I had a discussion with a guy on MSN that I thought would make an interesting thread for Mad Scientists. He is convinced that the theory of subduction is bunk and that the earth isn't a fixed size but is slowly expanding, and this explains all the continents developing from one mass.

So I'm curious as to what your opinions on this hypothesis is? I think it's a cool idea but I dunno if it is right or not.

Where does the extra mass come from? I mean, if the earth is getting bigger, then there either has to be more mass, or the material earth is made of is getting less dense.

And you'd think earths gravity would prevent it from getting less dense.

^ thats it. where is this mass coming from? it needs to be a very large amount to cause all the changes that this guy is attributing. something not easily missed.

but yeah, the idea of one plate sliding over another one isn't exactly complex, and if this guy doesn't belive in it then he is wrong.

this isn't so much interesting as tedious.

I asked him that too.

Since he can't get an account, but has seen the thread, I'm posting his reply for him:

Wait, first he says that continental drift (and, by extenion, subduction theory) explains the empirical evidence better than the idea of an expanding Earth, but then he posits his theory of planetary mass increase via sub-atomic pair production.

Which is it? The level of pair production that would be necessary to affect a significant increase in the size of the Earth is ridiculously large. This is a terrible theory.

this idea is just comming out of my ass so im not saying this is how it is, just an idea.

the earth surely gains some mass constantly, just from random stuff comming out of space. but also i would not be surprised if as the earth cools, for whatever reason (im not a geologist) it becomes less dense.

i really dont know though. i mean im sure about the stuff comming from space, but i doubt it would be noticable even over the entire course of human history.

Well here is his reply:

I feel like an interpreter between foreign countries. O.o

well since I'm open to new theories that attempt to describe natural phenomena, I won't flame, but simply ask:
If what you say is true, explain the cause of earthquakes and how mountain ranges are growing in size?

and also, your argument that ''no other planet experiences plate tectonics and subduction'' is a bit ridiculous, Venus-quakes for example are being studied by the E.S.A,

''It is as if the planet has completely resurfaced not long ago, by some massive planetary crust phenomenon. Moreover, it also seems that some surface features have formed only recently. This may suggest that the planet may still be internally active.''
source:
http://www.esa.int/SPECIALS/Venus_Ex...IX5TI8E_2.html

I will say the earth does gain like 10 tonnes of 'space dust' a day, however he is absolutely and completely wrong about everything else. One fact that was used to help prove plate tectonics is all the sedimentary build up on the ocean floors is relatively young, compared to the earths age. So the question was how could our earth that is so old have so little build up on its ocean floors? Well the answer is because the plates are continuously being push below with new oceans floors being created.

Um...no. The oceans are also on top of plates, they're just thinner. Plates float on the mantle.

Yes, the plates all ended up running into each other at one point. This is called Pangaea.

As for them being connected across the Pacific, what the hell? They didn't need to form a ring to all be connected. There was an ocean surrounding Pangaea, called Panthalassa.

There is a mid-Atlantic ridge where magma oozes up from the mantle, constantly producing new seafloor. This is not disputed, as he later says. However, I'm pretty sure the Pacific is mostly old seabed, and is shrinking as the Eurasian Plate and the North American Plate are pushed apart at the mid-Atlantic Ridge, causing them to be forced together on the other side of the planet. Thus, the Pacific Plate is being subducted beneath the Eurasian and North American plates, causing the Ring of Fire as the newly melted subducted parts of the Pacific Plate rise to the surface.

OK, the problem is that this guy had a really bad 8th grade science teacher. The plates DO NOT SAIL ACROSS THE OCEAN. Nobody claims this. All plates, oceanic and continental, are floating on top of the mantle.

The earth does pick up millions of tons of debris from space but I'm pretty sure its effect is miniscule plus that wouldnt be expanding.

Volume expansion.

Not mass.

/thread.

wtf? volume expansion? the earth is becoming less dense? why? how?

Let's assume, for one wild moment, that a supposed increase in crustal mass could be accounted for purely by gamma radiation emitted by the Sun. In order for that to happen, the emitted gamma radiation would have to strike the surface of the Earth for this process to occur.

And that's the problem - there's an atmosphere that absorbs all gamma radiation in the way, and it's been there for an extremely long time.

Guy's full of it.