The big bang wasn't inside the universe to push anything. The big bang was the universe.

Think of it like leaves on a puddle. As water(space/dark energy) flows into the puddle. It expands. The leaves don't. They just spread out over the surface of the puddle unless they are bound together with other leaves via surface tension(gravity).

I saw a really good demonstration of this once, but I can't seem to find a video of it.

Basically imagine a rubber tube with 4 balls equal distance apart from each other.

–0–0–0–0–

If you stretch the tube from both ends all of the balls move an equal distance apart.

----0----0----0----0----

There is no one ball that is the center or the starting point. However if you focus on one ball while stretching it will seem like the others are moving away from it. But in reality they are all moving away from each other at the same rate.

A lot of people describe the first moment of the big bang as infinitely small, dense, and hot. These descriptions may approximate that first moment of existence, but they slightly miss the mark because in the very first moment of existence, size, density, and temperature didn't exist. There was nothing to compare anything else against.

Instead, let's visualize that moment as infinitely same. Erase all thoughts of violent explosions happening very quickly and instead just imagine a single point of light. Not big, because size requires multiple things. Not small because it encompasses everything. Just one infinite same.

Now, since it's hard for us to visualize change in an infinite void that is simultaneously nothing and everything, imagine that point of light as a magical tank engine at the front of a never-ending train. And our job as conductors of that train is to get to the caboose at the end.

The train cars could theoretically go in any order, but because we conductors are beings of time who need them to arrive on a schedule, we must visit each car in a precise order. And before we can access a car, we must make it unique by showing it something that has never been seen before.

For the first car, this is easy. We simply show it the tank engine at the front of the train. So, the inside of the first car transforms its interior into a copy of the tank engine it's attached to.

But when we arrive at the second car, things are more complicated. The cars have already seen the tank engine. So, instead, we show the second car the first car. And the second car transforms into a copy of the first car and the tank engine attached to that. And inside the copy of the first car is another copy of the tank engine.

As you can imagine, the further down we get on this train, the more this starts to get out of hand. Copies of copies of copies abound. The magic train is powerful, but as mortal conductors of time, we worry our own powers may have limits. So, to reduce the burden on ourselves, we take some shortcuts. Instead of trying to visualize increasingly long nested copies of trains inside each new car we visit, we start to conceptualize these copies as amounts, or amplitudes. When we open the door to a new car, all of the amplitudes inside resonate and interact, becoming maybe more abstract than they are in reality. They form spatial dimensions and physical properties, as mediated by fundamental forces.

These aren't set in stone, but determined by the lens through which we view them. And when we look through specific lenses, we see these forces causing certain repeated amplitudes to intermingle and stabilize to the point that even though all of the train copies are further nested when we step into the next car, we can recognize and identify some of the same structures, just shifted slightly in their spatial relationships since we last witnessed them in the previous car. We call these persistent formations matter. And as their shared spatial relationships cause them to cluster and coalesce, we refer to that as gravity.

While in the early cars, this continuum of space and matter is not impossible to conceptualize, the more cars we travel through, the more apparent it becomes that these increasingly complex objects are becoming more and more isolated from each other. At every scale of amplitude, each nested car is attached to its own tank engine. While these engines can interact with each other virtually, at the end of the day, they are all just virtual copies of the train we are on. It is entirely impossible for any one of these tank engines to travel so far that it reaches the edge of its bounding box. Because that bounding box is just a lens through which we imagine overlapping traits of increasingly many very similar objects. And the more of them we imagine, the more space is required to provide the virtual framework of this lens.

So, when we feel like we are experiencing random events in our small subsection of the universe, those events are not truly random, but instead the result of our precise position in the the universal train we've been virtually sliding through for over 13 billion years. The universe has become so large that it contains every possible event that could have happened in this span of time. The events are not random but calculated, and duplicated every moment so that every time we enter a new train car, two copies of our observable universe exist at a distance so far apart it's impossible to comprehend.

And when we observe celestial objects apparently propelled away from each other at increasing speed, they are not really being pushed or pulled anywhere. It is simply an artifact of trying to keep track of the "same" object in rapidly advancing train cars, while each car doubles in size to contain everything the previous car had, as well as everything new that might emerge from the duplication event. The celestial objects year by year, and indeed ourselves from moment to moment, are never the same thing twice. It's an illusion brought forth by our brains being born into a cosmic flipbook.

Even something as simple as seeing multicolored pixels on this screen is not real, but the result of virtual "tank engines" moving into the same spatial zones occupied by our retinas, which are themselves constructed of virtual trains of varying size. The reason photons move at a set maximum speed which makes them exempt from experiencing time is because they are all just virtual copies of the real locomotive which is driving the whole train. Every photon in our universe is just a make-believe copy of the very first moment of the big bang. A specter of infinite sameness.

So, objects in our universe aren't moving apart as much as the space between them is increasing to account for the overhead of a universe with constantly growing entropy and uniqueness. The extra space represents a boundary which limits how far light can travel and affect matter in its realm of influence. If you're still reading this, somewhere out there, in a part of our universe so far away that light from our known universe will never even remotely reach, there is an opposite you made of antimatter reading the exact same thing as written by an opposite me. But we are only made of matter because of a virtual compression of sameness, so that antiverse may be the exact place where the curvature of the entire universe loops back around and is overlaid upon itself. And the uncertainty of photons may arise from the fact that there are two identical universes overlapped and constantly exchanging probabilities. And this may be the compressive property which allows the fundamental forces to exist in the first place. So, say hi to yourself. You're the reason you're here.

Here's another way to think about the location of the big bang.

If we look at the night sky, between the planets and stars, into the darkness we find there's a faint glow emanating from everywhere. This is the cosmic microwave background, the oldest electromagnetic radiation that has taken the longest possible time to reach us because by this construction you avoided all the other objects in the way. This extends your view of the past to its maximum value: the age of the universe, which is literally all of the available time for photons to travel. Note that this is a simplification because it makes some assumptions about the transparency of the early universe, but it suits us fine.

It's coming from everywhere because all of those places were there at the big bang. Where was the big bang? It was over there. And also in the opposite direction, there. Because all of those places were here.

Try this:

So everything in space, every object had to get to where it is via time. It travelled there. Everything can't be anywhere without time as without time it wouldn't have been able to move there. Time is a constant graph, and as it moves forward, things move around and as such, space is able to exist. This is why we consider space and time to be linked.

Now consider this: if one was to plot a graph of space and time on an x y axis to track an object, there is a point on the graph where time has to be zero, and as such space has to be zero.

This is the big bang.

It is the beginning of the graph. When time was zero, and as such so was space.

Space did not burst out from a single point that we could find out there in space, as there was no point. everything was still everywhere much like it is now, except everywhere just so happened to be so close to one another to be at the same point on the graph. When time began, it just about instantly expanded out, everywhere in every direction. There is no 'center' to this expansion, just like if you blow up a balloon there is no center on the surface of the balloon, it just expands everywhere, and more importantly with time we are able to quantify this.

Think of a balloon. Squish the deflated balloon as where everything was. All of it started at a similar point but then the balloon started expanding and everything is moving away at an accelerated pace from each other

When you look far away, you're looking backwards in time. If you look really far away, you look really far back in time. If you look far enough away, you'll see the big bang.

If you move a thousand light years to your left and do this again, you still see the big bang. Even though your "center" has changed. The big bang is more like a singularity in time than it is in space

Well, if the sphere was there all along, yes, it's possible. Very unlikely, but possible. If the whole universe is moving somewhere, we have no way to detect it. Note that this doesn't exclude the Big Bang, that still happened even in your scenario.

It's just one of those unprovable things - like whether there's a God or whether we live in a Matrix. Unprovable and thus irrelevant.

It is dark energy, and not dark matter, that is believed to be causing the accelerating expansion of the universe. Dark matter has the opposite effect - gravitational attraction.

No, the big bang happened everywhere, not just in a single point. The PBS documentaries will tell you as much.