Questions tagged [earth]

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

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Calculating Angle Between Two Planets In Heliocentric Orbit

My goal is to calculate the retrograde of Mercury. What I've been working from is the book, Practical Astronomy With Your Calculator 3rd edition. I've made some progress, but I seem to be stuck with ...
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Maximum and minimum masses and sizes of giant planets?

What are the minimum & maximum masses and diameters of giant planets? Minimum end of the scale Earth has mass of 1 Earth mass and a mean radius of 6,371.0 kilometers, and thus a mean diameter of ...
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Questions on apparent motion of superior planets

Question Why is it that superior planets seem to oscillate up and down of the ecliptic, from the view of an observer on Earth, with a period equal to the planet's orbital period? Additionally, why do ...
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Why does Earth have a dip in the CO2 absortion spectrum from 14 to 16 micron?

This paper shows that there is a dip in the CO2 absorption spectrum of Earth. In essence the trough of the absorption of CO2 for Earth is cut into two separate troughs instead of 1 large trough. Why ...
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What is the period of the 'cycle' of Earth's ecliptic variation, relative to the 'invariable plane'? 70,000 or 100,000 years?

The plane of Earth's path around the Sun, the ecliptic, is different from the average of the solar system's as a whole (the invariable plane) by about 1.57°.... Our path around the Sun, though, goes ...
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65 views

Did we adapt to Earth or Earth to us? [closed]

I often hear that Earth is a unique planet because it has life. We also see a proper balance between plants and humans and other animals. Why is life not possible on another planet? Often people say ...
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1answer
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How big and how far away would the moon be if earth was the size of Jupiter?

If the earth were the size of Jupiter, what would its 'moon' be in both relative size and distance? I did some quick figuring and think I roughly figured out that if placed at the position of the sun, ...
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Will the night sky ever be more stars than darkness? [duplicate]

Given enough time, will enough light from distant stars reach Earth so that our night sky will be more than 50% stars?
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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,...
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Other side of Earth when the Dinosaur-killer struck

When the (Chicxulub) asteroid hit Yucatan, what was it like in the minutes, days and weeks afterward on distant locations on Earth? Related How loud was the asteroid that killed the dinosaurs?
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Synodic Day and Sidereal Day

If given the sidereal day, is it possible to derive the synodic day of Earth? If a derivation is possible, could anyone illustrate it or point me in the right direction? Wikipedia's Synodic day begins:...
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Do the earth and the moon reflect the different fractions of total solar radiation proportionally?

Reading on this website that: "All of the energy from the Sun that reaches the Earth arrives as solar radiation". "Solar radiation includes visible light, ultraviolet light, infrared, ...
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How is bond albedo calculated?

According to this website, Bond albedos are computed by calculating the ratio of the flux reflected by a planet (integrated over wavelength) to the total stellar flux incident on the planet. Three ...
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What is the highest albedo of the earth's surface facing the sun ever measured?

This website (page 26) claims that full-earth-shine on the moon is 100 times greater than full-moon-shine on earth. The figure 100 is made up of the difference between the size of the earth and the ...
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How can the author of this article conclude that earth-shine on the moon is 100 times brighter than moon-shine on earth? [duplicate]

I don't understand the reasoning of the author of this article, on page 26. How can he conclude that full earth-shine on the moon is 100 times brighter than full moon-shine on earth?
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Which unit is most suitable in comparing needed light intensity for night reading on the Moon, vs on Earth?

Which unit is best to use, and why, when determining how many times easier it is to read a newspaper (or any other printed text) on the moons surface at night under a full earth, compared with reading ...
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Scholarly work on the gravitational disruption of a rocky planet by a close pass with another planet?

note: While the apparently abandoned question Effects of a rogue planet passing between the Earth and the Moon? (inspired by Thundarr the Barbarian) asks for speculation and was answered with it, this ...
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Formula to calculate the apparent magnitude of Earth from arbitrary distances

I would like to calculate the apparent magnitude of Earth from various distances, say from the Voyager probe at this moment or from various stars in the sky. I know there must be a formula that I can ...
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1answer
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Exact ecliptic position of Earth and Moon from Mars as photographed by Curiosity Rover?

I've been studying the idea of travelling through space and navigation - in particular: Apollo sextant (used by astronauts to plot the position of their spacecraft relative to stars). And, in order to ...
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1answer
100 views

Is Earth's rotation Slowing down or Increasing

Recently read that Earth is rotating faster than earlier1. However so far it is understood that earth's rotation is slowing down and to conserve the angular momentum Moon is going away from the Earth. ...
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Is it at all possible for the sun to revolve around as many barycenters as we have planets in our solar system?

Though it is understandable that the sun and the earth may be revolving around a barycenter, but, if so, not only the sun and Jupiter should also be revolving around some barycenter, the same should ...
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145 views

If it only takes 8 minutes for that light to reach the Earth, what took up most of the time? [closed]

If it only takes 8 minutes for that light to reach the Earth, what took up most of all that time to get to the Earth?
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Will Earth rotate backwards in the future?

Hello recently I heave heard the earth will eventually start rotating in the opposite direction (ie sunrise from the west) . I am not sure if this is true, but a lot of sites are claiming it to be ...
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Does the earth spiral around the sun's movement/motion path?

I have watched the following video (How Earth Moves by Vsauce) regarding how earth moves: Here are some screenshots: I have some questions: Does the earth spiral ...
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What would the Earth's peri- and aphelion have to be in order to have the same seasons due to its orbit?

Imagine the Earth had no axial tilt but had seasons due to a very elliptical orbit. How elliptical would the Earth's orbit have to be in order to have about the same seasons as it has now (just with ...
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Meteor size and frequency distribution for Earth vs. moon or other planets?

I struggle to find an answer to the at-first-sight simple question if or how the size distribution and frequency distribution of incoming rocks hitting the ground or the atmosphere vary from Earth, to ...
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North node, South node correct understanding

What is the correct concept of the North node and South node? There is some conflicting information on the internet. Which one of these two is correct? 1. Sourced from some Astrology material - How ...
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1answer
101 views

Where did the nickel in the Earth's core come from?

Why is there nickel in the core of the earth? Does it come from collisions of two neutron stars? And how did we know the core of our planet is made of nickel-iron alloy? Thank you.
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The electron–cyclotron maser emissions from Earth

The first-ever detection of radio signals caused by the electron–cyclotron maser mechanism outside of the Solar System, on Tau Bootis b was recently published (here). This phenomenon causes huge radio ...
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1answer
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How long was a lunar month in ancient times?

As the Moon is getting farther and farther from Earth, it's natural that the time it takes to circle around our planet is going to increase, thus the month will be longer. However, I read that the ...
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After what time interval do the closest approaches of Mercury to the Earth repeat?

The sidereal period of Mercury's revolution is 88 days and the synodic period — 116d. my solution, but in the question featured "the greatest rapprochement." And this is no longer so easy. ...
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1answer
63 views

Do planets have effect on velocity of Earth?

There is method for finding extrasolar planets called Transit-timing variation. If I understood correctly, exoplanets accelerate or decelerate each other (according on their position), so we can ...
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Why doesn't smashing larger and larger bodies incrementally into a rocky planet create a star?

Let's start with a stationary Earth. If we smash a few Mercury-sized objects into the Earth, the Earth begins to accrete mass. Repeat this step with larger and larger objects, until we start impacting ...
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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 ...
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How do I calculate the elevation angle to the horizon?

I'm creating an app to visualize the southern area of the moon from a first-person perspective. I'm trying to determine if a point on the surface is a "checkpoint," where the elevation angle ...
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Is “Zero Shadow Day” necessary to perform Eratosthenes' experiment?

Eratosthenes experiment to find the circumference of the Earth is usually said to be performed on the Zero Shadow Day at Syene. Is it necessary? Can this experiment be performed on any day for two ...
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Does the Sun and Moon basically appear to “move on the sky” identically regardless of location and date?

For a long time, I've been trying to use Stellarium (simulation) and many visualizations and animations in order to get a good idea of how the Sun and Moon move across the sky, as seen by a human from ...
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What orbital period would produce one New Moon (and one Full Moon) each year? What other effects would this produce?

I am interested to know whether it's possible for the moon to orbit the earth at such a rate that we would see only one New Moon and one Full Moon a year. If so, what other effects would we experience?...
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Which way does the Earth tilt? [closed]

On which side does the earth tilt to? I have tried figuring it out myself but I can't seem to find the answer.
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Why are the time zones calculated as 360°/24 and not 361°/24 or 360°/23.933?

Background: I'm training to be a geography teacher. Currently I have practice lessons and I'll be discussing solar time and standard time with the class. Now I stumbled over an issue to which I could ...
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143 views

How accurate is Stellarium at depicting the Earth, from the Moon, approaching a solar eclipse (from Lunar perspective)?

This is how Stellarium depicts the positions of the Earth and Sun 24 hours before the solar eclipse (from Lunar perspective) on Jan. 13, 2131 A close up of the Earth on that day (Jan 12) shows no ...
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Small changes to Earth's orbit caused by a large impact on the Moon

Is there any scenario where a large impactor striking the far side of the Moon would perturb the Earth's orbit enough to reduce the distance from the Earth to the Sun and still remain within the ...
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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 ...
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Why does time pass faster in moon than the earth?

One of my friends said that, time passes faster in moon than the earth Why does time pass faster on the moon than on the earth?
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If the solar system is nearly flat, then why don't all the planets appear to lie on the same axis when viewed from earth?

For instance, consider the image below. The location of the planets seem to be so random relative to Earth. If the solar system was indeed flat, then I would expect the planets to lie on the same '...
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Can we change Earth's orbit with modern technology? [closed]

It is well known that, according to Newton's 3rd law, spacecrafts entering or leaving Earth provoke tiny (insignificant) changes to Earth's orbit (see related question here). My question is about ...
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Can a single impact event trigger a runaway greenhouse?

Somewhat related to this question: Is the Earth going to evolve towards Mars' fate or Venus' fate? Human civilization may be fragile, but life itself is extremely resilient, with extremophiles and ...
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Has the computed change of the axial tilt ever been measured?

Earth, the 3rd planet from the Sun, sometimes faces earthquakes and seaquakes that are so strong that they reportedly change the axial tilt and/or the rotation velocity. These changes are merely ...
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105 views

As the Moon and the Earth are predicted to get into tidal lock, how slow would the Earth rotate?

This answer to Will the Earth ever be tidally locked to the Moon? supports the widely held thinking that during the Sun's red giant phase or later the Earth and the Moon should be tidally locked to ...
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206 views

How can the Earth and the Moon be in synchronous rotation if the Moon won't be in geostationary orbit?

It is said that the Moon moves away from Earth and that during the Sun's red giant or white dwarf phase the Moon will be about 40% farther than now and in a synchronous rotation ("hantle rotation&...

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