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. l0st

    Observing black holes inside black holes

    Can an observer, freely falling into a black hole observe another black hole, falling with him, after crossing horizon? I assume one should be, as for freely falling observer nothing special happens, when he crosses horizon. But just wanted to double-check.
  2. A

    Could the Event Horizon of black holes be the edge of expanding universes?

    I recently read a few articles that contradict Einstein's Singularity theorem. The idea being that black holes are wormholes to other universes; with a white hole on the other side of the black hole (Poplawski's theory). What if instead of being a portal to another universe, the Event Horizon of...
  3. MattRob

    Black Hole Hawking Radiation: Frame-Dependent Virtual Particles

    I was reading "Black Holes and Time Warps" by Kip Thorne, and right around p.442-443 it talks about how the quantum vacuum fluctuations that give rise to Hawking radiation from an infalling frame of reference give rise to an "atmosphere" of real, non-virtual particles in an accelerated frame...
  4. J

    Question from a 5 year old: Bell and Black Holes

    Seriously, a 5 year old asked me whether entanglement information survives/escapes a black hole. Specifically, he asked me (in only slight paraphrase) whether if one of the particles (headed in different directions) fall into black holes on either end, does the other one know it?
  5. NTW

    Why do black holes vanish over time?

    As I understand it, the Hawking radiation is produced when a pair particle-antiparticle are produced at a place close to the event horizon of a black hole, so that one of them, energy-negative for a distant observer, is swallowed by the hole, and the other appears as 'black hole radiation'. I...
  6. T

    Re-Examining Black Holes and the Standard Model

    I was thinking about this and either I have a misunderstanding of black holes or they are simply not how the standard model proposes them to be. Lets start out by setting a few a statements from the standard model that you agree with. If you disagree about any of these points please comment so...
  7. I

    Proof that black holes do not destroy information

    I have for you a simple proof that black holes do not destroy information, since wikipedia seems to be stating that it's an unsolved problem. http://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics 1. The second law of thermodynamics states that entropy must always increase. 2. If...
  8. rudransh verma

    Why Do We Discuss Light Cones and Black Holes If There's No Light Present?

    Why we talk and discuss about effects on light cones by black holes though we know there is no light left after a star dies and become a black hole? there should be no light and so no light cones...
  9. J

    Black Holes Colliding: Evidence & Expectations

    Has there been any evidence of black holes converging? What would we expect to see , if anything?
  10. stevendaryl

    Observational Evidence of Black Holes

    This seems like a question that would be in the Relativity FAQ, but I didn't see it. Briefly: I've seen the claim made that there is plenty of observational evidence for the existence of black holes. But I don't understand how, from the outside, one can tell the difference between a black hole...
  11. wolram

    How did massive black holes form and grow in the early universe?

    I am sure this question must have been dealt with before but i can not find an answer: What came first galaxies or black holes? How did supper massive black holes become so massive? List of most massive black holes http://en.wikipedia.org/wiki/List_of_most_massive_black_holes
  12. G

    How can black holes coexist with the expanding universe?

    It is said that black holes exist and are therorized to be very very abundant throughout the universe. These black holes are said to be sucking everything up around it, including light. It is also said that the universe is ever expanding, and that expansion is accelerating. How can the universe...
  13. MattRob

    Black Holes: Accretion Disks /Increase/ Angular Momentum?

    I've been reading Kip Thorne's "Black Holes and Time Warps," and it mentioned something rather counter-intuitive; apparently, when material forms an accretion disk and falls into a spinning black hole, it increases the angular momentum of it. Now, let's take a gas cloud, and put a spinning...
  14. J

    Black holes and the centrifugal force paradox

    Hi Is someone interested in this topic ? I'd like to share my idea with you, PF people. I also designed a "reverse geometry" to illustrate this paradoxical effect. Thank you for your answer Jean-Marc
  15. Useful nucleus

    Delocalized holes and trapped holes (polarons)

    Are delocalized holes and trapped holes (polarons) mutually exclusive? Most of the density functional theory literature that I read and related to holes in metal oxides treats polarons and delocalized holes as mutually exclusive entities. The one with the lower formation energy is always assumed...
  16. F

    Schwarzschild Radius of Masses Other Than Black Holes

    Recently I have been researching black holes, and came across the "Schwarzschild Radius". The wikipedia page on Schwarzschild radius's mentioned that the Sun has a radius of 3km. If that is so, then how can that be so, as that would mean that light cannot escape it. So when it said "3km", did...
  17. J

    Quantum Bounce & White Holes: Could Black Holes Create Them?

    Does quantum bounce provide a solution by which black holes could on some other side of the universe or in another universe create white holes Sent from my iPhone using Physics Forums Jim P
  18. soulmartyr

    Conservation of mass and black holes

    With this post I am hoping someone would be kind enough to lead me in the right direction. I am a layman who knows little about the actual math behind physics, nonetheless I have developed an interest in it and wish to expand my knowledge base. First question I have is if someone could...
  19. spacecadet11

    Black Holes & Infinity(Singularities)

    Hello. I would like to know. Does matter when heading towards a black hole then crossing the event horizon threshold reach the speed of light? I am guessing no. It simply crosses the threshold and at a finite velocity heads toward the center of the black hole. The escape velocity of a...
  20. T

    Do Black Holes become visible at relativistic speeds?

    Ok, so if I were to travel towards a black hole at close to c, would the event horizon become visible? Let us assume there are no stars, CMB, or any other luminous body in the universe.
  21. N

    Gravitons detected around black holes?

    Could Gravitons be causing this Black Hole turbulence? http://perimeterinstitute.ca/news/turbulent-black-holes In the article above they talk about how the Gravity around Black holes is bumpy or has Gravity turbulence. Does this discovery give any evidence to the undiscovered Graviton? Because...
  22. J

    Is Dark Matter Consumption by Black Holes Equal in a Galaxy?

    Is the amount of Dark Matter in a Galaxy equal the amount of Matter consumed by all the Black Holes in that Galaxy?
  23. W

    Black Holes and escape velocity

    It is my understanding that at the most fundamental level, a black hole is simply an object with a gravitational field so strong that there exists a sphere that lies outside the body of mass of that object from which the escape velocity is equal to the speed of light. In other words, a body of...
  24. marmstrong941

    Black Holes in the center of galaxies

    Is it still true that most if not all galaxies have at their center a Black Hole? And that the estimated gravity is about 10% of the total mass galaxies. And is it still true that all stars or 99 % of them are moving out and a way from the black hole. I was just wondering if these black holes...
  25. F

    Curvature from holes in space?

    I wonder if curvature necessarily means space has been removed. The typical example is forming a "curved" surface by cutting out a triangle from a flat surface, and then gluing the remaining side back together. This forms of a cone which is a type of curved surface. What is the generalization of...
  26. S

    Interaction of three black holes

    dear sir i want to know theoritically what would happen when three black holes are near by and exert influence on each other.
  27. C

    Trio of Big Black Holes Found in Galaxy Smashup

    by Dr. Ken Croswell Astronomers staring across the universe have spotted a startling scene: three supermassive black holes orbiting close to one another, two of them just a few hundred light-years apart. The trio, housed in a pair of colliding galaxies, may help scientists hunting for ripples...
  28. nuclearhead

    If black holes don't exist then neither does the cosmic horizon?

    So according to Stephen Hawking, non-penetrable event horizons don't really exist. So by the same argument the cosmic event horizon can't exist either right? Only an "apparent" horizon which may hold information from outside the visible Universe for a short while until it enters the visible...
  29. J

    Kinematic time dilation in black holes

    Black hole A moves at slow velocity, and there's an Einstein light clock hovering near the event horizon. Black hole B moves at high velocity, and there's an Einstein light clock hovering near the event horizon. The black holes are identical. And the light clocks are at the same...
  30. majormuss

    Dark matter distribution around black holes.

    For my research on astrophysics for the summer, a professor gave me this assignment but I don't know where to start. The question is: What methods could be used to find the dark matter distribution around a galaxy's central black hole?
  31. stevebd1

    Could Supermassive Black Holes At The Center Of Galaxies Be Wormholes?

    Not sure how speculative this is but thought it would be of interest- http://www.iflscience.com/space/could-supermassive-black-holes-center-galaxies-be-wormholes and the related paper- http://arxiv.org/abs/1405.1883v1 Distinguishing black holes and wormholes with orbiting hot spots by...
  32. Borek

    Can black holes have densities comparable to entire galaxies?

    Bear with me, I am (not even) a chemist. This is something that bothers me for some time. The larger the black hole, the smaller the density and the smaller the tidal forces. Supermassive black holes (expected to exist in centers of galaxies) have density comparable to that of water, and I...
  33. A

    Exploring the Mysteries of Black Holes

    I am no cosmologist, just purely curious as to what the explanations and if there are explanations currently to some of my questions: If it was possible can one fly far enough around a black hole in all 360 degree angles, i assume yes one could but what the question leads to is, does it have...
  34. L

    Faith of Quantum Entanglement once it enters two different black holes

    If I observe two particles that are entangled enter two different black holes and wait, will there eventually be 2 entangled photons radiating out of the black holes or do the black holes take possession of the entanglement as the 2 particles enter their respective black holes and said black...
  35. L

    Hawking Radiation and the Decay of Black Holes

    Hawking Radiation and the "Decay" of Black Holes I have been doing a lot of reading and thinking about certain quantum mechanics so that I can try and wrap my head around how it all works. However I have come upon something that I cannot find a good explanation for. I was reading about...
  36. MattRob

    Funny Story about Black Holes

    So, yeah. Here I am, a fledgling Undergraduate Freshman at Brigham Young University. I've been reading Brian Greene's books, and darn, do I love physics. This was the semester I decided to change my major from Mechanical Engineering to Physics-Astronomy. Well, one night, as some of this...
  37. B

    Exploring Black Holes and the Big Bang

    Has it ever been explored in science that the other side of a black hole could have caused the "Big Bang"? My thinking is that if a black hole sucks in matter and compresses this matter to a point where it can no longer contain it; would that not cause a collapse on the other end? It has been...
  38. C

    How to view black holes / horizon from a manifold perspective

    Hi friends, I was wondering about the following - in GR texts we always see these penrose diagrams and some line representing the horizon and all these timelike , spacelike curves and all that ... but the picture that I have of GR is just that of a smooth 4 manifold endowed with a metric . Can...
  39. F

    Cables in tension passing through board with holes.

    Hey guys, I'm looking for examples of real life systems which uses a board with holes to redirect cables in tension (as opposed to pulleys) for some inspiration on a project I'm working on. I've attached an schematic of what I mean. I've tried searching google for systems but it's a hard...
  40. Nugso

    Are Black Holes Necessary for the Universe to Function?

    As the title says, do we have to have black holes for the universe to run? Every galaxy has a suppermasive black hole at its center. What if there were a star at the center of our galaxy? I guess it would have to be so big but that means the star would soon run out of energy and then explode...
  41. Chronos

    Primordial black holes ruled out as dark matter candidate

    Primordial black holes as a dark matter candidate has been ruled out - http://www.nature.com/news/search-for-primordial-black-holes-called-off-1.14551
  42. J

    Exploring the Shapiro Delay of Light Beams Passing Black Holes

    Why is there a large Shapiro delay when a light beam passes a black hole? Coordinate velocity of the beam is slowed down in a gravity field, except for the straight down component of the coordinate velocity? Some part of the trip takes a long time anyway.
  43. Chronos

    Contracting Confusion: black holes and event horizons

    This paper, http://arxiv.org/abs/1402.3055 Black Holes, Firewalls and Chaos from Gravitational Collapse, reminds me why it is risky to get too close to a black hole. The authors suggest some the paradoxes posed by black holes may be a consequence of the cosmic censorship hypothesis. I may have...
  44. Eagle9

    Nuclear explosion and black holes

    The nuclear explosion occurs when the nucleus of atom of Uranium (of Plutonium) are split in two pieces by neutrons. These two pieces are repelled from each other due to (the same) positive charge; these pieces are moving quickly between other Uranium atoms, colliding with them. These collisions...
  45. A

    Why don't black holes look like neutron stars to outside observer?

    Yesterday, I read about Hawking's new proposal regarding the firewall paradox. A more general thought about standard black holes occurred to me. Black holes including stellar black holes are of course always presented as if the event horizon is an invisible barrier, which the unfortunate...
  46. zoobyshoe

    Hawking Says, There are no black holes.

    Hawking Says, "There are no black holes." More: http://www.nature.com/news/stephen-hawking-there-are-no-black-holes-1.14583
  47. Integral

    Steve Hawking's new take on black holes

    In a recent paper Steve Hawking is reexamines black holes.
  48. rjbeery

    Black holes may not exist after all

    I've posted a few threads over the years questioning the existence of black holes, and the response has been unequivocal defense of them... http://www.nature.com/news/stephen-hawking-there-are-no-black-holes-1.14583
  49. Y

    Unveiling the Formation of Black Holes: A Relativity Perspective

    According to general relativity, if a remote observer monitors an object falling onto a black hole, (s)he will never see the moment when the object crosses the event horizon. Due to the time distortion, the falling object will hover over the event horizon forever. With that in mind, how...
  50. Chronos

    Are Primordial Black Holes the Missing Piece in the Dark Matter Puzzle?

    It looks like the case for primordial black holes as dark matter is drawing to a close: http://arxiv.org/abs/1401.3025, Exclusion of the remaining mass window for primordial black holes as the dominant constituent of dark matter.
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