Earth is the planet on which we live, the 3rd planet from the Sun. Questions using this tag should be about Earth the planet and not Earth-like planets nor earth, as in dirt or soil.

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Deviation from Earth's orbit

How much orbital deviation is required for the Earth to get knocked out from current orbit so it either moves away from Sun or towards the Sun?
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2answers
749 views

Minimum size of an asteroid to actually impact earth

From what I understand, an object entering the atmosphere will start to burn up from the tremendous resistance of the atmosphere. Presumably, for asteroids under a certain size, they will burn up ...
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1answer
143 views

Is the Earth's atmosphere a Faraday cage?

X-ray telescopes are required to be above the atmosphere as the atmosphere blocks EM waves with wavelengths < UV . Does this mean that the Earth's atmosphere can be thought of as a Faraday cage ...
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4answers
1k views

Angular momentum power plant on Earth

If tidal power plants are slowing down Earth's rotation then is it theoretically possible to build a power plant that would drain energy from Earth's angular momentum (thus slowing down it's ...
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3answers
2k views

Escape velocity from Earth

We know the escape velocity from the Earth is 11.2km/s. Isn't it the velocity required to escape from earth if we go normal to the surface of earth? i.e while we derive the formula for the escape ...
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1answer
2k views

Why does the sun “shine brighter” some days?

Today, the sun seems extremely bright; more dazzling than usual, and even the roads seem to be brighter so it's not just when you look up in the sky. Is more light actually getting through (perhaps ...
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2answers
329 views

Exploding Earth

I have always heard that the Earth, due to its structure, cannot explode. Now, I'm quite fascinated by astronomy physics but I admit I only hold some more than basic knowledge. In any case, even ...
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1answer
2k views

Application of diffraction problem!

Here is a problem that I am working on, which is the applying the concepts of diffraction to the setting of the sun: Air has a small, usually negligible index of refraction. It is 1.0002926. This ...
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2answers
6k views

Does Earth's Rotation Affect Its Shape?

The question I am working on is, "Consider the following. (a) Find the angular speed of Earth's rotation about its axis. rad/s (b) How does this rotation affect the shape of Earth?" I am fully ...
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1answer
200 views

Earth is rotating [duplicate]

Possible Duplicate: Why does the atmosphere rotate along with the earth? If i take off from land on a helicopter straight above the earth surface to a certain height and stay there for few ...
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2answers
680 views

Result of increasing the radius of earth?

How can increasing the radius of earth may cause an impact on the solar system ? Like, would earth may start making a bigger orbit (due to increase in size and wait) or vice versa ? or else ? PS: The ...
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1answer
165 views

(Earth's) magnetic field

Always when we want to represent the magnetic field of the earth we see a similar image: My question is, what exactly does this show? What are the blue and orange lines, what do they represent? Why ...
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1answer
431 views

Deducing latitude from Foucault Pendulum

Suppose I set up a Foucault pendulum and observe that it precesses at a rate of 216.528 degrees per day. While I am observing this, a total solar eclipse occurs. Where am I, and what is the date? My ...
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2answers
259 views

Is it possible to use a balloon to float so high in the atmosphere that you can be gravitationally pulled towards a satellite?

A recent joke on the comedy panel show 8 out of 10 cats prompted this question. I'm pretty sure the answer's no, but hopefully someone can surprise me. If you put a person in a balloon, such that ...
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1answer
235 views

What is the gravity at the center of the Earth? [duplicate]

Possible Duplicate: Would you be weightless at the center of the Earth? Supposing there is a cavity at the center of the Earth, what is the gravity there? What will be its direction and ...
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4answers
26k views

Earth's Magnetic Field, Human Brain and Sleep [closed]

I remember reading somewhere: when you sleep in a way subjecting your body to cut the geomagnetic field at right angles, you become highly emotional whereas when it is Parallel, it cools your ...
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2answers
222 views

The earth's magnetic field

This might sound like a silly question. Is it possible for the earth's magnetic field to actually destroy or harm earth? (implosion, crushing etc.)
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1answer
288 views

Earthquake as a transverse wave

I have a very simple mental picture that earthquake waves travel like shear (transverse) waves through the earth. a. Does the speed of this wave give any valuable information about the mechanical ...
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2answers
142 views

Moon and the moving train

While travelling by train (travelling West to East), it seems the moon is moving in opposite direction when seen from the window, but then it reverses its direction, after a certain amount of time and ...
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1answer
82 views

what would my path look like using the sun for navigation

A theoretical question which thought about instead of writing my C++ code. I know it is poorly defined however I am now intrigued as to the answer! If you got into a boat in the middle of the sea ...
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2answers
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What does the phrase “limb of the earth” or “atmospheric limb” mean?

What does the term limb of the earth (see this question, for example) or atmospheric limb mean? The phrase strikes me as very odd, since earth is nearly spherical. Do other planets with atmospheres ...
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2answers
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how far away can something be from the earth and still be in orbit?

Just as the title asks, How far away can, say, a satellite be and still be in "orbit" ? How about for a given velocity? Fun Facts 200 miles (320 km) up is about the minimum to avoid atmospheric ...
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3answers
9k views

How long until the sun cannot sustain human life on earth?

The sun will last, at its current brightness for 9 billion more years. How long until the sun gets burned down to the point where it cannot sustain life on Earth anymore? Updated: I am more concerned ...
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6answers
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Where on Earth can you find plasma?

Ok, so not that 'where on earth', like literally - 'Where on Earth'. Where on Earth, can you find matter in the 4th state, i.e. the plasma state?
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3answers
232 views

How closely may an artificial satellite orbit Earth without decaying appreciably each orbit?

Just what the title states. An artificial satellite will orbit Earth with some defined angular momentum. An aircraft,on the other hand, relies upon it's engines to provide continuous forward velocity ...
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1answer
159 views

How can the properties of the Earth be determined?

How can the properties of the Earth be determined? And how is the gravitational constant then determined from them? A satellite can determine the G.M.. But, how they are individually determined ...
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0answers
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How far is the horizon, if a 2m tall man watches to the sea?

How far is the horizon, if a $r=2 m$ tall man watches to the sea? I have calculated that it would be even just about 6 km. if R = radius of earth( $6370 \cdot10^3$ m ). By pythagorean theorem we ...
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3answers
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If the earth would stop spinning, what would happen?

What would happen if the earth would stop spinning? How much heavier would we be? I mean absolutely stop spinning. How much does the centrifugal force affect us? If you give technical answers (please ...
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1answer
2k views

Do other planets have an effect in Earth's rotation and revolution?

Do Earth's rotation/revolution is regulated by other planets (and vice versa) in any way? How?
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1answer
473 views

How much does the curvature of space change the volume of Earth by?

If we assume space is flat the volume of Earth is: $$ V = \frac{4 \pi R^3}{3} = \frac{4 \pi (6378.1 km)^3}{3} = 1.086 \times 10^{21} m^3 $$ The Einstein field equations, however, predict that the ...
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4answers
2k views

Could we make a trebuchet that could launch objects to a stable orbit?

Inspired by this xkcd, which calculated the energy requirements for accelerating individual humans to escape velocity (regardless of consideration for what that would do to your organs), I am ...
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1answer
206 views

Impact of Apophis

I read about the near-earth asteroid 99942 Apophis. It is in the first place of Potentially Hazardous Asteroids (visiting earth at an altitude of about 36,000km on 2028). But, scientists have ...
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1answer
270 views

Does a coronal mass ejection change solar neutrino emission rates?

Does the CME and neutrinos have any relation? CME is measured by Corona graphs.. How do they measure neutrinos coming from the sun? Does any of these have effects on earth's magnetic field or ...
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1answer
268 views

What equations/constants were used to calculate the Kármán Line for Earth?

I am interested in how the original value of ~100 km was calculated for the Kármán line of earth. What equations and constants would need to be used to reproduce this value? Note: By constants, ...
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1answer
73 views

Sunrise time across the globe?

This question is more astronomy related, I started thinking when I heard from one of my friends living in Jiamusi, that Sun rise at 02:00 and sets at 14:00, I know that this place is more near to ...
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3answers
2k views

How long was a day at the creation of earth?

Since the earth is slowing its rotation, and as far as I know, each day is 1 second longer every about 1.5 years, how long was an earth day near the formation of earth (4.5 billion years ago)? I ...
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4answers
2k views

How do we know that earth is not perfect sphere?

I've just read here that: Equatorial radius = 6378.16 kilometers. Polar radius = 6356.78 kilometers, so the difference in circumference is 71.1 kilometers. It is not a perfect sphere, but kind ...
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2answers
126 views

Is reversal of magnetic polarity in a planet an instantaneous occurence?

Just what the title states - Does reversal of magnetic poles in a planet refer to the point in time when reversal is complete? OR Does it refer to the entire drawn out process (assuming the ...
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8answers
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Would it matter if the Earth rotated clockwise?

In the Futurama episode "That Darn Katz!" they save the world by rotating the Earth backwards saying it shouldn't matter (which direction Earth rotates). If Earth rotated clockwise and remained in ...
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4answers
914 views

Why doesn't the Earth leave you as soon as you escape it?

I've always wondered, that since the Earth is moving at a very fast velocity around the Sun, why is it that when astronauts leave the Earth, the Earth doesn't immediately move away from them at ...
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1answer
2k views

What will happen if a gamma-ray burst hits the Earth?

Is there any probability that a gamma-ray burst (GRB) could affect the Earth?
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1answer
218 views

Impact location that created the moon

I was reading an article today about the 1000th orbit of the Lunar Reconnaissance Orbiter, and as many of you know NASA created an animation that simulates the history of the moon. It is speculated ...
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5answers
510 views

sun-moon-earth anomaly

When one looks at the sun and the moon in the sky together, why is it that the illuminated crescent of the moon does NOT "point" at the sun? (More correctly the perpendicular bisector of the straight ...
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3answers
1k views

Earth-Centered Inertial (ECI) reference frame as approximate inertial frame of reference

In many practical applications, one can consider the Earth-Centered Inertial (ECI) reference frame approximately as an inertial reference system, though strictly speaking, it is non-inertial. Is ...
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5answers
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How does gravity work underground?

Would the effect of gravity on me change if I were to dig a very deep hole and stand in it? If so, how would it change? Am I more likely to be pulled downwards, or pulled towards the edges of the ...
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1answer
179 views

Why isn't sunset time in sync with solstice?

The winter solstice in the Northern Hemisphere in 2011 is on December 22. But if I look at the sunset times for a location such as Washington, DC on the USNO site, the sunset time starts reversing ...
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2answers
3k views

How much of sky can be seen on a typical night from a mid-latitude location?

I'm at about 40deg north so, assuming a clear southern horizon, I can't see things below about -30 or so (I actually don't know how far south). I also have a large portion that is circumpolar so it's ...
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5answers
2k views

Video of Earth spinning?

If the Earth is spinning or rotating at a really fast speed, why haven't we seen any videos from space of it spinning when we get a lot of photos of it?
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1answer
209 views

Axial Tilt and precession rate of exoplanets

The Earth's axis is 23.5 degrees away from othogonality to the ecliptic, and it takes about 26 000 years for it to precess fully. I have neither an intuitive sense nor the formula for precession ...
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3answers
238 views

On what planar regions are the Earth, Moon.. for that matter, all astronomical bodies, placed in the Universe?

When we are on Earth, we look UP in the Sky to see the Moon. How do we have to look at Earth from Moon.. Is it the way ? If so, how are these bodies actually placed in the space? Are all astronomical ...