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Message: <blockquote data-quote="freyar" data-source="post: 6681333" data-attributes="member: 40227">Haven't seen the movie, but that does sound pretty hokey!  But, just for fun, let's look at Umbran's suggestion that there's some kind of undiscovered particle that can change electromagnetism (and shrink atoms/molecules).  Actually, if it were a particle, you'd probably have to stick one inside every atom, which wouldn't be convenient.  Fortunately, every fundamental particle really comes from a field (like electromagnetic fields go with photon particles), and fields fill space.  So we need a field that controls the strength of electromagnetism.  This is not so far fetched, actually --- remember that the value of the Higgs field controls the masses of many fundamental particles in the Standard Model of particle physics.It turns out we have to look beyond the Standard Model for a field that can control the strength of electromagnetism (really, we're talking about changing the value of the electric charge).  But then it's not too hard to find something appropriate.  Most extra-dimensional models (whether in string theory or not) as well as "supergravity" models include fields called moduli, which can control the strengths of different forces, etc.  So you just have to find a way to adjust the value of the appropriate moduli fields for the person you want to shrink (but not anything else, I guess).  That, of course, is the hard part; like the Higgs particle, corresponding moduli particles have to be heavy, which means it takes a huge amount of energy to change the value of the field, so you'd probably actually vaporize the person you're trying to shrink.  Ooops!The fact that moduli control the strength of fundamental forces is a very appealing part of extra-dimensional physics/string theory/etc.  In normal particle physics, the strength of a force is just a number, and you just have to go measure it.  There's no way to figure out why it takes a particular value.  On the other hand, if the interaction strength is controlled by a field, you can in principle ask about what kind of physics determines what value that field should take.  Of course this is a hard problem, but it means that at least theoretically you can try to predict from first principles the strengths of fundamental forces.  It also opens up the possibility that maybe the field value and therefore the strength of the force was different in the very early universe.  There have actually been a number of studies that looked at galaxies very far away to determine if the electromagnetic force strength changed even a tiny amount over the age of the universe.  I think they're finally settling on the answer "no" (though it's not an easy measurement and I believe there have been claims in the past of "yes"), but, from a particle physics point of view, you'd expect the field value to be very well settled at its present day value long before galaxies could form.</blockquote>

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