Page 3 of 16 FirstFirst 1234513 ... LastLast
Results 61 to 90 of 474

Thread: Black Hole FAQ

  1. #61
    Join Date
    Oct 2001
    Posts
    73
    To a far away stationary observer time comes to a stop at the event horizon. To an observer falling through the event horizon time passes normally. How does the Finkelstein FoR reconcile this seeming contradiction? The FAQ addresses this but I don’t get it.

    Since we (Earthlings) are far away stationary observers does this mean all black holes are frozen stars (wrt to us)?

    Would an observer closely approaching a BH see the event horizon rushing towards him at the speed of light? Light must travel at light speed and light is trapped at the EH.

    At the event horizon the light cone closes up, does this mean an observer suspended just outside the EH would *not* see all time pass for the rest of the universe? Would he be fried by the blue-shifted incoming radiation?

    Edited to emphasize "not" in last paragraph

  2. #62
    Join Date
    Jun 2003
    Posts
    718
    I remember seeing a Discovery Science program about black holes that made a statement that made me wonder.

    Basically they said as the mass of the black hole increases to the super-massive level, the gravitational influence decreases.

    Would the gravitational influence eventually become zero or produce a negative gravity field?

    Would this eventually produce a 'white hole' spewing previously consumed matter back into normal space?

    Thanks for producing a great wesite and putting up with our(especially my) many questions!

  3. #63
    Join Date
    Dec 2001
    Posts
    1,853
    FAQ Do Black Holes REALLY exist? Are there more "conventional" alternative explanations that don't require a black hole to explain the observations?

  4. #64
    Join Date
    Sep 2002
    Posts
    10,448
    Quote Originally Posted by Ring
    To a far away stationary observer time comes to a stop at the event horizon. To an observer falling through the event horizon time passes normally. How does the Finkelstein FoR reconcile this seeming contradiction? The FAQ addresses this but I don’t get it.
    Would a distress call sent from just outside the event horizon move at less than the speed of light? Given that the effect of a black hole's gravity extends beyond the event horizon, would the still VERY heavy gravity affect the velocity of a photon?

  5. #65
    Join Date
    Oct 2001
    Posts
    7,732
    No. The lost energy results in a redshift, not a speed reduction. 8)

  6. #66
    Join Date
    Sep 2002
    Posts
    10,448
    Quote Originally Posted by Kaptain K
    No. The lost energy results in a redshift, not a speed reduction. 8)
    One day I gotta ask a photon how it does that, if I could just run faster by blushing, I'd save hundreds of dollars on gas money jogging to work.

  7. #67
    Join Date
    Dec 2001
    Posts
    1,853
    How about this one. What happens as antimatter encounters a black hole formed by regular matter? Does the black hole get lighter as the matter anti-matter annihilate?

  8. #68
    Join Date
    Oct 2001
    Posts
    7,732
    Quote Originally Posted by John Kierein
    How about this one. What happens as antimatter encounters a black hole formed by regular matter? Does the black hole get lighter as the matter anti-matter annihilate?
    Nope! E=mc^2. Or to rewrite it, m=E/c^2. The energy released by the annihilation of matter and antimatter is still trapped inside the black hole, so the total "mass equivalent" does not change. 8)

  9. #69
    Join Date
    Aug 2003
    Posts
    3
    Hi

    My two newbie questions :

    1. Why do black holes exist in the center of galaxies ?

    2. What would happen if a black hole was not surrounded by matter ? i.e. nothing to 'feed' the black hole.

    or

    What would happen to a black hole if it finishes 'swallowing' all matter around it ?

    -Vivek

  10. #70
    Join Date
    Oct 2002
    Posts
    1,860
    Quote Originally Posted by vivek
    What would happen to a black hole if it finishes 'swallowing' all matter around it ?

    -Vivek
    It would s-s-s-s-l-l-l-l-o-o-o-o-w-w-w-w-l-l-l-l-y-y-y-y evaporate. Depending on its size, over time periods that make the current age of the universe seem like the blink of an eye.

    At least, this was the story before dark energy. Now, i don't know.

  11. #71
    Join Date
    Jul 2003
    Posts
    664

    Re: Black Hole FAQ

    Quote Originally Posted by The Bad Astronomer
    Hey BABBers-

    As part of my day job, I am possibly going to write a black hole FAQ. There already is one on the web, but I am looking to be more up-to-date, make it my style, cover other topics, etc.

    So (seriously here), what kind of frequently asked questions would you like to see covered in a FAQ? I have my own list, but I want to see what others have. Check out the other one first and see if it didn't answer your questions.

    Thanks!

    The BA
    Anyone serious about grasping the concept of a black hole in 3 dimensions,ever considered that space may differ in density
    determined by gravity,and the concept of this can be understood
    by relating gravity to a colour?
    Nokton

  12. #72
    Join Date
    Oct 2001
    Posts
    7,732
    ??????????

  13. #73
    Join Date
    Jul 2003
    Posts
    664

    general astronomy

    Hi Mon Capitan,
    There are no gods,thought you would have grown
    beyond diatribe and embraced science and new concepts.
    The opponents of Darwin welcome you

  14. #74
    Join Date
    May 2002
    Posts
    2,045
    OK, my turn.

    ??????????????????


    OK, seriously,
    *nokton - KaptainK was saying that he did not understand what you were saying.

    And I think you missed the point of his signature line. It's a bit of an artistic expression.
    8-[

  15. #75
    Join Date
    Oct 2001
    Posts
    7,732
    Thanks Neb!

    My sig is merely a quote that caught my eye. It is one of several I have used since I joined this board. Whether I believe in God (or gods, for that matter) is immaterial and irrelevant!

    ?????????? means that I did not (and still do not) understand nokton's first post. :-? :-s

  16. #76
    Join Date
    Jan 2003
    Posts
    852

    Re: Black Hole FAQ

    Quote Originally Posted by nokton
    Anyone serious about grasping the concept of a black hole in 3 dimensions,ever considered that space may differ in density
    determined by gravity,and the concept of this can be understood
    by relating gravity to a colour?
    Nokton
    Do you mean illustrating the relationship of gravity and distance with colours?

  17. #77
    Join Date
    Jul 2003
    Posts
    664

    Three dimensional concepts of gravity wells

    Hi Rue,
    Was trying to grasp space,not as a fabric,but a colour,with density.
    Gravity controlling the depth of the colour.Hope you understand my concept Rue.Thankyou

  18. #78
    Join Date
    Oct 2001
    Posts
    11,227
    These are all really good questions! I appreciate the help.

    This FAQ will actually be a part of my day job websites (GLAST, Swift, XMM-Newton). These satellites observe lots of objects that have black holes in their hearts, so a FAQ seems like a good idea.

    There already is a FAQ out there (Ted Bunn's Black Hole FAQ) but I wanted one with more popular-level appeal, maybe even for schoolkids.

    I am also developing a popular-level public talk on black holes, and I'm trolling (!) for ideas. I have it mostly drafted out, but a couple of topics brought up here may make good things to mention in the talk too.

    I knew y'all would come through! Thanks!

  19. #79
    Join Date
    Aug 2003
    Posts
    6
    Taking the risk of being called an idiot:

    Since we know neutrino's hardly interact with normal mass, is it for a neutrino possible to escape from beyond the event horizon?

  20. #80
    Join Date
    Jul 2003
    Posts
    664

    general astronomy

    Hi Bachus,never would regard you as an idiot,an enquiring mind yes.
    Read Hawkings theory of how black holes will eventually dissipate.
    Think he makes sense.Am not into understanding,or venturing opinions
    about that I do not understand,but do question the 'experts' at times.
    Try to think always in reason and logic,not tied to rote learning.
    This really is what this site is all about,and what a wonderful site it is.
    You and I can express our opinions here,we may not have PHDs,
    but by hell we have brains and intellect,this is what the founder of
    this site in his wisdom realised.Thanx,BA.

  21. #81
    Join Date
    May 2003
    Posts
    313
    If quantum theory says that an event must be observed to exist then can we just say by the same logic that black holes do not exist since nothing can be observed beyond the horizon.

  22. #82
    Join Date
    Oct 2001
    Posts
    2,138
    Quote Originally Posted by Zamboni
    If quantum theory says that an event must be observed to exist then can we just say by the same logic that black holes do not exist since nothing can be observed beyond the horizon.
    Hi,

    To paraphrase Einsteinís criticism of the Copenhagen interpretation: "Do you really think a black hole isn't there if you aren't looking at it?" :wink:

  23. #83
    Join Date
    May 2003
    Posts
    313
    @Chip... or Einstein:
    No, I'm saying that it's not there even when I do look at it. Although the fact that we can observe its gravitational field defeats my last post...

  24. #84
    Dear Mr Bad Astronomer,

    Question for the Black Hole FAQ here in General Astronomy. (Didn't want to repeat the question.)

  25. #85
    Join Date
    Dec 2002
    Posts
    227
    Id like to see a case comparing how much we THINK we know vs how much we KNOW we know thru direct observation.

  26. #86
    Join Date
    Jul 2003
    Posts
    2,440
    Hope this isn't a repeat, but one question I'm interested in is how convinced are scientists that there are no sub-atomic particles denser than neutrons.

    In other words, why do the things we observe as black holes actually have to be considered singularities of zero volume. If they had a smidgen of volume (forgive the technical jargon), wouldn't they still attract mass at a tremendous rate, causing X-ray emissions and all of the other phenomena associated with "black holes"

  27. #87
    Join Date
    Oct 2002
    Posts
    16

    What about amateur telescopes?

    Not that I had problems with these questions, but finding answers was difficult.

    Why isn't the gravity - and acceleration into the hole - infinite if density and the gravitational well are infinite?

    Is there any more analysis on the quantum mechanics of a black hole than the Hawking radiation theory?

    Does general relativity _necessarily_ imply black holes?

    Is the singularity a particle?

    The state-of-the-art wormhole research results and ideas?

    Can you see black hole accretion disks with an optical telescope? If so, how big a telescope?

    (There is one quasar you can see with an amateur telescope. It'd be cool if there were accretion disks to see.)

  28. #88
    Join Date
    Apr 2003
    Posts
    1,623
    I just became curious as to another question.

    Is there a minimum or maximum size for black holes?

    Can we make a little one in 'the lab'?

    Would a 'granddaddy' take out the universe?

    I think I will post this in the "Black Hole FAQ" sticky thread as well.

    http://www.badastronomy.com/phpBB/vi...=139759#139759

  29. #89
    Join Date
    Feb 2003
    Location
    Depew, NY
    Posts
    11,881

    Black Hole Record Keeping

    If a distant observer cannot see objects fall into a black hole, instead they see a fainter and fainter object approaching the event horizon, how long until this object disappears from sight? How long could an image be viewed with instrumentation?

    Solphe

  30. #90
    Join Date
    Sep 2003
    Posts
    12,892
    Can a BH and it's EH oscillate? (Say from the impact of a massive star)

    If so, might it resonate? (If the EH expanded breifly would it "gulp" enough matter to cause another EH expansion and another "gulp"?)

    If so, could we not determine much about it from this resonance?

    If so, would it cause the B flat note as per this
    >>> thread <<<.

    If so, what tune does the Milky Way sing? :-({|=
    We know time flies, we just can't see its wings.

Similar Threads

  1. worm hole - black hole theory
    By htfdtw in forum Astronomy
    Replies: 11
    Last Post: 2012-Jan-17, 04:04 AM
  2. Replies: 0
    Last Post: 2011-Feb-23, 05:00 PM
  3. Whats the difference between a Black Hole and a White Hole?
    By emmylou in forum Space/Astronomy Questions and Answers
    Replies: 23
    Last Post: 2011-Feb-07, 02:51 PM
  4. Is the inside of a Black Hole not black?
    By rczmiller in forum Astronomy
    Replies: 13
    Last Post: 2008-Mar-03, 04:37 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •