I had a moment like this as a child, when I was told by many books I could not see the fourth dimension (including Sagan himself). I read the adventures Edwin Abbot describes in Flatland, in a story where a 2-d being is tossed into the third dimension. I have heard countless people speculate that the 4th dimension was time itself, including Einstein.
So I tried real hard to “see” the 4th dimension since age 12. My journey towards this has resulted in a very strange view on life, I can assure you. Most of it would sound totally crazy to anyone outside of fandom, and to half the people inside of fandom. And the best I can do is say I have a general idea, based on what I have seen and try and extrapolate it down to three dimensional theory; if I am correct at all.
But rather than break this down into a discussion of physics, let me tell you a rather odd side-effect.
*IF* the 4th dimension IS time, and I am not convinced it is, it makes for a very convenient way to use the concepts of three dimensional objects in space. Not only “where” it is (3D), but “when” it is(+ 1D = 4D). In this way, an object could exist in the same space if it were different times. The 4th dimension shape of any object shifts and changes like a stop-motion blur through time. Like an apple changes shape as time goes on. To “dumb it down to 3D,” you’d see an apple as a strange object like a cone that fades to nothingness. The thin point at one end is the apple’s creation from a bud, and then at the end, the destruction of the apple via consumption or rotting is where the parts return back to a fragmented atomic state.
But, since the apple is made of atoms, this is an illusion, which is why the 3D model is flawed. But the concept of what makes an apple and apple is what’s being tracked here, and you’d have to define in your model when does an apple become and apple, and when is an apple no longer one? So convert a model down to 2D, say you have a picture of an apple you want to scan on a white background. Where does the picture begin and where does it end? And when you see that apple on the paper, you know in your head that it looks different if the picture was taken at another angle.
When I realized this, I also realized not only is space relative to the observer, but so is time.
Taking our 3D apple, we are seeing a “slice” of the apple as it is NOW. It’s a solid 3D object, kind of round. I assure you a month or so ago, the apple looked very different. It was smaller, and green. A month or so from now, if you somehow did not let the apple get eaten, it would be a mushy brown lump.
After this mind blowing revelation (at age 13, no less), I started to realize that people could also be seen as the same. Indeed, people change as time goes on, but are the same people... but then again, what would you define as “the same person?” The spirit?
I post this not because I want to make a point, but to explain some of my writings at a later date.