Questions tagged [earth]

Questions regarding the planet on which humans live; the third planet from the Sun.

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141 votes
3 answers
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How loud would the Sun be?

Sound can't travel through outer space. But if it could, how loud would the Sun be? Would the sound be dangerous to life on Earth, or would we barely hear it from this distance?
Jamie's user avatar
  • 1,179
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
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48 votes
3 answers
15k views

If Earth is tilted, why is Polaris always above the same spot?

Why is Polaris, the North Star, always above (or near) the North Pole? If Earth is tilted, Polaris' path should be in winter 23 degrees away from its path in summer, or not?
Guest55's user avatar
  • 379
42 votes
5 answers
18k views

How old is the oldest light visible from Earth?

Because light can only travel so fast, all of the light we see in the sky was emitted at a previous moment in time. So if for example we see a supernova or some other great stellar event, by the time ...
Mark Rogers's user avatar
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
35 votes
3 answers
4k views

Could any known, living organisms on Earth survive on Mars?

No life has been discovered outside of Earth (yet?), but do we know if anything that would be considered "living" on Earth could conquer Mars? (or maybe Venus?) With the Mars One project on the way, ...
Thibault's user avatar
  • 1,344
27 votes
3 answers
5k views

Why is the solstice the first day of summer, and not the central day?

Summer in the Northern Hemisphere starts on the day of the summer solstice. This is the day that the Northern Hemisphere receives more light from the Sun, due to the Earth's tilt. To my knowledge, the ...
DaniPM93's user avatar
  • 395
27 votes
4 answers
6k views

Which is brighter, Mars as seen from Earth, or Earth as seen from Mars?

At their closest flyby, Earth is ‘new’ and dim from Mars, and Mars is ‘full’ from Earth and brightest as seen from Earth. When Earth is 39 degrees from the Sun then Earth is brightest as seen from ...
Mark Besser's user avatar
27 votes
1 answer
5k views

Why is the summer solstice night shorter than the winter solstice day?

I was looking at the sunrise and sunset times where I live (Aberdeen, Scotland) and I noticed something odd: the time between sunrise and sunset in winter is longer than the time between sunset and ...
Nierninwa's user avatar
  • 373
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
26 votes
2 answers
26k views

Why does the Earth have a tilt of ~23°?

Is there a reason that the Earth has the tilt that it does (~23°)? How do we know which way is supposed to be 0°? Does this tilt have major consequences on the planet? Has it changed and will it ...
Jackson's user avatar
  • 557
26 votes
3 answers
2k views

Are we made of the stuff of one star or more stars?

[T]his coincidence enabled stars in the late stages of their lives to turn helium into carbon, oxygen and most of the other atoms that you and I are made of. [...] [W]e're made of star stuff. Max ...
Řídící's user avatar
25 votes
9 answers
17k views

Simple experimental evidence that Earth revolves around Sun

What are the simplest experiments or calculations that give evidence that the earth revolves around the sun? Can you please explain them and reference the history? Many simple explanations such as ...
user7496's user avatar
  • 351
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
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
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
5 answers
25k views

Why would it be very light out at 3 AM?

My brother noticed something very odd last night: it was amazingly light out when he stepped outside for a smoke even though it was between 3 AM and 3:30 AM EDST and we are near Toronto Ontario Canada,...
Henry's user avatar
  • 311
20 votes
5 answers
13k views

Was the Geocentric Model correct at all?

It's easy to find resources stating that the heliocentric model is right and geocentric is wrong. But how wrong was it? Was it correct in any way? It was built on incorrect assumptions, but despite ...
Voy's user avatar
  • 311
20 votes
3 answers
5k views

Can an object from a natural process escape earth gravitation?

I'm no expert, but I once studied basic from advanced physics and understand gravity action/reaction escape velocity of 11.2 km/s from the earth surface escape velocity changing as the object go far ...
KeitelDOG's user avatar
  • 303
20 votes
4 answers
6k views

If suddenly "knocked" or perturbed from its orbit, would gravity eventually return the Earth to its original orbit?

If suddenly "knocked" or perturbed from its orbit, would gravity eventually return the Earth to its original orbit? I am curious as to whether this is even possible. It seems to me that ...
ifeoluwa king's user avatar
20 votes
7 answers
12k views

Why doesn't Earth's axis change during the year?

My understanding is that the Earth's axis points in the same direction in space during its entire orbit around the sun. And this is what causes our seasons. My question is why doesn't the axis follow ...
rmaddy's user avatar
  • 303
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
20 votes
1 answer
689 views

How stable are Lissajous orbits?

Now that the Gaia Space Telescope is on it's way to the Sun-Earth L2 Lagrangian point (SEL2), I start wondering about the stability of Gaia's orbit there. The Planck Telescope is already there, as was ...
Alexander Janssen's user avatar
19 votes
2 answers
4k views

How many planets have we discovered that can support human life?

I have heard a lot of buzz about distant planets that could potentially be second homes for human existence, but what is that approximate number?
nipponese's user avatar
  • 309
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
4 answers
5k views

Is the Earth going to evolve towards Mars' fate or Venus' fate?

Upon reading on this site (and many others), one can think that Mars might have supported life in a distant past (discovery of liquid water, valleys, mountains...). On the other hand, Venus is the ...
Nico's user avatar
  • 803
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
4 answers
5k views

Did the earth form outside the solar system?

Why isn't it possible that the earth formed outside the solar system and got attracted later by the Sun? I just need arguments to defeat this hypothesis.
Señor ABƵ's 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
2k views

Why haven't Earth and Venus got any tiny moons? Or have they?

Why haven't some meteoroids gotten caught in Earth's or Venus' orbit? AFAIK most meteors are tiny fragments from comets. Shouldn't some comet tail sometime have passed Earth orbit at velocities ...
LocalFluff's user avatar
  • 11.4k
18 votes
2 answers
4k views

Why do stars appear to twinkle?

Sometimes at night you will look up to the stars and they will appear to twinkle, getting brighter and darker in bursts. Why does this happen? Is this because of our atmosphere? Would they twinkle ...
user avatar
17 votes
4 answers
7k views

Official degrees of earth’s rotation per day

What is the official degree to one decimal point please, of the earth’s rotation in one single day. Can it be confirmed that it is exactly 360.0 degrees using official data? Thank you in advance.
Autodidact's user avatar
16 votes
2 answers
5k views

Why is there a year 1 B.C., a year 0, and a year 1 A.D. in NASA’s Five Millennium Canon of Solar Eclipses?

I was looking through NASA’s Five Millennium Canon of Solar Eclipses, and I am really confused by the fact that there is a year -1, 0, and 1. I was always taught that there was no year 0, that we just ...
Curious Layman's user avatar
16 votes
6 answers
7k views

Why don't we have 2 Summers and 2 Winters?

Due to Earth's elliptical orbit, its distance from Sun varies by almost 5 million Kilometers (147 million Kilometers at closest point & 152 million Kilometers at farthest point, i.e. almost 3% of ...
kmdhrm's user avatar
  • 279
16 votes
2 answers
4k views

Will the Earth ever be tidally locked to the Moon?

From my basic understating, Momentum is being transfered from the Earth's rotation to the Moon's orbit by tidal friction. The Earth's rotation slows down and the Moon receedes from the Earth as it ...
TheWhaleOnPluto's user avatar
16 votes
1 answer
681 views

If the moon wasn't receding from Earth, what would be the impact on the weather and tides?

Moon is slowly receding from Earth, which means that after its formation it was much closer to the Earth than now. How would weather look like if it wasn't receding at it would be now as close as at ...
Danubian Sailor's user avatar
15 votes
1 answer
4k views

What does the Earth look like when viewed from Saturn?

Are there any data from spacecraft that visited that planet? How large the Earth is when viewed from that planet?
user avatar
15 votes
4 answers
3k views

How did the Earth come to be in orbit around the sun?

I'm not sure if this post should be in the physics subject forum, but this seems to fit here too. I have been reading a book about chemistry and how the universe came to be with the theory of stars ...
user avatar
15 votes
5 answers
3k views

What will a lunar eclipse look like from moon?

What will a lunar eclipse look like from moon? Will earth become a completely dark circle?
Santhosh's user avatar
  • 161
15 votes
1 answer
7k views

Safest Place on Earth from Falling Meteorites

Where on Earth is statistically safer if an asteroid was to break up in the Roche limit and rain meteorites effectively resetting the Earth? I would imagine that a ring of falling meteors would form ...
Justintimeforfun's user avatar
15 votes
2 answers
5k views

How bright is the full Earth during the lunar midnight?

At lunar midnight (i.e. the new moon as seen from Earth), the Earth is in its full phase with its entire disk in sunlight, and it is the brightest object in the lunar sky. How bright is it, and how ...
Emilio Pisanty's user avatar
14 votes
8 answers
5k views

How one can establish that the Earth is round?

I am asking this question out of curiosity. Currently, I am reading the book: A Brief History of Time. In Chapter 1, the author discusses about Aristotle's conclusions about spherical Earth. For ...
YII's user avatar
  • 279
14 votes
7 answers
4k views

Does Sun have a reflection on Earth?

The new Google Maps1 presents an actual view of Earth, with the current position of Sun illuminating half part of Earth in real time. It is quite an exquisite view. My question is based on the ...
Farhan's user avatar
  • 701
14 votes
3 answers
7k views

What if Earth and Moon revolved around each other like Pluto and Charon?

What would be different for us if Earth and Moon revolved around each other like Pluto and Charon do?
cd1's user avatar
  • 249
14 votes
3 answers
6k views

Why are there no stars visible in cislunar space?

It’s very puzzling that the moon landing had no stars in the background, the ISS clips have no stars in the background. I listened to multiple astronaut interviews speak on what it looks like up in ...
Autodidact's user avatar
14 votes
4 answers
2k views

Can a satellite stay in one place but not above equator? [closed]

I know that there are geostationary satellites that are always seen in one place in the sky and that they all are located in the equatorial area. I wonder if it's possible for a satellite to "...
ALiCe P.'s user avatar
  • 1,017
14 votes
1 answer
3k views

Earth is Tilted, but in reference to What Object / relative to what?

I am asking basic question on trying to understand on tilt. I know if I (as a human) tilt when standing on feet, my tilt will be in relation to gravity. For Earth, I am not able to understand, what is ...
puzzled's user avatar
  • 617
14 votes
3 answers
7k views

Why does each and every planet of our solar system have an unique axial tilt angle?

Why do planets have an axial tilt? From the above image we can see that each planet's axial tilt angle varies and differs from the others. What was the cause of this, was this from the beginning of ...
Paran's user avatar
  • 904
14 votes
1 answer
1k views

"If earth had rings like Saturn": A few further thoughts on the consequences

I came across this video recently where artists depicted what it would look like if Earth had rings like Saturn. http://www.wimp.com/earthrings/ Please note: The video contains already some ...
Patric Hartmann's user avatar

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