I like to think of myself as a moderately sized human. I’m almost six feet tall and I weigh 80 kg. I can lift heavy objects and reach the cookies on the top shelf. I’m busy with university reading, homework, music, and all manner of other activities. I think I’m pretty important. Until I look up.
When I’m outside, I look up and I see the sky. Sometimes I see clouds, these vast collections of water vapour that usually appear white or grey. When they are particularly dark and laden with H2O, the vapour condenses and millions of water droplets fall to the ground.
I find myself saying the word “million” fairly often in daily life, but when I stop and consider the meaning of a million, I struggle with the concept. The human eye can resolve objects separated by only 1/60th of a degree. This means that we can just barely make out the width of human hair held at arm’s length. One million of the smallest thing we can see (a human hair) laid in the smallest way possible, would be longer than a football field. One million is a very large number. I will never know one million people. I will not live one million days.
On nice days, I feel the warmth of the Sun and even though I can’t look directly at it, it lights my walk to school and feeds the food I eat. This benevolent sphere in the sky, although I can block it out with a well-placed hand at arm’s length, is very large and very distant. With a radius of 695 000 km, it is by far the largest object in the solar system. It takes photons of light, the fastest possible particles in the universe, a full eight minutes to reach us 150 000 000 km away. The Sun understands one million. In fact, it understands much more than that. Every second, the Sun is estimated to release on the order of 1026 Joules of energy from its roiling, hydrogen-fusing core into the vastness of space. Only one billionth of that energy hits the earth, and that tiny, incomprehensibly small fraction is able to feed every organism from ebola to elephants and mushrooms to amoebas.
These thoughts remind me of how miniscule I am and it is at this point that I often return inside. I do some work, maybe take a nap, and a few hours later I find myself outside, looking up once more. That great reminder of my insignificance has finally dipped below the horizon and darkness begins to creep over the landscape. I’m just beginning to forget how small I am when I see it, the first star of the evening. That little point of light is most likely about the same size as the Sun. This means it must be very far away if it appears only as a dot in the sky. If the first star I saw was Alpha Centauri, the closest star to the Sun visible with the naked eye, that means the image I am receiving is already four years old. Light, travelling at the universe’s ultimate speed limit, takes more than four full years to make the 30 million million km journey (no typo, just trying to express how exceeding large 1013 is). I am looking back in time and it’s simultaneously awesome and terrifying.
I turn my eyes away from Alpha Centauri and I find the darkest patch of sky that I can. There is nothing there, nothing to scare me. Except that since I know about the Hubble Ultra-Deep field, I know that I am likely looking directly at several tens of thousands of galaxies. Each of these galaxies probably contains around a billion stars, many of which are larger than the Sun.
I am a moderately sized human living on a large planet, which orbits a massive star that turns about an enormous galaxy that is on a collision course with another huge galaxy. These two galaxies are but two in an estimated 170 billion that roam the universe. I think it is amazing that humans manage to find conflict, love, truth, and meaning despite the fact that they are so small.