I had a look at the first of the videos about comets and it was sooooo boring I couldn't stand it more than a minute, the guy has to be one of the worst speakers I have ever heard. So I didn't perservere to here what was said in detail
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I have read about some suggestions that magnetic fields and electric currents may be a factor in the creation of structure in galaxies (I think Alfven was one of the supporters of this), which is a bit "out there" but a possiblity, after all electrostatic forces are MUCH stronger than gravity...you only have to comb your hair to pick up bits of paper to overwhelm the gravity of the whole planet!
Usually if I hear a theory that has been supressed due to a cover up, I switch off. Such theories do themselves a severe disservice by adding stuff like this.