[Repost from earlier edition. (way back)]
(Expanding on tweet here. )
Earth enlargement by the accumulation of space dust won't work. It's a tempting idea if we think of the planet accreting from planetisimals and that infall is just a continuation of the same process that got the planet together in the first place, but it fails on simple mass considerations.
If we could roll the entire crust up like a carpet, including the crust of the ocean floors, and shove it down into the mantle, it wouldn't make one whit of difference to the size of the planet. That is, everything that ever fell, together with all redistributed sediments, as well as carbonate precipitates, volcanic extrusions and intrusions, and granites derived from the Earth's interior (which really shouldn't be counted at all) , ..the whole lot, .. from the Archaean to the present day, it would hardly make any difference. Even if all of it were cosmic dust it would make no significant difference whatsoever to the size of the Earth. So there's no way dust accumulation from cosmic infall could have anything to do with the growth of the planet. Case closed.
Unless the base of the crust is being resorbed into the mantle at the same time as stuff is falling on the top. But that can't be either, or stratigraphic sequence as we know it (right back to the Archean) would not exist. As things are, we do have continuity of stratigraphic sequence to the Archaean.
Nevertheless there's a certain logic in it that's appealing. Stuff needs to come from somewhere. And it needs to be added. So, what if we're just looking at the wrong scale? Could it be that cosmic infall is in the form of elementary atomic particles that are somehow swept up directly into the core of the earth, possibly via the magnetic field ? The Earth with its iron core rotating in the electromagnetic field of the sun's radiation is like a big electromagnet after all. And the atom comprises mostly space. And it is said that the size of particles to the size of the atom is something like the size of peas to a football park, ..or like the size of planets compared to the space between them. So the Earth is not as solid as it appears. At that scale there is plenty of space (theoretically) for particles to find their way through the Earth's interior even though to us matter seems impenetrable.
What is the interface that the stuff of matter must cross in order to have mass? What if once it has crossed it, mass is created out of mass? In other words, if mass 'grows', by a kind of cell division? We have seen how mantle material is added at the spreading ridges by cell division, ..So..?
[Added 20170404 :- See Gene Ellis's view on this who considers TIME could be the active ingredient. [Other links.]
But even though we might speculate on the process in relation to the mass of the Earth today, it has to begin at the beginning, and if we're going to have a mechanism to make the planet grow, then it has to be at least considered that it could be somehow related to the same process that created the Earth in the first place. And if for one planet, then for others too. This means that planet Earth cannot be considered in isolation, but as part of the family that includes the Sun and the Gas Giants. And we might as well throw in the Moons as well. It really gets to be quite a can of worms, once we start thinking about it.
Not only that, but it leads us into re-considering the way that material organises itself, from subatomic particles to atoms to molecules to crystals, and the part played by structured symmetry in growth.
What is the nature of the 'interface', the 'bridge' between electrical force that binds the atom and the gravitational force that, across the atomic interface, organises mass into such huge lumps of stuff as a star? If we're looking for a mechanism for the creation of mass then it makes sense to consider how the particles that make up 'mass' (in whatever form we consider that stuff) come into being, and to clearly recognise and understand the realms of scale of the interfaces at which different sets of processes operate. [The 'interface' effect - the scale at which stuff stops being what it was before and becomes something else instead.]
These are not questions that can be answered within the scope of geology, but there is something about the 'immaculate conception' ('creationist') model of planetisimal accumulation/ formation, where an invariant mass of 'stuff' was there in the first place - always was and always will be, imbued with the mass and rotational characteristics we see today - that seems very iffy. The increase in the size of the Earth that is empirically observed yet for which there is no known explanation, is making it clear it is time to ask some hard questions of quantum mechanics and astrophysics, that is, if 'science' as promulgated by real scientists can rise above their extraordinary capacity for being masters of the college ( with their view that what they don't know isn't knowledge), and consider the evidence staring them in the face instead of ignoring it - that the Earth is getting bigger. The evidence for, lies in the creation of the ocean floors (and all other Earthly parameters). The evidence against? .... lies in the hubristic assumption by scientists that this cannot possibly happen. Properly stated this should carry the riders, "there is no known way," ,,, and "within the bounds of understanding." Because when it comes to answering the really big questions we are still as babes in the wood goggling with fixed curiosity at what surrounds us.
Back to the future, flat Earth, and geocentrism.