At Center of Earth: Weightless or Crushed?

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Discussion Overview

The discussion centers on the conditions experienced at the center of the Earth, specifically addressing whether one would feel weightless or be crushed due to the immense pressure from surrounding mass. Participants explore the implications of gravity and pressure in this unique environment, considering both theoretical and conceptual aspects.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • Some participants argue that at the center of the Earth, gravity acts equally in all directions, leading to a sensation of weightlessness, while simultaneously questioning the effects of extreme pressure from surrounding mass.
  • Others propose that the experience of being crushed would depend on the existence of a cavity at the center, noting that the center is molten iron, which would pose additional hazards.
  • A participant suggests that gravity decreases with depth, leading to an environment of low gravity, which they argue contributes to the fluid nature of the core.
  • Some participants emphasize that while gravity may be negligible at the center, the pressure from the mass of the Earth would still be significant, challenging the notion of feeling weightless.
  • There are claims that pressure at the center is not zero and is instead proportional to the mass of the planet, despite the gravitational force tending toward zero.
  • One participant introduces a thought experiment comparing equal forces acting on a person, suggesting that even with balanced forces, one could still be crushed, drawing parallels to the pressure experienced at the Earth's center.
  • Discussions also touch on the differences between Newtonian and Einsteinian gravity, indicating ongoing debates about the nature of gravitational forces.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the effects of gravity and pressure at the center of the Earth. The discussion remains unresolved, with no consensus on whether one would feel weightless or be crushed.

Contextual Notes

Participants highlight the complexity of gravitational and pressure dynamics at extreme depths, noting that assumptions about uniformity and the nature of materials at the center may influence interpretations. The discussion also reflects varying understandings of hydrostatic pressure and its implications.

  • #61
cyrusabdollahi said:
Pressure is defined as force per unit area, but as we approach the infitesmal point mass with point area at the center of the Earth we would have pressure =force/zero,

but i guess the force would be infinite and the area would be zero, and we would have an indeterminate, of the form infinity over zero, so in oder to find the pressure we would have to use l'hospital ( that's EL hospital's :-) )rule, and that anwser would give us a definite anwser as we did the limit and what not, because obviously there is finite mass and so there will have to be finite pressure.

OOOhhhh, wow,
this is real science... :biggrin:
cyrusabdollahi,
listen to the answer of chroot, though, he is right...

Remember that physics is constructed in order to make the world more easy, understand it... :smile:

regards
marlon
 
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  • #62
Sorry for asking :-p , I will not post in this topic anymore :smile: what do you mean by real science? I think the question I posed in terms of an indeterminate is a valid, provided I were to have a function of the area and the force and knew the limits of my integral.
 
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  • #63
chroot said:
Cyrus:

You're making it way too complicated. At the center of the earth, there is no gravitational force. There is, however, enormous pressure.

- Warren

Sorry but this is not entirely true.

Gravity is "perceived" to be generated by the attraction of one mass against another. A body at the centre of the Earth would be attarcted by, and to, every particle that makes up the Earth around it. Thus gravity is in effect in every direction. However the NET gravitational effect would be ZERO.

Now pressure is created by the acceleration of a body against another body. The NET acceleration created by gravity at the centre of the Earth is zero, for the reason given above. So if only gravity was the cause of pressure, the pressure would be zero. However, their is both heat and motion in the Earth's core caused by friction, chemical reaction and gravity in the layers of the Earth beyond the centre. These energy sources generate acceleration of Earth particles which would apply pressure unevenly to any object at the centre of the Earth. As a result the contents of the Earth core are in constant motion. If these other sources of energy where not in place then the natural shape a planet such as the Earth would take is a hollow shell since a gravity inflexion point would be reached at a certain distance below the surface where there would not be sufficient gravity to hold the particles in place.
 
  • #64
Assuming a liquid planet, the pressure at the center is equal to the gravitational potential at the surface of the planet.
 
  • #65
stevo72 said:
If these other sources of energy where not in place then the natural shape a planet such as the Earth would take is a hollow shell since a gravity inflexion point would be reached at a certain distance below the surface where there would not be sufficient gravity to hold the particles in place.

lalbatros said:
Assuming a liquid planet, the pressure at the center is equal to the gravitational potential at the surface of the planet.

Two back-to-back nonsense posts to a five year old thread!

The first of the two is utter nonsense. You are ignoring the pressure from above, stevo72. The second doesn't make sense at all. Energy and pressure are different things with different units.
 
  • #66
D H said:
Two back-to-back nonsense posts to a five year old thread!

The first of the two is utter nonsense. You are ignoring the pressure from above, stevo72. The second doesn't make sense at all. Energy and pressure are different things with different units.

Pressure is a density of energy.
Indeed: Pa/m² = Pa.m/m³=J/m³.
I was simply suggesting to use the Bernouilli equation for this question.
 
  • #67
lalbatros said:
Pressure is a density of energy.
Indeed: Pa/m² = Pa.m/m³=J/m³.
I was simply suggesting to use the Bernouilli equation for this question.

I already got an answer to this question, years ago. I don't know why you're using Bernoulli for my question, as I didn't ask anything with regards to Bernoulli... :rolleyes:
 
  • #68
I was answering to stevo72, if you permit.
 
  • #69
Inside a solid shell there is no gravitational field. This come out though analysing Newton law of gravitation. So at the centre of the Earth g = 0.

F = G M1M2/r^2

M1 = mass of planet = (4/3)*pho*r^3
pho is the density of the planet assuming its of uniform denisty. The fact that is not does alter the result handily.
So F = (4/3)*G*M2*r

as F = mg

g = (4/3)*G*r

so as r tends to zero so does g!

Are more complete description using calculus to derive the result from first principles can be at
http://hyperphysics.phy-astr.gsu.edu/hbase/HFrame.html

Also a neat consequence of this is if you had an evacuated tube running through the centre of the earth, wore a spacesuit and jumped the time it takes for you to fall through the Earth to the other side and back again happily equals the time it would take for another intrepid explorer to orbit said planet just above the surface (agian the atmosphere has to pumped away.

So any takers on the ultimate ride? Smooth a path around the moon clearing it of all mountains and bore hole through the centre. Now jump and be shot out of cannon. The real reason why NASA wants to return to the moon. Make it a theme park so the engineers can play. After all what's the point of engineering if you can't do silly things with it.
 
  • #70
Ok listen up all u dopey heads.
You are using the right formula but you all made the same mistake. You would not experience a force of zero lols

Let me demonstrate:

Using Newtons law of universal gravitation

F=GMm/r^2 (which i am sure we all know)

G=Universal Gravitational constant
M=Mass of earth
m=mass of you
r=Distance between you and the centre of the earth

The force of gravity experienced at the centre of the Earth equals to

= 6.67 × 10^-11 x (Mass of Earth) x (Mass of you)
__________________________________________________
(Distance between you and centre of earth)^2

Since distance between you and the centre of the Earth is zero, we end up dividing the huge number at the top by zero.
As we all know, anything divided by zero is INFINITY (as 0 goes into any number an infinite number of times)

Therefore magnitude of gravity at the centre of the Earth is infinite

When we are at the centre of the Earth we will experience INFINTE gravity (theoretically).

We will not experience no gravity.
 
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  • #71
renek said:
Ok listen up all u dopey heads.
You are using the right formula but you all made the same mistake. You would not experience a force of zero lols

Let me demonstrate:

Using Newtons law of universal gravitation

F=GMm/r^2 (which i am sure we all know)

G=Universal Gravitational constant
M=Mass of earth
m=mass of you
r=Distance between you and the centre of the earth

The force of gravity experienced at the centre of the Earth equals to

= 6.67 × 10^-11 x (Mass of Earth) x (Mass of you)
__________________________________________________
(Distance between you and centre of earth)^2

Since distance between you and the centre of the Earth is zero, we end up dividing the huge number at the top by zero.
As we all know, anything divided by zero is INFINITY (as 0 goes into any number an infinite number of times)

Therefore magnitude of gravity at the centre of the Earth is infinite

When we are at the centre of the Earth we will experience INFINTE gravity (theoretically).

We will not experience no gravity.
Sorry, but this is completely incorrect. Only under certain circumstance can you treat the mass of the Earth as concentrated at a single point. To find the net gravitational field within the earth, you must add up the individual contributions from each element of the Earth's mass.

And this thread is years old.
 
  • #72
renek said:
We will not experience no gravity.
So in which direction will the gravitational force vector point, at the center of the Earth?
 
  • #73
didnt the original question suggest pressure...we should stop debating and revert to the original quest.
 
  • #74
robsharp14 said:
didnt the original question suggest pressure...we should stop debating and revert to the original quest.
What debate? The original question was settled years ago.
 
  • #75
i just noticed how old this post is
 

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