Quote:
Originally Posted by Sil_liS
What makes you think that parsec is used more than lightyear in reality?
|
That isn't actually what I said.
In response to your statement:
Quote:
|
The terms lightday and lighthour and lightsecond are also used, but they are not the best choice for measuring the distance between galaxies.
|
I made three assertions:
a) Light-year was also not the best choice for measuring distance between galaxies
b) Light-year is used more in science fiction than in reality
c) Parsec is the preferred unit (for measuring distance between galaxies)
And for the latter, as you accept NASA as a source:
http://heasarc.nasa.gov/docs/cosmic/milkyway_info.html
Quote:
|
Although the light year is a commonly used unit, astronomers prefer a different unit called the parsec (pc).
|
International Astronomical Union:
http://www.iau.org/public/measuring/
Quote:
|
Beyond the Solar System the distances in astronomy are so great that using the AU becomes too cumbersome. The IAU recognises several other distance units to be used on different scales. For studies of the structure of the Milky Way, our local galaxy, the parsec (pc) is the usual choice. This is equivalent to about 30.857×1012 km, or about 206,000 AUs, and is itself defined in terms of the AU – as the distance at which one Astronomical Unit subtends an angle of one arcsecond. Alternatively the light-year (ly) is sometimes used in scientific papers as a distance unit, although its use is mostly confined to popular publications and similar media. The light-year is roughly equivalent to 0.3 parsecs, and is equal to the distance traveled by light in one Julian year in a vacuum, according to the IAU. To think of it in easily accessible terms, the light-year is 9,460,730,472,580.8 km or 63,241 AU. While smaller than the parsec, it is still an incredibly large distance.
|