# A Parsec its not just for trekkies

### sandbox

I don't know about you folks but for some reason I always thought a parsec was a fictional unit of distance. I thought it was something like warp speed or 'stun mode' on a phaser. I never knew that it is actually the oldest and most widely used unit to describe distances on astronomical scales. The newspapers and popular magazines use the unit of a light year (the distance light travels in a year) because it is easier to understand what it is. Astronomers use distance measurements in units of parsecs to calibrate other techniques, like red-shift.

The word parsec comes from the phrase, "parallax of one arc second".

Parsec: A unit of distance equal to about 3.26 light-years (or, more precisely, equal to 206,265 Astronomical Units). Technically, a parsec is defined to be the distance from which the Earth and Sun would appear to be separated from one another by 1 second of arc (about the size a dime would appear to be if seen from a distance of 2 miles).

The closer an object is to the earth and the sun, the greater the observed angle between them. As you move farther away the earth and the sun appear to get closer together. This isn't a very good description of parallax, but hopefully it is clear.

The closest star is about 4 light years away, a little more than a parsec!

### ongnoai

I don't know about you folks but for some reason I always thought a parsec was a fictional unit of distance.  I thought it was something like warp speed or 'stun mode' on a phaser.  I never knew that it is actually the oldest and most widely used unit to describe distances on astronomical scales.  The newspapers and popular magazines use the unit of a light year (the distance light travels in a year) because it is easier to understand what it is.  Astronomers use distance measurements in units of parsecs to calibrate other techniques, like red-shift.

The closest star is about 4 light years away, a little more than a parsec!

211295[/snapback]

Hi there,

Nice to get to some basic topic, thanks Sandbox.

Now, the parsec took over the light year unit, just because light year is a confusing unit. It mixes time and distance, you see : it's the distance that light travels during one year. Now, if you are to cross-check that distance from say, Sirius, how can you be sure your clock gives you the exact same time measurement as it would on say, Earth or Antares? Nobody could really swear it does. Parsec is much more reliable in that it implies only physical distances and angles, which are much more reliable and easier to verify.

A good day to you.

### Cerebral Stasis

A very interesting article, sandbox. Thanks for the information.I'd just like to mention that Star Trek actually uses "light years" for most of it's measurements; Star Wars, on the other hand, uses parsecs ("It's the ship that made the Kessel Run in less than five parsecs." - Han Solo).

### no9t9

The use of parsecs in Han Solos line can be wrong. A parsec is a measure of distance and since he is implying that his ship is fast in that race, it seems that he is using parsec as a unit of time.Obviously, it can be argued that the use is correct because it is just a science fiction movie. We could say that since the ship travels in hyper space there are certain areas of space you might have to go around (like black holes). So to do the run in 5 parsecs might be a measure of how good the pilot is to navigate spatial anomolies.As you can see, I could easily be a star wars/star trek junkie.

### Cerebral Stasis

I'm not a junkie for either Star Trek nor Star Wars, but I've always found technology-intense episodes (in Star Trek) interesting; specifically, episodes concerning the Borg (in episode 16 of season 6 of Star Trek Voyager, it must have been a real pain to get those borg special effects on that baby "borg").

### juice

I also thought a parsec was a ubit of time. I know, well I think I know, that a jiffy is one billionth of a second. The common phrase is "I'll be there in a jiffy". Movies do miss-use words and scientific terms and they should try not to do that because the public take it as being real

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