physics of the Earth and its environment in space. Its subjects include the shape of the Earth, its gravitational and magnetic fields, the dynamics of the Earth as a whole and of its component parts, the Earth's internal structure, the generation of magmas, the hydrological cycle including snow and ...

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108
votes
15answers
30k views

How do I explain to a 6 year old why people on the other side of the Earth don't fall off? [closed]

Today a friend's 6 year old sister asked me the question "why don't people on the other side of the earth fall off?". I tried to explain that the Earth is a huge sphere and there's a special force ...
60
votes
6answers
5k views

Why is there a scarcity of lithium?

One of the major impediments to the widespread adoption of electric cars is a shortage of lithium for the batteries. I read an article a while back that says that there is simply not enough lithium ...
40
votes
7answers
3k views

Why is the Earth so fat?

I made a naive calculation of the height of Earth's equatorial bulge and found that it should be about 10km. The true height is about 20km. My question is: why is there this discrepancy? The ...
23
votes
3answers
2k views

Why has Earth's core not become solid?

The Earth is billions of years old, yet its core has not yet cooled down and become solid. Will this happen in the foreseeable future?
22
votes
4answers
1k views

Why does the sky change color?

Why the sky is blue during the day, red during sunrise/set and black during the night?
16
votes
3answers
748 views

Why the distribution of elements on Earth?

I've been wondering exactly why the elements are distributed the way they are on Earth. The heavier elements have their origins in the centers of stars, or in supernovae. After the death of the stars, ...
14
votes
3answers
763 views

How does uranium from supernovae explosions end up in mineral veins in a planet?

The reply to a question about nucleosynthesis, that heavier than iron elements are produced in supernovae explosions, raised for me the following question which I could not answer by googling. ...
14
votes
1answer
326 views

What is the evidence for the super-rotation of Earth's inner core?

What are the geophysical observations that support (or contradict) the hypothesis that the Earth's inner core rotates at a faster rate than the Earth's mantle? Summary of Answers: 1) Studies of ...
12
votes
3answers
872 views

Is the total energy of earth changing with time?

Many years ego, Earth was hot. Over time, it has lost energy and has become colder. Is it now in equilibrium or is its total energy changing?
12
votes
1answer
2k views

What would happen if the Earth was tidally locked with the Sun?

I'm thinking of writing a short story set on a version of Earth that is tidally locked to the Sun. I'm not exactly sure how to research the topic. Here's a number of questions about what would happen: ...
12
votes
2answers
4k views

What is the net charge of the Earth?

This question arose in a seminar today about the solar wind... This is my vagueish understanding of the problem - please correct if you see errors! The 'classical' picture of atmospheric electricity ...
11
votes
3answers
197 views

Radio-dating and the age of the earth

I understand there are a few radio-dating methods to determine the age of the earth, uranium-lead to name one (maybe not the best though). The ratio Pb206 + Pb207 to U allows you to find when the ...
10
votes
6answers
637 views

Tsunami dampening mechanisms

Encouraged by the zeitgeist let me ask the following: Is it feasible (now or in the future) to build systems a certain distance of a vulnerable coastline which can serve to dampen a tsunami before it ...
9
votes
3answers
2k views

How long does it take an iceberg to melt in the ocean?

This is a quantitative question. The problem is inspired by this event: On August 5, 2010, an enormous chunk of ice, roughly 97 square miles (251 square kilometers) in size, broke off the Petermann ...
9
votes
4answers
1k 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 ...
9
votes
1answer
2k views

What is the source of Earth's magnetic field?

I saw on Discovery channel that the source of Earth's magnetic field is the molten iron and metals in the earth's core. The spinning of these liquid metals produces the same effect as electric current ...
8
votes
3answers
666 views

How is it that the Earth's atmosphere is not “blown away”?

The Earth moves at a high rate of speed around the Sun, and the solar system is moving quickly around the Milky Way. How is it that the Earth's atmosphere is not “blown away”?
8
votes
3answers
455 views

Why does energy in earthquake waves seem to go up with the three halves power?

My question might be based on a false premise, so here's why I asked. If you look up the meaning of the moment magnitude scale for measuring earthquake size, the articles usually say that each ...
8
votes
4answers
502 views

Can a small change in the Earth temperature give rise to large-scale climate changes?

Earth's atmosphere is a chaotic system. In such systems arbitrarily small changes the conditions can give rise to very large effects. There are many rumors about the physical and large scale ...
8
votes
1answer
69 views

Do we have 2 minutes of extra morning?

my physics teacher told me about the refraction and its applications one of them was 2 minutes of early sunrise and after she explained this effect she concluded that days are 2 minutes longer than ...
8
votes
1answer
111 views

Deviation from power law distribution of earthquakes

One of the most accepted frameworks for the relationship between the magnitude and frequency of an earthquake is that of the critical phenomena. In this framework, the magnitude of events must be ...
7
votes
2answers
537 views

Is the total mass of Earth's atmosphere essentially constant in time?

Per a few questions and comments on this site such as Huge buildings affect earth's rotation? I wonder, is the mass of the Earth's atmosphere roughly constant? We're burning an incredible amount ...
7
votes
2answers
223 views

rotational oblateness

I am trying to compute the amount of oblateness that is caused by planetary rotation. I picture the force of gravity added to the centrifugal force caused by the rotation of the planet as follows: ...
6
votes
2answers
628 views

Why isn't the Earth's core temperature the average of its surface temperatures?

Assuming that the earth is spherical, that its temperature is continuous, and that some other more or less realistic conditions hold, we might think that the Earth's core temperature should be about ...
6
votes
2answers
211 views

Why are we not affected by the radiation of the radioactive decay going inside the Earth?

I was reading the question Why has Earth's core not become solid?, and one of the answers says that The core is heated by radioactive decays of Uranium-238, Uranium-235, Thorium-232, and ...
6
votes
4answers
631 views

Why the water remains on the surface of the Earth?

What makes the water stay on the surface? Why the earth does not absorb the water in it?
6
votes
1answer
60 views

Is it possible to determine astronomically/astrophysically whether other planets have ever encountered polarity reversal?

We know of geomagnetic flip in Earth's history by studying geologic data. Given other planets in the system also possess a magnetic field leads to the assumption that such polarity reversal may not be ...
6
votes
2answers
242 views

What is known about the Magnetic North Pole's location before 1800?

I was recently startled to find that the Earth's North Magnetic Pole is moving at upwards of 40 km per year, with an additional ~80 km daily elliptical drift about its mean position due to variations ...
6
votes
1answer
130 views

Amount of thermal energy in the Earth?

Does anyone know the amount of thermal energy that the Earth's mantle and core possess? I don't mean the maximum limit of electrical power we could generate with geothermal plants, but rather: if you ...
6
votes
2answers
135 views

Would it be possible for geophysicists/geoengineers to develop an artificial way of trapping carbon in the ocean?

There's a mechanism by which the southern ocean sequesters carbon from the atmosphere. It happens when strong winds displace a large slab of surface water, accumulating in a specific region where the ...
6
votes
1answer
71 views

What is “kinematic inversion” (from geophysics) in mathematical terms?

I am a mathematician working on a seismic imaging problem, and am currently (attempting to) read some geophysics papers (this one (Ruiz, Madariaga 2011) and this one (Di Carli, Francois-Holden, ...
6
votes
1answer
44 views

Refraction and scattered light for NLCs

For helping with judging NLC candidates (are they NLC or not) I have a set of formulas to calculate the minimum altitude (in km) of the candidate given an observed altitude (in degrees) of the ...
5
votes
5answers
2k views

What sustains the rotation of earth's core (faster than surface)?

I recently read that the earth's core rotates faster than the surface. Well, firstly, it's easier to digest the concept of planetary bodies, stars, galaxies in rotation and/or orbital motion. But, ...
5
votes
3answers
3k views

Can the Earth's magnetic be used to generate electricity?

Since the Earth has a magnetic field, can it, in theory, be run through a conductive metal coil to create electricity?
5
votes
1answer
67 views

How can I estimate confidence intervals around the forecasted temperatures for future days?

Weather.com will happily give me temperature predictions for the next ten days, but no indication of how reliable those predictions are. So if I want to plan something for a week from today, or four ...
5
votes
2answers
111 views

what determines the wavelength of waves on the open ocean?

Looking at the picture below, you can totally see that these are tiny boats. The water is practically washing over the hull of these boat models. But the water has boundaries that are very far ...
5
votes
1answer
286 views

A “global warming” problem

Suppose that a someone decided to calculate, for a given amount of heat added into a planet's atmosphere(an ideal gas), how much is the corresponding temperature rising of the atmosphere, $\Delta T$. ...
5
votes
3answers
3k views

Lowest gravity on Earth's surface?

I am trying to determine which on Earth's surface has the lowest gravity. Googling is not finding anything concrete. My natural inclination would be to think of Mount Chimborazo in Ecuador, being on ...
5
votes
2answers
261 views

Effect on length of day as the polar ice caps melt

If the polar ice caps of the earth melt, how will the length of the day be affected?
5
votes
2answers
432 views

How does Earth's interior dynamo work?

I'm interested in getting a basic physical understanding of how Earth's magnetic field is generated. I understand that it's a "dynamo" type of effect, driven by convection currents in the molten outer ...
5
votes
2answers
67 views

How about retrodiction, if climate prediction is difficult?

What I mean by the question is if retrodiction has been attempted back to, say, 50 or 100 years starting with the presently known state of climate as initial conditions using the same equations and ...
5
votes
2answers
203 views

Why does earth's magnetic field change its direction?

I know that the earth's magnetic field is due to molten metal and ions flowing in its core. It has been found that the Earth's magnetic field changes its direction and it has even flipped once! But, ...
5
votes
1answer
153 views

Readings of the detectors at Japan and Izu-Bonin-Mariana Trenches

Given the relevance of this subduction system, I would expect that a wide range of detectors (temperature, vibration, seismometers, whatever) are deployed in the depth of these trenches. What would be ...
5
votes
1answer
317 views

Why are cold thunderstorms rare?

FYI: I imagine the physics of thunderstorms involves wind stripping electrons from condensed water cells (raindrops or snowflakes). Like a Van De Graaff generator, sort of; I'm also using Wilson's ...
4
votes
1answer
651 views

Does the Earth rotate vertically too?

We know that the earth has seen several Ice Ages. And we know the Earth's magnetic poles seem to flip once in a while. Could all of this be explained by a once every 250 Million Years or so the ...
4
votes
2answers
188 views

Why do clouds appear black?

I have noticed clouds appearing black during rain. But I don't know what makes clouds to acquire that colour. This phenomenon doesn't appear every rainfall. There has to be distinction to white ...
4
votes
2answers
809 views

Where does the energy of a lightning strike go?

Lightning contains a lot of energy, so where does this energy go after lightning has hit the ground? Does it travel all the way to the core? What happens after that?
4
votes
1answer
637 views

What if the earth's core goes cold?

What effects would occur if the earth's core goes cold? Would the planet stay liveable after this happens?
4
votes
1answer
121 views

Why does air contain $Ar$ specifically?

Air consists roughly of $N_2$, $O_2$ and $Ar$. Why is $Ar$ the relatively common noble gas compound and not for example the lighter ones $He$ or $Ne$?
4
votes
2answers
374 views

Can the earth's magnetic field be generated by heat from a natural nuclear reactor?

I've come upon Dr. J. Marvin Herndon's theory that the earth's magnetic field is generated by a hot nuclear reactor operating in the center of the earth. This is backed by various papers, some of them ...