*I was lying in bed contemplating existence when i had an epiphany (as one does :P). As the title suggests; i was exploring the fourth dimension, more specifically the fourth dimension of space rather than ‘time’ as a fourth dimension. While my profession is logic based, i’m not a mathematician. Certain areas of maths and physics deal with up to and beyond eleven dimensions but i was trying to get a layman's understanding of the fourth spacial dimension. Something to satisfy subconscious curiosity.*

I imagined the fourth dimension as a long metal rod. If you were to slice that rod into paper thin discs, each one would represent the three spacial dimensions at a moment in time. That rod would be curved in certain areas representing the path of history. Lets say time travel was hypothetically possible. One might be able to go to a certain “disc” or set of discs and heat them up giving the rod the ability to change it’s shape thereby altering the course of history. The first thing that comes to mind when altering history is time travel paradoxes: if a person goes back and kills his younger self, will it erase the event of him from travelling back in time in the first place.

In the time travel paradox one can think of the rod instead as a tree-like structure; if a person travels from one branch and kills himself then the new branch will have a world without that person. The initial branch remains in the state it was in. While the tree could have an infinite number of possible branches, i think the number of probable branches is finite. Fractals are evidence that things tend to fall in place naturally.

There would also be an infinite number of possible trees. Each possibility being a different set of four spacial dimensions on a different timeline which i would imagine would be the introduction into the fifth spacial dimension. That’s what went through my head, if anyone can correct or expand on this please do so.

## 4 comments:

It depends what you think happens in the fourth dimension. If there's matter in it, it should be interacting with ours (the effects should be noticeable even if we have no inkling of what's going on). The forces they exert should be measurable. But all the large world physics I know of only has matter in 3D interacting. Which means it's most likely that the fourth dimension is mostly empty, with the universe's matter clumped up at a single coordinate in the fourth dimension.

I think of it like this - I start with a point, and drag it along a straight path to make a 1D line. Then I drag the line perpendicular to itself to make a 2D sheet. Then I drag the sheet perpendicular to make a 3D volume, which I can then drag to make a 4D hyper-volume and so on.

I think the fourth spatial dimension doesn't necessarily imply alternate histories - because the alternate histories don't physically interact. They'd be more like entire sheets of universes, lying on top of each other.

You should watch the movie Primer, the method of time travel used in that movie circumvents the paradox of being able to go back in time and stop yourself from going back in time (or being born etc etc) by limiting the device's scope to when it is turned on. In other words, I turn it on today, and I can only ever return to this point. It also deals with multiple instances of the same person.

But your 4 spacial dimensions theory is much better than the parallel universe theory in my opinion even though it is only subtly different from it.

I think my layman's explanation is a just simplified view of the parallel universe theory (i may be completely off though :P). Each "disc" is an entire 3D universe at a point in time. Each branch is a parallel timeline and the tree has infinite possible growth patterns.

@Alex de Oliveira The volume of a hypercube would be the the volume of the 3D cube multiplied by all the space it has ever occupied. That's how it "interacts" with the other three dimensions.

See http://www.tenthdimension.com/

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