Tag Archives: Scale


As is my usual routine I took my dog Cosmo out for our walk to the mailbox yesterday. Along the way I had a thought about the precariousness of our existence on Earth. We live in this sort of illusion as our daily life is wrapped in an assumption of stability. For the most part our human brains encounter the same environment everyday. Most of us wake up in the morning and are active during the day. The light from our sun scatters in our atmosphere, heating and lighting and otherwise presenting a world around us that seems stable. Somedays are cloudy, others sunny, often a mix of the two. As we go about our days we see a mix of human and non-human species, natural and human environments. We eat and breath, work, play, and talk.

But our life on this planet exists on the thinnest of onion skins. The biosphere of our planet, the zone in which all life happens is remarkably thin. While the actual thickness of the biosphere is not easily measured it generally falls within a range of 6.5 miles. At the highest we have birds flying as high as 1.1 mile and at the depth we have fish 5.2 miles below the water. There are examples of higher flying birds and deeper dwelling organisms but they are exceptions to the general. The diameter of the earth is 7,918 miles. The radius is 3,959 miles. Almost all life on our planet lives on the outer 6.5 miles of that.

The image above is to scale for size but not distance in orbits

The image above is to scale for size but not distance in orbits

As an amateur astronomer I've spent a good bit of time viewing and contemplating space and distance. For all of the beauty of the stars in the night sky, space is mostly empty. The space between stars is vast. The space between galaxies even more so. If we just turn our attention to our own solar system and what exists here well, again, it's mostly empty space. Our Sun makes up 99.86% of the matter in our solar system. Our Earth, though it is the densest planet in the solar system, is only the tiniest proportion of the mass of our solar system. It barely registers. On the scale of our solar system our Earth is merely a tiny point separated from the sun and other planets by vast distances. To get a sense of it watch this amazing video by Wylie Overstreet in which three guys drove out to the desert of Nevada with a to-scale model to demonstrate the spacing of our solar system.

Our lived experience, our world, is just a precarious, thin layer on what amounts to a very tiny planet. On a clear, dark night I can lookup and see several thousand stars with my naked eyes. In remote locations such as mine there is little light pollution and the atmosphere disappears. It is in this star-lit darkness that I can begin to experience the Earth as a space ship of sorts. It really is a living space ship. In our orbit around the sun we move through space at 67,000 miles per hour. But remember, our solar system is also moving around the center of the Milky Way galaxy at 490,000 miles per hour. Of course we don't see it or feel it directly but it is happening nonetheless.

Life on Earth is precarious. It's stability is not permanent. Our sense of day-to-day continuity is something we're used to and something we assume will continue. I'd suggest that if more people had a better sense of how it all works, had a better sense of just how thin the envelope of safety is, perhaps they might be more inclined to take seriously the warning of science regarding climate change, habitat loss and other aspects of biosphere stability. It's too late to stop much of what we've set in motion but if we don't make real change very soon we will experience the worst case scenarios.

Looking at other galaxies

One of the best things about living under really dark skies and having a decent telescope is viewing other galaxies. While I equally enjoy the many beautiful objects in our own galaxy such as nebulae and globular clusters, the hunt for distant galaxies has a meditative quality for me. Sometimes the finding is a bit of a let down. For example, last night I went looking for NGC 7042, a spiral galaxy. It took some doing but I found it. It’s 250 million light years away. Yeah. It was the faintest little smudge of light barely detectable on a very clear night with a decently sized telescope (12.5 inches). When I find these really faint ones I always laugh at my disappointment. Yes, it is a galaxy filled with billions of stars and yes, I just sighed in disappointment. But, but, it’s 250 million light years away I remind myself. Not only that it is moving away from us at 5,083 kilometers per second or, 1.7% the speed of light. There will come a time in the distant future when that galaxy and others are no longer visible from Earth. The stretched out light will no longer reach us. The Universe is expanding and that expansion is accelerating. Eventually galaxies that are currently visible to us will blink out. Of course, by that time we’ll likely not be here to notice.

The thing about viewing other galaxies is that it helps frame the scale of the Universe. When I look at the star Vega I’m seeing a star that is only 25 light years away. Yes, still a vast distance from our perspective. But it’s in our local neighborhood so to speak. In fact, it’s like a neighbor on our own street. Funny thing, the stars we see when we look up without a telescope are all in our local neighborhood. We’re only seeing about 6,000 of the very closest stars in our galaxy of 200 billion stars. When I look at the Orion Nebula I’m looking at something that is only 1,400 light years away. Sure, that’s a good bit further than Vega but again, remember that our Milky Way galaxy is an average of 100,000 light years in diameter. So, Orion is still very much in our local neighborhood.

The Andromeda Galaxy is the largest galaxy of the Local Group which consists of about 45 other galaxies including our Milky Way.

The Andromeda Galaxy is the largest galaxy of the Local Group which consists of about 45 other galaxies including our Milky Way.

But back to the viewing of galaxies, the easiest to view from the Northern hemisphere of Earth is Andromeda which is “only” 2.5 million light years away. It fills the eyepiece of my telescope and can actually be seen with the naked eye if you’re under dark skies. I have no problem picking it out from the stars of the Milky Way. It’s oval of faint light is actually quite large and fills an area larger than the full moon in our night sky. It’s quite close and in fact, billions of years in the future we will in fact merge with Andromeda. I viewed Andromeda just two nights ago. I also viewed the Bode’s galaxy, M81 and the Cigar Galaxy, M82 which are a pair of galaxies 12 million light years away and are fairly bright and easy to find with a telescope. In 2014 a star went supernova in M82 and we were able to view it from Earth. Quite a show! So the pair is, in the larger scale of things, quite close. A bit further than Andromeda but not nearly as far as the 250 million light years that makes NGC 7042 so faint.

Faint and distant or bright and close, viewing other galaxies is a thrill because it means looking at the starlight of hundreds of billions stars. As those photons stream into my eyes I’ve got a direct connection with the ancient starlight created by billions of suns. It is light that has been stretching through the Cosmos for millions of years and ends its journey in my eye. The experience is one which enhances my perspective and gives life on Earth an added dimension. In seeing such distant worlds I begin to contemplate and understand the scale of the Universe in a way I had not before. It has changed who I am as a human as well as my understanding of what it means to be human.