Conditions at the Centre of the Earth

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Discussion Overview

The discussion centers around the conditions at the center of the Earth, specifically focusing on gravitational and air pressure in a hypothetical hole drilled to the center. Participants explore theoretical implications related to gravity, air density, and pressure at extreme depths, considering both physical and conceptual aspects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that gravitational force decreases as one descends into the hole, suggesting a point of zero net gravitational force at the center.
  • Others argue that despite the zero net gravitational force at the center, the air pressure would still be extremely high due to the weight of the rock above.
  • A participant emphasizes the distinction between air pressure and rock pressure, noting that the air pressure is determined by the weight of the air column above it.
  • Some participants discuss the hypothetical construction of walls that could withstand extreme pressure, suggesting that this would affect the air pressure calculations.
  • There is a contention regarding how air density and pressure change with depth, with some asserting that air becomes more dense and compressible, while others challenge this view.
  • One participant highlights that the air pressure in the hole would not drop to zero, despite the gravitational conditions, and questions how the weight of the air column would be calculated.
  • Disagreement exists over the assumptions made about the rigidity of the rock walls and how this impacts the air pressure in the hole.

Areas of Agreement / Disagreement

Participants do not reach consensus on the relationship between air pressure and depth, with multiple competing views on how to interpret the effects of air density and the structural integrity of the hole. The discussion remains unresolved regarding the exact nature of air pressure at the center of the Earth.

Contextual Notes

Limitations include assumptions about the rigidity of the rock walls, the compressibility of air, and the specific calculations of air pressure based on varying densities. These factors contribute to the complexity of the discussion without clear resolutions.

  • #31
Yes, that does make sense, but it isn't what I was thinking. Since it is entirely a work of fiction I think either is fine, but obviously the higher the temperature the lower the density and the more reasonable the numbers.
 
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  • #32
Guys, thank you all for so much input and erudition. Frankly, I thought there would be a simple and straight forward answer. It's good to know that scientific debate is alive and well. I find it interesting that things, including air, are all trying to get to the centre of the Earth, but when they get there, if they could, through our theoretical tunnel, they would find that the force wanting them to be there has vanished. But the air would still express a sort of memory of that force through its pressure.
Now, how about a tunnel to the centre of a Black Hole? Will there be differing answers for that, or is it actually a simpler problem?
 
  • #33
John100 said:
Now, how about a tunnel to the centre of a Black Hole? Will there be differing answers for that, or is it actually a simpler problem?
Yes, the pressure is infinite and even unobtanium can't hold up. Of course, even this relies on a bad assumption, namely that quantum gravitational effects are negligible. We will know more about this when we have a working theory of quantum gravity.
 
  • #34
John100 said:
...things, including air, are all trying to get to the centre of the Earth, but when they get there, if they could, through our theoretical tunnel, they would find that the force wanting them to be there has vanished...
Let's clear this up. The force wanting them to be there is specifically the weight of everything above them pressing down on them. That is a very real force.

Think of it this way:

You are lying on the ground, with a 10 tonne rock on your chest. Almost. The 10 tonne rock is actually sitting on a block of wood, which is in turn, sitting on your chest. The wood only weighs 5 pounds.

The weight that is right on your chest (the wood) is contributing virtually nothing (a paltry 5 pounds) to the 20,005lb. force that is crushing the life out of you. The lightness of the wood does not eliminate the heaviness of what's on top of it.

Now back to the column of air. Just because the last few hundred miles of air weighs only 5 pounds, does not mean you are not feeling the 10 tonne weight of the 3600 miles of air on top of it.
 
  • #35
DaveC426913 said:
Let's clear this up. The force wanting them to be there is specifically the weight of everything above them pressing down on them. That is a very real force.

That seems rather misleading...

Fish swimming near the bottom of the deepest part of the ocean are not pressed down against the bottom, and a small bird would meet no resistance from the weight above it as it flew upward from the center of the earth.

OF
 

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