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. wraith

    A Paper Spelunking: "Particle Creation by Black Holes" - S.H.

    Hey all! I'm new to Physics Forums. I'm going through Hawking's famous 1975 paper "Particle Creation by Black Holes" which presents the phenomenon later known as Hawking radiation. I'm going through it for the sake of my own learning and benefit since the paper is a bit ahead of my edge as a...
  2. F

    Two Black Holes orbiting as a binary system

    Homework Statement In 2009, astronomers found convincing evidence of two such black holes orbiting as a binary system. From data collected, they estimated that the separation of the black holes was 3.2 × 1015 m and that their masses were 1.6 × 1039 kg and 4.0 × 1037 kg. The black holes orbit...
  3. B

    B Information paradox in black holes

    I have always been fascinated with black holes and information paradox. If quantum bits made up spacetime. Could the information getting inside a black hole be possibility encoded in its quantum bits? Look at https://www.quantamagazine.org/20150428-how-quantum-pairs-stitch-space-time/
  4. HARVEYU1E1

    B Are Black Holes linked to our Universe & Dark Energy/Matter?

    After a quick and not fruitful Google Search I leave this question in better minds than my own. Q- Has there been any discussion linking the start of our Universe with a black hole? <Reason behind Question> I feel as if certain phenomenon seems quite similar to one another. A) star dies...
  5. C

    Can entangled photons be used to explore black holes?

    Gabriela Lemos and her team successfully entangled photons. Would it be possible to explore the interior of a black hole by letting one of the entangled photons enter beyond the event horizon and observe the impact on the other?
  6. bluejay27

    I What Does 'Mass' Mean for Non-Existent Holes?

    What does it mean for the holes to have mass? But they are not physically existent.
  7. Alanay

    B Are black holes perfect spheres?

    Since it is practically impossible to artificially create a perfect sphere, are black holes the closest thing?
  8. acidmatic

    B Black holes are creating galaxies with their gravitational force

    I have never met such an idea... Can anyone comment?
  9. smodak

    Quantum Relativity, Elementary Particles and Black Holes

    Relativity, Elementary Particles and Black Holes by Thorne & 't Hooft Any idea what this book is and why it is unavailable? Is it a popular science book? I did not know that Thorne and 't Hooft co-authored a book.
  10. S

    I Why do quantum physicists claim that particles can tunnel out of a quantum well?

    Hi everyone,Every time I read an article about black hole evaporation through Hawking radiation, it seems to me that the writer didn't bother to connect all the dots so it will be clear for dummies like me.In many articles, I find 2 contradictory statements:1. Black hole emits a radiation (i.e...
  11. T

    I Any progress on realistic rotating black holes?

    Idealistic solution for non-rotating BH includes a "white hole part" However, realistic solution is different For the rotating BH we have an ideal solution with an "eternal" ring singularity inside, which can't be realistic, as ring, as I said, is "eternal" and there is no transition of...
  12. R

    I Energy Emission from Black Holes: Exploring the Mystery

    My understanding is that once light or anything else crosses the event horizon, it will not re-emerge. However, we detect high energy beams of radiation coming from opposite sides of some of the celestial bodies that I have been told are types of black holes. Obviously I'm missing something here.
  13. P

    B Can Dark Matter Explain Black Holes and the Mysterious Planet-Nine?

    so, i love physics, and the more i look the more it seems our understanding of things are wrong. no planet #9, but now a mysterious planet-nine, dark energy, etc etc. so my question probably lies in theory, but getting close to applied physics. planet-nine, from what i have seen, the...
  14. science_rules

    B Why do black holes have infinite density, mass, and gravity?

    If stars have finite mass, gravity, and density, why does a black hole have infinite density, mass, and gravity and why doesn't it attract everything around it with such infinite gravity? Also, with infinite density, why are black holes all different sizes?
  15. J

    B Black Holes & Time: How Do We Observe Movement?

    I'm not a physicist so I am very igorant on this subject. From I know time gets slower and slower as you approach a black hole and an outside observer would never actually see matter being gobbled up. But I have read about stars get observed getting eaten away. How is this possible? And how do...
  16. Buzz Bloom

    I Qs re dark matter when all baryonic matter is in black holes

    In my quote above from the thread https://www.physicsforums.com/threads/ultimate-fate-of-the-universe.898640/ I omitted consideration of dark matter because so very little is known about it. I am hoping someone here at the PF might be able to discuss the following questions. QUESTIONS Assume...
  17. A

    B Does dark matter make black holes bigger?

    I know that a black hole it's a singularity, but its event horizon gets bigger the more mass/energy you throw in. I thought that like dark matter interacts gravitationally with regular matter , it would interact with black holes, eventually falling , increasing the mass of the black hole and...
  18. phillovix

    B What would happen if 6 black holes surrounded a planet?

    Hey, was trying to think of what the safest possible place in existence would be and got to thinking of a planet surrounded by 6 black holes of equal size. Say the black holes met around this planet at the precious same time and are held in equilibrium, is there any particular reason that a...
  19. C

    B Black Holes & Time: A Closer Look

    I recently was watching a television show and something has lodged in my brain. They claim that as something approaches a black hole, it swirls in thru the accretion disk and speeds up to at times close to light speed before entering. They also claimed that it leaves an impression or image of...
  20. Will K

    B Unitarity and Entanglement: Examining the Fate of Information in Black Holes

    What happens to the information about the objects falling into the black hole? Are their states somehow contained in the Hawking Radiation, and if so, how? Or is the information scrambled as it passes the EH?
  21. wolram

    B Black holes and the singularity

    AFAIK, scientists do not believe in the singularity, one way out of the singularity is quantum gravity, but as we have no testable theory of quantum gravity what do scientists think a black hole is?
  22. K

    I Can string theory reproduce Hawking radiation in non-extremel black holes in 4D?

    can string theory reproduce hawking radiation in non-extremel black holes in 4D? i.e physically realistic black holes. do they exactly match hawking's calculations? what is the interpretation of hawking radiation in string theory?
  23. Will K

    I Black Hole Time Dilation: What Would an Astronaut See?

    So let's say an astronaut was being sucked into a black hole and was able to escape spaghettification and all the death a black hole brings. Since black holes bend space-time itself, the astronaut would experience a differen't time zone than an outside observer (time is relative). The astronaut...
  24. newjerseyrunner

    B Are black holes white or monochromatic?

    I was asked if black holes are white today. I answered no, they're perfectly black to fit with classical physics since it's a high school kid who asked. It did get me thinking about Hawking radiation though and I haven't been able to find an answer to my question online. Is Hawking radiation...
  25. Simon Peach

    B Exploring Black Holes: Beyond the Hole

    Is a black hole a hole? What I mean by that, the word hole implies a structure that is shall we say like a plug hole in a sink. But a B/H is the result of an imploding star so surely it would be spherical. So really we are talking about black spheres which make much more sense in my head, also...
  26. K

    Relativity Book on General Relativity -- especially on Black Holes and Graviational Waves

    Hi. (I'm sorry for my poor English.) I'm looking for a good book on General Relativity, specially on Black Holes and Graviational Waves. I got Schultz book once ago, but it has a fuzzy notation and does not deal with the math as I suppose to. I know the basics of Differential Geometry, Topology...
  27. Farang

    I Rotating Black Holes: Q&A with First-Time Poster

    Hi there! This has been on my mind for a while now, maybe someone here can help me understand. First of all, non-rotating black hole is an idealized concept, right? Why the term then? Other objects are not normally referred to as rotating stars, rotating planets, etc... And the main question...
  28. S

    I Can black holes split photons into elementary particles?

    Hello all, Is this a thing? I understand that a theory of quantum gravity is necessary to explain the physics at the core of a black hole, but it seems a black hole is the only environment energetic and dense enough to ignite a mass-energy feedback loop where colliding photons release the...
  29. wolram

    B Do primordial black holes exist

    A PBH is a hypothetical type of black hole that is formed not by the gravitational collapse of a large star but by the extreme density of matter present during the universe's early expansion. It has been proposed that dark mater is made up of primordial black holes. One theory proposes that...
  30. T

    B Do black holes have a world line?

    I'm referring to the black hole itself, not some object falling in it.Thanks.
  31. SteveManPhy076

    B Black Holes and The End of Spacetime

    Recently I was reading Stephen Hawking's brilliant book "A Brief History of Time" and I believe I can recall him writing multiple paragraphs about falling into a black hole. I think I remember him saying that if you were to fall in all of time begins to collapse and the singularity will always...
  32. R

    What are thermally excited holes and how do they aid in decomposition?

    I am looking at a paper that takes about thermally excited holes in relation to photocatalytic destruction, another paper with the same substance (TiO2) talks about decomposition of polycarbonates with the same method (thermally excited holes). I'm a little rusty on this topic. Please could...
  33. K

    A Can black holes convert matter/dark matter?

    Can black holes convert dark matter into matter and vice versa? Presumably, a black hole can gain its mass from eating normal matter, or dark matter, or light. Then, it will eventually evaporate into Hawking radiation. I guess the Hawking radiation should include light as well as both matter...
  34. wolram

    B Over-population of Black Holes

    I find this article hard to believe can there be so many Black Holes in one galaxy, if there are, why are there not many mergers recorded by Ligo. https://www.sciencedaily.com/releases/2016/09/160907215155.htm Computer simulations of a spherical collection of stars known as 'NGC 6101' reveal...
  35. H

    Do holes conduct electricity in metal?

    Homework Statement The conduction band of a metal is partially filled. When an electron of a metal from a lower band is excited and becomes mobile, the metal conducts electricity. The excitation also leaves behind a hole in the lower band. Q1. Does this hole contribute to the electrical...
  36. A

    A Exploring the Pauli Exclusion Principle and Black Holes

    The event horizon of a black hole appears to be plastered with 'afterimages' of everything that ever fell into it. (Because gravitational time dilation makes every such object appear to stop at the event horizon.) Now, suppose an event horizon is 'full' as defined by the Pauli exclusion...
  37. victorhugo

    I Why does hawking radiation in black holes slowly increase?

    First, what are these 'particles' that appear with their negative mass counterpart and suddenly disappear very quickly and why do they do that? Now, I know the positive mass ones are allowed to escape the event horizon while the negative mass doesn't, thus fall into the black hole, but how does...
  38. mgkii

    I Two black holes colliding - visual

    There's lots of other questions on the forum about 2 black holes, but I think this is different - and I can't get my head around which outcome is consistent with GR. Black holes here are simplistic - non-rotating and let's assume with a tiny accretion disk; just enough grains of matter to allow...
  39. naima

    A Exploring Black Holes in Loop Quantum Gravity: Insights from Spin Foams

    Hi PF Is there a way to see if a spin foam contains a black hole?
  40. parshyaa

    Is there a mathematical proof for the existence of black holes?

    Is there a mathematical proof for the existence of black hole.
  41. petrushkagoogol

    I "Black" holes and "White" holes

    What makes black holes "black" and white holes "white" ? :cool:
  42. M

    B Where Can I Find Math for Black Hole Firewalls?

    Hello :) Before I get to my topic I want to adress that I am new to this website and wish to apologize if my thread is incorrectly placed. I am interested in black holes and lately I have been trying to find some math which lays the basis for a black hole firewall. Sadly I haven't been able...
  43. W

    I Solar physics: coronal holes & sunspot cycles

    Does anyone know if there is a relationship between corneal holes and the sunspot cycle? As we move in now towards solar minimum should we expect to see a big decline in corona holes? I have noticed a lot less sun spots over the last few months but the frequency of coronal holes seems to be...
  44. B

    I Exploring the 3D Nature of Black Holes

    So having considered the classical depiction of a black hole resembling a whirlpool, my thought process is that a black hole must be a 3-d phenomenon. Therefore I can not see how a event horizon/swirlpool model could be plausible unless the centre of a black hole was spinning and literally was...
  45. BadgerBadger92

    I Are There Black Holes in Galaxy Clusters?

    I know that I'm most galaxies black holes live in the center. I'm wondering if this is true for Galaxy clusters. Are there black holes in the center of galaxy clusters?
  46. K

    A What if black holes can violate second law of thermodynamics

    GUT's violate baryon number b/c baryon conservation is an emergent phenomenon second law of thermodynamics clearly applies to macroscopic systems, and are the result of the many ways in which atoms of macroscopic systems can be arranged. what if second law of thermodynamics though is just...
  47. wolram

    B The universe is crowded with black holes

    I am not sure if this is true, if it is can these black holes be the dark matter we have been searching for. https://www.sciencedaily.com/releases/2016/06/160622144930.htm Date: June 22, 2016 Source: Rochester Institute of Technology Summary: Astronomers have presented one of the most complete...
  48. S

    I Black holes, pure classic micro-states and area laws

    Dear All Gravitinos, It seems that the current string theory and loop gravity's explanation for the micro-states of black holes are all quantum mechanical and have no classic correspondence. I, in this day's arxiv, post a pure classic interpretation for this question, titled "Black...
  49. DuckAmuck

    I Black Holes and Charged Particles

    What happens when charged particles fall into a black hole? Say like N electrons fall in, giving the black hole a net charge of -N. Since light cannot escape the event horizon, I imagine electric fields cannot either, since they are mediated by photons. So is that charge effectively lost until...
  50. K

    A Charged black holes and charge balance in galaxies

    Greetings, There seems to be a supposition in astronomy that charged black holes are uncommon. Is this assertion well supported? According to a paper I found by Briet and Hobill, if you look at gravitational lensing alone charged black holes look just like regular black holes, but with a mass...
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