questions about the natural satellites of other planets, use the tag [natural-satellite].

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81 votes
6 answers
11k views

Is the Moon only 60x60 pixels?

In doing research on vision, I have learned that "20/20" vision corresponds to a visual acuity of being able to resolve details 1 arcminute in size, that most people have around 20/15 vision,...
Phrogz's user avatar
  • 937
77 votes
4 answers
10k views

How does the Earth move in the sky as seen from the Moon?

I just want to be sure I am visualizing this correctly, because it seems odd. The Moon is tidally locked to the Earth but there are wobbles to its motion due to libration. So from a point on the ...
kim holder's user avatar
  • 1,569
73 votes
6 answers
17k views

Why is only one side of the Moon visible from Earth?

Why do we only ever see the same side of the moon? If this is to do with gravity are there any variables which mean we might one day see more than we have before?
Rob's user avatar
  • 849
59 votes
6 answers
7k views

Why does Io cast a hard shadow on Jupiter, but the Moon casts a soft shadow on Earth?

Io (source): The Moon (source):
stackzebra's user avatar
  • 1,429
54 votes
5 answers
20k views

Why is moon light not the same color as sunlight?

The light from the moon is light being reflected from the sun. The sun, in space, is white. But on Earth, when the light is filtered through an atmosphere, the light appears yellow. So then, why is ...
Andrew Johnson's user avatar
50 votes
3 answers
22k views

Is it possible to achieve a stable "selenostationary" orbit around the Moon?

Is there a stable geostationary orbit around the Moon? My feeling is, that the orbit would collide with Earth, because of the Moon's slow rotation.
Christian's user avatar
  • 673
42 votes
1 answer
9k views

Is Earth's moon the only one where a total eclipse of the sun covers the entire sun?

Is Earth's moon the only one where a total eclipse of the sun covers the entire sun? Are any other moons the same size as the sun as viewed from their planet like Earth's moon?
MB34's user avatar
  • 519
41 votes
4 answers
20k views

Can the moon appear to be in any position in the sky?

It seems to me that the Moon has appeared in many locations - apparent locations - in the 'dome of the sky'. I know that the Sun follows an arc from east to west and that the arc is smaller in winter ...
Donagh McCarthy's user avatar
40 votes
2 answers
8k views

How do we distinguish old craters from new ones on the Moon?

The following image is the observation made by the Dual Frequency Synthetic Aperture Radar (DF-SAR) onboard the Chandrayaan-2 Orbiter: Due to image size restriction, a lower resolution image is used ...
Vishnu's user avatar
  • 587
39 votes
4 answers
5k views

Why does the Moon appear gray when passing between the Sun and the Earth?

Shouldn't the Moon appear as bright as a full Moon seen at midnight from Earth? The photo was taken by DSCOVR at Lagrange point 1. In the picture, The Moon appears dark gray. Of course the Earth ...
Brian Leeming's user avatar
39 votes
3 answers
7k views

Is it a coincidence that on the far side of the moon almost no seas are visible?

Sorry for the maybe too large pictures. They do make the surface structures of both sides of the moon visible though. Is it just a coincidence that on the side facing us is so much sea is visible? It ...
Deschele Schilder's user avatar
39 votes
3 answers
975 views

If you lived on the far side of the Moon, how could you infer the existence of Earth?

Suppose that you deposit an astronomer, armed with our current knowledge of orbital mechanics, on a dome on the far side of the Moon, so that the Earth is perpetually hidden from them. (And, of ...
Emilio Pisanty's user avatar
37 votes
2 answers
9k views

Why doesn't the moon twinkle?

Stars twinkle because their light has to squeeze through several different layers of the Earth's atmosphere. So why doesn't the moon twinkle as well?
Ricky's user avatar
  • 1,345
34 votes
2 answers
6k views

Is oxygen really the most abundant element on the surface of the Moon?

I found this infographic that seems to say that oxygen is the most abundant element on the surface of the Moon. Is this really the case? If so, under what form is this oxygen?
usernumber's user avatar
  • 17.5k
31 votes
2 answers
50k views

Is this photocomposition of Andromeda's galaxy and the Moon accurate?

I recently saw the below image circulating around twitter/Facebook/reddit. It is titled "Andromeda's actual size if it was brighter": One of the comments provides a link to another ...
Federico's user avatar
  • 395
30 votes
6 answers
11k views

The moon has just the right speed not to crash on the Earth or escape into space. What are the odds?

My understanding is that the moon was created a long time ago when Earth was hit by a big asteroid. The debris then agglomerated into the Moon, which happens to be orbiting at the exact speed required ...
Zoltan's user avatar
  • 435
29 votes
3 answers
9k views

If months are based on the moon, then why are the months longer in the Gregorian calendar than lunation?

What I have always thought / known is that: Days are based on the period of rotation of the earth. Months are based on the moon. Year is the time taken by the earth to make one revolution around the ...
lunisolar's user avatar
  • 391
27 votes
2 answers
9k views

Where do we have it from that the Moon is migrating away from Earth?

I know Neil Armstrong placed a mirror on the Moon and people shoot lasers there which get reflected, thus measuring the time the light needs they can conclude the current distance of the Moon. But the ...
Ioannes's user avatar
  • 1,090
26 votes
7 answers
13k views

If the Moon were impacted by a suitably sized meteor, how long would it take to impact the Earth?

An answer to the question of How well would the Moon protect the Earth from a Meteor? mentions as a possibility that the Moon could get knocked into the Earth. What is the smallest change to the ...
gilliduck's user avatar
  • 404
26 votes
2 answers
3k views

Is it a coincidence that both the Sun and the Moon look of same size from the Earth?

The Sun is huge, when compared to the Moon. Despite the huge difference in their size and distance from Earth, is it purely coincidental that they both look almost the same from Earth?
Raj's user avatar
  • 371
25 votes
3 answers
3k views

Is it possible to completely see the edge of a half moon at night?

Some days ago, about 1 ~ 1.5 hours after the sunset I could see a very bright half moon, and the interesting part is, I think I could see the edge of the dark half of the moon, i.e. a whole circle, ...
bgusach's user avatar
  • 561
24 votes
3 answers
9k views

Why is the Moon's orbit so complicated?

I like to think I have a good enough understanding of astrophysics but there's still one thing that I just can't explain. Why does the Moon orbit the Earth the way it does? Many other moons in the ...
ChristieToWin's user avatar
24 votes
2 answers
5k views

Can the Moon eclipse Venus?

The title basically says it all. As seen from the Earth, is it possible for the Moon to eclipse Venus (or any other planet) or are the orbits inclined such that this never happens? If such an eclipse ...
CatchAsCatchCan's user avatar
24 votes
3 answers
6k views

What (the heck) is a Super Worm Equinox Moon?

Google News feed shows me the following. What does the term "Super Worm Equinox Moon" mean and has it ever been used before this 2019 clickbait instance?
uhoh's user avatar
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24 votes
2 answers
5k views

Can you see man-made lights on the dark side of the Earth from the surface of the moon with the naked eye?

This question is prompted from a comment on this answer: Could a person on the surface of the moon see man-made lights on the dark side of the Earth with the naked eye? If not, how much magnification ...
reirab's user avatar
  • 343
24 votes
2 answers
2k views

Why does the Moon stablize Earth's axis?

In an academic study titled 'The Moon and the Origin of Life on Earth' it is said that 'If the Moon did not exist, the orientation of the Earth’s axis would not be stable, and would be subject to ...
Kyriakos Kyritsis's user avatar
23 votes
2 answers
4k views

What ground-based observational evidence is there that the Moon doesn't have an atmosphere?

The Moon doesn't have any significant atmosphere (surface pressure is $3\times10^{-15}$ bar). Can the absence of atmosphere on the Moon be determined with ground-based observations? When was it first ...
usernumber's user avatar
  • 17.5k
22 votes
6 answers
8k views

Puzzling quotes from astronauts about earth size

I have no doubt that we have been to the moon. This question has nothing to do with a moon landing hoax. But, there are two quotes from two different astronauts regarding the size of the earth as ...
Lambda's user avatar
  • 514
22 votes
3 answers
4k views

Does the Earth have another moon?

I was just wondering what are the chances that there is a small object (say less than 1 km but more than few meters) that orbits the Earth but has remained undetected by us? Are we actually ...
Sathish's user avatar
  • 411
22 votes
1 answer
15k views

Is the moon moving further away from Earth and closer to the Sun? Why?

According to The NASA Moon Facts page: The moon is actually moving away from earth at a rate of 1.5 inches per year. Why is the moon moving further away from the Earth? Is this a result of the ...
user avatar
21 votes
2 answers
5k views

Where in space would the Earth and Moon appear to be the same size?

If I'm directly in between the Earth and Moon, what distance from the Earth would I have to be so that the Earth and Moon have the same apparent size? How big would the moon appear compared to it's ...
cowlinator's user avatar
21 votes
4 answers
6k views

Where is it possible to observe the Moon for 24 hours?

I wrote an astronomy olympiad yesterday and there was one task I couldn't figure out an answer to: Estimate at what latitudes it is possible to observe the Moon for at least 24 hours. Under what ...
ALiCe P.'s user avatar
  • 1,017
21 votes
4 answers
7k views

Why doesn't the Moon, like the Sun, turn bright red when it's close to the horizon?

Why does the Moon, being close to the horizon, turn red only slightly, or not at all? Aren't the causes that lead to the coloring of the Sun (atmospheric refraction) are also true for the Moon? In ...
Vladimir Orlov's user avatar
21 votes
1 answer
3k views

Have we ever observed a large meteor hit the Moon?

Since the moon has no atmosphere, its surface has many more meteorite impacts than Earth's does. Image source Have we ever observed a meteor strike the surface of the Moon?
user avatar
20 votes
1 answer
4k views

Apparent Ring of Craters on the Moon

I saw this picture on the BBC news website. There appears to be a ring of craters in the center of the picture, aligned in an approximate sub vertical orientation. Am I just seeing things or does ...
Fred's user avatar
  • 2,169
20 votes
4 answers
21k views

Is there any point on earth where the moon stays below the horizon for an extended period of time?

When I was teaching a class why the earth has seasons today, I mentioned how the poles of the earth experience months of daylight and darkness. Then one of my students asked whether the moon ...
Kupyn's user avatar
  • 301
20 votes
2 answers
38k views

What is the distance that the Moon travels during one orbit around the Earth?

Also, does it always take the same amount of time, or does it fractionally differ on each revolution?
Asadullah Ali's user avatar
19 votes
1 answer
5k views

Moon's unusual gravity

We know that the Moon's gravity is about one-sixth that of Earth. Then I recently read that the mass of the Moon is about one-eightieth the mass of Earth. Since gravity depends on the mass of the 2 ...
John Canon's user avatar
19 votes
3 answers
20k views

During an eclipse, how big is the shadow of the moon on the earth?

This picture was taken from the ISS during a solar eclipse. You can see the shadow of the Moon on the surface of the Earth. But how big is this shadow? How many kilometers is its diameter?
usernumber's user avatar
  • 17.5k
19 votes
2 answers
6k views

Why is the Moon receding from the Earth due to tides? Is this typical for other moons?

After reading the Q&A Is the moon moving further away from Earth and closer to the Sun? Why? about the tides transferring energy to the Moon and pushing it from Earth, I have a question: How is ...
Danubian Sailor's user avatar
19 votes
5 answers
3k views

Can impact craters on the moon act like giant radio telescopes?

Could large craters on the moon be used as reflective lenses for radio signals? Acting like a large radio telescope reflecting radio waves to a satellite positioned over the crater.
Reactgular's user avatar
19 votes
2 answers
3k views

Do other planets in our solar system experience eclipses or is this unique to Earth?

Here on Earth we get to experience lunar and solar eclipses. Is this pure coincidence that everything happens to line up? Do other planets in the solar system experience this phenomenon or is this ...
user avatar
18 votes
2 answers
22k views

Will Earth lose the Moon before the Sun goes into supernova?

I've read that the Moon is moving away from the Earth by 1-3cm per year. Is this enough to make the Earth lose the Moon before the Sun goes supernova? I'm asking because I would like to do the ...
hawaii's user avatar
  • 345
18 votes
6 answers
13k views

Moon's orbit around the Sun

The Earth revolves around the Sun and the Moon revolves around the Earth. Out of curiosity I started thinking about the orbit of the Moon around the Sun and expected (assumed) it to be as follows: ...
Umang Chaudhari's user avatar
18 votes
2 answers
21k views

Does the Moon have any oxygen in its atmosphere?

Since the moon has gravity, it's almost impossible that there aren't some gasses trapped on the surface by the moon's gravity. Has any free-floating oxygen been found on the Moon? If so, in what ...
user avatar
18 votes
3 answers
4k views

What is this 877-year cycle in the orbits of Jupiter & Saturn, and this multimillion-year cycle in the lunar orbit?

The book The Theory That Would Not Die (by Sharon Bertsch McGrayne, 2011) states the following on page 28: He [Pierre-Simon Laplace] used other methods between 1785 and 1788 to determine that Jupiter ...
r.e.s.'s user avatar
  • 323
18 votes
1 answer
4k views

Why does the moon sometimes appear giant and a orange red color near the horizon?

I've read various ideas about why the moon looks larger on the horizon. The most reasonable one in my opinion is that it is due to how our brain calculates (perceives) distance, with objects high ...
Larian LeQuella's user avatar
18 votes
1 answer
5k views

Is there any telescope on Earth that can see the lunar rovers on the Moon?

If I have the right numbers, it seems to me that even the Hubble telescope might barely be able to make out a carcass of a blue whale on the surface of the Moon, which puts objects as small as the ...
Mark Bailey's user avatar
  • 1,013
18 votes
1 answer
32k views

How does the Moon look like from different latitudes of the Earth?

I have heard, that on the northern hemisphere, you can estimate a direction of south if you imagine a line going through the tips of the border between illuminated and shadowed part of the Moon, and ...
user50222's user avatar
  • 281
17 votes
6 answers
5k views

How do we know the moon is smaller than Earth?

The moon is smaller than the Earth, but how do we know that (without the use of modern technology)? To be more specific, how can we show that the moon is smaller than the Earth (smaller diameter) with ...
Obama2020's user avatar
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