If the big bang happened is still in question to this theory. It also relies on more about what we do not know than what we do know. So this is more just suggestion than of fact, which facts are not known yet about the origins of our universe yet, everything is assumption based on limited observation.
It is said that by taking measurements of the stars movements the universe is expanding. That the distance between each galaxy is growing and growing at a faster rate as time progresses. The majority of these galaxies are moving away from each other. There are a few like Andromeda
Image of Andromeda galaxy: Pixabay. User:Xavi77
The Andromeda galaxy I said to be on a collision course with our own galaxy. this is not predicted to happen for millions of years yet. We have time to plan our escape.
This galaxy seems to be rouge in the grand scheme of things as it is not moving away from all other galaxies but heading toward ours. Why is this galaxy not doing the same thing as all the others. Or are we the galaxy that is out of sync with the rest.
Do you know of the Fibonacci sequence, The addition of one number added to the previous.
0 + 1 = 1
1 + 1 = 2
1 +2 = 3
2 + 3 = 5
3 + 5 = 8
Making the sequence go 1 2 3 5 8.
This sequence is seen in the spiral of galaxies and many forms of life. I bring this up to mention the spiral.
Image by user geralt on Pixabay.
This spiral pattern does seem to be a natural re-occurring thing is our universe and it is not beyond the realm of thought that maybe the galaxies are travelling a course through space on a spiral of orbit of this sort. This would explain the movement of galaxies and the appearance that each is moving away from all others at greater and greater speeds.
In some cases like with the Andromeda galaxy and our own. It is likely that our galaxies had a pull on each other due to proximity while on an inner part of the spiral.
For the increasing speed at which the planets are moving apart from each other. you will notice the same increase in the size ratio stays the same. While the distance between a set measurement will become straighter with each expansion of the spiral.
Taking a distance of 1000 miles, This can be the inner part of a spiral and complete one full rotation of a central point, as it complete another rotation of this central point and expands, 1000 miles will no longer be enough to complete a full spiral. This 1000 miles will have been reduced to part of a rotation and the angular curve needed to travel this distance would have straightened or lost some of its curve. Less curve means there will be less drag. Less drag means the galaxy will move faster. Explaining the increasing speeds galaxies are moving away from each other at.
We can only see one small part of the universe, and we are taking our measurement of the full thing from that, The universe and what it has to offer is not yet known, How big it is can only be assumed. The galaxies and starts have been moving for billions of years. we have watched the movement of them for a few thousand years. We have only gained understanding of what they are in the last few hundred years. To think we know enough to be able to figure out its mass is to place ourself above the knowledge we have.
The universe is infinite and expanding, and I don't think it's easy for anyone to imagine how big it really is.
The universe is too big for human imagination. It is...at least for me...the biggest mystery I can think of and the most fascinating.