Originally posted by coldangel_1:
I shall now narrow my eyes in mild disdain.
Have at it!
Level of existence or consciousness. In effect a *plane*. However many planes of existence there are, 'dimensions' as it were, they are what comprises a single Universe.
And there it is:
This seems to be the main bone of contention.
There are those who say such areas of space-time are a part of our own universe.
Others say they are separate universes.
Personally, I take no stand one way or the other.
If I may make an analogy:
Some weeks ago, the IAU “demoted” Pluto from its traditional status as a planet, calling it a “Dwarf-Planet.” This caused quite the uproar in the media, with newspaper stories, magazine articles, TV news reports, sound-bites, blog entries, and charts, and graphs, and pictures, yadda, yadda, yadda...
But
PLUTO had changed
not one whit!If such alternate universes, dimensions, planes, or whatever exist, they are what they are regardless of what human scientists, science-fiction writers, or
we, for that matter, choose to call them.
Honestly, what are they teaching in schools these days? Golly gosh, the drivel that passes for advanced quantum mechanics, I don't know...

I haven’t a clue either.
The only mechanics I’ve studied to any degree are auto-mechanics, and celestial mechanics... but that
was a few years ago.
I wanted to become a Quantum Mechanic, but I couldn’t afford the union dues... 
[Edit]
Originally posted by Shiny:
Okay, picture a two-dimensional universe. Now picture another two-dimentional universe laid atop it in the third dimension.."
In other words, "M-Theory."
"Another dimension" has long been science-fiction shorthand for "Another universe parallel to the first, located in the next unseen dimension."
It's a plot device (however you want to call it) allowing a writer to explain a situation, and then have the characters experience variations on it.
Not unlike Larry Niven's "All the Myriad Ways," or any what-if simulation in Futurama.
Note to self: Read all the *@&#^$%! posts first!