It’s nearly impossible to get a grasp on how truly vast space is. I got interested in space when I was a little kid growing up in Illinois farm country. I had a map of our solar system on my wall; although it wasn’t to scale it still gave me a sense of far apart things are, just in our solar system. The fastest speed anything can travel is the speed of light (at least according to physicists; sci-fi fans know that FTL—faster-than-light—travel is made possible by warping spacetime. Or something.) Anyhow, a theoretical something traveling at the speed of light (186,282 miles per second) would circle the earth about 7-1/2 times in one second. So for our purposes here on earth the speed of light is pretty much instantaneous. Or close enough it might as well be.
But the distances of space actually make the speed of light a handy measuring tool: space is so vast it’s necessary to think in the distance light travels in 12 months, called, logically enough, a light year. I knew that the sun was 93 million miles away and it takes a little over 8 minutes for light to travel to earth from the sun. That doesn’t seem like all that much, but Pluto (which was still a planet then) is so far away from the sun that it takes light about 5-1/2 hours to get there. Our closest neighbor (actually a star system consisting of 3 stars) is Alpha Centauri, just under 4 1/2 light years away. That means that when we look at that star system, the light we are seeing left Alpha Centauri 4-1/2 years ago. To put it a little differently, if our sun were the size of a grapefruit and was placed on the beach near my house on the west coast, Alpha Centauri would be all the way across the country in Boston, 2500 miles away. And that’s our closest neighbor.
We’re on the fringes of our galaxy, the Milky Way (a spiral-shaped galaxy of no particular note other than the obvious fact that it’s where we live). When we look up in the night sky like I did as a kid in Illinois, the swath of lighter sky is the center of our galaxy; we’re look back toward it from where we are in one of the outer arms. Our Milky Way is somewhere between 100,000 and 180,000 light-years across. Again, that means that light from a star on the other side of our galaxy left there up to 180,000 years ago and is just reaching us now.
And our galaxy is one of countless such galaxies. At the Griffith Observatory here in Los Angeles, there’s a huge mural that represents just a small section of the night sky. It’s fascinating because when you first look at it from across the hall it appears to be just dots on a white background and you figure each dot is a star. Walk closer and a different picture emerges (literally), because up close you see that what appear to be dots are actually photographs of other galaxies, placed in the proper position relative to the other “dots” (some are stars in our Milky Way; others are other galaxies visible from earth) in the night sky. So it’s actually a star map, accurately representing what’s out there.
Astronomers estimate there are over 100 billion (with a “b”) stars in our galaxy. But there’s more. Lots more. The universe has structure: Our Milky Way is part of a group of galaxies, called a Local Group In our Local Group there’s about 30 galaxies spanning about 10 million light years. Our Milky Way and the Andromeda galaxies are the largest in the group.
Our Local Group is part of a larger group, which is itself part of a yet larger group. And as I said, the Milky Way is not particularly notable as galaxies go; there are much bigger galaxies out there as well as more interesting ones (younger galaxies where stars are forming; galaxies with massive black holes at their center, and so on nearly ad infinitum).
Take a giant step backward: now the scale of distance becomes nearly impossible to grasp. I read an article in the news a couple of weeks ago indicating that astronomers have now come to understand that our galaxy and associated Local Group structures are part of a “supercluster” of galaxies that’s been named Laniakea. Our Milky Way is located in a remote arm of that. (See the small red dot in the right-center of the artist’s representation of Laniakea to the right? That’s covering the Milky Way). This Super Cluster is about 50 times bigger than our Local Group.
So here we are, living on a small planet in an unremarkable solar system, out on the outer edge of a galaxy, in the outer reaches of a supercluster of about 100,000 galaxies spanning 520 million light years. And that’s only one of five such super-clusters!
The reason this is interesting to me is twofold. First, and what initially stimulated this entry, was no more complicated than thinking about how staggeringly BIG the universe is, the incomprehensible distances it encompasses, and how insignificant we humans are. I mention above looking up at the night sky as a kid. My brother Jim (Jimmy at the time) and I would go out in out side yard in a summer evening when there was no moon and lie in the grass, looking up at the night sky. Out in the country and away from the corner streetlights there wasn’t a lot of ambient light, so the stars were in full glory. I understood a light year even then, so attempting to come to grips with how far away these little twinkly lights actually are was both entertaining and challenging. And more than a little awe-inspiring.
The second reason this interests me is more historical and takes another post to develop. Stay tuned.
About BigBill
Stats: Married male boomer.
Hobbies: Hiking, woodworking, reading, philosophy, good conversation.
Space is really, REALLY big!
It’s nearly impossible to get a grasp on how truly vast space is. I got interested in space when I was a little kid growing up in Illinois farm country. I had a map of our solar system on my wall; although it wasn’t to scale it still gave me a sense of far apart things are, just in our solar system. The fastest speed anything can travel is the speed of light (at least according to physicists; sci-fi fans know that FTL—faster-than-light—travel is made possible by warping spacetime. Or something.) Anyhow, a theoretical something traveling at the speed of light (186,282 miles per second) would circle the earth about 7-1/2 times in one second. So for our purposes here on earth the speed of light is pretty much instantaneous. Or close enough it might as well be.
But the distances of space actually make the speed of light a handy measuring tool: space is so vast it’s necessary to think in the distance light travels in 12 months, called, logically enough, a light year. I knew that the sun was 93 million miles away and it takes a little over 8 minutes for light to travel to earth from the sun. That doesn’t seem like all that much, but Pluto (which was still a planet then) is so far away from the sun that it takes light about 5-1/2 hours to get there. Our closest neighbor (actually a star system consisting of 3 stars) is Alpha Centauri, just under 4 1/2 light years away. That means that when we look at that star system, the light we are seeing left Alpha Centauri 4-1/2 years ago. To put it a little differently, if our sun were the size of a grapefruit and was placed on the beach near my house on the west coast, Alpha Centauri would be all the way across the country in Boston, 2500 miles away. And that’s our closest neighbor.
And our galaxy is one of countless such galaxies. At the Griffith Observatory here in Los Angeles, there’s a huge mural that represents just a small section of the night sky. It’s fascinating because when you first look at it from across the hall it appears to be just dots on a white background and you figure each dot is a star. Walk closer and a different picture emerges (literally), because up close you see that what appear to be dots are actually photographs of other galaxies, placed in the proper position relative to the other “dots” (some are stars in our Milky Way; others are other galaxies visible from earth) in the night sky. So it’s actually a star map, accurately representing what’s out there.
Astronomers estimate there are over 100 billion (with a “b”) stars in our galaxy. But there’s more. Lots more. The universe has structure: Our Milky Way is part of a group of galaxies, called a Local Group In our Local Group there’s about 30 galaxies spanning about 10 million light years. Our Milky Way and the Andromeda galaxies are the largest in the group.
Our Local Group is part of a larger group, which is itself part of a yet larger group. And as I said, the Milky Way is not particularly notable as galaxies go; there are much bigger galaxies out there as well as more interesting ones (younger galaxies where stars are forming; galaxies with massive black holes at their center, and so on nearly ad infinitum).
So here we are, living on a small planet in an unremarkable solar system, out on the outer edge of a galaxy, in the outer reaches of a supercluster of about 100,000 galaxies spanning 520 million light years. And that’s only one of five such super-clusters!
The reason this is interesting to me is twofold. First, and what initially stimulated this entry, was no more complicated than thinking about how staggeringly BIG the universe is, the incomprehensible distances it encompasses, and how insignificant we humans are. I mention above looking up at the night sky as a kid. My brother Jim (Jimmy at the time) and I would go out in out side yard in a summer evening when there was no moon and lie in the grass, looking up at the night sky. Out in the country and away from the corner streetlights there wasn’t a lot of ambient light, so the stars were in full glory. I understood a light year even then, so attempting to come to grips with how far away these little twinkly lights actually are was both entertaining and challenging. And more than a little awe-inspiring.
The second reason this interests me is more historical and takes another post to develop. Stay tuned.
About BigBill
Stats: Married male boomer. Hobbies: Hiking, woodworking, reading, philosophy, good conversation.