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.

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  1. D

    What happens when a black hole is a certain size?

    Okay, I am new here and I guess you could say I am a little new to Einsteins theory of relativity, but I am trying so bear with me here. Okay, I remember reading somewhere that the size (not mass) of a black hole makes a difference of what happens when your getting sucked in theoretically...
  2. R

    Div Curl: Black Hole Edge Explored

    What is the divergence and curl at the edge of a black hole?
  3. T

    Can Black Holes Absorb Massless Light?

    First of all, I have to say that I'm not sure if my post is on the good forum. If there's any problem about that, just tell me where i should post it. So my question is, why light can de be absorb by black holes if light has no mass. I mean if black holes have enormus gravitational force it...
  4. N

    Information loss via black Holes

    This question is about the relationship between information, entropy and heat. I think it was in the 1970's the Hawking claimed "information is lost in black hole evaporation". This did not mean it was just inaccessible, but that it has literally disappeared, gone forever. In the Black...
  5. L

    Exploring the Compression of Atoms in Black Holes

    How compressed are the atoms black holes are made of? Is there a limit to how much you can compress matter? It seems to me, the most you can compress matter would be until the individual subatomic particles are side by side touching each other. Are black holes compressed more than that? Are...
  6. R

    Time & Black Holes: Creative Perspective on Creation

    Hello everyone, before I start, I just want to say I feel a little out of place here. I am not a student of physics or cosmology, and I am definitely not a professional at anything scientific. I am an artist and going to school for Industrial design. I have always been fascinated with Science...
  7. P

    White Holes: Explaining How They Violate the 2nd Law of Thermodynamics

    I was reading a bit about wormholes and I run into white holes. Now, everyone keeps saying that white holes violate the second law of thermodynamics, but I can't really understand why. I suspect it has something to do with entropy, but I'm not really sure. Any help would be appreciated.
  8. F

    Black holes - a few questions from a newb

    so how are they actually created. i know it happens on a collapsing of a star due to the big gravity which it has, but what's the real physical concept behind it. it can't be just like everting your shirt, right? what do black holes concist of? or what are they? where does the matter...
  9. G

    Did the Big Bang create the most massive black hole in the universe?

    I've been watching videos and reading about black holes and big bang and many questions puzzle me. But here's one that I don't really get it. How the big bang even started since it had all mass of the universe in it. Therefore its gravitational pull in itself would surpass any mass of...
  10. S

    Very confused about black holes

    From my limited understanding, black holes supposedly have "event horizons" where everything near them just falls inside the black hole and becomes nothingness, totally anhilated. If this is the case then how is it that black holes emit stuff, like radio waves? If they suck things in and then...
  11. A

    Role of Exclusion principle in formation of black holes.

    I was reading something about formation of black hole, and it was given that exclusion principle has a role in BH (Black Hole) formation. It read "when star become small, the matter particle get very near each other, and so acc. to Pauli's Exclusion principle they must have different...
  12. P

    Bullet passing through two holes

    Homework Statement so this is a classic problem...if you know what i mean. The speed of a moving bullet can be determined by allowing the bullet to pass through two rotating paper disks mounted a distance .082m apart on the sam axle. from the angular displacement 24.9 degree of the two...
  13. rjbeery

    What is the Relationship Between Proper Time and Coordinate Time in Black Holes?

    I enjoy studying QM, but my knowledge of black holes is basically limited to the high school explanations as depicted below. As a body approaches the event horizon the gravitational forces on that body accelerate it to a velocity approaching c. The math implies that mass crossing the event...
  14. MTd2

    Self-dual Black Holes in LQG: Theory and Phenomenology: (title of the article)

    http://arxiv.org/abs/0905.3170 In this paper we have recalled the semiclassical metric obtained from a classical analysis of the loop quantum black hole (LQBH). We show that the regular Reissner-Nordstrom-like metric is self-dual in the sense of T-duality: the form of the metric obtained in...
  15. O

    Black holes, white holes, and time

    Please forgive me if I am posting in the wrong place, and also if this has been discussed before. Gravity is so strong in a black hole not even light can escape, Can the light be accelerated past c once inside of the event horizon? I know the universal answer that nothing can exceed c...
  16. R

    Can Black Holes Be Used for Space Travel and How Do They Compare to Wormholes?

    Hey guys, This may be a silly question. I saw star trek the other day, and I know it is science fiction but I was wondering...My understanding is that black holes are a region in space-time from which nothing can escape. However it seems like in the movie they are also used to travel through...
  17. N

    Gravitational redshift and black holes

    Questions: Gravitational redshift and black holes I have some questions: 1. What does gravitational redshift do to light trying to escape a black hole? Is the light destroyed? 2. And what is the physical cause of this redshift? (I’m not interested in equations and math, only the physical...
  18. P

    Can Black Holes Bend Light and Act as a Time Machine?

    The reason I heard that black holes are black is because any light that trying to leave the black hole's gravity gets sucked in by the massive amounts of gravity. So this implies that light can curve or even reverse direction if enough gravity is present. If this is the case then what stops a...
  19. MTd2

    Why black holes do not have color charge?

    I'm clueless.
  20. F

    Are black holes bosons or fermions?

    The question says it all. Black holes have mass, and they have angular momentum. - Is the angular momentum an integer or half an integer? Or neither/both? - What happens when two black holes are exchanged? François
  21. M

    Exploring Magnetism and Black Holes

    I read recently that magnetism plays an important role in cramming all that matter into a black hole. But how is it possible that magnetic force could escape a black hole, having an escape velocity higher than the speed of light, therefore an impossibility of matter(or energy) escaping?
  22. B

    How is it that black holes are black?

    It is generally accepted that light cannot escape a "black" hole because the singularity's gravitational pull is too strong for photons (or waves, or wavicles, or whatever) to achieve movement away from the singularity. Isn't gravity a warping of space? And isn't space a facet of a single...
  23. W

    Why can't electromagnetic radiation escape black holes?

    Why can't light escape black holes? Isn't light as an electromagnetic radiation massless, thus not affected by gravitational pull? --
  24. W

    Does black holes exist all around us?

    I read Wikipedia about black hole and interpreted it as such: that black holes exist all around us, most of them are very, very small. Suppose we have a drinking water glass (just suppose its mass is 10kg) hence at radius 1.48 E-26 m (far smaller than even the radius of an electron) there...
  25. R

    Questions about black holes for a fictional story

    The short version: Is it possible to engineer anything useful with black holes in our universe? The long version: I'm working on making the backstory for a fiction I've been thinking about, and I'd like to get a better understanding of theoretical black hole physics for that story. The...
  26. P

    Dark matter and microscopic black holes

    What I was thinking is that if dark matter particles don't interact electromagnetically or by nuclear forces then what is there to stop them coming arbitrarily close to each other thus forming microscopic black holes? And shouldn't we then be able to detect them by Hawking radiation? Does the...
  27. Phrak

    Are Black Holes Theoretical Phantoms?

    I understand that it takes an infinite amount of time for an event horizon to form. Give this, if there are any black holes, they have been around forever. Are there good comological models that include 'forever', or is my premise wrong?
  28. M

    Black Holes and Gravitational Waves

    As far as I know, a black hole is a singularity in the space-time. The space-time becomes so curved that the geodesics can't get out, i.e., the gravitational field becomes so strong that information can not get out. OK! But what about gravitational waves? As far as I know, gravitational waves...
  29. C

    How do Black holes radiate energy?

    Hi, I was wondering how black hole's radiate energy and to be specific what the geometry of this radiation is. Can they radiate it planar, polar like a gamma ray burster, or something else? I'm not sure how far astrophysicists have gotten in terms of the theory of this, so please include all...
  30. D

    Can black holes form without gravity in the early universe?

    Hey guys, I got a question that is kind of bugging me.. Need your opinion on it. Here are my thoughts from my notebook that i wrote while i was at work :) Sorry for the loose and simplified language.. In the paper titled "Greatest Story Ever Told", Neil deGrasse Tyson states that little...
  31. F

    Are gravitons consistent with black holes emitting them?

    If gravitons exist, how can black holes emit them? It cannot be like Hawking radiation, which increases as the black hole gets smaller. The gravitational field grows larger as black holes grow larger. Also, would not the energy of the graviton decrease to zero (and its wavelength increase to...
  32. U

    Why do scientists believe white holes are impossible?

    I have multiple reasons why white holes do not exist. But first let’s go over what a white hole is. It is: the same as a black hole, but in reverse. Instead of sucking up matter and light, it spits it out. This spit out matter and light are said to have been from a black hole, transported to the...
  33. D

    Black Holes have no gravity below the event horizon? - How can that be?

    blechman's statement: Gravitons are emitted FROM THE SURFACE of the event horizon (remember: gravitons are massless, and therefore move at the speed of light). THAT's what we see. There is NO information (gravitational or otherwise) that can escape from INSIDE the black hole. This is not a...
  34. D

    Black Holes: Is the Hubble Image Real?

    I had a conversation with a friend about Black Hole images. I showed him a picture of a black hole taken by the Hubble telescope shown here: http://hubblesite.org/newscenter/archive/releases/1995/47/image/a/ He claims that it's not a direct image of a black hole because we can't see black...
  35. H

    Can Black Holes Decay and How Does This Affect Their Event Horizon?

    http://www.superstringtheory.com/blackh/blackh3.html the URL above says that black holes can decay, but I don't understand, if the black hole sucks in an antiparticle and the particle gets ejected in the opposite direction, doesn't the event horizon of the black hole stay the same? How does it...
  36. C

    Questions About Black Holes & Event Horizons

    I read that if an observer were to watch as another observer fell into the black hole, eventually observer A would see B stop before reaching the event horizon. I'm having a little trouble with this and have to questions about it. 1)If we turned an extremely powerful telescope at a black...
  37. J

    Do Coronal Holes and Sunspots Represent the Same Phenomenon?

    Homework Statement Are coronal holes and sunspots the same things? Homework Equations The Attempt at a Solution
  38. S

    Exploring Black Holes and Quantum Entanglement in Cosmology

    Are black holes studied in cosmology at all, by any cosmologists? Are there any cosmological theories that investigate quantum exchanges, or entanglement (I had a vague idea there were one or two). Is the subject not allowed at this forum, or is it that entanglement "goes in the quantum...
  39. stevebd1

    Mass-inflation in rotating/charged black holes

    RE: Mass-inflation in rotating/charged black holes From page 42 'Evolution Problems of General Relativity' by Jakob Hansen www.nbi.ku.dk/english/research/phd_theses/phd_theses_2005/2005/jakob_hansen.pdf/ The above is also mentioned in- 'Developments in General Relativity: Black Hole...
  40. A

    Generating Energy from Black Holes: Reachable or Not?

    peace upon u .. though it's a fantasy but it's a scientific one .. i've read about the generating energy from black holes the issue that: is such an extreme science fiction reachable ?? no doubt that wireless connection was a science fiction once upon the time .. but there was a...
  41. D

    How Can We Be Sure About Black Holes and Galaxies?

    Couple of questions here; I know they may sound dumb but here they go. I'm "new" with some questions, so be gentle. 1.) So, if a black hole has enough gravitational pull to pull in stars and what nots, and nothing can pull away from this force once it is to close, its consumed by the black...
  42. D

    Exploring Black Holes: The Truth About Light and Disappearance

    Well, I'm currently reading The Black Hole War by Leonard Susskind, and one thing to me seriously doesn't add up. It says that when someone falls into a black hole, and observer from the outside would not see them fall into the singularity, but they would seem to stretch out and move slower and...
  43. V

    Anti-Gravity and Black Holes: A Theoretical Analysis

    I was wondering about a question that popped into my mind recently -Let's say, theoretically, a device existed that could reverse the force of gravity somehow, to the point were it created antigravity. Since black holes are held together by their own gravity, pushing molecules closer than...
  44. B

    Dark Energy, Light, the Universe, and Black Holes

    Hi, My name is Brandon, I am new here. My physics knowledge mostly comes from surfing the net, so I have a lot of gaps in my understanding. But i do love the stuff, and i try to stay open to it. Anyway, i know about dark energy and the expansion of the universe. and i guess the...
  45. D

    Black Holes effect on each other

    I am fairly ignorant in the area of cosmology, but I was wondering what the effect black holes have on other black holes may be.
  46. C

    Can Kerr Black Holes be Detected Through Gravitational Lensing Experiments?

    Hello, i was studying kerr black holes and i think i can understand most of the theory behind it but i was wondering how can you detect black holes that are actually rotating?. I thought like sending two light rays from the same point (like gravitational lensing) but since the black hole is...
  47. N

    Special Relativity and Black Holes

    Wouldn't an object traveling close the speed of light decrease in length and increase in mass, effectively creating a black hole? I attempted to do the calculations, but I don't know how to calculate the Schwartzchild radius of an accelerating body. Do you find out what the radius would be...
  48. A

    What Happens When a Wormhole Ends Inside a Black Hole?

    Hello, I have the following question: Let as assume that wormholes can exist. What happens if an advanced civilization is able to construct a wormhole with one end on its own planet and the other end of the wormhole below the event horizon of a black hole? Will they be able to see what is...
  49. S

    What are white holes and how do they differ from black holes?

    what r white holes
  50. G

    Q: Space expansion and black holes

    It is my understanding that with the passing of time, space actually expands in size. In about 14G years, space will be twice its current size. What will this do to black holes (BH)? If a BH is in intergalactic space and has nothing to consume, if space actually expands, the density of the BH...
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