Humans like to think big. Skyscrapers, bridges, interstate highways, that sort of thing. Lake Powell has about 1900 miles of shoreline. The Bingham Canyon open-pit copper mine is 2-1/2 miles wide and covers almost 2000 acres. The Great Wall of China stretches for 13,000 miles.
But the world is small, really. The coronavirus responsible for COVID-19, SARS-CoV-2, is big for a virus but still really small. A typical virion is about 100 nanometers across. Nano– means 10-9 so that’s 0.0000001 meters in length. You’d need 10 million of them laid end-to-end to get a meter’s worth. One virion has a mass of about one femtogram. The prefix femto– means 10-15 or 0.000000000000001 grams. It would take a quadrillion coronaviruses to get a gram!
Micro-organisms rule your world. You harbor a bacterial colony in your gut. Without them you can’t digest food, so you’d die. Plants need nitrogen to live. They have bacteria on their roots that extract nitrogen from the air and convert it to a usable form. Without those helpers living there, the plants would die.
Microbes are the oldest and most diverse of all life forms. When microbes started to photosynthesize and produce oxygen the planet eventually became inhabitable for species like us. Microbes are found in every possible habitat. No ecological process is possible without them.
Now a virus is not like a bacteria or other microbe. It doesn’t really meet the textbook definition of “alive” although it certainly acts like a living thing once it gets the chance. A bacterium is huge by comparison, about 10 times bigger or 1000 nanometers across. But on a human scale that is still tiny.
I got to thinking about very small things because I got my first dose of the Moderna vaccine. The dose is 100 micrograms (10-6) or 0.000001 grams. With two shots you get 200 micrograms of the mRNA vaccine.
A COVID infection is estimated to be between 109 and 1011 virions per person. That’s a mass of between 1 to 100 micrograms. So, if you want to fight a war on a very small front you need very small soldiers but you still want to have more than the other guy!
The number of coronavirus cases in the world is about 115 million. That means all the SARS-CoV-2 in the world has, roughly, a mass* of no more than a dozen kilograms. That’s it. Somewhere around 25 pounds!
We humans spend our days in the macro-world. We drive cars and watch TV and play golf and all of those things we can see and touch and feel. But the REAL world is the micro-world, and especially the nano-, pico-, and femto-worlds. An atom is on the order of 100 picometers (pico- is 10-12) in size, and in the end, all we are is collections of atoms.
So, like I said, it’s a small world, after all.
*1 microgram times 115 million (1 E-6)(115 E6) is 115 grams (0.115 kg) and 100 micrograms times 115 million (100 E-6)(115 E6) is 11,500 grams (11.5 kg).