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33

We know the the size of the inner core through seismology. From my answer to this question: How are subsurface wave speeds determined without subsurface sensors?, we can determine the speeds of the different layers of earth. Pictured below is a diagram of raypaths going through the earth from the 1994 Northridge Earthquake in Southern California: (image ...


32

Earth's inner core is solid even though the temperature is so high because the pressure is also very high. According to the Wikipedia article on the Earth's inner core, the temperature at the center is $5,700\ \text{K}$ and the pressure is estimated to be $330$ to $360\ \text{GPa}$ ($\sim3\cdot10^{6}\ \text{atm}$). The phase diagram shown below (taken ...


31

As Chris Mueller said, in short: it isn't, or at least highly infeasible. Projects to drill into the mantle, such as the Kola Superdeep Borehole, have all failed because drilling equipment can't withstand the heat at only ~15km deep. Even if we were to come up with some sort of cooling system that's able to cool to 6400km or 12800km deep (depending on ...


31

Part 1, see Neos answer. Earth will lose its heat no matter what we do, and our extraction of geothermal energy is insignificant (Wikipedia quotes a BP figure of 11.4 GW electrical, 28 GW heating). To answer part 2 of your question: if the Earth's core loses its heat, this will not have a major direct impact on climate. Internal heat generation is ...


26

Good question! Geochemists and geophysicists agree to disagree, sometimes quite strongly. There are also disagreements within each group as well as between the two groups. It's not just uranium. There are four isotopes whose half-lives are long enough that they can be primordial and whose half-lives are not so long that they don't produce much heat. These ...


21

In addition to the answers below and my comment above, I believe the following phase diagram, from DavePhd's answer here, sourced from here, is more appropriate for the pressure levels near the Earth's core of about 330 to 360GPa. We can see from the image that for pressures between 330 and 360GPa, the melting temperature ranges from about 6200 K to 6600 K, ...


20

Short answer: No. Long answer: Our deepest drills failed around 12km down when the drill bits were having to cope with temperatures hot enough to melt the drills. 12km down is only a tiny distance into the earth. The average distance to the center is over 6300km. So didn't even get to half of a percent of the way to the center. To do so, we'd have to ...


20

Earth's radius is about 6400 kilometres. That's 6400000 metres. Let's say that you have a mound 20 metres high, burying an older settlement. Your new "radius" is now 6400020 metres. Let's say that $g = 9.8\ \rm m/s^2$ at 6400, your new gravity will be $g = 9.799939\ \rm m/s^2$. Clearly, this is hardly "lower level of gravity". To make this even less ...


19

The first thing you should think about is how the accretionary disk cooled and the cosmochemical constraints this put on Earth (But I am not going into details here). From studying meteorites it is apparent that the oldest meteorites don't show signs of chemical differentiation (e.g. melting, ...) and are thought to represent the solids that formed from the ...


19

This question is relevant, Why is the inside of the Earth so hot? The short answer is the core is losing heat no matter what we do. You see, heat is transported from the core to the surface, but its important to think of heat in terms of energy. Since there is a finite amount of energy within the earth, we are actually transferring energy from the inside to ...


18

Put a frying pan on a stove burner and make the pan hot. Measure its temperature every minute over half an hour or so to get an idea of how rapidly it naturally cools. Then start the experiment over again. This time, take a needle and touch and hold its tip to the frying pan so that it acts as a heat sink. The relative sizes of frying pan and needle will ...


18

First, you need a phase diagram that goes to higher pressure. The pressure at the inner/outer core boundary is over 300 GPa. The one in the question would only get us into the mantle: (link to source) A typical temperature and pressure at the outermost part of the core would be 3750K and 135GPa, which is in the liquid region of the phase diagram. For ...


18

Global warming has to do with the surface only, and at best involves changes of 20 degrees at the outside extreme, in comparison to the earth's core, which is as hot as the surface of the sun. For complete accuracy, and to reflect what a commenter has pointed out, the inner core is solid already, but this is because of the extremely high pressure of the ...


17

The only elements that were formed on Earth are those produced by radioactive decay. There are four natural decay chains that start with transuranic elements and none terminate in iron; neither do the decay chains that are artificial or those that result from cosmic radiation. So all of our iron is from the Earth's formation or meteor impacts since then.


16

The pressure gradient is given by hydrostatic equilibrium. In a solid, this may not be exactly true, but creep will make it so. Let $p$ be the local pressure, $g$ be the local acceleration of gravity and $\rho$ the local density. Imagine a small element of volume with area $A$ horizontal and height $\Delta h$. Its mass is $\rho A \Delta h$ and it is ...


14

Could all the drilling and digging to use the earth's natural heat as geothermal energy be affecting Earth's core, causing it to cool down? Yes. But by how much? Let's do some rough math. We'll just be concerned with orders of magnitude here. Suppose we have a uniform sphere the size of the Earth. Call it 1021 cubic meters. Suppose this sphere is made ...


13

You are only considering the melting point at atmospheric pressure. Melting point depends upon pressure. The pressure in Earth's core is about 350 GigaPascals. It is important to study the phase diagram of the substance being considered. A phase diagram explains what phase (solid, liquid, gas) a substance is in at various temperatures and pressures. ...


13

Whether the high temperatures of the core is strictly necessary to maintain a habitable temperature at the surface I'm not sure, as the global temperatures are largely controlled by insolation and the greenhouse effect. The black-body radiation temperature of the Earth is about -18 °C, and even a more realistic estimate of the surface temperature ...


13

... causing it to cool down? This answer to the question 'Why has Earth's core not become solid?' over on Physics seems to claim the answer is no. The core is heated by radioactive decays of Uranium-238, Uranium-235, Thorium-232, and Potassium-40, all of which have half-lives of greater than 700 million years (up to about 14 billion years for Thorium). ...


13

One permanent threat to plate tectonics is the oceans vanishing. The scientific jury may still be out on this matter, but most geologists and geophysicists consider water to be the lubricant that makes plate tectonics possible. In a billion years or so, the Sun will have become 10% more luminous. This is conjectured to make the Earth to undergo an ...


13

This is a good observation. The reason we can measure S-wave (transverse) propagation in the inner core is because P-waves can set up S-waves and vice versa. When an S-wave hits the mantle-outer core boundary at an angle it has a vibration component which is normal to the boundary and this sets up a P-wave in the liquid inner core. The opposite happens at ...


13

The conventional explanation for the Earth's magnetic field is that some combination of differential rotation and/or convection occurs in the Earth's outer core, primarily in molten iron-nickel (+ sulphur, hydrogen etc.), which acts as a kind of dynamo. Whilst we can't prove it by direct observation, this seems an eminently plausible mechanism. If this is ...


12

There is one vaguely plausible method that has been proposed: blow open a crack in the Earth's crust using a hydrogen bomb and then fill the crack with molten iron. The iron then sinks to the core, and a small probe can sit on top of it and ride it all the way down. There's no way to get it back again, of course, but it could transmit its data back to the ...


11

Is it true that Earth's outercore rotates in the opposite direction to Earth's inner-core? No. You misread a badly written for-the-masses science article. The article summary is at best rather confusing and misleading. It invites a reader to misinterpret what's going on. So what's really going on? It's simple, conceptually. The mantle, outer core, and ...


11

All the material that eventually formed our solar system is essentially recycled star dust. All iron on Earth was produced by large stars that existed before our Sun formed: the iron was created during nuclear fusion and later released when the parent star(s) exploded, presumably supernova. After our solar nebula had formed and material had been ...


11

I can only answer the question of why is it mostly iron. Not too sure of the magnetic properties of iron versus nickel. As said in another answer, there is simply much more iron around than nickel. But the earth has also a large amount of other metals: silicon, magnesium, calcium, aluminium. So why is the core made of iron-nickel and not the other stuff? ...


10

Your guess A is correct. Iron, nickel, and other heavy metals like gold, are what makes up the core of the earth because they are the heaviest of the metals and so sank toward the center of the earth. Also, since the earth is believed to have been made out of loose material (asteroids) out in space, it would make sense that it would be made out of much of ...


9

Scientists used the seismic waves created by earthquakes bouncing off the core to map out the approximate size of the earth's inner core. The materials that constituted the core were guessed with the thinking that because it was once liquid, the heavier elements like iron and nickel were able to sink down into the center. It probably even has vast amounts ...


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