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. S

    White Holes created our Universe

    In general relativity, a white hole, is a hypothetical region of space-time which cannot be entered from the outside; but matter and light can escape from it. In this sense, it is the reverse of a black hole, which can be entered from the outside, but from which nothing, including light, has the...
  2. R

    What is the radiation pressure on Earth if the sun was replaced by a black hole?

    Since black holes have a temperature, and emit (Hawking) radiation, do they also exert a radiation pressure on things? Say the sun was replaced by a gravitationally equivalent 1 solar mass black hole, what would be the radiation pressure felt by the earth?
  3. Radarithm

    Do black holes violate conservation laws?

    I was arguing today with a friend and the argument seemed pretty pointless because we had nothing to back up our facts with, so I thought about hearing your opinion(s). Do black holes violate laws such as the conservation of matter + conservation of energy? I'm currently leaning towards 'yes'...
  4. mrspeedybob

    Question about extreemly large black holes.

    If we define the density of a black hole to be it's mass divided by the volume within it's event horizon then as the mass of a black hole increases it's density decreases. At some point the density would be equal to the ambient mass density of the universe. Can we correctly consider ourselves to...
  5. Saladsamurai

    ANSYS: Axisymmetry - Modelling of holes

    Hello all! I am curious. Sometimes I would like to do a trade study on a mechanical component; so in the interest of time, I think I would use 2D analysis techniques so that a) I can save time on the front end in the CAD package and b) save time on the analysis side of things. But I want...
  6. E

    Evidence of Orbiting Black Holes?

    Do we have any evidence that either: 1. There exist stellar black holes which orbit supermassive black holes in the centers of galaxies, or 2. There exist black hole pairs which orbit each other, around their shared center of mass?And if the second scenario were to exist, what would happen...
  7. F

    Dark matter build up near Black holes, thoughts?

    Dark matter build up near or inside Black holes, thoughts ? I can see it making a real mess of the motions and energies of normal matter in and around a black hole or other very dense body that confines dark matter to a small adjacent region. Unslowed by frictional forces...think angry...
  8. G

    Colliding Black Holes: Antimatter vs Normal?

    Can they exist? What happens when an antimatter black hole and a normal black hole collide?
  9. T

    Could black holes be empty points of spinning systems? A scientific exploration

    Hi, I had posted wanting a specific question answered and it was closed b/c i kept repeating my thoughts to try and get an answer. I'm not an expert, so I was wondering if any of you intelligent folks could enlighten me. I am not asking for a crash course on black holes, which is what i...
  10. R

    Why are Black Holes such massive gravity pools?

    Hi guys, Simple question for my first post. If nothing escapes Black Holes, how come they're such massive gravity pools? While I can accept that in certain cases the gravity may come from all the mass near the event horizon that did not yet got through (center of Galaxies where it...
  11. Low-Q

    What is the structure of a black hole's singularity?

    I have a couple of questions I cannot find a good answer to in the internet, so I ask you guys. I have heard about singularity as a infinite small point with infinite gravity - I talk about what I assume is the center of black holes. The scientist are talking about quantum gravity - the...
  12. V

    Question on Gravity, Big Bang, Dark Energy and Black Holes

    Sorry to have such a broad subject line but I was in a contimplative mood yesterday and the mind was wondering and pondering… From the publication of Sir Isaac Newton,”Philosophiæ Naturalis Principia Mathematica”, the science world has been challenging the findings around gravity proposing...
  13. S

    How is it that black holes can have angular momentum?

    It's confusing to me how black holes can conserve angular momentum in relativity. In order to define rotation, there needs to be a 1 dimensional line that represents a radius. Considering that a black hole singularity has no dimensions, it seems impossible that a singularity, and hence a black...
  14. F

    Higgs Mechanism and Black Holes

    If seems to me that the conditions in the early universe which led to the activation of the Higgs field might be found inside a black hole, but in reverse. This might explain the mystery of infinite density inside a black hole, uniting Gen Rel and QM. Might a black hole then be a baby universe...
  15. mrspeedybob

    Is the space-like distance to a black holes event horizon infinite?

    From a distant frame of reference a falling object never reaches the event horizon due to time dilation. If I drop a meter stick into a black hole lengthwise I should see both ends of the stick getting asymptotically closer and closer but never reaching the horizon, thus the stick should appear...
  16. B

    Black holes and time invariance.

    Einstein's field equations are time invariant. So is it conceivable that a reverse black hole can exist i.e a "white hole"? Or would the second law of thermodynamics prevent such a thing?
  17. anorlunda

    Liouville's Theorem and Black Holes

    In Professor Susskind's lecture 7 on Classical Physics, he discusses Liouville's Theorem. He said that a consequence was that points in the phase space can not coalesce and lose their identity. In Professor Susskind's book, Black Hole War, he discusses why destruction of information at the...
  18. MathematicalPhysicist

    Empirically testing black holes.

    How much is it feasible for us to send some probe/s to the event horizon of a black hole? Perhaps Voyager will arrive at the centre of our galaxy, where if I remember correctly there's a massive black hole. How much time will that take? Probably Voyager will collapse way before arriving at...
  19. A

    Can Black Holes Be Stabilized to Prevent Decay?

    Till sometime it was believed that Black Holes were impossible to create ( made by men ), now some theories which were added to the Standard Model show that the Particle Accelerators having energy levels of TeV can actually produce black holes ( like LHC ) ! Okay but now they are unstable...
  20. H

    I have holes in my math, help me.

    What is happening here? x2 – x – 2 = 0 (x – 2)(x + 1) = 0 x = 2 or x = –1 This is related to domain and ranges, finding the possibilities of the domain. I would like to just see the process of how to solve this and then knowing what this actually is in mathematical terms (I'm...
  21. S

    Can Exotic Matter Escape the Gravitational Pull of a Black Hole?

    A thought experiment. C is considered to be a constant speed, that can not be exceeded. Once light passes the event horizon of a black hole however, the gravitational pull is strong enough to exceed, C. This is indicated by the supposition, that not even light can escape the event horizon of...
  22. G

    Light & Black Holes: Exploring the Paradox

    Hey guys, I was reading that even light can't escape black holes due to the huge gravitational force which they have. I have been mulling it over for awhile now and I am still stumped. How can a force dependent on the mass of the two bodies act on a body-light/photons which have no mass?
  23. Eagle9

    Can the black and white holes combine?

    Good day :smile: Black hole White hole The characteristics of these two kinds of wholes are opposite to each other. I would like to know can they combine when colliding to each other? The Black hole cannot enter the white one (since the latter does not accept anything) but the white hole...
  24. F

    Density of holes on a sprinkler for uniform water distribution

    Hi all, My classmates and I have been at this problem for some time, and it doesn't look like we're getting anywhere. We'd really love any help in the right direction! Homework Statement A lawn sprinkler is made from a spherical cap (max angle  = 45\) with a large number of...
  25. S

    Singularity in black holes

    Gravity is zero at the center of the earth. how come the same set of equations predict the gravity to be infinity at the center of a black hole? where does the singularity really come into picture? how is a black holes center different from Earth's center?
  26. D

    Position of holes in p-type semiconductors

    where are the holes in the p-type semiconductor situated? in the conduction band or the valence band? i am talking about the holes formed because of the acceptor impurities, not the thermally generated ones.
  27. Digitalism

    Can Colliding Black Holes Solve the Mystery of Short-Duration Gamma-Ray Bursts?

    If two black holes with equal mass were to collide when they reach the point where their respective centers are at the schwarzchild radius of the other black hole could the spacetime distortions caused by their masses cancel out in such a way that matter/energy could escape along the plane of...
  28. C

    Why are functions not differentiable at holes?

    I understand at cusps, corners, etc, because the negative and positive directions do not agree with each other. But what about at jump discontinuity on a graph? Why wouldn't a function be differentiable there? I understand that from the definition of differentiable that it just isn't, but I...
  29. 1

    Are black holes related to the big bang?

    In a very simplified, very elementary description: Black holes (AFAIK) suck in huge quantities of light and matter and compresses matter into a singularity. The big bang (AFAIK) was the start of our universe through which huge quantities of energy and matter exploded from a singularity...
  30. G

    Does Dark Matter Impact the Properties of Black Holes?

    We know that DM interacts gravitationally with ordinary baryonic matter, so we should assume that any DM particles close enough to a black hole will also fall into it, shouldn't we? If so we should assume that black holes must have some DM inside them, perhaps impossible to estimate in which...
  31. alemsalem

    Can black holes have net color charge? can a BHs help separate quarks?

    similar to the rough picture of how BHs radiate if I put a proton next to a BH can one of the quarks be absorbed into the BH and the other two escape? I don't really understand confinement very well but does the confinement picture change next to BH horizon?
  32. R

    Black Holes: Real or Not? Magnetic Poles & Jets Explained

    Im a little confused...If a black hole has a true point of singularity how does it have magnetic poles, and how does it have jets of charged particles shooting out from its poles,how does this escape the event horizon if light cant? are black holes real?
  33. Crazymechanic

    Black holes , gravity upper limit

    Now I thought about this while writing my "electric field strength ' question , as it was about has the electric field got an upper limit of strength and the answer is that it hasn't (theoretically) then I thought the same thing about gravity. Does gravity have an upper limit to it's...
  34. bcrowell

    Significance for LQG of Sen's result on entropy of black holes?

    Sen 2013 says, How serious a problem is this for LQG? Does this mean that LQG doesn't have GR as its semiclassical limit? Does that mean it's a dead theory, or maybe just that it needs to be modified? Is the technique using Euclidean gravity reliable? Since I'm not a specialist, I'd be...
  35. DiracPool

    Various varieties of black holes

    Here's a quote by Modred from another thread: https://www.physicsforums.com/showthread.php?t=683377 My question isn't about the Hawking radiation part of the statement, its about the "uncharged non-rotating black hole" part. how do we know if a black hole is charged, what it's charge is...
  36. A

    To find volume of a cylindrical shell with holes around it

    ITS NOT A HOMEWORK PROBLEM PROBLEM::- THINK OF A CYLINDRICAL SHELL WITH NUMEROUS SPHERICAL HOLES ALL AROUND IT. (FOR EG. http://sell.lulusoso.com/upload/20120317/Underground_Water_Pipe.jpg) HOW TO FIND VOLUME & SURFACE AREA OF SUCH A CYLINDRICAL SHELL. (A GENERALIZED CASE FOR N HOLES AROUND...
  37. Y

    Quantum entanglement to communicate from inside black holes

    I have just joined this forum as I am curious to discover from experts if my idea is physically possible. Once you pass the event horizon of a black hole nothing can escape as the space time "fabric" is moving into the black hole at equal to or greater than the speed of light. But I hear from...
  38. M

    Black Holes & Time: A Collision of Forces

    I was just reading upon black holes, collision and how it bends space and time.. I know for a fact that time stops after the event horizon, but during the collision of two black holes, can the gravity 'overlap' between them to make it strong enough to bend space which in result be enough to...
  39. O

    Black holes, Creating Black holes

    Hello everybody, I am a first year physics student and I've got two more questions. Assuming that particles in a black holes event horizon have huge kinetic energy, if they collide, can't they create a black hole? I am asking that, because if we have a probability or pontentially be able to...
  40. B

    Black Holes & Stars - What Do We Know?

    Hi, One can register waves of light. Is there anything known different then stars where we receive information from? Say black holes? I really guess.
  41. R

    Question combining - black holes & conservation of angular momentum

    had a thought. suspect that i am wrong but not sure where. no idea of the maths involved but suspect As an object approaches the speed of light relativistic forces come into play – effecting time dilation density etc Can the same theory be rearranged to show that As you approach the density &...
  42. A

    Is it possible electrons fallen into holes and go straight to collecto

    I took this picture from forum aboutcircuits to illustrate current flow in NPN transistor. Here is what I am confused: A few at Figure above(a) fall into holes in the base that contributes to base current flow to the (+) battery terminal. Why these electrons that fall into holes necessary...
  43. D

    What do black holes look like?

    They have to have some color, yeah?
  44. Q

    Shouldn't objects entering black holes be instantly shredded?

    Nothing can escape a black hole, so as an object enters the event horizon, the atoms currently inside the black hole wouldn't be able to bond with the atoms currently outside of the black hole, causing it to sever. But I've never heard of any physicist saying that this would happen, so I'm...
  45. C

    Are black holes bound to galactic revolution?

    A couple of quick questions after watching a video on the helectic model that the solar system follows on it's course around the galactic center. Please bare with me these maybe idiotic questions. A) Are black holes bound to the spin of the galaxy or do they sit in place on the galactic plane...
  46. JK423

    Is there a minimum mass for black holes?

    Hi all, I was (superficially) reading about the information loss paradox. Of what i understood it's based on the complete evaporation of the black hole via hawking radiation, so in some sense all the energy of a black hole will eventually become radiation. The following question immediately...
  47. J

    Construct uncountably dense and holes everywhere

    I want to define a set X\subset [0,1], without using the axiom of choice, with the following property: Both [a,b]\cap X and [a,b]\backslash X are uncountable for all [a,b]\subset [0,1] where a<b. I don't know how to define X so that [a,b]\cap X would always be uncountable without X containing...
  48. D

    Hawking Radiation and Shrinking Black Holes

    I was wondering whether anyone could provide an explanation as to why when two particles are created near the event horizon, only the negative energy particle is captured by the black hole, and the positive particle travels outward and is seen as Hawking Radiation. I have read numerous posts...
  49. DARKSYDE

    Why aren't black holes the brightest objects in the universe?

    I've seen many examples that an observer witnessing an object approach the event horizon will see it slow down to a point where it never seems to cross. Why then do we not see "everything" that has crossed into this horizon frozen in time?
  50. medgalis

    Virtual particales and black holes.

    Hello, So i have heard that virtual particlees just pop-in and pop-out of existence, but if a black hole is near those particlee one of the pair of the virtual particlees gets sucked in. So what happens to the other particlee?
Back
Top