[CanYouExplainThis (OP)]

Going by the Big Bang theory - EVERY single planet/star/moon/rock etc..ABSOLUTELY EVERYTHING and anything!! - especially the things with solid physical attributes would had to have started off from one big rock that went bang. One massive big starting point. Planets don’t just spawn out of thin air. This surely implies that at the very start of creation there must have been one ridiculously big ass rock that broke into infinite amount of pieces. Either that or planets and everything else physical just spawned out of nowhere and expanded by themselves? As I understand planets do not grow by themselves, they can gather mass and size through external causes such as meteors, asteroids etc crashing and into them. Do people just think that there was a Big Bang and an infinite ammount of measurable physical rock (Rock is definitely not the right word but you get my point) was born? If the universe is infinite then this theory does not make any sense.

[Kryptid]

The Big Bang theory does not posit some giant, primordial rock. Rock is composed of elements such as silicon, aluminum, iron and oxygen. Those elements were not around early in the Universe. Instead, those elements formed as a result of the fusion of hydrogen inside of stars. That hydrogen, in turn, formed very early in the Universe when single protons and electrons combined to form hydrogen atoms. Before that, the Universe was too hot for atoms to exist. Instead, there was a kind of "soup" of subatomic particles.

[Janus]

In the earliest stages of the big bang, the universe was much different than it is now, under these conditions, those properties that cause what we consider "solid physical attributes" didn't even exist.  What makes a rock "solid"?  It's the interaction of electromagnetic fields.  These fields hold  the atoms in position with respect to each other.  Even the atoms themselves are held together by a combination of interactions between particles.  And despite the tendency of thinking of these particles like little billiard bars, they aren't.  They would be better described as dimensionless points with a set of properties.  There is nothing "solid" there in the way that we use the words in everyday usage.
And in early stages of universe, these properties didn't even exist as they do today. the Four fundamental forces were one unified force and haven't separated yet.  earlier than that, the very laws of physics may not have even been the same as they are now.
It later yet that the elementary particles were able to form, and then atoms ( mostly hydrogen).   Clumps of this hydogen gathered together to form early stars. Planets weren't able to form until enough of these first generation stars went supernova and seeded the universe with heavier elements.
The universe being infinite or not has no bearing on this.  The Big Bang theory doesn't require that everything in the universe was compressed into some finite volume, only that it was denser and hotter earlier than it is now.  In other words, if you take any large enough representative volume of space in the universe, the material within it was squeezed closer together in the past.  Again, it doesn't matter if the rest of the universe is infinite or not.

I'm sorry, but it appears to me that you are jumping to a conclusion of "it doesn't make sense" based on a very limited grasp of the physics involved, and quite frankly are unqualified to make such a declaration.

[jeffreyH]

The layman can make the mistake of trying to understand the complicated bits of science without learning the basics first.

Step away from the big bang for a moment. Imagine that the only element in the universe is hydrogen. It is a molecular gas. This has its own gravitational field and so it clumps together. It gets denser until it eventually creates stars.

This will lead to the creation of heavier elements but that is not what I want to talk about. It is the change in density that is important and what exactly prevents that density from increasing.

It is the electromagnetic forces that prevent a runaway increase in density. As Janus mentioned, solid is a word that is misinterpreted. You have to ask what breaks down the resistance of the electromagnetic force to runaway density increase?

This occurs when the gravitational field overwhelms the electromagnetic field's resistance. When not even light can escape. You are now talking black holes and singularities. The sort of possible conditions before the big bang.