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KB2VXA > TREK 09.02.04 03:04l 49 Lines 1987 Bytes #999 (0) @ WW
BID : 19872_WT3V
Read: DB0FHN GUEST
Subj: PARSEC
Path: DB0FHN<DB0THA<DB0ERF<DB0FBB<DB0GOS<ON0AR<ON0AR<VE3FJB<ON4HU<N2BQF<
KD4GCA<N1UAN<W1GMF<K1UGM<W1ON<W1ON-5<K1UOL<K1UOL<WA2PNU<KC2COJ<WT3V
Sent: 040208/2135 19872@WT3V.#CNJ.NJ.USA.NOAM $:19872_WT3V
From: KB2VXA@WT3V.#CNJ.NJ.USA.NOAM
To : TREK@WW
Hi Trekkies and sci-fi buffs,
That oft misunderstood term, the parsec, is finally explained! Well, ask
an astronomer and you'll get the right answer (;->), so here it is.
The correct question should be how far is a Parsec as it is a measure of distance, not as some seem
to think, time.
The short answer is 3.26 light years, which is nearly 31,000,000,000,000,000 metres.
Parsec stands for parallax second. It's pretty hard to directly measure interstellar distances from
Earth. So, an indirect method is needed. One way is to use parallax. To use parallax you need 2 va
ntage points. The Earth orbits the sun, so we can use the U.
1 AU is about 150 million kilometres, so the opposite sides of the Earth's orbit are about 300 mill
ion kilometres apart.
OK. If we look at a distant star right now, and then sight the exact same star six months later, th
e location of that star will appear to have moved. Actually, it is we who have moved. Now we have a
n angle so we can use Pythagoras old theory to get the disess accurate.
If I have explained it properly you will realise that as the Earth goes around the Sun, a very near
by object would have a very large parallax angle, and a very distant object such as another galaxy
will have a tiny parallax angle. About a millionth of a dea 60th of a degree, not a second in time.
The terminology relationship came about right here on Earth with measurements of latitude and longi
tude being time related. That's why a position is given in hours, minutes and seconds which can lea
d to confusion of those who don't understand the relationect of nautical navigation.
Phew..
73 de Warren, KB2VXA@WT3V.#CNJ.NJ.USA.NOAM
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