What is Holes: Definition and 1000 Discussions

A hole is an opening in or through a particular medium, usually a solid body. Holes occur through natural and artificial processes, and may be useful for various purposes, or may represent a problem needing to be addressed in many fields of engineering. Depending on the material and the placement, a hole may be an indentation in a surface (such as a hole in the ground), or may pass completely through that surface (such as a hole created by a hole puncher in a piece of paper). In engineering, a hole may be blind or through if it is partial or complete depth.

View More On Wikipedia.org
Recent contents Top users
  1. B

    Is the Entropy of Black Holes Proportional to Their Size?

    Hi, I'm not a physicist so the answer to this question may be elementary but I can't figure it out for myself. I posted this elsewhere before finding this particular part of the forum. Black holes are famous because (almost) nothing can escape from them. Once an observer has crossed the event...
  2. B

    Can Black Holes Have Entropy?

    Hi, I'm not a physicist so the answer to this question may be elementary but I can't figure it out for myself: Black holes are famous because (almost) nothing can escape from them. Once an observer has crossed the event horizon, no more contact may be made with him or her. Thus it will...
  3. M

    String stars instead of black holes?

    Hey guys. If the string theory is correct (and strings are fundamental and the last building block) I had a thought that if and when a star collapses (due to whatever reason) it can reach neutron star status. Add more mass and it can collapse to a quark star. Now say that we add more mass and...
  4. A

    Probability of winning four holes in golf

    -------------------------------------------------------------------------------- Hi All, I just wanted to be sure I am calculating this correctly: In a golf game, Player A and Player B are competing in 4 holes of golf. The probabilites for 4 holes are below: Player A Prob. Draw Player B...
  5. T

    Exploring the Possibility of White Holes Beyond Black Holes

    From watching "The Universe" on the History Channel, I have heard that there is a theory suggesting that on the "other side" of black holes may lie white holes that spew everything back out into another universe. I'm not sure how great of a source that show is, but that's not the issue here...
  6. A

    Exploring Black Holes: Proving Existence and Locating in Space

    How we can prove the existence of black holes? And how they are located in in the space as they can absorb light too?
  7. P

    Exploring the Math & Physics of Wormholes & White Holes

    Hi, I've recently finished a course on GR, and would like to read up more on wormhole and white hole. May I ask if there are any papers, websites or books that introduces the mathematical and physical structure of these stuffs?
  8. nomadreid

    Entropy of Schwarzschild black holes

    I am trying to reconcile three things: (1) The entropy of a black hole is proportional to the logarithm of the number of possible states of that object to give the same event horizon. (2) The only parameter for a S. black hole is its mass, since its electric charge and angular momentum are...
  9. D

    Black holes giving birth to stars?

    Is it possible for a cloud of gass to condense around a black hole and for fusion to start? Or another way to ask. Is it possible for a star to have a black hole at it's center?
  10. W

    Colliding Black Holes: Will the Smaller Get Pulled In?

    I am sure this must have been asked before but here goes. If two black holes were on a collision course with each other or would pass close to each other. Would the smaller one get pulled into the bigger one?
  11. J

    On black holes and relativity.

    Ok, starting with a 'test' universe with only two objects, a single particle and a neutron star just under the mass required to collapse further into a black hole. If the particle was set in motion near the speed of light, in it's reference frame the neutron star would gain (significant)...
  12. L

    Super black holes and stars orbiting them

    seen a programe about super black holes in which some stars where orbiting them . speeding up as they are slingshoted around them or whatever the proper term for this is . so why if the black hole is strong enough to pull them in the first place why do they not get pulled in completely ... what...
  13. R

    Rotating black holes in Penrose diagrams

    hello, in Penrose diagrams it says that once you have crossed a first Cauchy horizon(of a rotating black hole) , then, with the repulsive singularity, it is possible to cross another Cauchy horizon, and then another event horizon to escape the black hole and go into another universe. so I...
  14. 2

    Special Relativity and Black Holes

    Hello Forum, This is my first post :) Einstein's special relativity finds that length is contracted if the observer is moving at high speeds. Now, assume there is a mass at rest in space that is below critical density of a black hole. If an observer were traveling at high speeds past this...
  15. K

    Black Holes containg a Universe.

    I am very intrigued with the suggestion that what we understand of as our universe, may actually be inside of a black hole. also that black holes may contain universes Can anybody suggest any good reading on the above as I would like to understand things better. Thanks Keith
  16. S

    Black Holes are Tears in Space

    First post. Please be gentle. I`m not a scientist, i`m actually a 3D Artist. I just have a lot of faith in science unfortunately didn`t have the attention span to pay attention enough in high school and even more tragic is that my university didn`t offer any science courses! I was hoping it...
  17. D

    Exploring the Relationship Between Dark Matter and Black Holes in Cosmology

    Hello fellow Cosmology fans and professionals! Does Dark Matter form into Black Holes, and do regular Black Holes attract and trap Dark Matter? Thanks!
  18. Spinnor

    Evaporating black holes, a kind of flux of space?

    If a black hole can "evaporate" via Hawking radiation then there is a radial flux of energy from the black hole? Put a box around on such evaporating black hole. When the black hole is gone there is less space in the box? If so is that space carried away by the Hawking particles? Thanks for...
  19. Astronuc

    Hundreds of Rogue Black Holes May Roam Milky Way

    Hundreds of "Rogue" Black Holes May Roam Milky Way http://news.nationalgeographic.com/news/2008/01/080110-black-holes.html Astronomers have long known about rogue black holes? How long? Is this a new revelation about DM and BHs?
  20. A

    Black holes and the accelerating expansion of the Universe

    Ok; I'm not a physicist... I'm not a mathematician... I'm not even in school, I'm just a computer guy who watches the Science channel a lot :) So don't yell at me... be gentle :) I've heard and read that the rate of expansion of the Universe may be increasing. Is it possible that it...
  21. D

    Explore Black Holes & Time: Is Time Stopping Possible?

    hello, I am new to this forum so I am not sure if this is the right spot for me to post my idea, but here it is. :smile: i was talking to a friend about differnt questions about how things work when he asked the fallowing question: "is it possible to creat a bubble where time completely...
  22. C

    Quasars - how do they emerge from black holes?

    According to everything I've read and heard (as a non-scientist), nothing can come out of a black hole. However, on a couple of documentaries I've seen on the Nat Geo channel in the last week, the astronomers talk about quasars as being massive jets that come out of black holes, because the...
  23. S

    The Entropy of Black Holes: Exploring the Structure of Matter

    I read recently that the entropy of a black hole is proportional to the surface area of its event horizon. Being that surface area is a two dimensional measurement, only requiring length and breadth, what does that say about the structure of matter contained in the event horizon? I'm not sure...
  24. bcrowell

    Best review paper on the observational status of black holes?

    Suppose I have to pick one review paper on the observational status of astrophysical black holes. It should: -be as up to date as possible -be available for free online (preferably on arxiv) -cover both supermassive and solar-mass black holes Does anyone have any suggestions? This one...
  25. S

    Exploring the Possibilities of Black Holes

    Hey guys I'm new here :D , i came across this read online Edit by Evo: Removed link to blog Please scroll down to a big post by xodiac21. Its very interesting, but I'm here wondering about the part where you jump into the black hole and ur friend watching if u really GET into the black hole, i...
  26. L

    Black holes (didnt know where to put this question)

    this is buggin me. could some one please explain in lay terms what they believe happens when 2 black holes are close enough to be in an elyptical orbit around each other at speeds that would be approaching the speed of light pryor to the smaller one being absorbed into the larger they would...
  27. J

    White Holes: Connections to Other Universes?

    Does the theory allow White Holes to exist? I read "somebody" thinks that black holes are connection to other universes; as b.o. continuously capture materials... couldn't they be emitting this material in the other universe? Could they be "white holes"... or, in other words, "big bangs"?
  28. I

    Interesting thought about black holes

    Well since we will never see something go into a black hole, won't we see everything the black hole tries to swallow around it? So wouldn't it be possible to see a black hole since a bunch of things would be around the event horizon. Answers are appreciated.
  29. rjbeery

    Is it possible that black holes do not exist?

    Please correct this if a widely accepted answer exists; please forgive my layman's terminology; lastly, forgive me for posting this to two forums but my first attempt got no takers... The "infinite" (unaffected by the local gravity effects) observer A knows that a rocket ship carrying...
  30. bcrowell

    White Holes & Eternal Black Holes: Stephen D.H. Hsu

    White holes and eternal black holes Stephen D.H. Hsu http://arxiv.org/abs/1007.2934 I though this was very interesting, and partially cleared up some of the confusion I'd had about this topic in the past. The introductory section is very nontechnical and accessible. One thing that wasn't...
  31. N

    Do black holes swallow dark matter?

    What do we know about black holes swallowing dark matter? Dark matter exhibits gravitational effects, right [lensing and keeping star orbital speeds about galactic centers rouighly independent of their distance from a galactic center]? So it seems black holes should consume both normal and dark...
  32. B

    Could an object survive passing through two intersecting black holes?

    Would it be possible for something to pass through 2 event horizons,falling into both black holes? also,if it can,what would happen if the objecct in question (lets say a proton) was at a point where the forces acting on it were equal in every direction? say being at the centre of these two...
  33. Z

    Slight confusion with black holes

    Hey, I am a little confused with the nature of black holes. I am under the impression that time is infinitely slow at a black hole's existence. I am also under the impression that black holes are a point of singularity, but have a defined mass. Gravitational force is only caused by mass...
  34. C

    Ideas about black holes, light, and time.

    Alright, so I'm kinda new to posting here, sorry if I don't understand things fully at this time. As for questions, I have a few of them. Firstly, what is the force of gravity at the event horizon of a black hole. Since photons have no mass, what would be the force required to trap it...
  35. R

    Time dilation and length contraction for rotating black holes

    hello, how is it possible to calculate the only GRAVITATIONNAL time dilation and length contraction factor in the Kerr metric and/or the Kerr-Newman metric, for an object falling but otherwise at rest, since there is frame dragging, and the metric contains dt^2 components but also dt.dphi...
  36. A

    Black Holes and Variable Infinities

    Hi all, I have been thinking about black holes and the different sizes that they come in. With regular black holes and super massive and all of the in between black holes it begs a question. Can one infinity be bigger than the other? All black holes are said to have infinitely dense centers...
  37. R

    What are the Properties of 4D and 5D Black Holes?

    I have a question concerning upper dimensional black holes. Basically my question would be: what are 4d and 5d black holes? But being more precise about my question, I would like to ask about their properties. I guess there is an analogy between 3d black holes and the other ones, so is then...
  38. @

    Can Black Holes Break the Rules of Time?

    hey people..! I need to ask that whether time travel is possible ?.If speed of light is achieved..however besides this i also think that if speed of light is achieved nothing could stay at that speed virtually...what do you people think..?? Secondly, i was thinking that how do we know that...
  39. M

    Safe Fluid Flow in Modified Microwaves: How to Protect Yourself?

    Hi, Rather than jump on the other thread about microwaves, i thought id start this one! If i were to drill a couple of holes in a microwave oven in order to have a coil of plastic pipe with fluid flowing through it coming out of the holes, how would i protect myself from being cooked? I...
  40. marcus

    Black holes in AsymSafe gravity (new Easson paper)

    http://arxiv.org/abs/1007.1317 Black holes in an asymptotically safe gravity theory with higher derivatives Yi-Fu Cai, Damien A. Easson 22 pages, 3 figures (Submitted on 8 Jul 2010) "We present a class of spherically symmetric vacuum solutions to an asymptotically safe theory of gravity...
  41. P

    Are Black Holes Real? Examining Empirical Evidence and Astronomical Distinctions

    Do we have empirical evidence proving that black holes, rather than stars with density close to black holes, exist in our universe? To put it more clearly, are astronomers able to distinguish a black hole from a compact object with a surface gravitational redshift of, say, z=100? Of course, if...
  42. B

    Can black holes absorb gravity waves?

    From what I understand, black holes can generate gravity-waves in orbit with each other. But can they absorb them? Since gravity waves travel at the speed of light, I would think that they would not be able to escape BH gravitation. But since they are so massive and powerful, I wonder if they...
  43. C

    What Would Happen if a Photon Was Caught Between Two Colliding Black Holes?

    This may be a dumb ? , but what would happen if two black holes were coming together and when they were coming together we got a photon extremely close to their event horizons , and when the came together the photon was right on the overlap of their event horizons which way would the photon...
  44. K

    Black holes and extended horizons

    I'm currently writing a sci-fi/fantasy novel and although I know everything in this genre doesn't have to be technically accurate I still like to keep one foot firmly in the realm of reality and combine it with aspects of the fantastic. At the moment I'm working on a plotline that involves a...
  45. B

    Black Holes & Time: Literal or Figurative?

    Okay, this is me beating a dead horse, but i have a rather simple question. Is the time dilation effect described in reference to a black hole literal or figurative? for example, a man falling toward a black hole will appear to slow as he approaches the EH. This effect obviously increases...
  46. H

    Question about black holes and white dwarf

    hi i want to ask aquestion what is the biggest qatar: black hole or white dwarf or nutron star or the sun please i want to know the biggest one and then and then and the smallest one thaaaank you very much
  47. K

    Exploring the Possibility of an Expanding Universe Beyond Black Holes

    I was wondering if someone agrees: Is it possible that on the other side of the black hole is an expanding universe? It seems an iteresting idea to me: in our universe a star collapses onto itself with an explosion, creating a black hole and on the other side a big bang happens with matter...
  48. Z

    Are black holes a point of singularity?

    Are black holes a point of singularity of infinite density, approaching that point as a limit, or just really massive and really dense? Is light really being "sucked in" by the gravity and actually being attracted to the object, or is it really just following the really really steep bend in...
  49. J

    Entropy and Black Holes: Understanding the Second Law of Thermodynamics

    I am a little confused over something, so perhaps someone can tell me which one of the following statements is incorrect. (I don't know a lot about this, so forgive my ignorance). Suppose that we have a closed system of some size, and we start in a state where we have a black hole at the...
  50. marcus

    Asymptotic safety and black holes (new Mattingly paper)

    Dave Mattingly has been a frequent collaborator with Ted Jacobson (his thesis advisor). You know of Jacobson if, for example, you followed the recent discussion of "gravity as entropic force" by Erik Verlinde and others. In 1995 Jacobson derived the Einstein field equation from thermodynamics...
Back
Top