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	<title>Comments on: The Milky Way&#039;s (almost) identical twin</title>
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		<title>By: Beyond and within &#124; In the Glen</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2011/01/07/the-milky-ways-almost-identical-twin/#comment-272877</link>
		<dc:creator>Beyond and within &#124; In the Glen</dc:creator>
		<pubDate>Sun, 13 Mar 2011 18:03:04 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/badastronomy/?p=25551#comment-272877</guid>
		<description>[...] The Milky Way&#8217;s (almost) identical twin (blogs.discovermagazine.com)     GA_googleAddAttr(&quot;AdOpt&quot;, &quot;1&quot;); GA_googleAddAttr(&quot;Origin&quot;, &quot;other&quot;); GA_googleAddAttr(&quot;LangId&quot;, &quot;1&quot;); GA_googleAddAttr(&quot;Autotag&quot;, &quot;science&quot;); GA_googleAddAttr(&quot;Tag&quot;, &quot;sunday-scribblings&quot;); GA_googleFillSlot(&quot;wpcom_below_post&quot;);     This entry was posted in Sunday Scribblings by Hazel. Bookmark the permalink.   LikeBe the first to like this post. [...] </description>
		<content:encoded><![CDATA[<p>[...] The Milky Way&#8217;s (almost) identical twin (blogs.discovermagazine.com)     GA_googleAddAttr(&quot;AdOpt&quot;, &quot;1&quot;); GA_googleAddAttr(&quot;Origin&quot;, &quot;other&quot;); GA_googleAddAttr(&quot;LangId&quot;, &quot;1&quot;); GA_googleAddAttr(&quot;Autotag&quot;, &quot;science&quot;); GA_googleAddAttr(&quot;Tag&quot;, &quot;sunday-scribblings&quot;); GA_googleFillSlot(&quot;wpcom_below_post&quot;);     This entry was posted in Sunday Scribblings by Hazel. Bookmark the permalink.   LikeBe the first to like this post. [...] </p>
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		<title>By: Wissydig</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2011/01/07/the-milky-ways-almost-identical-twin/#comment-272876</link>
		<dc:creator>Wissydig</dc:creator>
		<pubDate>Mon, 07 Mar 2011 00:21:06 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/badastronomy/?p=25551#comment-272876</guid>
		<description>Spirals are sooo tweesty i loveeit. thanku</description>
		<content:encoded><![CDATA[<p>Spirals are sooo tweesty i loveeit. thanku</p>
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		<title>By: Compilation Video : Best of NASA UFO&#039;s &#171; Illusion of Power</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2011/01/07/the-milky-ways-almost-identical-twin/#comment-272875</link>
		<dc:creator>Compilation Video : Best of NASA UFO&#039;s &#171; Illusion of Power</dc:creator>
		<pubDate>Wed, 26 Jan 2011 06:05:34 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/badastronomy/?p=25551#comment-272875</guid>
		<description>[...] The Milky Way&#8217;s (almost) identical twin (blogs.discovermagazine.com) [...] </description>
		<content:encoded><![CDATA[<p>[...] The Milky Way&#8217;s (almost) identical twin (blogs.discovermagazine.com) [...] </p>
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		<title>By: Nigel Depledge</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2011/01/07/the-milky-ways-almost-identical-twin/#comment-272874</link>
		<dc:creator>Nigel Depledge</dc:creator>
		<pubDate>Thu, 13 Jan 2011 12:35:53 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/badastronomy/?p=25551#comment-272874</guid>
		<description>reidh (42) said:
&lt;blockquote&gt;so its around 4 times its diameter in distance from us? Thats close. Good thing the universe is expanding instead of contracting.&lt;/blockquote&gt;

Er ... no.

It&#039;s about 4,000 times its diameter away from us.</description>
		<content:encoded><![CDATA[<p>reidh (42) said:</p>
<blockquote><p>so its around 4 times its diameter in distance from us? Thats close. Good thing the universe is expanding instead of contracting.</p></blockquote>
<p>Er &#8230; no.</p>
<p>It&#8217;s about 4,000 times its diameter away from us.</p>
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		<title>By: UGC12158 &#171; QuarkScrew</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2011/01/07/the-milky-ways-almost-identical-twin/#comment-272873</link>
		<dc:creator>UGC12158 &#171; QuarkScrew</dc:creator>
		<pubDate>Thu, 13 Jan 2011 05:08:26 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/badastronomy/?p=25551#comment-272873</guid>
		<description>[...] From Bad Astronomy, whose Bad Astronomer Phil Plait describes it as &#8220;The Milky Way&#8217;s (Almost) Identical Twin.&#8221; [...] </description>
		<content:encoded><![CDATA[<p>[...] From Bad Astronomy, whose Bad Astronomer Phil Plait describes it as &#8220;The Milky Way&#8217;s (Almost) Identical Twin.&#8221; [...] </p>
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		<title>By: Nigel Depledge</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2011/01/07/the-milky-ways-almost-identical-twin/#comment-272872</link>
		<dc:creator>Nigel Depledge</dc:creator>
		<pubDate>Wed, 12 Jan 2011 15:42:45 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/badastronomy/?p=25551#comment-272872</guid>
		<description>Sam H (17) said:
&lt;blockquote&gt;I’m going to investigate authors on both sides, and leave aside ad hominem (as several here cannot seem to do), and attempt to dig as deep as I can, leaving aside arguments from authority unlike kuhnigget.&lt;/blockquote&gt;

So, you reject the expertise of the world&#039;s leading biologists, right?  What is your basis for this radical approach?

Good luck with understanding Dembski&#039;s writing, BTW, as he has specifically tossed his word-salad to confound the lay reader into thinking he might have a point.  Particularly his &quot;complex specified information&quot; concept.  See if &lt;i&gt;you&lt;/i&gt; can work out what that means without having to resort to an analogy.

Also BTW, if you are going to go throwing accusations around (ad hominems  and arguments from authority), how about you back up those claims with specific examples, huh?</description>
		<content:encoded><![CDATA[<p>Sam H (17) said:</p>
<blockquote><p>I’m going to investigate authors on both sides, and leave aside ad hominem (as several here cannot seem to do), and attempt to dig as deep as I can, leaving aside arguments from authority unlike kuhnigget.</p></blockquote>
<p>So, you reject the expertise of the world&#8217;s leading biologists, right?  What is your basis for this radical approach?</p>
<p>Good luck with understanding Dembski&#8217;s writing, BTW, as he has specifically tossed his word-salad to confound the lay reader into thinking he might have a point.  Particularly his &#8220;complex specified information&#8221; concept.  See if <i>you</i> can work out what that means without having to resort to an analogy.</p>
<p>Also BTW, if you are going to go throwing accusations around (ad hominems  and arguments from authority), how about you back up those claims with specific examples, huh?</p>
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		<title>By: Nigel Depledge</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2011/01/07/the-milky-ways-almost-identical-twin/#comment-272871</link>
		<dc:creator>Nigel Depledge</dc:creator>
		<pubDate>Wed, 12 Jan 2011 15:31:32 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/badastronomy/?p=25551#comment-272871</guid>
		<description>Sorry to encourage OT talk but . . .

Sam H (17) said:
&lt;blockquote&gt;And while I know that ID is ideologically inclined, it doesn’t mean that it isn’t totally false.&lt;/blockquote&gt;

Every claim made by the ID authors that we can objectively detect &lt;i&gt;design&lt;/i&gt; has been shown to be false.  This is not to say that we might be able to detect it at some undertermined point in the future, but none of the methods proposed by e.g. Bill Dembski are real - all of them are arguments from analogy (which rely on extraneous information that we already possess), false dichotomy or some other fallacy of reasoning.  Dembski&#039;s &quot;deductive filter&quot; explicitly excludes the set of all hypotheses no-one has thought of yet for no justifiable reason.  Furthermore, he constrains his range of hypotheses in such a way that any combination of chance and natural law is excluded as a possible answer.

What we &lt;i&gt;can&lt;/i&gt; detect is manufacture.  And there&#039;s no sign of that in biology.

&lt;blockquote&gt; Yes I’m sympathetic toward them due to my Christian longings and upbringing, but it don’t mean that I can’t attempt to objectively investigate the evidence.&lt;/blockquote&gt;

But why do you not accept that this process has already occurred, and the answer is - overwhelmingly - that ID is a load of rubbish?

All of the arguments made to support ID have been shown to be wrong.  All of them, without exception.

&lt;blockquote&gt; ID is by nature a philosophy,&lt;/blockquote&gt;

What makes you think this, when the Discovery Institute went to such lengths to tell people like you that it was genuine science?

If you consider ID as a philosophy, then you can find plenty of aspects that simply cannot be refuted, but that are - pretty much by the same token - intellectually sterile.  I.e., they result in mere navel-gazing, not any actual progress towards anything.

&lt;blockquote&gt; but it doesn’t mean it can’t become a scientific theory.&lt;/blockquote&gt;

As expounded by Behe, Wells, Dembski et al., no, it cannot ever become a scientific theory.  Perhaps a form of ID that looks a lot more like Theistic Evolution (TE) may eventually have some scientific basis, but this is mere idle speculation.

&lt;blockquote&gt; If a possible intelligent cause was to be determined in creating an organism,&lt;/blockquote&gt;

How?  How can you - in principle - detect &quot;design&quot; without requiring information that tells you &quot;artificial manufacture&quot;?

&lt;blockquote&gt; the characteristics of said designed object could be used to produce a theoretical extrapolation of the designer’s own characteristics.&lt;/blockquote&gt;

I agree in principle, but this is again mere speculation.

&lt;blockquote&gt; But theorizing design is indeed shaky,&lt;/blockquote&gt;

That&#039;s putting it mildly.

&lt;blockquote&gt; so the pursuit of naturalism must come first UNLESS unviable by the weight of the observable, hard evidence.&lt;/blockquote&gt;

If evidence for biological design were ever to come to light, then biological design would be known to be a part of nature.  End of.

&quot;Naturalism&quot; is merely a vaguely scary and bugbear-ish label applied by the creationists to investigations that deal with facts rather than fantasy.  Reality is the only reliable arbiter of truth when it comes to our ideas about how the world functions.

&lt;blockquote&gt; I don’t think absolutely strict naturalism should be a rule of science when &amp; where required (emphasis on previous 3 words):&lt;/blockquote&gt;

Again, it sounds like you&#039;ve fallen for the propaganda.  What exactly do you mean by &quot;naturalism&quot; and how can a set of investigations that demand real evidence in order to draw conclusions ever seriously consider the supernatural?  Surely &quot;we don&#039;t know yet&quot; is a far more honest answer than &quot;god did it&quot; when you have no evidence to indicate the god even exists?  How can the not-natural (if you&#039;ll pardon a rather clumsy expression) ever have a serious place in improving our understanding of the world?

&lt;blockquote&gt; when it does it leads to your own “God-of-the-gaps” arguments.&lt;/blockquote&gt;

I&#039;m not sure I see what you&#039;re trying to say here.  How does &quot;naturalism&quot; ever lead to GOTG arguments?

IIUC, GOTG is the insistence that god operates in the areas that science has yet to elucidate.  And, as science advances, those gaps get smaller.  At heart, it is an argument from ignorance: for instance &quot;evolution cannot explain X, therefore god did it&quot;.  This is a fallacy, because it assumes that science will &lt;i&gt;never&lt;/i&gt; explain X.  It also rejects &quot;we don&#039;t know yet&quot; as a valid answer.

&lt;blockquote&gt; As for Occ’s razor, just remember that if the evidence were to suggest an external agent, then that external agent is the simpler hypothesis.&lt;/blockquote&gt;

To some extent, and provided it is not in clear conflict with well-established laws of nature.  So what?

Thus far, all of the millions of pieces of evidence that support evolutionary theory point to a purely natural - indeed an inevitable - process.

&lt;blockquote&gt; It doesn’t matter if some yet-to-be natural explanation possibly exists and so we should bet on it, cuz a designer necessitates it’s own explanation – IT MATTERS WHETHER OR NOT THE HYPOTHESIS WORKS RIGHT HERE, RIGHT NOW. Nothing is simple if it doesn’t work.&lt;/blockquote&gt;

If I have understood you correctly, then you are missing two key points:
1. If evolutionary theory were wrong in any substantial or gross way, we would already know it by now.  The core of the theory has been around for 150 years, and has been tested very thoroughly.  Therefore, we can conclude that this core of evolution is &lt;i&gt;at the very least&lt;/i&gt; a good approximation to how biology really works.
2. ID does not work right here, right now.  If you parse through all of the fallacies amd strawman attacks on evolution, ID boils down to nothing more than &quot;someone somewhere designed some stuff in biology, somehow&quot;.  ID has no ideas about when it happened, how it happened, or (officially at least) who did it.  It was designed to be sufficiently vague that it could include YEC, OEC, TE and everything in between.

To expand slightly, if evidence were ever to come to light indicating that biological organisms on Earth were deliberately designed, we would already know that evolution was that designer&#039;s toolkit.

Furthermore, consider this: if one accepts ID with all its vaguenesses, the concept of multiple designers &lt;i&gt;makes a damn sight more sense&lt;/i&gt; than the idea of a single solitary designer.  How else, for instance, to explain the platypus?  Or the &lt;i&gt;Ichneumonidae&lt;/i&gt;?  Or the diversity of eyes?  Or the human pelvis?  Additionally, the competing theory of Incompetent Design is also a better fit for what we know of biology than the ID that is expressed by the luminaries of the Dscovery Institute.</description>
		<content:encoded><![CDATA[<p>Sorry to encourage OT talk but . . .</p>
<p>Sam H (17) said:</p>
<blockquote><p>And while I know that ID is ideologically inclined, it doesn’t mean that it isn’t totally false.</p></blockquote>
<p>Every claim made by the ID authors that we can objectively detect <i>design</i> has been shown to be false.  This is not to say that we might be able to detect it at some undertermined point in the future, but none of the methods proposed by e.g. Bill Dembski are real &#8211; all of them are arguments from analogy (which rely on extraneous information that we already possess), false dichotomy or some other fallacy of reasoning.  Dembski&#8217;s &#8220;deductive filter&#8221; explicitly excludes the set of all hypotheses no-one has thought of yet for no justifiable reason.  Furthermore, he constrains his range of hypotheses in such a way that any combination of chance and natural law is excluded as a possible answer.</p>
<p>What we <i>can</i> detect is manufacture.  And there&#8217;s no sign of that in biology.</p>
<blockquote><p> Yes I’m sympathetic toward them due to my Christian longings and upbringing, but it don’t mean that I can’t attempt to objectively investigate the evidence.</p></blockquote>
<p>But why do you not accept that this process has already occurred, and the answer is &#8211; overwhelmingly &#8211; that ID is a load of rubbish?</p>
<p>All of the arguments made to support ID have been shown to be wrong.  All of them, without exception.</p>
<blockquote><p> ID is by nature a philosophy,</p></blockquote>
<p>What makes you think this, when the Discovery Institute went to such lengths to tell people like you that it was genuine science?</p>
<p>If you consider ID as a philosophy, then you can find plenty of aspects that simply cannot be refuted, but that are &#8211; pretty much by the same token &#8211; intellectually sterile.  I.e., they result in mere navel-gazing, not any actual progress towards anything.</p>
<blockquote><p> but it doesn’t mean it can’t become a scientific theory.</p></blockquote>
<p>As expounded by Behe, Wells, Dembski et al., no, it cannot ever become a scientific theory.  Perhaps a form of ID that looks a lot more like Theistic Evolution (TE) may eventually have some scientific basis, but this is mere idle speculation.</p>
<blockquote><p> If a possible intelligent cause was to be determined in creating an organism,</p></blockquote>
<p>How?  How can you &#8211; in principle &#8211; detect &#8220;design&#8221; without requiring information that tells you &#8220;artificial manufacture&#8221;?</p>
<blockquote><p> the characteristics of said designed object could be used to produce a theoretical extrapolation of the designer’s own characteristics.</p></blockquote>
<p>I agree in principle, but this is again mere speculation.</p>
<blockquote><p> But theorizing design is indeed shaky,</p></blockquote>
<p>That&#8217;s putting it mildly.</p>
<blockquote><p> so the pursuit of naturalism must come first UNLESS unviable by the weight of the observable, hard evidence.</p></blockquote>
<p>If evidence for biological design were ever to come to light, then biological design would be known to be a part of nature.  End of.</p>
<p>&#8220;Naturalism&#8221; is merely a vaguely scary and bugbear-ish label applied by the creationists to investigations that deal with facts rather than fantasy.  Reality is the only reliable arbiter of truth when it comes to our ideas about how the world functions.</p>
<blockquote><p> I don’t think absolutely strict naturalism should be a rule of science when &amp; where required (emphasis on previous 3 words):</p></blockquote>
<p>Again, it sounds like you&#8217;ve fallen for the propaganda.  What exactly do you mean by &#8220;naturalism&#8221; and how can a set of investigations that demand real evidence in order to draw conclusions ever seriously consider the supernatural?  Surely &#8220;we don&#8217;t know yet&#8221; is a far more honest answer than &#8220;god did it&#8221; when you have no evidence to indicate the god even exists?  How can the not-natural (if you&#8217;ll pardon a rather clumsy expression) ever have a serious place in improving our understanding of the world?</p>
<blockquote><p> when it does it leads to your own “God-of-the-gaps” arguments.</p></blockquote>
<p>I&#8217;m not sure I see what you&#8217;re trying to say here.  How does &#8220;naturalism&#8221; ever lead to GOTG arguments?</p>
<p>IIUC, GOTG is the insistence that god operates in the areas that science has yet to elucidate.  And, as science advances, those gaps get smaller.  At heart, it is an argument from ignorance: for instance &#8220;evolution cannot explain X, therefore god did it&#8221;.  This is a fallacy, because it assumes that science will <i>never</i> explain X.  It also rejects &#8220;we don&#8217;t know yet&#8221; as a valid answer.</p>
<blockquote><p> As for Occ’s razor, just remember that if the evidence were to suggest an external agent, then that external agent is the simpler hypothesis.</p></blockquote>
<p>To some extent, and provided it is not in clear conflict with well-established laws of nature.  So what?</p>
<p>Thus far, all of the millions of pieces of evidence that support evolutionary theory point to a purely natural &#8211; indeed an inevitable &#8211; process.</p>
<blockquote><p> It doesn’t matter if some yet-to-be natural explanation possibly exists and so we should bet on it, cuz a designer necessitates it’s own explanation – IT MATTERS WHETHER OR NOT THE HYPOTHESIS WORKS RIGHT HERE, RIGHT NOW. Nothing is simple if it doesn’t work.</p></blockquote>
<p>If I have understood you correctly, then you are missing two key points:<br />
1. If evolutionary theory were wrong in any substantial or gross way, we would already know it by now.  The core of the theory has been around for 150 years, and has been tested very thoroughly.  Therefore, we can conclude that this core of evolution is <i>at the very least</i> a good approximation to how biology really works.<br />
2. ID does not work right here, right now.  If you parse through all of the fallacies amd strawman attacks on evolution, ID boils down to nothing more than &#8220;someone somewhere designed some stuff in biology, somehow&#8221;.  ID has no ideas about when it happened, how it happened, or (officially at least) who did it.  It was designed to be sufficiently vague that it could include YEC, OEC, TE and everything in between.</p>
<p>To expand slightly, if evidence were ever to come to light indicating that biological organisms on Earth were deliberately designed, we would already know that evolution was that designer&#8217;s toolkit.</p>
<p>Furthermore, consider this: if one accepts ID with all its vaguenesses, the concept of multiple designers <i>makes a damn sight more sense</i> than the idea of a single solitary designer.  How else, for instance, to explain the platypus?  Or the <i>Ichneumonidae</i>?  Or the diversity of eyes?  Or the human pelvis?  Additionally, the competing theory of Incompetent Design is also a better fit for what we know of biology than the ID that is expressed by the luminaries of the Dscovery Institute.</p>
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		<title>By: Anchor</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2011/01/07/the-milky-ways-almost-identical-twin/#comment-272870</link>
		<dc:creator>Anchor</dc:creator>
		<pubDate>Mon, 10 Jan 2011 07:36:18 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/badastronomy/?p=25551#comment-272870</guid>
		<description>#40  icemith Says: &quot;But one thing that bothers me. A photo, for want of a better name, (maybe it is very appropriate as we are talking about photons from a distant past), of this galaxy, being perpendicular to the trajectory of those photons that terminate their life in our sensors, are arriving at about the same time. True those from the central bulge will arrive somewhat sooner, (we’ve already missed them), as the “top” of the bulge is slightly closer, maybe by quite a few thousand light years. So we actually get an updated view of that bulge, or at least the peak of it.&quot;

The actuality is we never see what we habitually think of as a &quot;snapshot&quot; confined to a particular instant of time that &quot;preserves the moment&quot; for galaxies, or anything else for that matter. Whenever we look at images of galaxies we are only recording all the photons that arrive within the span of the cameras&#039;s exposure. Galaxies are huge and so we are compelled to see features within them that are considerably displaced in time.

Suppose, for example, that UGC 12158 happened to be oriented nearly edge-on to our line-of-sight: we&#039;d be viewing photons that launched off of its background arms up to 140,000 years EARLIER than those that sprung from its foreground arms. All galaxy &#039;snapshot&#039; images are necessarily &#039;distorted&#039; in this way - they are &#039;smeared out in time&#039;. Considering that a galaxy like this probably gives forth a supernova at rate of perhaps a few times per century (say), the number of these relatively extremely brief events over the course of 140,000 years can exceed a quarter of a million such blasts! But because we can only sample each part of the galaxy at a time, we must still wait about a half century, on average, to witness them.

But even a camera taking a SUFFICIENTLY SHORT exposure of a friend is similarly smeared out in time, albeit to a far lesser extent: an image recording a portrait of your friend shows her ears to be slightly &#039;younger&#039; (from the point of view of your friend) than the tip of her nose (if she is facing you), by the time it takes light to travel those several inches that separate them. Instead of a displacement on the order of 100,000 years, as with edge-on galaxies, the time displacement between the background ears and foreground tip of the nose (say, a depth-distance of roughly 10 centimeters) in your friend&#039;s image would amount to only about 30 billionths of a second.

Of course, ordinary cameras operate with exposures that last a great deal longer than that, typically with exposures lasting around a relatively humongous hundredth of a second. So what you get is an image that records your friend&#039;s ears and nose smeared over the course of that 1/100 second exposure, with all of those overlapping photons, whenever they leap from distant ears to nearby nose, contributing to the image.

With a typical shot of a distant galaxy, however, an hour-long exposure (say) is only about one part in 876.6 million of a hundred thousand years. But if the 100,000 light-years of depth-distance with typical edge-on spiral galaxies the size of our Milky Way were equated with the ten centimeter depth-distance between the ears and nose of your friend, and you scaled up the 1/100 of a second exposure time typical of ordinary point-and-shoot photography in typical human portraits accordingly to match, astronomers would have to keep their telescopic camera shutters open and scrupulously trained and focused on the target galaxy for roughly 100,000 years. (That&#039;s the crude order-of-magnitude figure I come up with...you are free to check the math for yourselves).

It&#039;s a good thing that stars in distant galaxies are bright and that cameras have been developed that come equipped with photo-sensitive means to record light over a modest amount of time that doesn&#039;t unduly press the patience of beings who live, typically on average, about 660,000 times longer than an hour-long exposure. (And some exposures, such as the Hubble Ultra Deep Fields, have been constructed out of exposures totaling DAYS). If circumstances had dictated either that our lifespans were significantly shorter and/or we had evolved a lesser visual capacity as well as engineering dexterity than we have, our ability to eke out information about a universe filled with a froth of galaxy clusters might never have entered our ken...and we would then by now be even more ignorant than we are. ;)</description>
		<content:encoded><![CDATA[<p>#40  icemith Says: &#8220;But one thing that bothers me. A photo, for want of a better name, (maybe it is very appropriate as we are talking about photons from a distant past), of this galaxy, being perpendicular to the trajectory of those photons that terminate their life in our sensors, are arriving at about the same time. True those from the central bulge will arrive somewhat sooner, (we’ve already missed them), as the “top” of the bulge is slightly closer, maybe by quite a few thousand light years. So we actually get an updated view of that bulge, or at least the peak of it.&#8221;</p>
<p>The actuality is we never see what we habitually think of as a &#8220;snapshot&#8221; confined to a particular instant of time that &#8220;preserves the moment&#8221; for galaxies, or anything else for that matter. Whenever we look at images of galaxies we are only recording all the photons that arrive within the span of the cameras&#8217;s exposure. Galaxies are huge and so we are compelled to see features within them that are considerably displaced in time.</p>
<p>Suppose, for example, that UGC 12158 happened to be oriented nearly edge-on to our line-of-sight: we&#8217;d be viewing photons that launched off of its background arms up to 140,000 years EARLIER than those that sprung from its foreground arms. All galaxy &#8216;snapshot&#8217; images are necessarily &#8216;distorted&#8217; in this way &#8211; they are &#8216;smeared out in time&#8217;. Considering that a galaxy like this probably gives forth a supernova at rate of perhaps a few times per century (say), the number of these relatively extremely brief events over the course of 140,000 years can exceed a quarter of a million such blasts! But because we can only sample each part of the galaxy at a time, we must still wait about a half century, on average, to witness them.</p>
<p>But even a camera taking a SUFFICIENTLY SHORT exposure of a friend is similarly smeared out in time, albeit to a far lesser extent: an image recording a portrait of your friend shows her ears to be slightly &#8216;younger&#8217; (from the point of view of your friend) than the tip of her nose (if she is facing you), by the time it takes light to travel those several inches that separate them. Instead of a displacement on the order of 100,000 years, as with edge-on galaxies, the time displacement between the background ears and foreground tip of the nose (say, a depth-distance of roughly 10 centimeters) in your friend&#8217;s image would amount to only about 30 billionths of a second.</p>
<p>Of course, ordinary cameras operate with exposures that last a great deal longer than that, typically with exposures lasting around a relatively humongous hundredth of a second. So what you get is an image that records your friend&#8217;s ears and nose smeared over the course of that 1/100 second exposure, with all of those overlapping photons, whenever they leap from distant ears to nearby nose, contributing to the image.</p>
<p>With a typical shot of a distant galaxy, however, an hour-long exposure (say) is only about one part in 876.6 million of a hundred thousand years. But if the 100,000 light-years of depth-distance with typical edge-on spiral galaxies the size of our Milky Way were equated with the ten centimeter depth-distance between the ears and nose of your friend, and you scaled up the 1/100 of a second exposure time typical of ordinary point-and-shoot photography in typical human portraits accordingly to match, astronomers would have to keep their telescopic camera shutters open and scrupulously trained and focused on the target galaxy for roughly 100,000 years. (That&#8217;s the crude order-of-magnitude figure I come up with&#8230;you are free to check the math for yourselves).</p>
<p>It&#8217;s a good thing that stars in distant galaxies are bright and that cameras have been developed that come equipped with photo-sensitive means to record light over a modest amount of time that doesn&#8217;t unduly press the patience of beings who live, typically on average, about 660,000 times longer than an hour-long exposure. (And some exposures, such as the Hubble Ultra Deep Fields, have been constructed out of exposures totaling DAYS). If circumstances had dictated either that our lifespans were significantly shorter and/or we had evolved a lesser visual capacity as well as engineering dexterity than we have, our ability to eke out information about a universe filled with a froth of galaxy clusters might never have entered our ken&#8230;and we would then by now be even more ignorant than we are. <img src='http://blogs.discovermagazine.com/badastronomy/wp-includes/images/smilies/icon_wink.gif' alt=';)' class='wp-smiley' /> </p>
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		<title>By: reidh</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2011/01/07/the-milky-ways-almost-identical-twin/#comment-272869</link>
		<dc:creator>reidh</dc:creator>
		<pubDate>Mon, 10 Jan 2011 05:45:20 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/badastronomy/?p=25551#comment-272869</guid>
		<description>so its around 4 times its diameter in distance from us? Thats close. Good thing the universe is expanding instead of contracting.</description>
		<content:encoded><![CDATA[<p>so its around 4 times its diameter in distance from us? Thats close. Good thing the universe is expanding instead of contracting.</p>
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		<title>By: Uriel</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2011/01/07/the-milky-ways-almost-identical-twin/#comment-272868</link>
		<dc:creator>Uriel</dc:creator>
		<pubDate>Sun, 09 Jan 2011 19:40:03 +0000</pubDate>
		<guid isPermaLink="false">http://blogs.discovermagazine.com/badastronomy/?p=25551#comment-272868</guid>
		<description>What always gets me about pictures like this, is the feeling of just how SMALL we are. I just stare at the pictures and feel both amazing and insignificant at the same time.</description>
		<content:encoded><![CDATA[<p>What always gets me about pictures like this, is the feeling of just how SMALL we are. I just stare at the pictures and feel both amazing and insignificant at the same time.</p>
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