distance

[metalmind]

does anyone know a site i can go to so i can get the distance in miles between mars and the asteroid belt,and the asteroid belt and jupiter?

 

[yevaud]

My advice would be to purchase the <i>Audobon Guide To The Night Sky</i>, an incredibly useful book. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[yevaud]

Sorry, I was rushed, and wanted to add some informative links:<br /><br />This is a good "Gateway" site to further links.<br /><br />Hope this helps.<br /> <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[metalmind]

Thank you very much yevaud.

 

[nyrath]

This is my favorite. NASA's incredibly useful Planetary Fact Sheets.<br /><br />http://nssdc.gsfc.nasa.gov/planetary/planetfact.html

 

[zarnic]

When we read, hear... however, that a galaxy is x miles from us what points are being measured... center to center, our sun/planet to its outer rim... where? If it is to that galaxy's center then that would mean a large galaxy would be closer than x miles, if we knew its size. Actually here on Earth we do the same thing... Paris (city center?), for example, is x miles away, from....? <div class="Discussion_UserSignature"> <p><em>Wisdom doesn't automatically come with old age. Nothing does - except wrinkles.</em> A. Van Buren, 1978<br />* <em>An unbreakable toy is useful for breaking other toys.</em>  -- according to Van Roy</p> </div>

 

[zarnic]

Now that that is settled the 'where' still lingers. <div class="Discussion_UserSignature"> <p><em>Wisdom doesn't automatically come with old age. Nothing does - except wrinkles.</em> A. Van Buren, 1978<br />* <em>An unbreakable toy is useful for breaking other toys.</em>  -- according to Van Roy</p> </div>

 

[MeteorWayne]

There was no "where" in your original question, so I'm not sure what you mean. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[SpeedFreek]

Conceptually, most cosmological distances are measured from here on Earth to the centre of distant galaxies.<br /><br />We use a combination of factors to determine these huge distances, including the brightness and redshift of a galaxy. These are measurements of that galaxys light, which would be an average of all the light emitted from it. Seeing as the mass that emitted that light was mostly concentrated in the centre of those galaxies (the middle is brighter than the edges), we can consider our measurements to be from here on Earth to the centre of those galaxies.<br /><br />Consider that the Earth is around 8 light minutes from the Sun and around 30,000 light years from the centre of our galaxy. If we are looking at a galaxy similar to our own that is 10,000,000,000 light years away the difference between the centre and the edge of that galaxy is a small fraction of the overall figure, and it is a lot harder to determine where a galaxy ends than it is to determine where its centre is. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[zarnic]

Now that my question has been answered it may take me a while to absorb the signifcance of it all. In answer to your response, MW, my 'where' is right before the the first question mark. TY, speedfreek. <div class="Discussion_UserSignature"> <p><em>Wisdom doesn't automatically come with old age. Nothing does - except wrinkles.</em> A. Van Buren, 1978<br />* <em>An unbreakable toy is useful for breaking other toys.</em>  -- according to Van Roy</p> </div>

 

[MeteorWayne]

Sorry I missed your "where". My bad.<br /><br />Still, what do you mean by where? In what direction? How far?<br /><br />As has been pointed out, at a galactic scale, whether you measure the distance from the galactic centers or edges makes no significant difference.<br /><br />It means much more in the solar system where the diameter of the Sun, Earth, or Moon is a larger percentage of the distances involved.<br /><br />Direction is not involved in your question, as I understand it. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[zarnic]

I get the idea, now. It all boils down to whether or not one wants to be completly accurate or not... I mean, who cares if an item is say 200 miles away or only 199 miles away, as long as we know where it is. Ummm, guess I am just knit-pickin. OK, guys, thanks. I'm sure there are more important questions to answer. <div class="Discussion_UserSignature"> <p><em>Wisdom doesn't automatically come with old age. Nothing does - except wrinkles.</em> A. Van Buren, 1978<br />* <em>An unbreakable toy is useful for breaking other toys.</em>  -- according to Van Roy</p> </div>

 

[brigandier]

You mean 99.9999, right?

 

[MeteorWayne]

Actually, he probably meant 9999.999999999 <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[SpeedFreek]

0.99999999.... = 1 <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[heyscottie]

It's like asking how far it is from Des Moines to London. Nobody will care if you are measuring from the centers of the cities or from the edges; those differences don't matter to a general person.<br /><br />The same thing with galaxies. The larger ones are about 100000 to 200000 light years across. The closest large galaxy is 2000000 light years away. Most galaxies we get distances for are hundreds of millions of light years away, or even billions. We can't measure accurately enough for the widths of the galaxies to even come into the picture. If we say a galaxy is 5 billion ly away, we have uncertainty in that measurement. Let's say it's as low as 0.1 percent. That is 5 million ly. Our uncertainty already swamps any consideration of which parts of the galaxies we are measuring.

 

[nexium]

Some will care even if the difference is parts per billion. Likely there is inconsitancy among even top experts. I suggest (unless otherwise specified) that the distance is from the present position of Earth's mass center to the center of the galaxy (or whatever) at the moment that the light left which is now arriving at Earth. As others have suggested this is often only about one part per thousand different than other more or less logical criteria. Neil

 

[zarnic]

A billion is not the same everywhere; in the US a billion = a thousand million but many in Europe, especially Britian, believe a billion = a million million.&nbsp; When it comes to stellar distances which version is observed? <div class="Discussion_UserSignature"> <p><em>Wisdom doesn't automatically come with old age. Nothing does - except wrinkles.</em> A. Van Buren, 1978<br />* <em>An unbreakable toy is useful for breaking other toys.</em>  -- according to Van Roy</p> </div>

 

[SpeedFreek]

Pretty much everyone uses the short scale (1000 million) for a billion nowadays and that includes astronomers. The UK abandoned the long scale in 1974. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[zarnic]

Well ... since it is doubtful that everyone will be willing to change I guess the best way to go is to use the <em>Scientific</em> notation method, 10 with a superscript for number of zeros, that way everyone wins.&nbsp; <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-wink.gif" border="0" alt="Wink" title="Wink" /> <div class="Discussion_UserSignature"> <p><em>Wisdom doesn't automatically come with old age. Nothing does - except wrinkles.</em> A. Van Buren, 1978<br />* <em>An unbreakable toy is useful for breaking other toys.</em>  -- according to Van Roy</p> </div>