tag:blogger.com,1999:blog-38085367.post8464703996374432789..comments2024-03-19T09:06:21.507-04:00Comments on Irtiqa: Friday hodgepodge: Cats mastering physics, science cheerleaders, and a galaxy from far-far awaySalman Hameedhttp://www.blogger.com/profile/04327330113822656571noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-38085367.post-2943874231280482412010-11-17T07:14:44.926-05:002010-11-17T07:14:44.926-05:00Thanks again for simple yet effective explanation....Thanks again for simple yet effective explanation. Will keep bothering you with such questions. :)Atif Khanhttps://www.blogger.com/profile/07137026009148344854noreply@blogger.comtag:blogger.com,1999:blog-38085367.post-29781081313615388632010-11-16T23:56:29.165-05:002010-11-16T23:56:29.165-05:00Atif,
The blackholes just become dormant. So for...Atif, <br /><br />The blackholes just become dormant. So for example the black hole at near the center of our own Milky Way is a relatively uneventful black hole. And by that I mean that, at present, it doesn't have much gas/dust around it (there is some - but this is small compared to other galaxy centers). If you completely run out of matter to swallow, black holes will just sit there - just like other dead stars like white dwarfs and neutron stars. <br /><br />Now I don't want to get side-tracked here...but very small blackholes (if they exist) should evaporate after some time. This is a prediction from Stephen Hawking (these mini-black holes are supposed to give-off radiation - that we now call Hawking radiation - and this should lead to the evaporation of these mini-blackholes after a long period of time (I don't remember the scales for this). <br /><br />But as far as the regular blackholes are concerned, they will just simply sit there without matter around them.<br /><br />Hope this answer is in the ballpark range that you were expecting.Salman Hameedhttps://www.blogger.com/profile/04327330113822656571noreply@blogger.comtag:blogger.com,1999:blog-38085367.post-30031420768380341582010-11-16T00:00:23.947-05:002010-11-16T00:00:23.947-05:00Thanks for the reply. One more basic question (tho...Thanks for the reply. One more basic question (though I read fewer websites about that but couldn't find simplest answer). What happen to blackholes in longer run when they go out of the matter/gas around. We know there is a blackhole in almost every galaxy out there. How do those blackholes end up?Atif Khanhttps://www.blogger.com/profile/07137026009148344854noreply@blogger.comtag:blogger.com,1999:blog-38085367.post-27363930777261518932010-11-15T18:05:49.588-05:002010-11-15T18:05:49.588-05:00Atif,
Good question - and you are right, it is th...Atif,<br /><br />Good question - and you are right, it is the red-shift that tells us about the distance. For nearby objects, there are many different ways of measuring distances - but when it comes down to some of the farthest objects, then redshift is our only resort. Now each chemical element has a unique structure - and that structure produces unique lines that can be identified with telescopes. Hydrogen lines are usually used to measure the redshift. This means that hydrogen lines will be seen at longer wavelengths (redder) than we know them from the laboratory. And this is due to the expansion of the universe - where the farther away a galaxy is, the faster it will be moving away from us. (some demos for expanding universe <a href="http://www.av8n.com/physics/expansion-of-the-universe.htm%22" rel="nofollow"> here</a>)<br /><br />As far as accuracy is concerned - yes, uncertainties increase the farther away (and fainter) we are looking at. I don't know the specific error-bars here, but it won't change the distance too dramatically.Salman Hameedhttps://www.blogger.com/profile/04327330113822656571noreply@blogger.comtag:blogger.com,1999:blog-38085367.post-22882009453214953492010-11-14T11:45:21.972-05:002010-11-14T11:45:21.972-05:00Here is a very layman question.
How do we know th...Here is a very layman question.<br /><br />How do we know the light coming from far far galaxy took 13 billion years? It could have been closer so how do we verify? Is it gravitational lensing or red shift that we study to calculate the distance?Atif Khanhttps://www.blogger.com/profile/07137026009148344854noreply@blogger.com