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	<title>Comments on: News: Do black holes really exist?</title>
	<link>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/</link>
	<description>I am an astronomer, writer, and skeptic. I likes reality the way it is, and I aims to keep it that way. My real name is Phil Plait, and I run the Bad Astronomy blog.</description>
	<pubDate>Sat, 10 Jan 2009 04:14:32 +0000</pubDate>
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		<title>By: Seehart</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/#comment-125675</link>
		<dc:creator>Seehart</dc:creator>
		<pubDate>Wed, 15 Oct 2008 11:43:19 +0000</pubDate>
		<guid>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/#comment-125675</guid>
		<description>Please excuse the typos.  

First paragraph should end with "... so both are considered to be in the same inertial /frame/ of reference)."

The main thing that I would particularly like to get confirmation on is this:  Time dilation approaching infinity at the event horizon is a fact in present time, in the reference frame of a distant observer (as opposed to an artifact of waiting for light to arrive).</description>
		<content:encoded><![CDATA[<p>Please excuse the typos.  </p>
<p>First paragraph should end with &#8220;&#8230; so both are considered to be in the same inertial /frame/ of reference).&#8221;</p>
<p>The main thing that I would particularly like to get confirmation on is this:  Time dilation approaching infinity at the event horizon is a fact in present time, in the reference frame of a distant observer (as opposed to an artifact of waiting for light to arrive).</p>
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		<title>By: Seehart</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/#comment-125671</link>
		<dc:creator>Seehart</dc:creator>
		<pubDate>Wed, 15 Oct 2008 10:53:39 +0000</pubDate>
		<guid>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/#comment-125671</guid>
		<description>My confusion about physics times my incertitude that I am not a duck is greater than h.  Therefore, since I am a witch, and I want to understand physics better, I should not weigh myself.</description>
		<content:encoded><![CDATA[<p>My confusion about physics times my incertitude that I am not a duck is greater than h.  Therefore, since I am a witch, and I want to understand physics better, I should not weigh myself.</p>
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		<title>By: Seehart</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/#comment-125669</link>
		<dc:creator>Seehart</dc:creator>
		<pubDate>Wed, 15 Oct 2008 09:46:57 +0000</pubDate>
		<guid>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/#comment-125669</guid>
		<description>There is a distinction between an event happening and me finding out that an event has occurred.

Correct me if I am wrong, but my understanding is that what I see now is distinct from what I consider to be happening now in my reference frame.  To illustrate, consider a really trivial SR case.  When I look at Alpha Centauri in my telescope, I consider what I see to be what happened 4.37 years ago in my frame of reference, not what is happening now in my frame of reference.  I know that what is happening now at Alpha Centauri will take 4.37 years to reach me.   (I am ignoring the difference in velocity between myself and Alpha Centauri, so both are in the same inertial from of reference).

Likewise, what I see now when I look at a black hole is not what I consider to be happening now in my frame of reference.  When I look at a (forming) black hole I see things slow down asymptotically to zero.  This has been described as an "optical illusion" caused by the fact that photons take longer to reach me as the escape velocity approaches c.  This seems to be a misleading, though partially correct, description. 

My current understanding is that the passage of time actually slows down near the (forming) event horizon in the frame of reference of a distant observer, even after taking into consideration the travel time of the photons.  This is tricky because two distinct (not even complementary) phenomena imply the observation of things slowing down, the optical illusion caused by ever increasing travel time of photons on the one hand, and relativistic time dilation on the other.   Or do I have it wrong?  Are these two phenomena complementary rather than distinct?

A related source of confusion is sometimes seen in sci-fi B movies, when you hear phrases like "...meanwhile, back in the present...."  What the heck does "meanwhile, back in the present" mean?  Anyway, if the time dilation at the event horizon is merely an "optical illusion" due to the fact that I have to wait forever to actually see the black hole form, even though I know that really it has already formed, then I can say things like "meanwhile, back at the black hole".  Otherwise, I have to say that as far as I am concerned, the black hole will never form.

I don't think that it is quite correct to say this: "Hey, it looks like that neutron star is almost frozen.  But that's just because I'm looking at what happened millions of years ago.  The photons describing what's happening now will never reach me since it is a real black hole by now."

More correct would be this: "Hey, it looks like that neutron star is almost frozen.  But that's just because I'm looking at what happened millions of years ago.  The photons describing what's happening now will take a very long time to reach me.  Nevertheless, my understanding of physics tells me that even now, it is not yet a real black hole." 

If it is the case that black holes do not form in finite time in my frame of reference, then it is also the case that no information leaves my version of the universe.  No matter how long I wait, it is possible in principle for any object (including any part of the collapsing neutron star) to suddenly decide to send me a message (since escape velocity is not yet c), which I will eventually receive.  Therefore I will never experience the phenomenon of information loss.

If my version of the universe (i.e. the universe as described by my frame of reference) will never lose information to black holes, then what about that wad of paper?  Well, the wad of paper experiences nothing special when crossing the event horizon.  All the information of the universe is available to the wad of paper, so the wad of paper has nothing to complain about (other than being mercilessly shredded).  Unless I improperly combine these two distinct frames of reference into one interpretation, I don't see the problem.  What observer can say that information is being lost?

Let me put it another way.  Assuming that I can easily create a 20 solar mass neutron star destined for collapse in my lab and I have nearly Godlike powers of perception (subject to the limitations of quantum mechanics) what experiment can I do that detects the phenomenon of information loss?  Quantum mechanics demands that we pick no more than one observer to witness our experiment.   It seems to me that it would be completely improper for me to consider the frame of reference of an in-falling observer when attempting to model what will happen in my experiment with me as the observer.</description>
		<content:encoded><![CDATA[<p>There is a distinction between an event happening and me finding out that an event has occurred.</p>
<p>Correct me if I am wrong, but my understanding is that what I see now is distinct from what I consider to be happening now in my reference frame.  To illustrate, consider a really trivial SR case.  When I look at Alpha Centauri in my telescope, I consider what I see to be what happened 4.37 years ago in my frame of reference, not what is happening now in my frame of reference.  I know that what is happening now at Alpha Centauri will take 4.37 years to reach me.   (I am ignoring the difference in velocity between myself and Alpha Centauri, so both are in the same inertial from of reference).</p>
<p>Likewise, what I see now when I look at a black hole is not what I consider to be happening now in my frame of reference.  When I look at a (forming) black hole I see things slow down asymptotically to zero.  This has been described as an &#8220;optical illusion&#8221; caused by the fact that photons take longer to reach me as the escape velocity approaches c.  This seems to be a misleading, though partially correct, description. </p>
<p>My current understanding is that the passage of time actually slows down near the (forming) event horizon in the frame of reference of a distant observer, even after taking into consideration the travel time of the photons.  This is tricky because two distinct (not even complementary) phenomena imply the observation of things slowing down, the optical illusion caused by ever increasing travel time of photons on the one hand, and relativistic time dilation on the other.   Or do I have it wrong?  Are these two phenomena complementary rather than distinct?</p>
<p>A related source of confusion is sometimes seen in sci-fi B movies, when you hear phrases like &#8220;&#8230;meanwhile, back in the present&#8230;.&#8221;  What the heck does &#8220;meanwhile, back in the present&#8221; mean?  Anyway, if the time dilation at the event horizon is merely an &#8220;optical illusion&#8221; due to the fact that I have to wait forever to actually see the black hole form, even though I know that really it has already formed, then I can say things like &#8220;meanwhile, back at the black hole&#8221;.  Otherwise, I have to say that as far as I am concerned, the black hole will never form.</p>
<p>I don&#8217;t think that it is quite correct to say this: &#8220;Hey, it looks like that neutron star is almost frozen.  But that&#8217;s just because I&#8217;m looking at what happened millions of years ago.  The photons describing what&#8217;s happening now will never reach me since it is a real black hole by now.&#8221;</p>
<p>More correct would be this: &#8220;Hey, it looks like that neutron star is almost frozen.  But that&#8217;s just because I&#8217;m looking at what happened millions of years ago.  The photons describing what&#8217;s happening now will take a very long time to reach me.  Nevertheless, my understanding of physics tells me that even now, it is not yet a real black hole.&#8221; </p>
<p>If it is the case that black holes do not form in finite time in my frame of reference, then it is also the case that no information leaves my version of the universe.  No matter how long I wait, it is possible in principle for any object (including any part of the collapsing neutron star) to suddenly decide to send me a message (since escape velocity is not yet c), which I will eventually receive.  Therefore I will never experience the phenomenon of information loss.</p>
<p>If my version of the universe (i.e. the universe as described by my frame of reference) will never lose information to black holes, then what about that wad of paper?  Well, the wad of paper experiences nothing special when crossing the event horizon.  All the information of the universe is available to the wad of paper, so the wad of paper has nothing to complain about (other than being mercilessly shredded).  Unless I improperly combine these two distinct frames of reference into one interpretation, I don&#8217;t see the problem.  What observer can say that information is being lost?</p>
<p>Let me put it another way.  Assuming that I can easily create a 20 solar mass neutron star destined for collapse in my lab and I have nearly Godlike powers of perception (subject to the limitations of quantum mechanics) what experiment can I do that detects the phenomenon of information loss?  Quantum mechanics demands that we pick no more than one observer to witness our experiment.   It seems to me that it would be completely improper for me to consider the frame of reference of an in-falling observer when attempting to model what will happen in my experiment with me as the observer.</p>
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		<title>By: York</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/#comment-121632</link>
		<dc:creator>York</dc:creator>
		<pubDate>Sun, 28 Sep 2008 06:04:42 +0000</pubDate>
		<guid>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/#comment-121632</guid>
		<description>OW OW OW OW OWreading the main thing then robs then everyone else's OWWWWWW haha i kinda understood what ya all said AND I"M 13!!!!!!!!!! YAY ME


i had a thought: what if a blackhole is just a matter converter yeah with the dense gravity and such but when it gets sucked in the matter gets converted into energy then spit out as the jet stream of energy; so now we know how its formed and were it goes after its sucked in...........did that make any sence?</description>
		<content:encoded><![CDATA[<p>OW OW OW OW OWreading the main thing then robs then everyone else&#8217;s OWWWWWW haha i kinda understood what ya all said AND I&#8221;M 13!!!!!!!!!! YAY ME</p>
<p>i had a thought: what if a blackhole is just a matter converter yeah with the dense gravity and such but when it gets sucked in the matter gets converted into energy then spit out as the jet stream of energy; so now we know how its formed and were it goes after its sucked in&#8230;&#8230;&#8230;..did that make any sence?</p>
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		<title>By: G...G</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/#comment-38930</link>
		<dc:creator>G...G</dc:creator>
		<pubDate>Tue, 17 Jun 2008 09:04:38 +0000</pubDate>
		<guid>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/#comment-38930</guid>
		<description>jingo your joke is laim- is it a joke? Jainebelle i agree with you and Nelson no, no your so wrong in so many ways.</description>
		<content:encoded><![CDATA[<p>jingo your joke is laim- is it a joke? Jainebelle i agree with you and Nelson no, no your so wrong in so many ways.</p>
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		<title>By: Logan</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/#comment-38929</link>
		<dc:creator>Logan</dc:creator>
		<pubDate>Sun, 06 Jan 2008 05:59:12 +0000</pubDate>
		<guid>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/#comment-38929</guid>
		<description>instead of happening i should have said going</description>
		<content:encoded><![CDATA[<p>instead of happening i should have said going</p>
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		<title>By: Logan</title>
		<link>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/#comment-38928</link>
		<dc:creator>Logan</dc:creator>
		<pubDate>Sun, 06 Jan 2008 05:57:05 +0000</pubDate>
		<guid>http://blogs.discovermagazine.com/badastronomy/2007/06/19/news-do-black-holes-really-exist/#comment-38928</guid>
		<description>so is the stuff in a black hole like string theory type stuff??? but like string theory by string theory??? lol

And with time *slowing down to almost a stop but not quite reaching there* since it exists doesn't it mean that it needs to be going at the same speed or what every you want to call it as everything else is happening.

Or does time not really exist and we just want to say when something happens.

As everyone else has said "i think my brain just melted!"</description>
		<content:encoded><![CDATA[<p>so is the stuff in a black hole like string theory type stuff??? but like string theory by string theory??? lol</p>
<p>And with time *slowing down to almost a stop but not quite reaching there* since it exists doesn&#8217;t it mean that it needs to be going at the same speed or what every you want to call it as everything else is happening.</p>
<p>Or does time not really exist and we just want to say when something happens.</p>
<p>As everyone else has said &#8220;i think my brain just melted!&#8221;</p>
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