Could the 'Upside Down' be real?

In honor of tonight's release of Stranger Things season 3, I present the following argument in favor of the existence of the 'Upside Down'. Not like in the TV show, of course! The title of this post is just click-bait :-)

But in all seriousness, and apropos of nothing, I have been thinking about the difference in Einstein's famous equation for energy, e=mc^2, and how it differs from other similar physics equations. (Actually, I think this whole chain of thought began with a wistful memory of how much math I learned in college, including the derivation of e=mc^2... oh, well!)

THE PROBLEM

There are many examples of math and physics equations of the form:
  'TOTAL'  =  one-half-of-something  (multipled-by)  something-else-squared

For instance, kinetic energy = one-half MASS x VELOCITY-squared

So why does Einstein's energy equation = ALL-OF-MASS x light-velocity-squared?

THE SOLUTION

My conclusion: the MASS we can measure is only HALF the actual mass. In other words, there's another entire 'mirror' universe equal in size to our visible universe. We just don't know how to access it...
__________

This conclusion is actually supported (maybe...) by the current models of a Grand Unified Theory (GUT) of physics which predict multiple additional dimensions  -- though I think they predict that those dimensions are extremely extremely small. I'm reminded of the classic novel, "Flatland", which discussed the idea of how our 3-dimensional world would appear to someone accustomed to a 2-dimensional world. You could 'pick up' that 2D person and they would 'disappear' from their world, even though they were still entirely intact and whole. Then, you could return them to another spot in their world and it would appear as if they'd transported. If we could demonstrate and control our position in one of these hypothetical extra GUT dimensions, we could effectively do the same thing in real life.

Another cool idea: if we could understand what causes gravity in the same way that we now understand magnetism, we could build our own artificial gravity-generators. This would make space travel much easier since we wouldn't need rockets, instead we would just generate 'reverse' gravity and we'd be launched into orbit by our centripetal motion!

P.S. Don't quote me, I don't really know what I'm talking about ;-) In fact, the 'one-half' in kinetic energy comes from the fact that we're integrating (adding-up) the energy required to accelerate something from zero to some-velocity, and if you graph that it looks like a right-triangle where the area is HALF the height (x) width.