John Dobson died in Burbank last week, and when I read his obituary in the Los Angeles Times, I remembered him as the first person to stun me with the size of the universe. My brief encounter with him changed the way I see the world, influenced what I studied at university, and it still affects me to this day.
Dobson founded the Sidewalk Astronomers in San Francisco, an amateur group of astronomers who built homemade reflective telescopes out of whatever they could find, including gigantic cardboard shipping tubes, metal rings, and discarded timber.
I saw the planet Saturn for the first time through a Dobsonian telescope that was painted with whorls of bright colors, on the roof the California Academy of Sciences in San Francisco. John Dobson himself was hosting the viewing party, and I was twelve years old.
I was interested in the cosmos, so my parents signed us up for a mid-winter, mid-week astronomy class. Every Wednesday we’d get in the car and drive into Golden Gate Park and attend a lecture at the California Academy of Sciences, in the Morrison Planetarium. It’s a round theater with a raised platform in the middle, on which stands a star projector, which recreates the stars of the night sky on the domed ceiling above you.
The professor would speak --
This is what the stars in the Northern Hemisphere look like on the first day of summer...
-- and the machine would whir and click into place and project the exact array of stars in the sky for that night. I would stare at the mechanical marvel in front of me, and then stare at the projected stars above me, amazed by both.
To this day, I still remember how to find the visible planets in the night sky, and I know some of the secrets hidden in the constellations, like the middle star in the three star dagger that hangs from Orion the Hunter’s Belt is actually the Crab Nebula.
On one moonless Wednesday night, the professor invited us to climb to the roof of the Academy building, where the Sidewalk Astronomers had set up a 12-foot long reflective telescope pointed at Saturn. I loved that we were allowed up there on the tar and gravel, and I could see over a mile in every direction. I remember that there were several astronomers up there, including Mr. Dobson himself. He was a tall and lanky guy with glasses and long brown hair, sort of a tall hippie version of Bill Gates.
It was finally my turn to put my eye up to the lens. When I looked inside I saw the planet Saturn, floating perfectly in black space. It looked like a Kodachrome slide from science class, it looked so perfect. As I looked in the lens, it seemed to be about as big as my thumb. The planet and its rings were mostly black and white but there was yellow and brown mixed in, and it was in sharp focus, and I could actually see the separate rings. I was convinced it was a trick, and that the man had just stuck slide behind the lens somehow.
This is an approximate recreation of my conversation with Dobson, from several decades ago:
Is that really Saturn?
Yes, it’s really Saturn.
It looks like a picture. It’s so clear.
It’s a clear dark night, and earth’s orbit is fairly close to Saturn’s right now.
How close is that?
About 900 million miles.
How far is 900 million miles?
I’ll show you.
Dobson then gestured for my parents and I to follow him close to the edge of the building, which was about 600 feet long.
Imagine that the sun is a ball about a foot in diameter, and we put it on the edge of the building. The earth is about 100 feet away from that basketball, so that’s about 30 steps for me.
My dad, my mom, and I then followed John Dobson as he walked his 30 steps, and we were about 100 feet away the edge, and about a fifth of the length of the entire building. John Dobson held up his fingers and made a pinching motion in front of us.
This distance is about the radius of earth’s orbit, about 93 million miles, and our Earth is smaller than a pea.
We were so stunned, that we could only giggle. He then pointed off into the distance, past the building, and towards the dark trees of Golden Gate Park.
Saturn is about ten times further away, which is almost twice the length of this building. It’d be in those trees over there, and it’s the size of a small plum.
At this point, I was beyond words. I stared into the trees in the distance, imagining an orbiting plum out there somewhere. It didn’t seem conceivable that a plum would feel the tug of gravity and orbit a basketball a thousand feet away. Even more mysterious is how we, on our pea, could even see that plum. I think he saw that he was blowing my mind, and he smiled and then launched me into infinity.
And guess how far away the nearest star, Alpha Centari, is?
It’s a beach ball in Japan.
To this day, it’s hard to conceive of scale this way. When I read his obituary, I fondly remember that night on the roof when John Dobson exploded my mind.
To explode your own mind, check out this website, and enter in some numbers of your own to get a sense of the scale of the universe. It’s courtesy of the Exploratorium:
I later learned that the distances between the atoms in our body (when you increase their electrons and nuclei to the size to plums and basketballs) are just as vast and empty. Go big or small, most of the universe is empty. Yet there are more cells in our bodies than in our own galaxy. They estimate we have 3.72 x 10(13) cells in our body (that’s 3,720,000,000,000,000 cells) and our galaxy has about 10 (12) stars. However, our universe as 10 (12) galaxies, maybe more. And if certain math and physics models are correct, there may be that many “universes” beyond our own. We may be part of a multi-verse. That’s a lot to think about, sitting on our tiny orbiting pea.
Around the same time, I discovered what became another great influence on how I view the universe -- Monty Python. Life is silly, and the more you embrace that, the happier and wiser you will be. John Cleese and Michael Palin may be the absurdist comic geniuses behind some of their best writing, but the composer and lyricist for their best songs is Eric Idle. His Galaxy Song sums it up for me, and I have these words laminated and pinned to the bulletin board in my office at home. It’s a constant reminder of who I am, where I am, and how to put it all into perspective...like John Dobson first did for me when I was 12 years old. Thank you John Dobson. Your sidewalk astronomy lessons worked on me.
THE GALAXY SONG -- by Eric Idle and John Du Prez
Just remember that you're standing on a planet that's evolving
And revolving at nine hundred miles an hour.
That's orbiting at ninety miles a second, so it's reckoned,
A sun that is the source of all our power.
The sun, and you and me, and all the stars that we can see,
Are moving at a million miles a day,
In an outer spiral arm, at forty thousand miles an hour,
Of a galaxy we call the Milky Way.
Our galaxy itself contains a hundred billion stars;
It's a hundred thousand light-years side to side;
It bulges in the middle sixteen thousand light-years thick,
But out by us it's just three thousand light-years wide.
We're thirty thousand light-years from Galactic Central Point,
We go 'round every two hundred million years;
And our galaxy itself is only one of millions of billions
In this amazing and expanding universe.
The universe itself keeps on expanding and expanding,
In all of the directions it can whiz;
As fast as it can go, the speed of light, you know,
Twelve million miles a minute and that's the fastest speed there is.
So remember, when you're feeling very small and insecure,
How amazingly unlikely is your birth;
And pray that there's intelligent life somewhere out in space,
'Cause there's bugger all down here on Earth!
Check out these two links on Mr. John Dobson: