Date: February 7, 2012
Title: Encore: Your Nook in the Incredible Universe
Podcaster: Dave Mosher
Organization: Discovery Space
Links: http://dsc.discovery.com/space/
This podcast originally aired on March 3rd, 2009:
http://365daysofastronomy.org/2009/03/03/march-3rd/
Description: The sight of the night sky from a place removed from the hazy city lights can be mind-blowing in of itself, but it makes one wonder: How big really is the universe? How many stars are in it? How many galaxies? And where do we fit into it all? In this podcast, we’ll take a journey through the size and scale of the known universe and learn some of its surprising secrets.
Bio: Dave Mosher is the producer for Discovery Space (http://space.discovery.com) — the Discovery’ Channel’s Web site about space — and maintains the Space Disco blog (http://blogs.discovery.com/space_disco). As a science journalist, Mosher has covered both human and robotic rocket launches, and his work has appeared in Discover Magazine, news@nature.com, ScienceNOW, LiveScience.com, SPACE.com, MSNBC, AOL, USA Today and other publications. He currently lives in New York City, where a perfect slice of pizza is never far away.
Sponsor: This episode of 365 days ofAstronomy is sponsored by John Cary. Thank you to all involved with thesewonderful podcasts.
Transcript:
Howdy listeners — this is Dave Mosher, producer for the Discovery Channel’s space site at space.discovery.com. Thanks for tuning in. Or downloading in. Or however it goes these days. My day job is to guide you through some of the most fascinating, surprising and downright puzzling stuff in the cosmos. Whether it’s astronomers listening for alien signals, physicists hunting for mysterious particles or cosmologists pondering the fate of the universe, there’s always something to keep me busy.
But probably like most of you, I spend a LOT of time chained to my desk – kind of computer zombie. Even as a zombie, however, it’s hard to get outside at night, look up at the stars and appreciate where we fit into this simply astounding universe.
So right now I’m going to take you on a journey, and you won’t even have to leave your desk. Let’s set the mood a bit… there we go.
When I was younger, I spent my summers away from the bright city lights at a remote summer camp. In the dead of night, I’d sneak out of my tent to a quiet meadow, find a spread of soft grass, gaze up at the charcoal-black sky, and wonder: Where does all of this start, and where does it end?
Let’s imagine for a moment that we can break a handful of natural laws. Say, that we can fly. As far and as fast and as long as we want. Superman, look out!
Our first stop is to zoom above the Earth; most astronauts spend their time about 200 miles above it with a big blue marble filling their view. To get to the closest companion to the Earth — aka the moon — we’ll have to fly about 1,200 times farther, or 239,000 miles.
Distance can be tough to comprehend when it comes to space, so join me on a small Gedanken experiment.
If the Earth was a mid-sized grapefruit, the moon would be a golf ball more than 6 1/2 feet away. And while it pains me to say this, I need to: The moon is drifting away from us at the rate of about 1 1/2 inches per year. Since Apollo 11 astronauts landed on the moon, it has backed off 5 feet.
We didn’t hurt the moon’s feelings; it’s just that the Earth’s gravity is our lunar companion with orbital energy, causing it to rise to a higher and higher orbit. Now let’s talk about the sun — our very own backyard star.
As part of our grapefruit/ping pong ball system, this yellow dwarf star which tans our backs is more than 100 times wider than our citrusy planet. Think of it as a super-sized beach ball that, when placed to scale, sits about 2,600 feet or half a mile away.
Now the light that the sun emits is generated within its ultra-dense core, where 550 million tons of hydrogen fuse together each second. The pieces of light, called photons, take more than eight minutes to reach us from the surface. Shockingly, however, their journey out of the core can take about 100,000 years.
Why? Once a photon is emitted, it is almost instantaneously re-absorbed by nearby plasma to be re-emitted later. Now that’s what I call a traffic jam.
The sun is great, but we have places to go and things to see. If zoom way past poor ol’ Pluto and reach the edge of the solar system, we’ll have to go 30,000 times farther than the Earth is from the sun. That’s half of a light-year, or 2.8 trillion miles for those of you who want to keep count.
Continuing on this pass, we’ll eventually reach the closest star at 4.2 light-years away — Proxima Centauri. Looking back from this red dwarf’s neighborhood, the entire solar system looks like just another bright pinpoint of light in space.
But let’s keep moving.
Proxima Centauri and the sun are just one of 1,500 other blazing gas balls parked in a nook of the cosmos about 250 light-years across — or 59 times the distance between these two stars. Quite a bit of space.
The neighborhood only gets bigger from here. The small chunk of space we call home is part of the 4,000-light-year-thick Orion Arm, a minor offshoot of the much-fatter Sagittarius spiral arm within the Milky Way. If we could really move, we’d try hovering above our host galaxy so that it’s in full view. At 100,000 light-years wide, the Milky Way is an astonishing sight.
Oh, and while we’re up here, let’s do some astronomers a favor: study the remaining quarter of the galaxy we can’t make out from Earth. Why? It’s obscured by stars, gas and dust between it and the 16,000-light-year-thick core of the galaxy.
The Milky Way and its 200 to 400 billion stars aren’t alone, of course. It’s just one of several dozen galaxies in a cosmic cluster stretching 5 million light-years. And that vast piece of space is only one part of thousands within the 100-million-light-year-wide Virgo Supercluster. Its name sounds mighty, but our home supercluster is just a smaller part of a “complex” of clusters that likely span 1 billion light-years wide.
Thinking about this can make one feel small, but we’re not done yet.
Consider this: Several other superclusters of galaxies work together to form a “cosmic web” stretching billions upon billions of light-years. In fact, some scientists estimate the boundaries of our universe are more than 150 billion light-years apart, and continuing to expand at a faster and faster rate. Pretty soon, space will stretch so thin that we’ll be the only galaxy around.
And we’re still not done. As far as we know, the cosmos is home to about 200 billion or more galaxies, each of which harbors some 100 to 200 billion stars… which means the stars of the cosmos could number in at more than 4 followed by 22 zeros.
Think we covered it all? Not even close! There’s another, entirely unseen universe right at your fingertips — but you’ll have to wait until my next podcast for that cosmic field trip. Until then, don’t forget to look up!
End of podcast:
365 Days of Astronomy
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