1) The way the earth tilts, and us knowing about it. We can look at the autumn sky and think, "The sun is so different now than in summer, and that is because our part of the world is tilted away from it." I love thinking about stuff like that.
2) How we can see inside our own bodies with x-rays and ultrasounds and MRIs. A few years back one of my kids broke her elbow. Looking at the x-ray, I felt overwhelmed at the beautiful perfection of her bones (except in that one place, of course). Isn't it amazing that we are put together so exquisitely? Just think if we were put together in random ways. Now, that would be weird.
3) Number patterns. For instance, the way that 9x2=18 and 1+8=9 and 1 is one less than 2... 9x3=27 and 2+7=9 and 2 is one less than 3... that pattern keeps going through the 9 times table all the way to 9 (9x9= 81, 8+1=9, and 8 is one less than 9). Or the Fibonacci sequence, found throughout nature, in which the next number is found by adding together the previous two numbers in the sequence-- nature as a gorgeous afghan of numbers knotted together, woven through, and laced with color. Isn't the world wonderful?
4) How much there is to know. No matter how deep we go, there is something else to learn. Knowledge (like Shrek) is an onion. ;) In ancient times someone thought there must be molecules. Eventually, we discovered them. But that wasn't the end of the subject, because atoms. And after we found atoms, we learned to split them. What next? We are making strides in neuroscience, correcting errors in understanding the human brain, but also discovering the vast unknown that is the world of thought. And what about nutrition? Twenty years ago, although we understood that veggies are good for you, we knew nothing of micronutrients. More and more, I agree with Charles Kingsley-- man is simply playing with colored shells on the edge of a vast sea of knowledge. We will never know it all.
5) The Creator. I am amazed at the one who formed this world. He put it together and knows all about how it works. He knows the hidden health of breastmilk. He knows beyond a doubt what causes cancer. He knows of the worlds hidden in and out of our universe, what lies beyond life here on earth. And He is good. What if He had not been good? Whether our lives are good or bad, we do not understand Him. But He understands us, and he has created things for us we know nothing of. When the kids were smaller, we read a story about a little dragonfly grub that lived in a pond. His friends and relatives thought the pond was all there was to life. But the little dragonfly baby longed for more, to see the world that shone through the murky water above. He drove his friends distracted with his questions, research and speculations. Then one day he swam to the surface and opened himself to the upper world. They never saw him again in the water. He unfurled his wings and flew into the sky. Lovely. I say with Hamlet, "There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy."