I Spy With My Little Eye

Measuring the Universe

Pre-Copernican Solar System

Greetings, everyone.  Today I’m going to talk about astronomy, a subject that I’ve been very fond of ever since I was a young man. I started reading about astronomy out of boredom and curiosity, but that quickly turned into fascination and awe as I came to understand more about what I actually looking at when I looked up into the sky. Time is what you see. Vast swaths of time, stretching back so far as to be incomprehensible. And big, although ‘big’ is such an unsuitable word for trying to describe what you see in the sky that it’s laughable. The best I’ve ever come up with that is at least a little satisfying is ‘endless’, although that is also most likely inaccurate. There were lots of incomprehensible numbers that I came across in my studies, most of them used for measuring distances. I’ll be using these terms in future articles on astronomy, so I’ll acquaint you with some of them now. These will appear on a test.

The astronomical unit or AU, is the distance from the Earth to the sun, and is used for many distance measurements in the solar system. Its value is 92,955,807.3 miles or 149,597,870.7 kilometers for you Francophiles. I like 93 million miles myself.

The size of the solar system can vary a lot depending upon who you talk to. The figure I like is the distance from the sun to the edge of the Oort cloud, or about 50,000 astronomical units (AU).

The light year, the distance that light in a vacuum will travel in a Julian year, is probably the most common measurement you’ll come across and its value is 5,878,625,373,183.608 miles precisely, or 9,460,730,472,580.8 km, but is more usually thought of as about 6 trillion miles.

The parsec , which I don’t see being used much anymore, is “an abbreviated form of ‘a distance corresponding to a parallax of one second’”, and its value is around 3.26 light years.  I’m not going to use the term because it is awkward to use, and I didn’t like Herbert Turner, the man who thought it up. He stiffed me on two restaurant tabs and his teeth would scare an angry dragon.

The diameter of the Milky Way, our galaxy, is about 100,000 light years. That works out to around 6,000,000,000,000,000,000 miles for those of you that want to punch it in to your GPS unit (hah).

The number of stars in the Milky Way, another value that can vary wildly depending upon whom you ask, is ~400,000,000,000 (400 billion) stars.

The nearest galaxy, Andromeda, is around 2,500,000 light years distant. Consider that for a moment. The light we see when we look up in the sky at Andromeda, left that galaxy 2.5 million years ago. When that light left Andromeda, our ancestors were still merrily beating each other’s brains out with antelope femurs somewhere in Africa. There was coffee, but we were too stupid to make it. I’m glad I missed this era.

The most distant objects that have been observed (so far), lie around 13 billion light years away. Now think about that for a moment. That light has been travelling for 13 billion years. What in the world was going on 13 billion years ago? Our solar system didn’t exist yet. Most of the stars that we see in the sky didn’t exist yet. The universe itself is thought to be around 13.75 billion years by the current best estimates. We can glimpse the universe’s baby pictures. How cool is that?

That’s all I’m good for today. Next time, we’ll work on feeling really insignificant.


The values I use in this article were gleaned from Wikipedia, which is usually trustworthy on this sort of thing.

  • MrHowser

    Space is like the economy – once the numbers get past a certain point, you can't really comprehend them anymore. They're just… big.

  • She'll do the Kessel Run in less than 12 parsecs.

    • dmilligan

      Argh!! The first time I heard that line in Star Wars, I went "What? This guy is a starship pilot? Why is he still alive?". It still bothers the hell out of me. Technobabble is fine, but at least use real terms properly. "Yep, she'll do 100 miles in a board foot."

      • Deartháir

        Personally, I love the fact that the fans managed to come up with a reasonable explanation that got around the fact that Lucas couldn't be bothered to fact check.

        • MrHowser

          According to Wookiepedia (careful, you could get lost for hours), the explanation was that average pilots couldn't navigate the shorter, more dangerous routes, so it was an 18-parsec journey. Solo's claim of less than 12 parsecs speaks to the quality of his ship and piloting.

          The other explanation is that Solo is essentially boasting about his turbo encabulator, assuming that the simpletons he's transporting won't know he's talking rubbish.

      • I prefer to do my meters in a fathom.

        I figured that would set you off. Welcome to the team!

        • OA5599

          It's hard to fathom you would be using a unit of measure that should be six feet under by now.

          • Preferably deep-sixed into a watery grave.

        • I happen to know off the top of my head that there are 3038 fathoms to the league.

      • BlackIce_GTS

        "Yep, she'll do 100 miles in a board foot."
        Could be some measure of space folding efficiency.
        (Space folding requires the endpoints to be made of lumber, for some reason.)

      • I just assumed that long ago in a galaxy far, far away, they had a unit of time measurement that coincidentally had a name pronounced just like one of our units of length.

        It's just like the movie Galaxy Quest, in which the Thermians looked around the galaxy long enough to find a hitherto undiscovered molecular compound that has all unique physical and chemically reactive characteristics of the fictitious "beryllium sphere" that powered the fictitious NSEA Protector, and then figured out how to use it to power the real, Thermian-built Protector.

        They continued to call it the "beryllium sphere," even though it clearly had no correlation to the substance we call beryllium on Earth. After all, beryllium exhibits none of the characteristics necessary to power a spaceship, and doesn't visually look anything like the prop the original TV designers dreamed up. The Thermians somehow managed to find something that was both a visual and functional match.

  • I'm sorry, my mind just assploded. I can't wrap my head around the hole "we are seeing the light from its birth but it is really old now. I mean I can wrap my head around it but that means if we ever get a signal from little green dudes in another galaxy they'll likely be dead by the time we return their call.

    Someone needs to get working on this whole 'warp speed' thing.

    • That's okay, I still get hung up when watching someone split wood at a great enough distance that there's a noticeable delay between the sight and the sound of the axe strike.

      • dmilligan

        I like it when you can watch an explosion and watch the shock wave moving across the landscape. The speed of sound, stalking the earth.

        • Once, as part of a seismic study, I got to stick around quite close to the buried detonation that was to provide the source of the signal intended for imaging. It was great fun feeling the ground ripple as the waves propagated.

          It was less fun when a group that was late getting there arrived immediately after the blast, as we all suddenly realized to our horror that they had driven their vehicle right along the line of seismometers during their active collection windows. Instead, that group was supposed to have stopped at the far end of the one-lane dirt road to keep anyone else from doing exactly that.

          They hopped out and asked when we were going to start, so they would know when to go back and begin stopping traffic.

  • tiberiusẅisë

    Wikipedia is no match for the Pythons of Monty.

    [youtube buqtdpuZxvk http://www.youtube.com/watch?v=buqtdpuZxvk youtube]

    • dmilligan

      Excellent choice, I haven't watched that in years. The Pythons have a wonderful grasp of reality, and I wish that I was half as eloquent as Eric Idle.

  • coupeZ600

    O.K., Mister-Smarty-Professor-Pants (or Lab Jacket, because I doubt you actually wear pants), if the Universe is constantly expanding, what the hell is it expanding into? And if you buy into all that mumbo-jumbo gobbledy-gook about "parallel universes" that String Theory needs or it falls flat, are we all going to keep expanding until we start crashing into each other? Talk about a car wreck waiting to happen……

    I vote to hit the collective "N-Button" and turn it off so we can stop making that stupid eNtropy stuff, because while it's fine and dandy in the right here and now, in the long-haul that sh*t is going to kick our ass.

    • <img src="http://www.pbfcomics.com/archive_b/PBF111-Reset.jpg&quot; width="600">

      It's self-limiting.

      • skitter

        There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.
        There is another theory which states that this has already happened. – Hitchhiker's

    • dmilligan

      Of course I wear pants (checks), what a ridiculous question. What's the universe expanding into? Damned if I know, but I'd like to go look and see. I'm having a hard time finding a ride, however.
      As for your other questions, I don't do theory, oh my, no. I rather like to bang on them until the rivets fall out though.
      As you can see, my lovely commenters can also help you with your questions. They'll set you straight, yes indeed.

    • mr. mzs zsm msz esq

      There's an idea to test the existence of a multiverse. If our universe has been expanding it may have collided with other universes. This may be seen as ripples in in cosmic background radiation. I probably got that all wrong, but I think I read it on a Science blog.

      • dmilligan

        Hmm, it will be interesting to see what they come up with, if anything. I remember when they first tried mapping the microwave background radiation, and they had one hell of a time trying to separate the signal from the noise. The second mission did a better job, but there isn't much signal to work with after, what, 13.7 billion years? I wish them all luck, but they have a lot of work to do.
        Personally, I like the "membrane" theory of multiple dimensions and universes.

  • [youtube lhTSfOZUNLo http://www.youtube.com/watch?v=lhTSfOZUNLo youtube]