fundamentals 101 : everything is the same... everything is different.
I became fascinated with astronomy and space science when I was very young, approximately the same time as the "key event" at age 4 that shaped my nature, character and personality (described in first post).
I've always had a terrible memory, so I don't remember many events of my early life. But I do remember the huge impact of one of my first hints about the nature of reality that I encountered shortly after becoming interested in astronomy and starting to read and observe and investigate the universe with my first small telescope.
Even with my first small telescope I could observe many brighter galaxies... enormous spiral, elliptical and irregular configurations of billions of stars, clusters and nebula millions of light years away. If astronomy books were telling truth, billions or trillions more galaxies were beyond the reach of my small telescope, but displayed beautifully in B&W and color photographs through larger telescopes.
So, what is the "fundamental" in this early observation. Answer: two very similar ones.
The first "fundamental" was... when we look for billions of light years in all directions with tiny and huge telescopes on remote mountaintops, EVERYTHING IS THE SAME.
Okay, not exactly the same, but fundamentally the same. What could I see with my telescope? Stars, nebula, planets. That's pretty much all I could see above the horizon, no matter where I looked and no matter how far I looked. And assuming photos I saw in astronomy books were not fake, the same was true with larger telescopes.
Perhaps this fact is so well known now that most people cannot recall the mental impact of learning that... fundamentally... EVERYTHING IS THE SAME. Wow!
To notice this first "fundamental" at age 4 had quite the impact on my puny little brain. If you recall the content of my first post, you may understand my early assumption that I would never understand very much about reality.
That assumption was a direct consequence of my recognition that I could not learn from adults or books or from any other human being, directly or indirectly. How could a single ignorant little kid every accumulate substantial knowledge about a universe so vast as to defy comprehension?
Do you recognize how this discovery of the "fundamental" nature of reality made that impossible goal seem just a little less impossibly overwhelming? If the entire universe was indeed more or less the same as the universe near me, then maybe I could infer the nature of the eternal, unlimited expanse of the universe by observation, experiment and thought directed at the nearby universe that was easier for me to observe.
Maybe the fundamental goal I had set for myself... to understand the universe... was not quite as absurdly impossible as I had assumed at the start.
The second "fundamental" was just a more detailed and encompassing variant of the first fundamental. Though I was not able to build the equipment to confirm this by my own observations for two or three years, I certainly read claims in astronomy books that spectra of all galaxies no matter how remote, and all bright stars in galaxies no matter how remote were the same.
The spectrum of a star or galaxy is fundamentally the same as a common rainbow. Pass "white light" (light of all colors) from a star or any object through a prism, and the path of light is "bent" by the material. This is called "refraction".
However, all transparent materials bend shorter wavelength light (deep violet) more than they bend longer wavelength light (deep red). While wavelengths of light AKA "electromagnetic radiation" can be extremely short (less than 1 angstrom) to extremely long (more than 1 meter), the range that humans can see with their eyes is extremely limited and ranges from deep-violet at about 4000 angstroms to violet to blue to green to yellow to orange to red to 7000 angstroms (deep-red).
What is so amazingly convenient from the perspective of scientist or little kid like me at such a young age is... how light at very specific limited wavelengths is created (emission lines) and absorbed (absorption lines) by various elements.
When I say "elements" here, I mean the "atomic elements"... hydrogen, helium, lithium, beryllium, boron, carbon... yada, yada, yada... protactinium, uranium, and so forth.
And so, we can point telescopes at nearby stars a few light years away... and at stars billions of light years away in distant galaxies... and look at the wavelength of emission and absorption lines in their spectra.
And guess what? No matter where we look in the universe, we find everything is composed of the same atomic elements (and configurations of atomic elements, which we call "molecules").
Wow! Talk about fundamental. Not only do we find "everything is the same" at the large scale (stars, nebula, galaxies), but they are composed of exactly the same components at the nanoscopic scale of light, atoms, molecules.
And so "everything is the same".
But on the flip side is "everything is different".
Fortunately the "same" is amazingly pervasive, so we can understand a great deal about any portion of the universe we have not yet encountered. This lets us have confidence to travel to other planets, star systems (or continents on earth) and have a reasonable degree of confidence that "we can deal with anything". Hopefully. At least we have a chance. Which is all any conscious being in this universe can hope for.
Of course the flip side is also true... "everything is different". Even something as fundamentally identical as hydrogen atoms (in the same nominal "state") are not literally 100% identical. Every hydrogen atom on the far side of the universe (or as nearby as 10 angstroms away) is being pulled, pushed, tugged, twisted and tweaked by a different set of "forces" and influences caused by the nature and configuration of reality (other atoms, light, etc) both nearby and far away.
So indeed, in a very fundamental sense, "everything IS the same".
And indeed, in a very fundamental ways, "everything IS different".
Yes, I know... sounds stupid and self-contradictory. If you are like me, cute sound bites meant to obscure understanding or manipulate thought is annoying & unappreciated. However, understood clearly (as described above), I do consider those two sentences together as concise statements of fundamental aspects of reality.
So I offer these very simple fundamentals for your consideration and enjoyment. Perhaps they will remind you of some of those moments of frustration and joy when your very young mind started to grapple... and grasp... the reality you are part of.