# Questions tagged [earth]

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

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### Umbra, penumbra and antumbra

I'm trying to understand following schema of the wikipedia page here. Image subtitle is "Umbra, penumbra, and antumbra, for a lunar eclipse". Distances and sizes are not to scale. If distance ...
219 views

### Problem about orbiting of a satelite

Problem: There is an satellite that orbits the Earth. Its orbit is circular and its orbital plane is perpendicular to Earth's Equatorial Plane. It orbits is such that a person who is on equator see ...
249 views

### How far away does the Moon have to be until Earth doesn't feel its effects? [closed]

How far in miles does the Moon have to be for the Earth not to feel its effects?
675 views

### Calculating length of summer solstice day using tilt and latitude

I want to be able to predict how long the summer solstice lasts at any part of world given the maximum tilt angle $φ = 0.4101524 \; \mathrm{rad}$ and the latitude $θ \; \mathrm{rad}$. I specifically ...
462 views

### Which constellation would appear to revolve around Denab,Vega or Thuban when axis of the earth would point toward them?

We have been calling the star by looking at which we can make out the direction of the North Pole the North Star. This was the only method at the disposal of the sailors during the days when they did ...
291 views

### Stellarium simulation

I'm interested lately in Stellarium and the functionalities which it provides especially scripting. I want to make a simulation that shows the celestial sphere with some planets like Venus, Mars, and ...
116 views

### Hole through the earth [closed]

I have a problem: If I would dig a hole through the earth, and jump right in, disregarding the rotation of the earth, I should come back out on the other side. However, orbital mechanics say ...
495 views

### If there was air between the Sun and Earth, how warm would we get?

Based on this question: How loud would the Sun be? If instead of a vacuum we had air between the sun and earth (let's say of the same composition we have here on earth) how warm would our planet get?
4k views

### About how many revolutions has the Earth made around the sun?

The Earth is about 4.543 billion years old. However, the length of a year can be changed by anything from an impact to a natural cycle of orbit changes to a slow drift toward or away from the sun to ...
620 views

### As the Sun dies, does the Earth's orbit change?

As the Sun nears the end of its life and expands, would the Earths orbit get bigger as it moves out or would it stay in the same orbital plane and not move out? Therefore in the far off future, we'd ...
492 views

### Can Earth have a ring?

Why doesn't the earth have a ring? If solid material such as dust and moonlets, and common components of satellite systems are brought nearer to the Earth, then what will happen? Will it take the ...
960 views

### If earth changed its orbit, what would happen to the moon?

Let there be an accelerating force acting on earth over an arbitrarily long time to change its orbit around the sun (e.g. by asteroids repeatedly passing by close to earth (intentional or not) or ...
1k views

### Determining latitude and longitude in bad weather

In Sobel's famous book 'Longitude', she described the story of Harrison. I still have one question. What if it is cloudy on the sea? In this case, the sailors have nothing to compare with, right? This ...
3k views

### Could an object block out the Sun from Earth's view for 3 hours?

how large, massive, far away (from earth), and fast would an object (planet-like) have to be to block out the Sun for 3 hours and not disturb Venus, Earth, or the Moon?
504 views

### Why does the traslation movement of the earth last the same time as the four seasons?

Why does the traslation movement of the earth last the same time as the four seasons? The seasons could take 100 days or 200 or 20 years (aprox. like in GoT)... but exactly (exactly???) 1 year. Why? ...
82 views

### Age of a planetary body

We quote that the Earth is about 4 billion years old. However earth started with billions of cigarette smoke sized particles. What event or size or something do we use to say this is the start of ...
1k views

### What causes the Earth to have gravity?

I've always wondered how our planet Earth or any other large spheroid-shaped thing in our universe has gravity? Does it have a small black hole on its core causing it to have gravitational force? ...
3k views

### Transformation from Geocentric Coordinates into Equatorial Coordinates?

I have the moon's position in equatorial coordinates (RA and Dec) and now I want to calculate same moon's position in terms of earth centered coordinates i.e. Geocentric (latitude & longitude). My ...
1k views

### 'Very High Noon' - Sun directly overhead

Twice a year the sun is at a certain angle south (or north) of the equator between The Tropic of Cancer and The Tropic of Capricorn. At that time the sun will be exactly overhead for people at the ...
196 views

### What would be the difference in distance between earth and moon on supermoon night (14 November 2016)

As we all know the usual distance between earth and moon is 384,400 km. But i was thinking how much closer it will be on 14 November 2016, as it will be a supermoon, the brightest and biggest moon in ...
7k views

### Is it same distance Equator & Prime Meridian? [closed]

i just want to ask in earth what the difference between Equator & Prime Meridian & also want to know is it same distance Equator & Prime Meridian?
2k views

### Distance to Sun at Perihilion and Aphelion at max and min Eccentricity

Title says it all. I'm putting together a presentation on Milankovitch Cycles, and I would like to bring up the difference in distance to the sun (km) at aphelion and perihelion when the earths orbit ...
3k 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 ...
2k views

### Sudden Effects of Sun Disappearing [duplicate]

It takes 8 minutes for the sun's light to reach earth. If the sun were to instantly disappear, what would happen? I imagine that Earth would fly away on a path tangential to its orbit. What would ...
4k 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.
243 views

### Energy deposition in planet Earth due to gravitational waves

The gravitational wave detected by the LIGO observatory acted on planet Earth streching and shrinking it a little bit. I assume that not all of this action was fully elastic and that some energy of ...
842 views

### Can Earth host another natural satellite than the Moon?

Are there orbits with long-term stability (astronomical time scales) around Earth? Low altitude orbits will decay due to friction with Earth's atmosphere. Inside Earth's Roche limit, a Moon could not ...
920 views

### What makes the Earth infinitely rotating around its axis

I was reading two sites before I posted the question here. One site says something like that the collisions in Universe eventually set the planets rotating, another site says that our planet is formed ...
95 views

### Measurement precision of celestial events

The local weatherman declared that fall starts at exactly 10:21am (local time). Ignoring the fact that seasonal boundaries have multiple definitions (meteorological, astronomical, etc.), what he ...
600 views

### The Hollow Moon Story [closed]

I've heard on various programs (yes TV) with "supposed" experts in various fields that there is evidence which would suggest that the moon could be hollow. The experts ranged from scientists, sound/...
503 views

### Effects of the solar tide on planets

It’s well known that (lunar) tides on Earth result in a transfer of angular momentum from Earth proper to the Earth–Moon orbital motion. That’s why the Moon resides now in a high Earth orbit, and ...
1k views

### Angles of sunrise and sunset viewed from a surface anyway oriented

I need to understand how to calculate the angles of the sunrise and sunset viewed from a surface oriented against the azimuth and the horizon plane, and for any day of the year. For example, I have ...
57 views

### Observations of a perigee coincident with a full Moon

Hopefully this will be a quick and easy question, with a quick and easy answer, but why is it that we observe a perigee Moon coincident with a full Moon approximately every 13 months? Is this related ...
1k views

### Decreasing rate of Earth's rotation: where does the power go?

I understand from Wikipedia that, "The length of the day, which has increased over the long term of Earth's history due to tidal effects, ...". If the angular velocity of the earth is decreasing then ...
8k views

### What point does Earth actually orbit?

If we consider the two largest masses in our solar system - the Sun and Jupiter, by themselves, they will orbit a common barycenter which is somewhere offset from the Sun's center in the direction of ...
2k views

### Why do our clocks not go out of sync with the day over a year?

Our clocks use 24 hours for a day, our planet takes 24 hours to rotate completely and our planet revolves around the sun in 365 days. Imagine at the start of the year, the side of Earth facing Sol is '...
235 views

### Jupiter orbiting time in Earth's orbit?

Imagine if Jupiter orbited the Sun at the Earth's orbital distance of 1AU. Would a planet of this size orbiting the Sun take 1 Earth year (365 days) to complete an orbit, or would the size of ...
4k 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 ...
107 views

### Do differentials in the Earth's density cause the flyby anomaly?

The flyby anomaly is an occasional, unpredictable, and as yet unexplained discrepancy in acceleration of satellites when they pass close by the Earth. It causes an increase of up to 13 mm/s during ...
1k views

### Inverse of the sunrise equation - finding locations with a given sunrise time on a given day

I'm working on a project for fun where I represent some sleep data geographically. For a given day, I have a date, a time for falling asleep that night, and a time for waking up the next day. The idea ...
2k views

### How fast would Earth need to rotate to fling someone off due to centrifugal force?

If Earth started spinning fast enough, would the centrifugal force eventually overcome Earth's gravity enough enough to fling someone (let's assume 75 kg) into orbit or into space? If so, how fast ...
445 views

### What color is earthshine?

What color is earthshine (e.g the average color of earth that shines on the moon)? I am making a solar system exploration game, and would like to know this for the lighting of my moon level at night, ...
203 views

### Two moons and one Earth? [closed]

Can any one explain to me What will happen to Earth if its has two moons? Same Distance & two sides of earth (North & south)? Will it be good for humans or bad?
718 views

### How close would merging black holes have to be to feel gravitational waves? [duplicate]

Recently LIGO discovered gravitational waves caused by two black holes that were orbiting each other, and then collapsed into one black hole. A few months later, we find out that this actually happens ...
470 views

### What would Earth be like without the Moon?

If somehow our moon was destroyed (for example by an asteroid) what would happen to Earth? Would the Earth be affected by the absence of the moon? Would humans be able to live normal lives without ...
178 views

### Is Earth slowing down in order to stay on its orbital track?

The Sun is losing some of its mass during explosions. The Gravitational force between Sun and Earth will change (probably decrease). If Earth maintains its speed, it will change its orbit. Hence, ...
147 views

### Would the (orbitting) speed of the Earth change if suddenly the sun disappear and the Earth is thrown into space?

Usually an orbit is considered as an acceleration. So if the Earth has a speed of about 100.000km/h around the sun. Now I think there is some relativity involved, so from which point of view shall we ...
2k 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 ...