I remember the exact moment that I knew I had to become a scientist. I don’t remember when science first became an interest of mine, but then I’ve always been someone with a lot of interests. My mom tells me that I was always curious about how things worked, and maybe the fact that I’ve always had countless interests speaks to the fact that I’m just curious about everything, and ultimately science seeks to explain everything. Still, being interested in a thing and devoting your life to it are two very different concepts.
The exact moment I realized that becoming a scientist was the only choice available to me is burned into my brain. I was in the fourth grade and had checked out a few science books from the library geared toward kids around my age. There I was leaning against a tree in my grandparent’s front yard learning about atoms, the building blocks of all the stuff in our Universe. Atoms are mostly empty space, with a core of protons and maybe some neutrons orbited by electrons. The core is packed pretty tight, but the electrons orbit at a relatively massive distance from the core. Atoms are separated from one another by an even bigger distance, and since atoms make up all the matter we touch that means that most matter is actually empty space. Absolutely empty, since there is nothing that can fill that gap. This knowledge blew my mind, and I looked around in wonder as if a veil had been lifted. I smacked the tree with my hand, knowing that both my hand and the tree were mostly empty nothingness.
Hydrogen contains a single electron orbiting a single proton, which makes it the simplest structure that we would still call an atom and accordingly (by any measure) the smallest atom in existence. The diameter of a hydrogen atom is approximately 0.0000001 millimeters (one ten millionth of a millimeter), and one millimeter is about three times thicker than a typical human fingernail. That means that if we stacked hydrogen atoms end to end that it would take roughly three million of them to be as thick as your fingernail. If the width and length of your fingernail were a perfect square (it’s not, but roll with me here) a typical length would be about one and a half centimeters, or 15 millimeters. That would give a volume of one fingernail of 67.5 cubic millimeters (= 0.3 x 15 x 15). That volume can hold 6.75 x 1022, or 67,500,000,000,000,000,000,000 hydrogen atoms.
Atoms clearly exist on a scale massively different from the one we exist on. At the same time, there’s a lot of room for life between our macroscopic scale and the extreme microscopic scale of atoms and molecules. What exists between these scales? What life inhabits that gulf and what shapes exist way down there?
Electron microscopes use beams of electrons focused with electromagnetic lenses to image objects as small as a nanometer (0.000001 millimeters, or a millionth of a millimeter) in diameter. On that scale it is possible to image individual biological cells. In contrast, a traditional optical microscope uses photons (individual particles of light) to image things about 0.001 millimeters in diameter. As a result, electron microscopes open up an entire nano-universe of life for us to explore. On that scale the tiniest creatures are monsters from my darkest nightmare. Science constantly challenges us to cast aside fear and embrace knowledge, so let’s see what life we can find at ever decreasing scale.
Let’s begin with this pretty little fella, Atteva aurea, a species of moth commonly found in the United States.
Clearly a member of our macroscopic world, we can nonetheless gain a new appreciation for the way it sees our shared Universe by zooming in on its head – which is about two millimeters wide – with an electron microscope. Note the shed “scales” covering its eye.
That’s neat, but let’s go deeper. How about a typical house spider, a little five millimeter wide fellow that you might find in your shower? From left to right this image covers 2.69 millimeters. Think about how fine those hairs are, and notice the little bricks of crud stuck here and there on its body.
Tetranychus urticae, commonly called a spider mite, is a tiny creature that feeds off plants and is not even a half millimeter long (just a bit thicker than a fingernail). At their own scale they look like giant beings marching across an alien landscape.
Mites are some of the tiniest creatures on Earth, and one could spend an entire lifetime exploring images of their world. Let’s jump down in scale by a factor of ten and look at a group of leaf mites. It’s easy to lose perspective looking at things this small. The scale at the bottom of the image is labeled 50 µm which is equal to 0.05 millimeters, making these creatures one hundred times smaller than the spider above!
Let’s double the magnification and take a closer look at its mouth and “arms.”
All of these creatures are alive. They are born, eat, breed, give birth, and die only ever seeing our shared Universe from their scale. If they have any conception of it, they don’t see their world as strange or tiny. In fact, on their scale the Earth itself is huge on a scale that we can scarcely comprehend. Even a small human town is an inconceivably large world for them. The fact that life exists and thrives on this minuscule scale fills me with awe and wonder for our Universe.
Yet even to that spider these mites seem tiny. Below is a closeup of the hair on another mite species. Note the scale which is the same as the last image above. These leaf mites could crawl between the hairs on the back of another mite.
The most natural thing is for us to live our lives thinking that the world we see is The World. Yet here are these little creatures, oblivious to anything much bigger than themselves, and us much the same until science showed us – as it often does – that we were wrong.
The images in this article come from FEI’s Flickr page. FEI is one of many manufacturers of electron microscopes for a variety of uses. The image at the top of this article is of a bark beetle larva and measures approximately half a millimeter left to right.
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