Infinite vs. Finite Universe | Solidifying the Basics

It's also time to note that this book (and my journey through it) is a book "about God...or perhaps the absence of God." A touchy subject as always, but at this point in my life, I am a man of science, but still very respectful to other views.

So continuing our journey through the wormhole, let's get to some (relatively) weirder things. Again, this is all still very basic and just for me to keep my ideas together.

Here's the thing: Newton knew all the math that dealt with gravity, but he didn't actually know how it worked. His numbers matched observations all around, but he had no idea why there was gravity in the first place. That's when Einstein steps in.

But before we get into that (which will be left for the next post), here are some questions he asked using the information he did know. What's the universe actually like? Is it finite or infinite? Had it existed forever or did it begin at a particular point in time?

If all bodies attract one another, that means all bodies should be in a constant state of motion. So, that would also mean that they should all fall together at some point. This scenario would occur if there were "a finite number of stars distributed over a finite region of space". However, if there were actually an infinite number of stars distributed over an infinite spacial region, then this would not occur since there would be no central point for stars to fall toward.

Whoa, hold up. So either everything falls to a single point or space is infinite?

In an infinite universe, every point would be the center of the universe since there would be an infinite amount of STUFF on all sides of that point. Instead, it was realized later that the correct way to approach this dilemma was to consider the finite scenario, in which all stars fall in on each other. What happens if we add more stars on a more or less even distribution outside of this region? Well, according to Newton's law, it would make no difference to the average gravitational attraction on all the other stars, so everything would fall in just as fast. Thus, it's quite impossible to have an infinite static model of the universe where gravity is always attractive.

No one in the past suggested that the universe was either expanding or contracting. It was assumed that it always existed in an unchanging state. Here's why this can't be:

Another reason why the universe cannot be infinite and static: think about it, if the universe were endless in all directions and was never-changing, then every line of sight into the sky would eventually land on a star. That's just the definition of "infinite". Direct a straight line from your eyes to the sky and eventually, being an infinite universe, that line would end up on a star. This means that there should be light coming from every single point in the sky and our sky should be lit up brighter than the sun. That's obviously not what we see. Therefore, the stars had not been burning for eternity. Rather, they were turned on at some definite point. In this case, some stars' light simply may not have reached us yet.

And we come to it at last: How did these stars turn on?

In 1929, Edwin Hubble peered into his telescope and discovered that distant galaxies were rapidly moving away from us. This means that the universe is expanding, which also means that at some point in the past, everything was much closer together. It can further be said that once upon a time, all points were the same point. At this stage, the universe will have been infinitely dense.

Hubble's observations suggested that there was a time when the universe was infinitely small and infinitely dense. Under these conditions, all laws of physics and science familiar to us break down, including concepts of time. The idea of cause and effect, it is claimed, is nonexistent. Anything that occurred before this state had no influence on events that followed. After this point, however, time was "created" from the event known as the Big Bang.

So the final, ultimate, rewarding, heavenly-angel-choir-resounding goal here is to find a Theory of Everything (TOE), a theory that works to explain all of the workings of the universe, from the scale of galaxies to the most elementary particles of matter. It turns out, though, that it's pretty tough to find that theory in one go. For some reason or another, the laws at the very very very large scale behave differently than the laws at the very very very small scale. These two behaviors are the main categories of theoretical physics: the general theory of relativity and quantum mechanics, respectively.