# Thread: Pole shift compared to position of magnetism.

1. Is the north pole off set to the hole in the magnetic field?

Hole meaning, on the diagrams I have seen, of magnetic field shape , around the earth, it is shown to have a hole at the top and bottom of the shape.
An intake and an out take.

Is this the correct shape of the magnetic field?

Main question - If the North pole, is offset, to the magnetic <hole>, is this where the poles have shifted from in time?

magnetism.gif

2.

3. There is no hole.

4. Originally Posted by Dywyddyr
There is no hole.
Thank you that answers that, magnetic poles?

5. Originally Posted by theorist
Is the north pole off set to the [magnetic pole] in the magnetic field?
It depends what you mean by "north pole". There are several different north poles.

There is the magnetic north pole which is, by definition, in the same place as the magnetic pole ("hole"). This drifts around all the time and even goes as far as the south pole sometimes.

There is the north pole corresponding to the axis of rotation of the earth. This rarely (if ever) coincides with the magnetic north pole. It also wobbles about a bit due to the uneven rotation of the earth.

Then there is the geographic pole which is a fixed location used for surveying, etc.

There may be others.

6. Originally Posted by Strange
Originally Posted by theorist
Is the north pole off set to the [magnetic pole] in the magnetic field?
It depends what you mean by "north pole". There are several different north poles.

There is the magnetic north pole which is, by definition, in the same place as the magnetic pole ("hole"). This drifts around all the time and even goes as far as the south pole sometimes.

There is the north pole corresponding to the axis of rotation of the earth. This rarely (if ever) coincides with the magnetic north pole. It also wobbles about a bit due to the uneven rotation of the earth.

Then there is the geographic pole which is a fixed location used for surveying, etc.

There may be others.
Thank you Strange , the movement of the magnetic north pole, explains the answer, to why the north pole and south pole are cold due to the axis. I can see this now.

7. Originally Posted by theorist
Thank you Strange , the movement of the magnetic north pole, explains the answer, to why the north pole and south pole are cold due to the axis. I can see this now.
Errr. Yeah. If you say so.

(say what?)

8. Originally Posted by Strange
Originally Posted by theorist
Thank you Strange , the movement of the magnetic north pole, explains the answer, to why the north pole and south pole are cold due to the axis. I can see this now.
Errr. Yeah. If you say so.

(say what?)
I no longer think the hole/magnetic north pole, caused the north pole to freeze.

Is the shift of position, of the magnetic poles, caused by the big iron marble in the center/core ,of the planet, swashing about in the lava?

9. Originally Posted by theorist
Is the shift of position, of the magnetic poles, caused by the big iron marble in the center/core ,of the planet, swashing about in the lava?
Given your level of knowledge, I'm going to say: yes.

(Don't get too upset when you find it is a little more complex than that )

10. Originally Posted by Strange
Originally Posted by theorist
Is the shift of position, of the magnetic poles, caused by the big iron marble in the center/core ,of the planet, swashing about in the lava?
Given your level of knowledge, I'm going to say: yes.

(Don't get too upset when you find it is a little more complex than that )
Thank you, I do understand that it is friction and heat from the lava that gives our core the magnetic charge is that correct?

And doe's this then make all other iron particles in the planet have magnetic force?

11. Originally Posted by theorist
Thank you Strange , the movement of the magnetic north pole, explains the answer, to why the north pole and south pole are cold due to the axis. I can see this now.
No it doesn't.
And what you see is total bollocks.

12. Originally Posted by Dywyddyr
Originally Posted by theorist
Thank you Strange , the movement of the magnetic north pole, explains the answer, to why the north pole and south pole are cold due to the axis. I can see this now.
No it doesn't.
And what you see is total bollocks.
see-post 7-first line

13. Originally Posted by Dywyddyr
Originally Posted by theorist
Thank you Strange , the movement of the magnetic north pole, explains the answer, to why the north pole and south pole are cold due to the axis. I can see this now.
No it doesn't.
I think that what 'e means is that evidence that the magnetic poles move while the location of ice doesn't disproves 'is idea (and therefore makes it possible to accept the real explanation). Or something like that. It isn't quite clear 'ow 'is mind works.

'ope that 'elps.

(Thought leaving the aitches off might 'elp t'eorist understand )

14. Originally Posted by Strange
Originally Posted by Dywyddyr
Originally Posted by theorist
Thank you Strange , the movement of the magnetic north pole, explains the answer, to why the north pole and south pole are cold due to the axis. I can see this now.
No it doesn't.
I think that what 'e means is that evidence that the magnetic poles move while the location of ice doesn't disproves 'is idea (and therefore makes it possible to accept the real explanation). Or something like that. It isn't quite clear 'ow 'is mind works.

'ope that 'elps.

(Thought leaving the aitches off might 'elp t'eorist understand )
Yes exactly, that is evidence provided by you that the magnetic poles shift, and yes that proves that the north pole is froze from other means.

I did not know that the magnetic poles move, I thought they were over the north pole, hence why I thought this is what froze the poles.

Unless at one time the earth did not spin, and then maybe the magnetic poles would be in a fixed position.

Ok, to my question that is not yet answered,

Our magnetic poles are made by the earths core, correct?

So doe's all the other iron in the planet, hold a magnetic charge, do all other iron elements by the force of the cores magnetism, become magnetic themselves?

If not why can a paper clip become magnetic from in contact with a magnet?

15. Originally Posted by Strange
(Thought leaving the aitches off might 'elp t'eorist understand )
Are you trying to communicate to him through the medium of Cockney?

Kinda like: "A fakin orse as dunna turd rand the back of my aas."

16. Originally Posted by PhDemon
"I did not know that the magnetic poles move" So what was all that crap you posted in the other thread about shifting magnetic fields all about then.
I thought the magnetic poles were moving with the switch of north and south pole, not randomly jumping around the planet.
I thought it was all one central point and it was moving together.

added- meaning central to the respective poles of north and south.

17. Originally Posted by theorist
Our magnetic poles are made by the earths core, correct?
Yes (but I suspect it is more complicated, something to do with electric currents, etc. but I don't know any more detail than that.)

So doe's all the other iron in the planet, hold a magnetic charge, do all other iron elements by the force of the cores magnetism, become magnetic themselves?
I'm not sure why you start that with "so". The fact that iron and many other materials are magnetic is not connected with the Earth's magnetic field. (They are magnetic materials in the sense they can be magnetized, or become magnets. They are not necessarily magnetized.)

However, minerals can become magnetised by the Earth's magnetic field (if they are heated and then cooled). This is how we are able to see the geological record of changes in the Earth's magnetic field.

If not why can a paper clip become magnetic from in contact with a magnet?
That clearly has nothing to do with the Earth's magnetic field. The magnet temporarily induces magnetism in the paper clip. Given time, the paper clip can become permanently magnetised. This can be speeded up by physical shock or heating. This is because magnetising a material depends on aligning all the tiny little magnets (domains) within it; they are more likely to become aligned if shaken (physically or by heating).

18. Originally Posted by Strange
Originally Posted by theorist
Our magnetic poles are made by the earths core, correct?
Yes (but I suspect it is more complicated, something to do with electric currents, etc. but I don't know any more detail than that.)

Yes a lot more complicated, but keeping it simple for conversation.

So doe's all the other iron in the planet, hold a magnetic charge, do all other iron elements by the force of the cores magnetism, become magnetic themselves?
I'm not sure why you start that with "so". The fact that iron and many other materials are magnetic is not connected with the Earth's magnetic field. (They are magnetic materials in the sense they can be magnetized, or become magnets. They are not necessarily magnetized.)

However, minerals can become magnetised by the Earth's magnetic field (if they are heated and then cooled). This is how we are able to see the geological record of changes in the Earth's magnetic field.

If not why can a paper clip become magnetic from in contact with a magnet?
That clearly has nothing to do with the Earth's magnetic field. The magnet temporarily induces magnetism in the paper clip. Given time, the paper clip can become permanently magnetised. This can be speeded up by physical shock or heating. This is because magnetising a material depends on aligning all the tiny little magnets (domains) within it; they are more likely to become aligned if shaken (physically or by heating).

What I am struggling to understand now, the paper clip becomes magnetized with contact of a magnetic force, so if the earth has such a strong magnetic force,
Why for example, do cars not become magnetized?

The magnetic force on our surface of the planet should magnetize all metal, so why not, what is the difference?

Doe's metal have to make contact with a magnet before it is magnetized?

Also is the shape of magnetism of the planet, perceived from the shape of an oblong magnet? or is the shape calculated from the earths orbital test of the magnetic field, by satellites?

19. Originally Posted by PhDemon
The earth's magnetic field is actually pretty weak at about 0.25-0.65 G whereas a fridge magnet is about 100G this is on the wikipedia page for Earths magnetic field, do some basic research before spouting guff.

Not all metals are magnetic do some basic research before spouting guff.

Read Stranges post again and do some basic research and you will find the answers to your questions.

Can you see a common theme...

errmmm, basic research done I am asking you what you think and the whys in simple terms, far easier to understand.

Your explanation gives me the answer though thanks, 0.25-0.65g and the fridge magnet explains why, I thank you that is a easy explanation.

Your thoughts on the shape of earths magnetism?

20. Originally Posted by theorist
What I am struggling to understand now, the paper clip becomes magnetized with contact of a magnetic force
Remember the inverse square law? As the paper clip gets closer to the magnet the magnetic field strength increases. I haven't tried it (experiment for you) but I imagine that a paper clip held a few mm away from the magnet would still be magnetised but much more weakly. As you move the paperclip away from the magnet, the "induced" magnetism in it will rapidly decrease. (In fact, I think that magnetism follows an inverse cube law because of the two poles, and so it will decrease very rapidly.)

, so if the earth has such a strong magnetic force, Why for example, do cars not become magnetized?
For one thing, the Earth's magnetic field is incredibly weak. Do you see all your paper clips pointing north? No. It is just about strong enough to rotate a very light compass needle on a low friction bearing.

Whereas, modern rare-earth magnets can be so strong that they can require surgery if you accidentally stick two of them to you (DO NOT TRY THIS AT HOME).

A car could become magnetised if it always kept the same orientation to the Earth's magnetic field. But we drive them about at random so, if anything, thet tend to get demagnetised.

The magnetic force on our surface of the planet should magnetize all metal, so why not, what is the difference?
It is weak. It is hard to permanently magnetise most things.

Also is the shape of magnetism of the planet, perceived from the shape of an oblong magnet? or is the shape calculated from the earths orbital test of the magnetic field, by satellites?
It can be measured at the Earth's surface using a compass: as you approach the poles, the needle will start to point down. It is also measured from planes and satellites.

21. Originally Posted by Strange
Originally Posted by theorist
What I am struggling to understand now, the paper clip becomes magnetized with contact of a magnetic force
Remember the inverse square law? As the paper clip gets closer to the magnet the magnetic field strength increases. I haven't tried it (experiment for you) but I imagine that a paper clip held a few mm away from the magnet would still be magnetised but much more weakly. As you move the paperclip away from the magnet, the "induced" magnetism in it will rapidly decrease. (In fact, I think that magnetism follows an inverse cube law because of the two poles, and so it will decrease very rapidly.)

, so if the earth has such a strong magnetic force, Why for example, do cars not become magnetized?
For one thing, the Earth's magnetic field is incredibly weak. Do you see all your paper clips pointing north? No. It is just about strong enough to rotate a very light compass needle on a low friction bearing.

Whereas, modern rare-earth magnets can be so strong that they can require surgery if you accidentally stick two of them to you (DO NOT TRY THIS AT HOME).

A car could become magnetised if it always kept the same orientation to the Earth's magnetic field. But we drive them about at random so, if anything, thet tend to get demagnetised.

The magnetic force on our surface of the planet should magnetize all metal, so why not, what is the difference?
It is weak. It is hard to permanently magnetise most things.

Also is the shape of magnetism of the planet, perceived from the shape of an oblong magnet? or is the shape calculated from the earths orbital test of the magnetic field, by satellites?
It can be measured at the Earth's surface using a compass: as you approach the poles, the needle will start to point down. It is also measured from planes and satellites.
Thank you for clarifying what I have looked at, I now understand it.

22. Originally Posted by PhDemon
"Basic research done" "Shape of Earths magnetism"

Obviously not very well, the very first paragraph on the Wiki page answers your question:

Earth's magnetic field
(also known as the geomagnetic field) is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun. Its magnitude at the Earth's surface ranges from 25 to 65 µT (0.25 to 0.65 G). It is approximately the field of a magnetic dipole tilted at an angle of 11 degrees with respect to the rotational axis—as if there were a bar magnet placed at that angle at the center of the Earth. However, unlike the field of a bar magnet, Earth's field changes over time because it is generated by the motion of molten iron alloys in the Earth's outer core (the geodynamo).
Thank you Ph, I just did not quite understand it, I do now thank you.

23. Originally Posted by theorist
Originally Posted by PhDemon
"I did not know that the magnetic poles move" So what was all that crap you posted in the other thread about shifting magnetic fields all about then.
I thought the magnetic poles were moving with the switch of north and south pole, not randomly jumping around the planet.
I thought it was all one central point and it was moving together.

added- meaning central to the respective poles of north and south.
Nothing in our universe is actually still. Electrons flow across atoms, atoms move and rotate within molecules, molecules twist and interact and reform. Everything is in a state of movement or chemistry. Even the blackness of space isn't frozen at absolute zero.

24. Hey , I just had a thought, you say that the magnetic north pole and the southern magnetic pole, shift position on a regular basis.

That would not work!

Are you joking with me?

MY compass needle would constantly change direction, north would no longer be north in a navigation sense when the north field moved?

25. Originally Posted by theorist
Hey , I just had a thought, you say that the magnetic north pole and the southern magnetic pole, shift position on a regular basis.

That would not work!

Are you joking with me?

MY compass needle would constantly change direction, north would no longer be north in a navigation sense when the north field moved?
....

Over the course of a few hundred thousand years, Theorist...

26.

27. Originally Posted by Neverfly
Originally Posted by theorist
Hey , I just had a thought, you say that the magnetic north pole and the southern magnetic pole, shift position on a regular basis.

That would not work!

Are you joking with me?

MY compass needle would constantly change direction, north would no longer be north in a navigation sense when the north field moved?
....

Over the course of a few hundred thousand years, Theorist...

I would of considered the movement of 40 miles a year, is somewhat quicker than a few thousand years?

28. Thank you for the great links.

29. mshift.JPG
Is the shift anything like this diagram?

30. You mean messy and meaningless? No.

31. Originally Posted by AlexG
You mean messy and meaningless? No.
Explain please, did I need to write an explanation to go with it?

I thought the drawing was good lol , compared to science blackboard drawings.

Is the magnetic pole shift connected to the Suns magnetic pole shifts?

If not the above question, is the magnetic pole shift connected to a magnetic belt on the sun?

How far has the magnetic pole already shifted from the starting recorded point?

A calculation I made lol, from starting point of the shift, to a 90 degrees angle ,it will have shifted, is approximately 155 years based on 40 miles per year shift.

When the shift reaches a 90 degrees angle, I then would expect to see an instance flip for the other 90 degrees.

Would this happen , would we get an instant flip at 90 degrees angle of shift?

If so would this have catastrophic effect?

and lol don't laugh at the math's I may have done that wrong.

32. Originally Posted by theorist
Explain please, did I need to write an explanation to go with it?
maybe. It didn't mean anything to me.

Is the magnetic pole shift connected to the Suns magnetic pole shifts?

If not the above question, is the magnetic pole shift connected to a magnetic belt on the sun?
As far as I know, the Sun's magnetic field is far to weak to have any such affect on the Earth.

How far has the magnetic pole already shifted from the starting recorded point?
Right now, the magnetic north pole, where the field is vertical, is located at 84.97 degrees North and 132.35 degrees West, above the Arctic Ocean and drifting generally north-northwest toward Siberia at about 55 kilometers (34.2 miles) per year, according to Love.
Earth

A calculation I made lol, from starting point of the shift, to a 90 degrees angle ,it will have shifted, is approximately 155 years based on 40 miles per year shift.
That assumes it is just steadily moving from North to South. My understanding is that it pretty much wanders around at random. Some years it may be closer to the poles, other years further away.

When the shift reaches a 90 degrees angle, I then would expect to see an instance flip for the other 90 degrees.

Would this happen , would we get an instant flip at 90 degrees angle of shift?
It certainly wouldn't be instant; there is too much inertia involved.

"Reversals typically take about 10,000 years to happen," said Jeffrey Love of the U.S. Geological Survey. "And 10,000 years ago civilisation did not exist. These processes are slow, and therefore we don't have anything to worry about."

Magnetic north shifting by 40 miles a year, might signal pole reversal | MNN - Mother Nature Network

If so would this have catastrophic effect?
We don't really know (see article above). It may disrupt some things, including wildlife. Probably not catastrophic. Just awkward.

33. Originally Posted by Strange
Originally Posted by theorist
Explain please, did I need to write an explanation to go with it?
maybe. It didn't mean anything to me.

Is the magnetic pole shift connected to the Suns magnetic pole shifts?

If not the above question, is the magnetic pole shift connected to a magnetic belt on the sun?
As far as I know, the Sun's magnetic field is far to weak to have any such affect on the Earth.

How far has the magnetic pole already shifted from the starting recorded point?
Right now, the magnetic north pole, where the field is vertical, is located at 84.97 degrees North and 132.35 degrees West, above the Arctic Ocean and drifting generally north-northwest toward Siberia at about 55 kilometers (34.2 miles) per year, according to Love.
Earth

A calculation I made lol, from starting point of the shift, to a 90 degrees angle ,it will have shifted, is approximately 155 years based on 40 miles per year shift.
That assumes it is just steadily moving from North to South. My understanding is that it pretty much wanders around at random. Some years it may be closer to the poles, other years further away.

When the shift reaches a 90 degrees angle, I then would expect to see an instance flip for the other 90 degrees.

Would this happen , would we get an instant flip at 90 degrees angle of shift?
It certainly wouldn't be instant; there is too much inertia involved.

"Reversals typically take about 10,000 years to happen," said Jeffrey Love of the U.S. Geological Survey. "And 10,000 years ago civilisation did not exist. These processes are slow, and therefore we don't have anything to worry about."

Magnetic north shifting by 40 miles a year, might signal pole reversal | MNN - Mother Nature Network

If so would this have catastrophic effect?
We don't really know (see article above). It may disrupt some things, including wildlife. Probably not catastrophic. Just awkward.
Thank you for the links Strange, I will read up on them and come back with some more questions.

Just one question though, You say it would take a lot of inertia for an instant flip, I just see it as , compared to the sun, we are just a compass needle.

So are you saying inertia because of the density surrounding the earths core?

It is the core that doe's the flip?

And would the flip not be easy ,because of the magna ,acting like a football in water compared to density?

34. Originally Posted by theorist
So are you saying inertia because of the density surrounding the earths core?

It is the core that doe's the flip?

And would the flip not be easy ,because of the magna ,acting like a football in water compared to density?
To change the magnetic field, the pattern of rotation of the core must change. That is about 1700000000000000000000000 kg. You don't get that to change direction "instantly".

35. Originally Posted by Strange
Originally Posted by theorist
So are you saying inertia because of the density surrounding the earths core?

It is the core that doe's the flip?

And would the flip not be easy ,because of the magna ,acting like a football in water compared to density?
To change the magnetic field, the pattern of rotation of the core must change. That is about 1700000000000000000000000 kg. You don't get that to change direction "instantly".
Thank you Strange, I understand that now, that you could not get an instant shift and the why's.

36. A slight confusion, you have probably already said this, what are you saying creates the magnetism, the inner core<iron ball>, or the outer core<lava with iron in it>?

37. core.JPG

Is this how the core works?

38. grind.JPG

Explaining the earths noise it makes and the wobble, the bearing grinds.

39. Originally Posted by theorist
A slight confusion, you have probably already said this, what are you saying creates the magnetism, the inner core<iron ball>, or the outer core<lava with iron in it>?
From Earth's magnetic field - Wikipedia, the free encyclopedia
The Earth's magnetic field is mostly caused by electric currents in the liquid outer core, which is composed of highly conductive molten iron.

I have no idea what your diagram is supposed to show. But there are no positively and negatively charged areas, like that.

Outer_core_convection_rolls.jpg

40. Originally Posted by theorist
grind.JPG

Explaining the earths noise it makes and the wobble, the bearing grinds.
There are no "bearings" (although there is a Bering Sea).

41. Originally Posted by Strange
Originally Posted by theorist
A slight confusion, you have probably already said this, what are you saying creates the magnetism, the inner core<iron ball>, or the outer core<lava with iron in it>?
From Earth's magnetic field - Wikipedia, the free encyclopedia
The Earth's magnetic field is mostly caused by electric currents in the liquid outer core, which is composed of highly conductive molten iron.

I have no idea what your diagram is supposed to show. But there are no positively and negatively charged areas, like that.

Outer_core_convection_rolls.jpg

Yes I have seen this diagram, and my second diagram would have the same look to it.

How can the inner core hold its position?

It would surely be magnetized as with the paper clip example, direct contact?

Have we observed these whirl pool effects through technology?

The whirl pools would surely push the inner core to one side?

And not negative or positive as in charged, but negative and positive of polarity of magnetism.

42. grind.JPG

If I flip the image it makes more sense to the opposite of the north pole,

added - and more sense to bouyency

43. Most estimates for the duration of a polarity transition are between 1,000 and 10,000 years. However, studies of lava flows on Steens Mountain, Oregon, indicate that the magnetic field could have shifted at a rate of up to 6 degrees per day about 15 million years ago

extrpolating
(up to)6 degrees per day for 30 days = 180 degrees (or so)

geologically speaking that's almost instantaneous

(from wiki)

44. Originally Posted by sculptor
Most estimates for the duration of a polarity transition are between 1,000 and 10,000 years. However, studies of lava flows on Steens Mountain, Oregon, indicate that the magnetic field could have shifted at a rate of up to 6 degrees per day about 15 million years ago

extrpolating
(up to)6 degrees per day for 30 days = 180 degrees (or so)

geologically speaking that's almost instantaneous

(from wiki)
15 million years ago, would there of been less lava, meaning less diameter of the outer core?

45. It is my understanding that the earth has been almost constantly increasing in size through accretion
as we gain particles from space including water, and some organic molecules

as/re lava, the simple model is the earth recycling heavy plate margins, liquifying the material, and offering a mix back up in the "ring(s) of fire"
doesn't account for the hotspots, nor traps
and as with all models, it's just the map, not the terrain

46. Originally Posted by theorist
Originally Posted by sculptor
Most estimates for the duration of a polarity transition are between 1,000 and 10,000 years. However, studies of lava flows on Steens Mountain, Oregon, indicate that the magnetic field could have shifted at a rate of up to 6 degrees per day about 15 million years ago

extrpolating
(up to)6 degrees per day for 30 days = 180 degrees (or so)

geologically speaking that's almost instantaneous

(from wiki)
15 million years ago, would there of been less lava, meaning less diameter of the outer core?
What does that have to do with anything?

Here's how lava flows can record magnetic pole flip:

When lava solidifies, the rock that forms ends up magnetically aligned with the magnetic field of the Earth. We new lava flows and cools, it will also align with the magnetic field. If the Magnetic field changes direction rocks formed from later lava flows will magnetically aligned with the new direction. Thus lava flows can record the change of direction of the Earth's magnetic field over time. Different layers will be aligned differently.

47. Originally Posted by sculptor
It is my understanding that the earth has been almost constantly increasing in size through accretion
as we gain particles from space including water, and some organic molecules
That is an incredibly insignificant amount. I'm not going to work it out again, but from memory it is about a metre over the lifetime of the planet.

Overall, the planet might be getting lighter: BBC News - Who, What, Why: Is the Earth getting lighter?

48. duplicate post

49. strange
when the planet/solar system was/were young,
'twasn't "an incredibly insignificant amount"?

surface of earth = about 510 trillion square meters.........? so yer saying we 've gained 510,000,000,000,000 cubic meters(or 1/2 that)?-----in what timeframe?

what i meant was that it is an ongoing process with an almost continual net gain, so---------even if only by a cubic inch a year, the planet should have a larger diameter today than 15 million years ago.

.......................................
side note
long ago i read a suggestion that the rotation of the planet was speeding up due to water impounded behind high latitude dams...(like a rotating skater pulling her arms in).....
and
I wonder---if so, then so true for the periods of glaciation?---lower sea levels and higher high latitude mass--
thoughts?
rebounding land masses free of the weight of the glaciers comes into play?

..............................
edit:
no offence to alan moore, but, for me, the center of the observable universe is closer to 41.789 degrees north by 91.59 degrees west

50. Originally Posted by sculptor
surface of earth = about 510 trillion square meters.........? so yer saying we 've gained 510,000,000,000,000 cubic meters(or 1/2 that)?-----in what timeframe?
That is something like 0.00004% of the volume of the earth. Which, given that over 1,000kg falls on earth every second, isn't unreasonable. I think the number was worked out extrapolating the current amount of "stuff" every year over the entire 4 billion years. But obviously there used to be a lot more.

Actually, it looks like it would be about a third of that:
http://www.wolframalpha.com/input/?i=%28%2840000+tons+per+year+%2F+%281+g%2Fcm^3%29% 29+*+4.54+billion+years%29+%2F+%28surface+area+of+ earth%29

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