I've read a bit about "dark energy" to explain how the expansion of space can accelerate and overcome gravity's tendency to pull space together again.(adsbygoogle = window.adsbygoogle || []).push({});

I'm just a curious layperson, so please have me excused if my questions don't make sense or are very naive. I've tried searching for answers in the forum search, but didn't find specifically what I was looking for.

My questions are in short:

1: Is space actually the 4D "surface" of a 3D sphere?

2: If so, why is it assumed that gravity works in 4D and not 3D?

3: And why is it assumed that the expansion of space is governed by forces and rules in 3D space and not 4D?

And here a better explained version of what I'm trying to understand:

To explain why every point in the universe sees it as being homogenous in every direction and it seems that we are in the center of the expansion, it is often assumed that space is the 3D volume that forms a surface of a 4D sphere, and to illustrate this, it is often reduced by 1 dimension and shown as analogous to a 2D space (with ants!) on the surface of a 3D sphere (ie. balloon that is being inflated so that it expands).

So my first question is: is this a correct representation of the Universe? Is it actually (at least) 4 spatial dimensions?

Secondly, in this analogy, the true expansion of the balloon is from the 3D center of it. The true center of the balloon is outside 2D space and at a 90° angle to every point in 2D space. Why would gravity, which is only (or is it?) observed to attract massive objects toward each other along the 2D surface be expected to slow the 3D expansion that is happening in relation to the 3D center of the balloon? Shouldn't gravity work only along the 2D surface of the balloon?

Thirdly, if this 3D balloon's expansion is accelerating, shouldn't that force (or dark energy or whatever is causing the acceleration) be the one that actually works from the center of the balloon to the surface (in 3D space) due to processes happening inside the balloon, and not necessarily within the 2D universe that we mere ants can observe?

To a layperson it might seem that the ants are trying to create complex mathematics for forces and dark energy working along the surface of the balloon in 2D to explain why the 3D balloon is expanding faster and faster while the real answer lies deep within the 3D balloon, in other words outside our entire 2D universe - perhaps not detectable in 2D at all as the true expansion and its associated forces and mechanisms are exactly at a 90° angle to every point in the 2D universe (assuming they work from the center of the balloon outward).

Just increase all I've written by one dimension and you have our universe.

But as a layperson I also know that this may be an over-simplification of things, and I'm not trying to yell "hey, all those scientists have got it all wrong!", I'm just here to learn from those who know a lot more than me about this stuff. :)

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# Why would gravity slow down the Universe's expansion?

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