Aptera writes:
Gravity is observable (please, don't get riled about this one) where as basically what I have heard on here nobody knows about the big bang theory, this is. So the universe was created through a space-time "gap"?
I think you've misunderstood what Mr Jack was saying, but a little more detail should clear it up.
When astronomers peer out into space using their powerful telescopes they find that the more distant a galactic group the more rapidly it is receding from us. When all galactic groups in the universe are receding from all other galactic groups it can only mean that the entire observable universe is expanding.
If the universe is undergoing expansion then that means that last year it was smaller than it was this year. And the year before that it was even smaller, and the year before that even smaller. If you continue extrapolating backward in time then you find that the universe becomes smaller and smaller. If you go far enough back in time, approximately 13.7 billion years, then you find that all matter must have existed in a very small region of space, smaller than a single atom.
It is from this very tiny and dense region containing all the matter and energy currently in the universe that the Big Bang sprang. There it was, all this matter and energy in a very tiny volume, and we don't know how it got there or where it came from, but we know it was there. It had to be there, because when we retrace the path of the matter we see in the universe today we see that it is all moving away from a single point.
Not knowing where the material comprising the Big Bang came from is not the same thing as not knowing whether the Big Bang happened. It had to have happened, because if it didn't then the galaxies we see through our telescopes couldn't be where there are with the motion they have.
The Big Bang was initially very hot and was comprised of a quark plasma, but as it expanded and cooled matter was able to condense out of this quark soup, mostly hydrogen. There was also a little helium and a smattering of lithium. As it happens, these are the three lightest elements, and these clouds of mostly hydrogen dispersed into space. No planets formed out of the Big Bang. The Big Bang produced only the three elements I mentioned.
But within a half-billion years or so after the Big Bang the mostly hydrogen clouds had cooled to the point where tiny irregularities could serve as seeds from which the first stars could begin condensing. The first stars were probably huge, and if they had planets then it wasn't planets as we know them because there was no carbon, no oxygen, no sodium, no calcium, no iron, no elements at all other than hydrogen, helium and a little lithium. If there were planets then they must have been comprised mostly of hydrogen gas, because that was mostly all there was.
Huge, massive stars burn up and exhaust their hydrogen fuel relatively rapidly, in as little as a few million years. The process by which they burn their fuel, nuclear fusion in the star's core, "cooks" the lighter elements like hydrogen into heavier elements like helium. Once the hydrogen is used up then the helium is used to cook even heavier elements, like lithium, beryllium and carbon. As more and more of a star's nuclear fuel is consumed it switches to other nuclear processes that create heavier and heavier elements, all the way up to iron (Fe, atom number 26).
When a star no longer has sufficient fuel to generate sufficient heat to maintain the matter comprising it as a ball of very hot matter then it collapses in upon itself. This greatly increases the density of matter in the star's core and creates the conditions necessary to cook the nuclear fuel into elements heavier than iron, but the same process also causes the star to explode (nova for small stars, supernova for larger stars). Exploding stars going nova and supernova send most of their contents, including their newly formed heavier elements, out into the gas clouds already resident in space.
As time went by in the early universe more and more heavier elements accumulated in the gas clouds from these early novas and supernovas, and now new stars condensing from these gas clouds containing heavier elements could form planets as we know them today, since elements like aluminum and iron and manganese (rocks) and oxygen (necessary for water) and carbon (necessary for organic molecules) were available.
Approximately 9 billion years after the Big Bang our own sun condensed out of a gaseous cloud in our Milky Way galaxy, along with a suite of planets of which our planet Earth is one.
--Percy
Edited by Percy, : Add subtitle.
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