IN A WAY THIS PAGE JUST COMPARES TWO SIZES. This might not be so interesting except that big means the biggest thing there is, which of course is the universe. And small is the seed, or more technnically, a "singularity" which given our topic is (naturally) the smallest thing that can exist. Unless you have a scientific curiosity and have done some reading (of perhaps have a PhD in physics) will take a little explaining.
From my perspective the human part of this story means knowing where we came from because it will force you to alter your thinking a bit. So how big is big? And how small is small. And, since we will have to kick around reall big and really small numbers, a tiny bit of math will make life easier.
Really big and really small numbers always have lots of zeros. So we could use names like billion and trillion except we will need things like a billion trillion trillion. Or we could write out 44 zeros. There is a really logical and simple way around this. We simply write down the number of zeros, and put a plus sign in front of the number if it is big, and a minus sign if it is small. So a trillion, which we would write as 1,000.000,000. The easy way to write a trillion is 109which is pronounced as 10 to the 9th, which means 1 followed by 9 zeros. So when I say the universe weighs about 1044 you easily know what I mean and you know it is big. Fourty four zeros is one of the largest numbers you will run into in science.
And if I say the firecracker was small, I mean the smallest thing that can exist (I will skip why' you can Google "Planck Distance" and "Planck Time."
So the firecracker was 10-33 centimeters and lasted 10-42 seconds. An atom is much larger. So, why bother with this. Well in that super tiny singularity was all the energy it took (once it cooled and became matter instead of light) to mskr the universe (see the big numbers above). it is giving us a rather phenominal sense of who we are. And we were all in this singularity as a single infinite point of energy. And if this doesn't blow your mind just a little bit, you are not paying attention.
Now skipping over a whole bunch of physics courses I am going to tell you what strikes me as the most important steps that got us from there to here. Stay with me, we are almost ready to talk about the Earth and climate. And while we didn't get into first principles, we were definitely in the neighborhood. And you are probably smarter because you know "scientific notation" and feel a bit in the know when you read the science section of The New York Times.