Right. Good point. So looking at it from at least a 4D perspective, the universe is simultaneously at it's beginning and it's end, but we only see the part of it that is in our current "now," slice of time. Gonna have to think some more about how that might manifest as looking like everything is moving away from the observer no matter where he might be.
As Dinosawer said, the fourth dimension here isn't time. Time is often considered a half-dimension when we discuss these things. I know it would make Emmett Brown cry, but Marty really needed to think 3.5 dimensionally. Even in 3.5 dimensions, the universe isn't simultaneously at its beginning and its end. That would require the beginning and ending of the universe to have the same time coordinate. That can only occur of the lifespan of the universe is identically zero.
Modern Big Bang cosmology is built on top of General Relativity, helped along with over a century of supporting evidence. As it sounds like you're trying to reinvent the wheel here, you'll have to do it with the past 150 years of data in hand, starting specifically with the study of electrodynamics, which began in earnest with the publishing of Maxwell's equations in the 1860s.
General Relativity is one of the most successful scientific models in history. The only other theories that have survived as many critical tests over the years have been Quantum Mechanics (and Quantum Field Theory), and the Theory of Evolution by Natural Selection. That isn't to say that there aren't aspects of GR which could use improvements (as a Popperian, I'm obliged to admit that even if we got a theory exactly right, we would never, ever be able to be 100% certain of that, and would have to strive for improvements even if improvements would never be possible) -- every scientific theory must be continually and perpetually subjected to critical tests and analysis -- but as far as our knowledge of the universe is concerned, GR is Really Damned GoodTM
GR is built on the concept of differentiable manifolds. That's a fairly densely packed bit of jargon if you don't study multi-dimensional calculus. A manifold is a region which, when looked at closely enough, can look like a geometrically flat region (think of how the Earth's surface appears flat to us on the surface, even if the Earth itself isn't flat on a global scale). Here "flat" means that parallel lines remain parallel. Differentiable, on the other hand, means that the region has no creases and no edges (there is nowhere in the region to which you can fit more than one tangent line/surface/hyper-surface). This means that GR very strongly suggests that our universe has no edges. Without edges, you simply cannot define a centre.
Now, there are two ways you can get a universe (or anything, for that matter) without an edge. You have it curve in on itself, like a circle or sphere (or doughnut, or something like that -- just generally an enclosed, smooth shape), or you let it be infinite in extent. The first case is known, technically, as "finite and unbound", while the second is, well, infinite. In either case, the lack of edges makes it impossible to identify any specific point as a centre.
Another way to think of this is that every place is the centre. If you stand outside and look around, you will see the world extend outward in every direction, and in every direction it will end at the horizon. From your point of view, you are at the centre of the world! But if I go outside and look around, I will see the same thing. I will appear to be at the centre of the world! And so, too, will Dinosawer, or anybody else, for that matter. If we move, we will each continue to appear to be at the world's centre. Not encountering any kind of edge in our explorations, we will never come across any evidence that contradicts our claim -- except for each others' counter claims! So, if we all appear to be at the centre of the world, that strongly suggests that everywhere
is the centre of the world! This is the same thing as saying that nowhere is the centre of the world (if everybody's first, than nobody is truly first).
Alright, so this is where the stage is set for a dynamic universe: It's locally "flat", it has no edges, no gaps, no sharp creases. Space is now a thing with properties of its own (like shape!), and one of those properties is that it can shrink or grow, or twist and fold (but not
crease). From Special Relativity (which is a smaller part of GR), we also know that space and time are different aspects of some greater whole, and that, under certain conditions, and to a prescribed (and now well tested) degree, can exchange properties with one another. We, very creatively, call this greater whole "Space-Time".
This is all well and good in an empty universe. An empty universe turns out to be infinite in extent, flatter than paper, and completely static. Once you start adding stuff
to this universe, though, it actually wants to collapse in on itself. I don't mean that the bits of stuff that you seed into the universe are attracted to one another, so they start floating toward one another, either. I mean space itself starts to collapse; the stuff gets closer together without
having to actually move through
space. This is kind of like letting the air out of the balloon mentioned up thread (blow up a balloon, draw some dots on it, and then let some of the air out; the distance between the dots will shrink, and it will shrink in every direction
Now, it's also possible to make the universe expand, too. It just requires the proper kind of energy. This is what led to what is commonly called the Big Bang (in Big Bang cosmology, it's known as the "inflationary period" or "hyperinflation"; the "Big Bang" isn't usually considered to be an event in and of itself; there is merely pre-inflation, inflation, and post-inflation). It also drives the continued expansion, and the acceleration of the expansion, of the universe.
Space is growing.
Now, keep in mind that this isn't speculative. We know the universe was expanding quickly 13 billion years ago, because we can measure that. We know that the expansion slowed for about 8 billion years, because we can measure that, too. And we know that about 5 billion years ago, the expansion started to speed up again; we can also measure that.
We also know that space exhibits geometry, because we can measure it (hell, we can see
it; look up "gravitational lensing", where the curving of space itself acts like an optical lens). We know that space and time can exchange properties, because we can measure that
. We know that the amount of curving, and the amount of exchange, matches what's predicted by Relativity Theory, because we can compare measurements to calculations.
Keep in mind, too, that nuclear power was a prediction of Relativity Theory. E = mc2
(or, for the nit-pickers out there, E2
) is straight out of Einstein's papers on Relativity. This is also the basis for our understanding of how stars are powered, and as our ability to see ever deeper beneath the surfaces of stars increases, those predictions and the predictions derived from them are agreeing with our measurements.
In short, Relativity Theory is repeatedly upheld by increasingly specific and careful measurements across multiple fields, and Relativity Theory predicts that the universe has no edges and no centre. It predicts that space can, and does, grow or shrink depending on what can be found in that space. Finally, it predicts that "the Big Bang" happened everywhere, simultaneously, and that it continues to this very day (just at a slower rate; this was discovered in the 1930s by Edwin Hubble). It also strongly suggests that the universe is, in fact, infinite in extent.
The Big Bang wasn't an explosion. It was an expansion of all of space itself, everywhere, in all directions, which resulted in a universal decrease in density.