Re: Parnips, er, parsecs

["Gordon Bird" <gobird@vbe.com>]

Scott, thanks so much for the explanation.  Now I feel that my Audi owership
experience is complete!
Gordie
'62 MGA
'86 4kcsq


> Okay, here's a little reminder about what parallax is.  You stand here
> and look just past that tree (no, not that one, the big one over there),
> you see a cow out in the field.  You move a couple feet to your left and
> the cow is now hidden behind the tree.  That's parallax.
>
> Now, let's apply this to space.  Today is Sept. 1.  You look in the sky
> this evening and you see a star and, because you're an astronomer (or at
> least playing one on the Net), you mark its location very, very
> carefully.  You wait six months; it's March 1, the Earth is 180 degrees
> away from its current location, you look and you see that same star,
> only it's now moved one second of arc (that is, 1/60th of a minute,
> which is 1/60th of a degree, for a total displacement of 1/3600th of a
> degree) away from the place it was on Sept. 1.
>
> So how far away does an object have to be for its parallax to equal one
> second of arc?
>
> One parsec -- one SECond of arc when viewed at two locations defined by
> the PARallax of the Earth's rotation around the Sun.
>
> This works out to 3.25 light years (though I could have SWORN that I'd
> learned it as 4.3 light years; ah well, the Earth has slowed down since
> I were a lad, it's probably got a shorter orbit these days too... "Ah,
> no, young Padewan, it's the distance from Earth to Alpha Centauri which
> is 4.3 light years, which works out to 1.33 parsecs.").
>
> So the space geek response to Lucas' joke about "She's the ship that
> made the Kessel run in less than 12 parsecs" is that Han Solo is using
> the parsec as a measure of time (duh, well, it's 3.25 of some kinda
> year, innit?)  This falls into the same category as Lucas' sound effects
> for explosions in space, which only exist according the the Looney Tunes
> Laws of Physics ("But where was the kaboom?  There was supposed to be an
> earth-shattering kaboom!")
>
> And it will surprise no one, I'm sure, when one works out the number of
> light years equivalent to 12 parsecs.  What else COULD it be?
>
> To bring this topic around to something more appropriate to this list, I
> propose the following:
>
> You know how people in the passenger's seat always seem to think you're
> going faster than you do in the driver's seat, even though the speed is
> the same?  Well, I propose that the relative difference between
> perceived speed when the observer shifts from the left-hand seat to the
> right (or in Phil's case, from right to left) be referred to as "the
> carsec."
>
> As in "Honeeeeeeeeeeeey, slow DOWN, you're making me carsec!"
>
> --Scott "Rocket science at short notice was his specialty" Fisher
>