# Tag Info

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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 ...

8

This is more a geophysics than an astronomy question—and thus the available methods of investigation are greatly increased. An Earth model also is not a one-person-show based on one measurement, but requires many different measurements from different fields with greatly different methods which form a unique picture which leaves only few possibile ...

7

The medium for a solar flare is plasma, so nothing like that occurs in the Earth's core. The outer core fluid is highly conductive and has a low viscosity, so changes may occur in the core's field, but the mantle has enough electrical conductivity to filter out the more rapid changes (those with periods of roughly a year or less). See Merrill and McElhinny ...

5

To address your original concern, no, the fact that there are buildings underground does NOT mean that the surface of the earth is higher than in the past. What is actually happening is that these buildings are subsiding into the ground. How? Believe it or not, earthworms. Worms were once constantly tunneling through the soil underneath ancient buildings, ...

5

From the comments: And indeed, after browsing trough a few sections they seem to assume that "Liquid metal separates rapidly from liquid silicate", like oil and water, and they don't mix later. Very interesting. I wonder what's @Gimelist opinion about this. You are very correct. The answer is simple: the core and mantle are immiscible. The core ...

4

We know the density of the core from seismology. We also know the density of pure iron at given pressure (P) and temperature (T). From these two, people have long noticed that there is a discrepancy: the actual core is lighter than a theoretical core made of pure iron. This is known as the Core Density Deficit (CDD). To explain this CDD, we need to add light ...

3

On a quick approach: Magnetism. The copper itself have a weak magnetism, so a copper core will not create a magnetosphere. Chek here or here. Gravity. The Iron density is 7.874 g/cm³ and the nickel density is 8.908 g/cm³. Copper density is 8.96 g/cm³. So with those density data, the core will be heavier. (The actual core is supposed to have a 9.9-12 g/cm³ ...

3

If waves would travel only through a medium while keeping their form (i.e., P-waves remain P-waves and S-waves remain S-waves), you would obtain something a bit like this video: https://www.youtube.com/watch?v=YctV5crEXyM . However, standard models for wave propagation are more complicated than that. Upon hitting an interface, P-waves both reflect off and ...

3

Are there any other measurements that have contributed to current understanding of Earth's core besides these two? The answer is of course "yes". Other answers have already alluded to laboratory experiments that attempt to re-create conditions similar to those well inside the Earth. I'll provide two others; there are many more. One is radio ...

3

The whole mass of the Earth, mantle, crust, atmosphere and sea, contributes to the Earth's gravitational field, not just the core. Unless you want to split hairs, the Earth's gravity is the same now as it always was. In case you do want to split hairs, the Earth collects a substantial amount of space dust, meteorites and cosmic debris every year, but no one ...

2

I think the answer is 'no', in the sense that 'seismology (i.e., the study of waves propagating within the Earth) tells us the details in a far superior way'. See this paper for an informative treatise: Brush, S. G. (1980). Discovery of the Earth’s core. American Journal of Physics, 48, 705-724, and these lecture notes http://www.geo.uu.nl/~berg/geodynamics/...

1

The idea that the heat of the earth is from the time of its formation dates back to the late 1800s before radioactivity was known. Unfortunately for that theory it was shown that an initial blob of molten rock would cool to a solid chunk, radiating its heat into space, in a few tens of millions of years. When radioactivity was discovered it was seen as a ...

1

The comments to the other question have already alluded to some physical answers that also come out of the lab: One might think that the heaviest elements in primordial Earth should have all sunk into the core by now. But that's not actually the case: For example, uranium with a density 2.5 times that of iron (19.1 vs 7.9 g/cm3) has an abundance of about 4 ...

1

The Earth's core is both solid and liquid. The outer core is molten and produces currents of molten nickel/iron which generate the Earth's magnetic field in a dynamo effect, while the inner core is solid. The reason the inner core is solid is that it is under tremendous pressure, more so than the outer core. Scientists know this from the analysis of seismic ...

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