Wondering about wild grapes

Wednesday, April 3, 2013

Wondering about distances in the Universe.

Sometimes, scientists use terms that the general public has no idea what it means.  Now, I have always been interested in sciences, especially astronomy, but I am confused by some of the terms.  Just like last October, the Carnegie Observatories reported that their most recent measurement of the value of the Hubble Constant (the expansion rate of the Universe) is 74.3 +/- 2.1 kilometers per second per megaparsec.  OK???  I was going along with them just fine until I got to the "megaparsec" part.  You all probably know what it is but I have no idea.  I was wondering if it had anything to do with "light years", which is a logical definition of distance.  One light year is the distance that light (which travels through space at a constant speed) travels in one year.  Although that, too, is hard to comprehend (like all distances in the universe) it is something that is in more commen use and we all seem to understand what is meant by it.  OK, so tell me, what is a megaparsec?

Well, let me try to explain.  This is something that I didn't know so I am learning this right along with you.  As the earth circles around the sun once a year, it makes the closest stars to us apear to shift back and forth against the rest of the stary background.  Scientists can use this shift to determine distances to these stars.  That process is called a trigonomic parallax.  Stars shift less than a second of an arc (you know, a degrees, minutes, seconds) which is about about the width of a quarter seen from three miles away.  To see this shift in a star, it would have to be 3.6 light years away.  This is the distance of one parsecGot that??  I think we should stick to the old reliable light year, what do you think?  Now, please don't worry too much about megaparsecs but have yourself a mega-good day teday, you hear?


  1. You go,,,boy. lololol,,,have no idea what you said.

  2. Simple the kilometers are directional proporsional to the"megaparsec" at 74.3 +/- 2.1 kilometers per second >

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  4. Light years are bad enough. Let's not confuse things more with another measurement. By the way, a lot of "constants" don't seem to hold up all that well to careful measurement. Seems like there's some wobble.

  5. I am with Trouble...even with an explanation...I have no idea what you said :(

  6. I'm right along with most of your other readers today... but I asked Bill and he immediately told me what a parsec is etc etc etc. I didn't understand him either. Nevermind, I'll probably never have to figure out the mileage between the earth, the sun and the stars. When I die I'm hoping I'll have wings so I can see some of this stuff up close. ;-)

  7. I was still trying to figure out your one on GMT mean time until the wife showed me by wanting to stop at the fabric store. Boy, that was some mean time spent in that place, must of been a couple mega-light years. Time is relative, huh?

  8. Trouble, I am not sure I do either. . .

    Justastick, I would have understood it a lot better if it had been in English units like miles per hour, or light years, or gallons, or pounds, or bushels or pecks or . . .

    Sixbears, Everything wobbles, especially me since I have gotten older (grin).

    MsB, I have said before that English is my least understood subject, and maybe I don't know what I said either (grin).

    The Odd Essay, I think Bill and I would get along fine. Maybe when you get back to Texas we could meet someday, someplace.

    Jimkabob, yep, there is some kind of time warp in fabric stores, Hobby Lobby, Micheals, and other yarn, fabric, and craft stores. It is like a black hole where wives make all your money disappear.

  9. The old light year of 186,000 miles per second, or something like that, always made sense to me.

    I mean, doesn't it take something like 8 minutes for the light to travel to us from the sun. I guess that means, if the sun blows up, we wont know until another 8 minutes. Y'all have fun, you hear?


  10. You are correct about that. We only see history. We never know what is going on in this very instant. Even if it is a fraction of a second, it is in the past. Then too, it takes your brain a wee bit of time to realize what you are seeing. .

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