-Neil deGrasse Tyson
Stop. Look around. What do you see? A computer perhaps? A chair? A pen? A cup of coffee?
We're surrounded by objects scaled to our existence: clothes that fit us (hopefully), cars to move us, buildings to shelter us.
Your immediate world, the one in which you exist each and every day, is -- in a way -- a deception, a cleverly constructed ruse that skews your sense of scale. There's nothing wrong with this. After all, why shouldn't we tailor our environment to be exactly proportionate to ourselves and our needs?
But there's a vast universe out there, filled with organisms and objects invisible to our direct perception, or too gargantuan for us to comprehend.
There are neutrinos: tiny, subatomic particles moving close to the speed of light. At any given time, about 30 million of these particles flit around inside you. If you sliced a pencil in half (length-wise) seventy-three times, you'd whittle down to about the size of a neutrino -- one yoctometer (0.000000000000000000000001 meters).
Much, much farther up the size ladder, we find the carbon atom, the basic unit of the element fundamental to all life on Earth (yes, including you). With an atomic radius of 70 picometers, it's positively gigantic compared to a tiny neutrino. Yet still, if I placed 50 septillion (10^24) carbon atoms onto the open palm of your outstretched hand, you'd only be holding a measly mass of one kilogram.
The carbon atom is dwarfed by one of the smallest carbon based lifeforms: a ciliate protist. These microscopic, single-celled organisms inhabit lakes, ponds, oceans, rivers, and soils. You can't see them with your naked eye, but you can view them clearly under a microscope, provided, of course, that you've magnified at least 100 times.
4.2 billion kilometers away from Earth, lies the dwarf planet Pluto. You might be surprised to find out that its diameter (about 2,300 kilometers) is a little more than half of the length of the United States (4,200 kilometers). No wonder why it lost its planet status!
Just outside our galactic neighborhood, 18,000 light years away, we find the comparatively small Stingray Nebula. I say comparatively because it's only one-tenth the size of other known planetary nebulae. But this astronomical infant is still 130 times the size of our solar system!
Alas, the blobby, green and red Stringray Nebula is but a blip compared to the Milky Way Galaxy. Grab a piece of printer paper and make a dot with a fine point pen anywhere on the sheet. The dot would approximately be the Stringray Nebula. The sheet would be the Milky Way.
Our wondrous universe contains objects and organisms great and small. It's difficult to precisely determine where we fit in on this grand scale. The average human is 7 x 20^18 times more massive than a small virus, and 2.43 x 10^29 times less massive than the largest known star, VY Canis Majoris. Depending upon how you want to picture yourself in the grand scheme of things, you can elect to be a giant or an invisible dot.
But no matter where you fit in within the Universe, the one thing for certain is that you do fit in.
(Image: Stingray Nebula via NASA, Matt Bobrowsky)