Can anyone tell me when the term "light-year" was first used?

I would appreciate it!

"ZMarc" wrote in message...
m...

I would appreciate it!

'Lo ZMarc --

This term goes back to the first half of the 19th century. Three
astronomers were attempting to measure the "parallax" of three
different stars. Up to this time, 1838, nobody had even a close
clue as to how far away stars actually were.

Using the most powerful telescopes of the day were...

Thomas Henderson (1798-1844), British astronomer --
attempting to measure to Alpha Centauri from Capetown
in South Africa.

Friedrich Georg Wilhelm von Struve (1793-1864), German
astronomer -- working in Russia on the distance to Vega.

Friedrich Wilhelm Bessel (1784-1846), German astronomer
-- chose the star 61 Cygni to measure.

While Henderson was the first to make the determination, the
credit goes to Bessel for being first to publish his results. Bessel
measured the distance to 61 Cygni to be about 35 quadrillion
miles away.

The best calculation of light speed at the time was 176,000 miles
per second as determined by James Bradley, British astronomer,
in 1728. So, soon after these tremendous distances had been
accurately determined, and since working with such large figures
of miles proved very awkward, someone evidently gasped, "My
god, Friedrich! It would take light a total of about 6 YEARS to
travel from 61 Cygni to Earth!" Not very long after that,
astronomers began to use the "light year" when analyzing stellar
distances.

Then at some point, probably late 1800s or early 1900s, the
phrase lost favor in science. Astronomers developed another
term which turned out to be more useful to their equations.
While the word "parsec" (short for parallax second) rose to
power in science to denote huge stellar distances, popular use
of "light year" has remained unchangably embedded in the
nonscientific jargon of uncredentialed astronomy lovers.

....and one light year = 0.307 parsec,
one parsec = 3.26 light years

BTW, the only time the term is hyphenated, as in "light-year",
is when it becomes a descriptive (adjective) phrase, as in...

light-year measurement

When standing alone as a noun phrase, there is no hyphen.

hth

happy days and...
starry starry nights!

--
A smidgeon of fear, a sprinkle of strife
And a whole lot of love till your cold...
Everyone here wants to live a long life,
But nobody wants to get old.

Paine http://www.painellsworth.net

In message ,
Painius writes
"ZMarc" wrote in message...
om...

I would appreciate it!

'Lo ZMarc --

This term goes back to the first half of the 19th century. Three
astronomers were attempting to measure the "parallax" of three
different stars. Up to this time, 1838, nobody had even a close
clue as to how far away stars actually were.

The best calculation of light speed at the time was 176,000 miles
per second as determined by James Bradley, British astronomer,
in 1728. So, soon after these tremendous distances had been
accurately determined, and since working with such large figures
of miles proved very awkward, someone evidently gasped, "My
god, Friedrich! It would take light a total of about 6 YEARS to
travel from 61 Cygni to Earth!" Not very long after that,
astronomers began to use the "light year" when analyzing stellar
distances.

Then at some point, probably late 1800s or early 1900s, the
phrase lost favor in science. Astronomers developed another
term which turned out to be more useful to their equations.
While the word "parsec" (short for parallax second) rose to
power in science to denote huge stellar distances, popular use
of "light year" has remained unchangably embedded in the
nonscientific jargon of uncredentialed astronomy lovers.

Thanks Painius. I tried looking this up but didn't get very far. Oddly
enough, we do know when and by whom the word parsec was coined.
--
What have they got to hide? Release the ESA Beagle 2 report.
Remove spam and invalid from address to reply.

"Jonathan Silverlight"
wrote...
in message ...

In message ,
Painius writes

"ZMarc" wrote in message...
om...

I would appreciate it!

'Lo ZMarc --

This term goes back to the first half of the 19th century. Three
astronomers were attempting to measure the "parallax" of three
different stars. Up to this time, 1838, nobody had even a close
clue as to how far away stars actually were.

The best calculation of light speed at the time was 176,000 miles
per second as determined by James Bradley, British astronomer,
in 1728. So, soon after these tremendous distances had been
accurately determined, and since working with such large figures
of miles proved very awkward, someone evidently gasped, "My
god, Friedrich! It would take light a total of about 6 YEARS to
travel from 61 Cygni to Earth!" Not very long after that,
astronomers began to use the "light year" when analyzing stellar
distances.

Then at some point, probably late 1800s or early 1900s, the
phrase lost favor in science. Astronomers developed another
term which turned out to be more useful to their equations.
While the word "parsec" (short for parallax second) rose to
power in science to denote huge stellar distances, popular use
of "light year" has remained unchangably embedded in the
nonscientific jargon of uncredentialed astronomy lovers.

Thanks Painius. I tried looking this up but didn't get very far. Oddly
enough, we do know when and by whom the word parsec was coined.
--
What have they got to hide? Release the ESA Beagle 2 report.
Remove spam and invalid from address to reply.

Your welcome, Jonathan.

Some anomalies need to be mentioned...

Checking the figures, it seems that either Asimov was incorrect
about the distance measured by Bessel, or that the measurements
were extremely inaccurate.

If Bessel measured the distance to 61 Cygni as 35 quadrillion
miles, then this would come to over 6,000 light years distance.
(According to the Britannica, Bessel's measurement was
61 trillion miles, or about 10.3 light years.)

In any case, Cambridge gives the distance to 61 Cygni as 3.4
parsecs, which comes out to about 65 trillion miles or 11 light
years. My SSN gives a distance of 11.4 light years.

While Asimov is infrequently inaccurate, he's still considered
to be one of the best astronomy writers!

happy days and...
starry starry nights!

--
I'm a fool upon a hill,
See my planet spinning still?
Sun goes down and stars arise
Warm and pleasing to mine eyes.

See my little telescope?
People say I'm such a dope;
I don't mind because I nurse
Secrets of the Universe!

Paine http://www.painellsworth.net

In message ,
Painius writes

Some anomalies need to be mentioned...

Checking the figures, it seems that either Asimov was incorrect
about the distance measured by Bessel, or that the measurements
were extremely inaccurate.

If Bessel measured the distance to 61 Cygni as 35 quadrillion
miles, then this would come to over 6,000 light years distance.
(According to the Britannica, Bessel's measurement was
61 trillion miles, or about 10.3 light years.)

In any case, Cambridge gives the distance to 61 Cygni as 3.4
parsecs, which comes out to about 65 trillion miles or 11 light
years. My SSN gives a distance of 11.4 light years.

While Asimov is infrequently inaccurate, he's still considered
to be one of the best astronomy writers!

Where did the figure in miles come from? It isn't in "Asimov on
Astronomy" AFAICS (collection of his articles on astronomy from "Fantasy
and Science Fiction"). That quotes the modern figure of 11 light years.

Your welcome, Jonathan.

Some anomalies need to be mentioned...

Jonathon,
O oui,
Appele
Yes,
Clever, brilliant
Shining star ~
Carves l'air.
Exquisite
Choreographer.
Top, tier.

_______
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A
HREF="http://journals.aol.com/virginiaz/DreamingofLeonardo"http://journal
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Clever, brilliant
Shining star ~

And Joseph,
MIA?

_______
Blog, or dog? Who knows. But if you see my lost pup, please ping me!
A
HREF="http://journals.aol.com/virginiaz/DreamingofLeonardo"http://journal
s.aol.com/virginiaz/DreamingofLeonardo/A

Painius wrote:

[snip]

In any case, Cambridge gives the distance to 61 Cygni as 3.4
parsecs, which comes out to about 65 trillion miles or 11 light
years. My SSN gives a distance of 11.4 light years.

Hipparcos gives parallaxes of 285 & 287 mas for the A & B components
-- I guess it's a bit tricky separating them -- for a distance right
around 3.50 parsecs (11.4 LY, 67 trillion miles or 1.08 Pm).

--
Odysseus

"Jonathan Silverlight"
wrote...
in message ...

In message ,
Painius writes

Some anomalies need to be mentioned...

Checking the figures, it seems that either Asimov was incorrect
about the distance measured by Bessel, or that the measurements
were extremely inaccurate.

If Bessel measured the distance to 61 Cygni as 35 quadrillion
miles, then this would come to over 6,000 light years distance.
(According to the Britannica, Bessel's measurement was
61 trillion miles, or about 10.3 light years.)

In any case, Cambridge gives the distance to 61 Cygni as 3.4
parsecs, which comes out to about 65 trillion miles or 11 light
years. My SSN gives a distance of 11.4 light years.

While Asimov is infrequently inaccurate, he's still considered
to be one of the best astronomy writers!

Where did the figure in miles come from? It isn't in "Asimov on
Astronomy" AFAICS (collection of his articles on astronomy from "Fantasy
and Science Fiction"). That quotes the modern figure of 11 light years.

Got that figure from _Asimov's Chronology of Science
and Discovery_ on page 301. He was describing events
of the year 1838, and i especially liked his last paragraph
in this section...

"These distances made the Universe suddenly much larger
than astronomers till then had dreamed. The entire Solar
System shrank to a dot in space in comparison to the
distance of even the nearest stars."

....a mere 166 years ago.

happy days and...
starry starry nights!

--
Tender is my love for thee
Oh star so close at hand,
Warming those so dear to me
As we lay on the sand...

It's so easy to believe
In all this beachin' fun,
That some day you and i will be--
Altogether one.

Paine http://www.painellsworth.net

"Odysseus" wrote...
in message ...

Painius wrote:

[snip]

In any case, Cambridge gives the distance to 61 Cygni as 3.4
parsecs, which comes out to about 65 trillion miles or 11 light
years. My SSN gives a distance of 11.4 light years.

Hipparcos gives parallaxes of 285 & 287 mas for the A & B components
-- I guess it's a bit tricky separating them -- for a distance right
around 3.50 parsecs (11.4 LY, 67 trillion miles or 1.08 Pm).

--
Odysseus

The "Flying Stars" --

61 Cygni might be an interesting study in terms of the possibility
of life. 61A and B orbit each other at a distance just a bit over
twice that of Pluto from the Sun. Scientists have deduced that
the mean distance of an Earth-like planet from 61A would be
about 0.3 AU, and for 61B only about 0.2 AU. These distances
are respectively about 3/4 and 1/2 the distance of Mercury from
the Sun.

So a "year" on A's planet would be about 2.5 months, and on
B's the year would only last 1.5 months. Fascinating!

And check out the amazing proper motion...

http://www.solstation.com/stars/61cygni2.htm

There might even be a system of small planets revolving around
these, as there are orbital anomalies that have yet to be resolved.

happy days and...
starry starry nights!

--
Tender is my love for thee
Oh star so close at hand,
Warming those so dear to me
As we lay on the sand...

It's so easy to believe
In all this beachin' fun,
That some day you and i will be--
Altogether one.

Paine http://www.painellsworth.net