We Are Who-ville

I used to think Planet Earth was a pretty big place. That was before I gained a little perspective.

A few months ago, my husband and I were driving to a friend’s house. While looking up at a streaky afternoon sky, I was jabbering on about how far away the moon was, since it was already visible. (I had only recently started reading up on the subject, and the whole thing was freaking me out, quite frankly.)

When I mentioned how big our galaxy is, my husband paused for a moment, then proclaimed, “We are Who-ville!”

And that’s a very good way to wrap your mind around it. Remember the book Horton Hears a Who by Dr. Seuss? Our Earth (which seems so very, very huge to us), is equivalent to a speck on a clover being carried around by an elephant on top of something else that is the size of our Earth.

Except, actually, we’re much, much smaller than that.

Size is relative, of course. To a human standing at the edge of the Grand Canyon, the Grand Canyon is enormous. Ditto for someone at the foot of Mt. Everest, or someone flying over the Pacific Ocean. To our own personal scale, the earth is simply gigantic, and living here, it’s very easy to get myopic about the big picture. Since we have no personal context for the kind of distances involved in outer space, they are as difficult to process as the concept of eternity.

In his fan-freaking-tastic book A Short History of Nearly Everything, Bill Bryson (who should write all science books, ever, from here on out) illustrates why school textbooks weren’t able to show us anything remotely close to scale when it comes to distances in space. Stop to visualize this in your mind, as it goes along.

On a diagram of the solar system to scale, with Earth reduced to about the diameter of a pea, Jupiter would be over a thousand feet away and Pluto would be a mile and a half distant (and about the size of a bacterium, so you wouldn’t be able to see it anyway). On the same scale, Proxima Centauri, our nearest star, would be almost ten thousand miles away.

Here is the famous “Pale Blue Dot” photo, taken in 1990 by Voyager I (which at that point had been hurtling away from us for 13 years.) The photo shows Planet Earth as a tiny speck against the background of deep space.

When I first started delving into all of this, the reported distances in space sounded so completely absurd. How do they even know all of this? I wondered. Aren’t they just guessing?

Here is what I discovered.

A long time ago (in 1676, if you must know, and I must), it was determined that light did NOT move instantaneously (as it appeared to), but that it had a finite speed. Scientists spent the next 299 years narrowing that speed down, until they finally pinpointed it: light travels at 186,282 miles per second.

(I know: Sounds Ridiculous. That speed is impossible to wrap your mind around. Astonishingly enough, humans have been able to make matter move at very, very close to that speed, in the Large Hadron Collider – about which I’ve previously blogged, here.)

Anyway, once they had it pinned down, scientists started using the speed of light to gauge extreme distances in space. During the Apollo program, we planted retroreflectors on the moon and by aiming lasers at these, we were able to determine the distance to the moon, based on how long it took the light to come back (which was 2 1/2 seconds, so, around 237,674 miles.)

A “light year” is simply the distance that light could travel in a year, which comes out to 5879 billion miles (that bears writing out: 5,879,000,000,000 miles.) Thus, every time you see a single “light year” designated for space distances, it stands for nearly 6 trillion miles.

In A Short History of Nearly Everything, Bill Bryson explains the following: if you want to go just to the edge of our own solar system, and you board a rocket ship going 35,000 miles an hour (which is the speed of our Voyager 1 and 2 spacecrafts which, I must tell you, might get their own future post), it would take you a decade or so just to reach Pluto (the farthest used-to-be-a-planet in our system.)

And at those same speeds, (35,000 mph, remember), to get to the Oort cloud, which is at the edge of our solar system? Well, that would take you another 10,000 years.

(This sounds insane, but I checked the math, as best I could. Bryson’s right.)

After the Oort cloud, you reach the rest of our galaxy (the Milky Way), which contains every star you can see in the night sky. Of course, we can’t plant retroreflectors on stars, partly because most of them have a surface temperature of at least 5000 degrees, and partly because they are so freakishly far away.

To calculate distances to stars, scientists use the “parallax shift.” That’s the effect that you see if you hold your thumb up and look at it with one eye closed, then the other – objects in the distance appear to move, in relation to your thumb. Because of Earth’s revolution about the sun, scientists can measure how much the more distant stars appear to “move,” in relation to closer stars. This gives them approximate distances. (This method only works for objects that are up to 100 light-years from Earth. Beyond that, we have to use the brightness of stars, their motion, the space-time continuum, and a lot of other things that I don’t have room to go into, here.)

The closest star to us is Proxima Centauri – and it is 4.2 light years from Earth. (In other words, multiply 6 trillion by 4.2, and you’ll get the rough mileage.)

And now I’m out of time, and I’ve only gotten you to the edge of our own galaxy. And here’s the truly, truly insane thing. With instruments like the Hubble Telescope (which I blogged about here), we have been able to take pictures of not just our galaxy, but many, many others. As in, scientists estimate – are you sitting down? – 125 billion. Entire galaxies. That’s some of them pictured, above.

I will leave you with one final figure: the edge of the observable universe (the parts of the universe that we can see with our instruments, from Earth) is estimated to be 46.6 billion light years away. (Don’t bother trying to work out the mileage on that. Your calculator will explode.)

Who-ville, indeed.


18 thoughts on “We Are Who-ville

  1. I am so not a space geek…(that’s not to say you’re a geek) or maybe my brain just can’t take in any more infinite information. It makes me too dizzy, and well, I am already a blonde. lol 🙂

      • I love all the stuff about nebulas, galaxies, and stars and I think the idea of “to infinity and beyond” is cool in the abstract, but it freaks my brain out to think that there’s no end to the universe and we don’t know exactly where we are on the big map. :-0)

  2. Wow. Just wow. I knew I was quite small compared to neighboring planets, but you just made me feel almost as if I didn’t exist.

    Wonderful post!

  3. The size of the universe is pretty incredible, isn’t it? The illustration I heard way back when was that if you put a picture of the Milky Way (whole galaxy, not a planet or solar system) in a 1 inch x 1 inch square at the center of a map, that map would have to be 1 mile x 1 mile to chart the “observed” universe. Big place…..

    There so many assumptions (that aren’t really verifiable) underlying all the calculations that we can’t really say how accurate the numbers are, but we do know the universe is a BIG place!

    Good post!

    • Thanks, Dan!
      Yesterday I read: “When asronomers say that the galaxy M87 is 60 million light years away, what they really mean (but do not often stress to the general public) is that it is somewhere between 40 million and 90 million light years away – not quite the same thing.”

      Frankly, I can no sooner wrap my mind around 40 million light years than I can 90 million. In fact, a single light year is beyond my comprehension! 🙂

      • yup….. 40 million to 90 million…. give or take a couple miles…. better top off the tank to make sure we don’t run out of gas getting there, huh?

        Now, you know I believe in God and creation, but the literal 24 hour days, not so sure. There’s one odd corollary: if the speed of light truly is constant everywhere in the universe (that’s one of the biggest assumptions being made if you ask me), and scientists have observed galaxies that are apparently 60 million light years away, if the universe was less than 10,000 years old (ie, new creation), the light from those distant galaxies couldn’t have traveled this far yet.

        I did hear a theory once that said the speed of light is not actually constant, that it is slowly decreasing over time on a logarithmic scale. (ie, nearly infinite at start, curve drops quickly then levels out). If that turned out to be true, then everything we “know” about time and distances would be turned on it’s head — a “young”universe would appear to be old, and carbon dating , which relies on formulas for radio active decay which are dependent on the speed of light would make “young” fossils appear very old. If someone ever proves that theory (speed of light is actually decaying), then I’ll be more inclined to believe in a young universe, but there are probably as many holes in that theory as there are in the theory of evolution. Guess I’ll be content to be amazed at all of creation and wonder how God did it…..

  4. I think it was Lincoln who said it was easy to look at the ground and believe in the devil, but it was impossible to look at the stars and not believe in God. I thought about that when I read your post.

    • Some Christians don’t like science-y stuff like this, for various reasons. Science has only ever reaffirmed my faith and made it stronger.

      All I can tell you is, after spending hours researching this stuff on Saturday, I sat in church on Sunday, and when they sang “Our God is greater, our God is stronger, God you are higher than any other,” I simply could not sing, for crying.

  5. Regarding your abot comment, I don’t think I would have a faith if not for all the thousands of ways science reaffirms it. Whoville is a great analogy. I would need a lot more faith to believe that everything you described just happened because of time+matter+chance.

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