Flat Earth's Underside

Quote from: magellanclavichord on October 14, 2018, 09:31:41 AM

So, being fairly new to FET, I'm wondering what's below? In another thread I made a joke that if you dig down far enough you'll hit turtles. But I'm wondering, what does FET say would happen if you could dig far enough down? People have dug and drilled pretty far down, so we know that the Earth is at least a mile or so thick because nobody has ever come out the bottom. But assuming it were possible to dig to an arbitrary depth, or if it were possible to get past the ice wall and over the edge, what would we find?

Is there an under-side to the Earth? And if so, what's it like? Or is there a dimensional distortion so that there is no bottom, but you'd dig forever, or curve around and come out at another point of the surface, as predicted by RET?

What's underneath the Earth?

I hope this thread will not become a debate on the truth or not of FET. I would like to find out what FET says about what's down there.

A material like water. Like the dome side.

The earth has been created stratified layers. the top of one layer is the bottom of the other layer. So that;

Whenever you look at the sky, meanwhile you see the bottom of this earth.

Wise, I have moved this to the Debate sections as I want more information on this.

Are you saying that the Earth is inside a layered sphere?

Here is a photo showing the land mass down on the "Earth's Underside "Or was it the "Flat Earth's Underside" intended ?

Just moving it from Q&A so I went with how the question was originally posted.  Should have added Flat, although being a FE Forum I assumed that would be the assumed case.

I can't speak for rabinoz here, but my impression is that what lies beneath the Earth is still an open question. I personally don't subscribe to this multiple-layer, turtle-stacking theory that magellan described either; I think the sky is blue because of Rayleigh scattering, as is the common understanding. Rather, I think the best lead we have on what's down there is seismic data.

What emerges looks superficially like what you would get from a spherical Earth (for instance, tremors on one side of Antarctica are very strong on the other side) but the rate at which the wave's strength attenuates is all wrong. Locally around the epicenter, the inverse-square law is a decent approximation, but it all starts to break down outside even a few hundred km.

So all these corrective terms get introduced: shadow zones (which introduce their own slew of problems about the composition and origin of Earth's core, and have little to no effect on any measurements besides P-waves), normal modes (which are more of a mathematical model than a fully-formed theory about physical phenomena), and mantle convection  (which isn't really coherent for incompressible fluids, and leaves much room for post-hoc hand-waving). And even after all this, the Lehmann discontinuity goes unexplained and seemingly uninvestigated.

What's needed, I think, is a drastic rethinking of the geometry of the planet, while preserving the topology, i.e. the link across Antarctica. This sort of shift was the key insight that led to Einstein's theory of general relativity, and I don't think his job is done. Although I'm not a mathematician, I have a hunch that embedding a flat Earth in a Lorentz space, and in turn reducing that to a projective space, would at least give something close to accurate. Then, once we actually know what sort of space it is we're looking at, we can begin to analyze what's going on down there.

What emerges looks superficially like what you would get from a spherical Earth (for instance, tremors on one side of Antarctica are very strong on the other side) but the rate at which the wave's strength attenuates is all wrong. Locally around the epicenter, the inverse-square law is a decent approximation, but it all starts to break down outside even a few hundred km.

The inverse square law isn't what you would expect for a spherical Earth, unless you had no attenuation and the source was the centre of Earth.
The inverse square law is based upon the energy being spread out over ever larger spherical shells.
If you have any attenuation, that will result in the energy being reduced below that of an inverse square law.
If you don't have a continuous and homogeneous medium and instead have a surface/interface or a gradient that will reflect or refract the energy you can get different results as well. (note: this includes different media).

So all these corrective terms get introduced: shadow zones (which introduce their own slew of problems about the composition and origin of Earth's core, and have little to no effect on any measurements besides P-waves)

You act like these corrective terms are just thrown in with no basis.
We know waves travel differently through different media. We know when transitioning from one to another they refract. We know that not all media support the propagation of all types of waves.
The core affects both S and P waves.

You also have it seriously backwards. We study how waves propagate through Earth to determine the structure of Earth.

I have a hunch that embedding a flat Earth in a Lorentz space, and in turn reducing that to a projective space, would at least give something close to accurate.

And I'm fairly certain that that is completely wrong. FE models have continually failed to explain even simple aspects of reality while RE models predict it quite well. Why would anyone use a FE model? FE models can't explain how seismic waves propagate, at least for a RE there is a reason for the shadow zones.
Also, as soon as it gets embedded in anything other than flat space it raises the question of what it means to be flat.

You're right about that first part. I hadn't considered the interface between ground and air. I retract that. Still, I'm skeptical about any model that's built up from only one kind of measurement or observation, or at least ones as complex as the ones in this area. I accept that the ground/air interface exists because there is more than one way to show its presence (to ignore the fact that it's just obvious), but there's only one way to observe the interfaces under the Earth's surface.

Again, I would be willing to accept that if the proposed system were sufficiently simple or sufficiently accurate. Yet geologists need a constant stream of data to keep their models from going off the rails, as they inevitably do when left alone for too long. There's far too much opportunity for qualifying, adjusting, and finagling, like adding epicycles onto the celestial tracks of Mars. Soon enough, we'll have a model that can trace a picture of Homer Simpson on the Pacific Ocean.

And the idea of what's "flat" in non-Euclidean space is actually pretty well-defined, just as it's well-defined to say that a geodesic on a curved surface is "straight". We inhabiting the space would observe the ground as flat, even though the space it's embedded in wouldn't be. Anything we could use to measure flatness would also be curved by the space's shape. In other words, the Earth would be a flat object in a curved space. On the other hand, the round-Earth model places a curved object in a (mostly) flat space. The difference here is huge.

... as soon as it gets embedded in anything other than flat space it raises the question of what it means to be flat.

Maybe the Earth is flat, but space is an oblate spheroid. Put a flat Earth in a spherical space and voila! we have rectified the contradiction between FET and RET. Both are right! 

You're right about that first part. I hadn't considered the interface between ground and air. I retract that. Still, I'm skeptical about any model that's built up from only one kind of measurement or observation, or at least ones as complex as the ones in this area. I accept that the ground/air interface exists because there is more than one way to show its presence (to ignore the fact that it's just obvious), but there's only one way to observe the interfaces under the Earth's surface.

Not really.
There are other methods.
We know that the pressure will increase as you go down, as it needs to support the weight of everything above.
We also know that it is significantly hotter and quite likely to have some sorting of matter based upon density (and we know the composition is not the same from magma which has leaked to Earth's surface).

We also have strong evidence indicating that there is a molten core from Earth's magnetic field. Earth's magnetic field changes over time including flipping. This matches spinning balls of molten metal which undergo convection. A solid core wouldn't explain it.

But we don't have much in the way of possibilities of investigating what the structure of Earth is.
If you have any suggestions I am sure the geologists would welcome it.

And the idea of what's "flat" in non-Euclidean space is actually pretty well-defined, just as it's well-defined to say that a geodesic on a curved surface is "straight".

It can actually be a lot more complicated than that.
There is really only one way to define a straight line. You have a point and you have a direction. The curvature of space just means you follow that and get a geodesic. You can start at any point along the line and go forwards and backwards to make the rest of it.
But there are many ways to define a plane. One simple idea is a point, normal, which works in 3D space. You take a point and then consider all lines passing through that point which are normal to the normal.
Depending upon the geometry of the space, you can move along the surface, take a new point and the vector normal to that and construct a surface and get a different surface.
You can also construct a plane by taking a line and a vector and translating the line along that vector. Depending upon the geometry of space and what vector you choose you can get different surfaces. You can also pick another line on the surface and another vector and use that and generate a different surface.
This can also be interpreted as the same surface looking flat from one perspective (e.g. one point and way of measuring flatness) but curved from another.
For a flat space, all the planes constructed are the same. For a non-flat space, they will not necessarily be the same.
This makes the concept of a flat surface not as easy to move to a non-flat space as the concept of a straight line.

The other issue is that unlike a line, we can measure the curvature of a surface (at least if it is of constant curvature) with gaussian curvature, which gives a result independent of the space the surface is embedded in.
i.e. a curved surface in flat space would show its curvature, a "flat" surface in curved space would show the curvature of the space.


But yes, the difference between this hypothetical Earth and a RE in flat space would be huge. This hypothetical Earth wouldn't have a horizon. If you were high enough you would be able to observe the ground repeating. If you looked up you would see multiple images of the sun (and other stars) from the light "circling" Earth.

I can't speak for rabinoz here, but my impression is that what lies beneath the Earth is still an open question. I personally don't subscribe to this multiple-layer, turtle-stacking theory that magellan described either; I think the sky is blue because of Rayleigh scattering, as is the common understanding. Rather, I think the best lead we have on what's down there is seismic data.

What emerges looks superficially like what you would get from a spherical Earth (for instance, tremors on one side of Antarctica are very strong on the other side) but the rate at which the wave's strength attenuates is all wrong. Locally around the epicenter, the inverse-square law is a decent approximation, but it all starts to break down outside even a few hundred km.

Inverse-square would apply only if the medium were isotropic, that is, uniform in all directions, not stratified or variable laterally. As JB notes, there's also attenuation, there is also reflection every time the wave encounters a change in acoustic impedance (that's the acoustic velocity times density of the medium) and refraction when the acoustic velocity changes (it generally increases with depth, so waves are generally bent upward). As a result, clean spherical seismic wavefronts simply don't exist within the earth. 

Reality is not confined to be simple and uniform so that it's easy for you, me, or anyone else to understand.

So all these corrective terms get introduced: shadow zones (which introduce their own slew of problems about the composition and origin of Earth's core, and have little to no effect on any measurements besides P-waves), normal modes (which are more of a mathematical model than a fully-formed theory about physical phenomena), and mantle convection  (which isn't really coherent for incompressible fluids, and leaves much room for post-hoc hand-waving).

The shadow zone (an area that lacks direct P-wave and S-wave arrivals) is observed, not "introduced". In the shadow zone, the direct arrivals from even a very strong distant earthquake are not recorded. Stations nearer the epicenter record direct P- and S-waves strongly, and stations further away record direct P-wave arrivals strongly. An explanation of its existence is that those waves have to go through a volume that doesn't support the transmission of S waves (liquids have no shear strength, which is what makes them liquid, thus S [shear] waves can not exist within them), and the acoustic velocity is so much higher that P-waves are refracted in a way that none can arrive in the shadow zone directly. A liquid core with higher acoustic velocity than the mantle would cause this, thus the liquid core is imputed.

Normal modes (long-persistent seismic waves after a large earthquake) are also observed, not "introduced". They are understood to be the effect of a finite-sized elastic sphere "ringing" (which they are known to do).

Thermal expansion exists even in incompressible solids and liquids, so mantle convection is not nearly as far-fetched as you want to believe.

The mantle is solid, by the way; it supports S-wave transmission, so it's not a liquid. Its shear strength is not infinite, however, so it is subject to plastic deformation, which means that force applied to it unevenly will cause it to change shape. A large volume of material that is hotter than the surrounding material (so it expands, which reduces its density) will produce a buoyant force, and will slowly deform the material around it, and it will rise.

Your "corrective terms" are simply the difference between a homogeneous, isotropic earth and reality. You're the one doing the hand waving here.

And even after all this, the Lehmann discontinuity goes unexplained and seemingly uninvestigated.

It is not fully understood, but evidence shows that it exists. To say it goes uninvestigated is a bit of an overstatement.

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