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. mitosis

    I Why can't LIGO detect collisions of super massive black holes?

    Does anyone know, and is there an instrument that could?
  2. M

    A 2D Harmonica Oscillator For Holes In Magnetic Field

    Hello I am bemused by a sign convention for Holes, My questions are as follow: For an electron inside the 2D Circular Quantum Well. We can write our Hamiltonian as H = 1/2m * ( p - q A)^2 + 1/2 m w^2 r^2 (Should we use minus in the momentum term? I think for Holes, it is) If we expand this...
  3. D

    B Can black holes truly be infinite?

    Good morning. Not sure if I am doing this right, but I just wanted to ask a question.
  4. C

    B Black Holes: Observing & Understanding | Astrophysics

    I’m very new and uneducated but extremely interested in astrophysics. That said, I’m also tainted by popular science fiction with my theories. My question...is it possible that since black holes carry so much mass and with said mass slow space time down to a degree that we are moving too fast...
  5. Cerenkov

    B What is the 'proof' of the no-hair theorem of black holes?

    Hello. In chapter 3 (Quantum Black Holes) of this book... https://www.amazon.com/dp/069116844X/?tag=pfamazon01-20 ...Stephen Hawking writes... "The no-hair theorem, proved by the combined work of Israel, Carter, Robinson and myself, shows that the only stationary black holes in the absence of...
  6. C

    Projectile Question -- Kicking a soccer ball through two holes in two walls....

    Homework Statement Find the initial velocity for the above soccer kick. Note that ball must cross the 2 points in the diagram within the two walls. Linked below is the diagram Homework Equations dx = v1(cos theta) * t dy = v1(sin theta) * t - 0.5at^2 The Attempt at a Solution I tried using...
  7. S

    B Big Rip Theory & Black Holes: Relativity Explained

    According to the Big rip theory if Black holes tear apart after a very long time, then according to the theory of relativity an object that reaches the event horizon should see time passing infinitelty and by the time the object was swallowed wouldn't the black hole not exist anymore because of...
  8. D

    B Can event horizons cross for passing black holes at high speed

    Scenario: You have two black holes approaching, one from the left (A), one from the right (B), each at speed S. They are offset vertically. S is sufficiently high that they will deflect passed each other without merging. Question: Suppose the speed S is high enough so that the event...
  9. M

    I Uniqueness theorems for black holes

    I am under the impression, there is no unique solutions to Einstein's field equations for a cosmological constant, or for higher dimensional spacetimes. Has anybody got a counter example for a solution including the cosmo constant to show there are multiple solutions, for example, i know of the...
  10. C

    Flow of Water into a Bowl with Holes

    I'm facing a problem with that rhyming title up there. The design is thus: a downward-facing, vertical pipe with known constant flow and diameter has water flowing out of it, into a short (15cm-91cm) free fall. At the end of that fall is a bowl of indeterminate depth made of steel with holes...
  11. T

    Calculating the drag force on a spherical object with holes

    I am looking for a bit of guidance on how one could calculate the drag force of a sphere with holes in the sphere falling through a fluid, in my case water. So I know for a low Reynolds number the drag force on a sphere is given by stoke law, but what I would like to do is calculate the drag...
  12. L

    I Massive Particles in Sonic & Slow Light Black Holes

    I am working on a research project where I intend to describe what the Penrose process would like in a sonic black hole. I have found what a rotating (Kerr) black hole looks like in the sonic analog: https://arxiv.org/pdf/1802.08306.pdf I have also found that the analog of massless particles...
  13. L

    I Harnessing Energy from Black Holes: Possibility or Fantasy?

    Whether it be through Hawking radiation, miniature black holes, or even white holes, is it possible that one day energy could be harnessed from black holes and used on earth?
  14. Robert Friz

    B Hawking Radiation and Shrinking Black Holes

    Stephen Hawking theorized the creation of virtual particle pairs at the event horizon of a black hole, with one of the particles escaping the event horizon (Hawking Radiation) and the other particle falling into the black hole. Sean Carroll states on page 272 of From Eternity to Here that "if...
  15. S

    B Do Black holes reach a critical mass?

    Are there any theories on Blackholes becoming so massive that the forces generated by the matter within them exceeds the forces compressing them and the tipping point leads to a Big Bang?
  16. steroidjunkie

    Semiconductor chemical potential and the density of holes

    Homework Statement [a) Show that chemical potential in intrinsic semiconductor at T = 0 lies exactly in the middle of the energy gap. At what temperature is the chemical potential equal ##(3/4)(E_c + E_v)##, where ##E_c## and ##E_v## are energies od the bottom of the conduction band and of the...
  17. Green dwarf

    I Formation of super-massive black holes

    It seems that the super-massive black holes at the centres of galaxies formed very early in the history of the galaxies (e.g ULAS J1342+0928, which had about 800 million solar masses 13.1 billion years ago). Presumably, in the very early days, matter in the universe was much less clumped than...
  18. S

    I Information Paradox in Black Holes and BSM

    If they could solve the information loss paradox in black hole https://en.wikipedia.org/wiki/Black_hole_information_paradox What other related problems it could solve in Beyond Standard Models or unsolved quantum questions, etc.? If the LHC could no longer detect new particles, could beyond...
  19. H

    B What Happens When We Cross the Event Horizon of a Black Hole?

    When we approach a black hole, the effect of gravity is such that relative to us, time far from the black hole would approach infinity as the distance to the Event Horizon approaches zero. But what happens when we cross the Horizon? How do we measure time outside? Will infinite time have have...
  20. bbbl67

    I Black holes with a naked singularity?

    Yes, I understand that this is all kind of hypothetical, there have been no black holes discovered with a naked singularity. A black hole which is spinning beyond the speed of light is said to expand its event horizon to drop below the speed of light again. When it does that, it creates a...
  21. gneill

    I Colliding black holes: when will linear acceleration end?

    I was musing about black hole mergers and what an observer might see for a particularly simple (i.e. blatantly contrived) scenario. Suppose that there are two (non rotating, un-charged, bog standard) black holes of dissimilar masses heading for a head-on collision. They will accelerate towards...
  22. Alfredo Tifi

    B Dark matter is "normal" matter in black holes?

    I read that 1. dark matter has to be concentrated in galaxies; 2. McGaugh & Co discovered a precise relationship between visible-ordinary matter and the calculated sum of ordinary + dark matter from thorough observation of actual acceleration of more than 150 galaxies. 3. First experiments to...
  23. mitosis

    I What happens to a star's heat when it gets torn apart by a black hole?

    I'm sure this is a really basic question for the black hole experts here. Consider a situation where a star approaches and then crosses the event horizon of a super massive black hole, the star gets torn apart eventually undergoing spaghettification as it approaches the singularity. My question...
  24. Tree Universe

    B How to annihilate black holes?

    Hi Everyone, I'm interested in how to annihilate black holes (they are like blenders separating all the things apart and agglomerate like "tumors/cancers" in the universe). However, I'm new to this field and need some clarifications on some of the basic concepts like "annihilation" and...
  25. B

    Calc Electron & Hole Concen in Silicon at 300K

    Homework Statement For silicon at T=300K with donor density ND=2×109cm−3, acceptor density NA=0 and ni=8.2×109cm−3, calculate the equilibrium electron and hole concentration Homework Equations n_0=\frac{N_D-N_A}{2}+\sqrt{\frac{N_D-N_A}{2}^2+n_i^2} p_o=\frac{n_i^2}{n_0} The Attempt at a...
  26. R

    B Formation of Supermassive Black Holes

    Are there theories to explain the formation of supermassive black holes?
  27. D

    Problem finding the distribution of holes in a semiconductor

    Homework Statement Long and thin sample of silicon is stationary illuminated with an intensive optical source which can be described by a generation function ##G(x)=\sum_{m=-\infty}^\infty Kδ(x-ma)## (Dirac comb function). Setting is room temperature and ##L_p## and ##D_p## are given. Find the...
  28. M

    How Black Holes Absorb Light Despite Photons Being Massless

    We know light made up of photons which is massless, but why it can absorbed by black hole? Is it becuz the Einstein's relativity about every object can curve time space
  29. S

    I Can Black Holes Store More Information Than We Think?

    I have a question about black holes. So imagine that we start putting energy in some region of space, until we reach Schwarzschild radius. We also reach the maximum amount of information we can store in that region of space. Still, the energy continues to collapse in smaller and smaller space...
  30. DaveC426913

    B Could a Particle Accelerator Create a Black Hole That Destroys Earth?

    This may be condensed matter physics topic, but I'm looking for a layperson answer. Scares of the CERN accelerator creating a black hole that swallows Earth are in the news once again. https://www.newsweek.com/earth-shrunk-tiny-hyperdense-sphere-particle-accelerators-1145940 From 10 years ago...
  31. jha192001

    B Black Holes -- What methods to use to find them?

    How many are the ways a Black hole without *ACCERTION DISK* can be spotted?
  32. S

    I Do black holes accumulate neutrinos?

    Do black holes accumulate neutrinos ? Do the neutrinos that fall in, decay in some way , maybe interact with the condensed matter, or just stay "parked" in perpetual loops ?
  33. A

    B Black Holes Collide at 0.999c - What Happens?

    The relative speed of two supermassive black holes moving directly towards each other is 0.999 c. What happens when the two black holes collide directly (so the black holes aren't orbiting each other) at such high velocity? Where does all that energy go and how would it effect space time/what...
  34. Spinnor

    B Galactic Collision Creates a Ring of Black Holes and Neutron Stars....

    From, https://www.syfy.com/syfywire/wham-bullseye-galactic-collision-creates-a-ring-of-black-holes-and-neutron-stars ..."“So you have a nice, normal spiral galaxy, right, just out there doing its thing, when BAM! A smaller galaxy careens right through the middle of it like a bullet! Chaos...
  35. DarkStar42

    I What problems would 'black holes' not being formed solve?

    So when a star collapses, if the event horizon doesn't form, but the object remains in ordinary space, in increasing gravitational time-dilated collapse, what problems with these objects would be solved or more easily addressed? I would think at least the information loss problem, and then there...
  36. H

    Quantum Exploring Quantum Mechanics: ER=EPR, Black Holes, Firewalls & More

    ER=EPR, black hole complementary, firewalls, vacuum entanglement etc.. Where do I begin studying these new ideas? I have a solid understanding about Quantum Field Theory and the classical theory of gravity, but no knowledge of string theory. Are there some advice or book recommendations anyone...
  37. F

    I Can an object be both a black hole and not a black hole?

    According to Special Relativity, objects moving fast have more mass than objects at rest. So what if there is an object having a mass density near that required to create a black hole. Now if it were moving fast enough as well, it would gain enough mass density to become black hole. But to the...
  38. Islam Hassan

    I Black Holes: Draining Empty Spacetime?

    If a black hole that is feeding is actually ingesting the spacetime around it (and hence whatever may lie in that spacetime including light) what does it do when it is not ingesting but nonetheless has very strong gravitational attraction? Does it sit there dragging empty spacetime into it? If...
  39. F

    I Can Black Holes Transport Mass Back in Time?

    According to Einstien's theory of evolution, the closer to the speed of light that an object travels, the slower it appears to move to an outside observer. (see https://www.thenakedscientists.com/forum/index.php?topic=40951.0) To take this to the next step once an object crosses the event...
  40. Sveinbjoern

    B Limitless Momentum of Black Holes

    I am a hobby reader/listener of pysics, astronomy, special relativity, black holes and more. And a question arose that no amount of YouTube has touched on. Sorry if this is just a stupid question from a hobbist but it truly has me stumped. Or maybe I just have been taught by...
  41. Mark Scalabrin

    B Thought Experiment from my daughter regarding black holes

    My daughter is 12 and we like to discuss black holes. Here is our thought experiment: Gravity bends space and time lengthening both from the observers perspective. Does time slow down the farther you get from objects with density? Is there a place way way out, out of the range of the Big...
  42. avischiffman

    B Real-Life Demonstrations of Black Holes for Video

    Hi, I am working on a video, and I was wondering if any of you knew of some real-life demonstrations I can do about black holes? So far I have the gravity well, and the balloon covered by foil that you crush to show same mass but denser. My video is about the anatomy of a black hole, so I cover...
  43. TheQuestionGuy14

    B Do Black Holes Destroy Information?

    Stephen Hawking proposed that black holes will eventually evaporate due to Hawking radiation, thus all information eaten by the black hole is destroyed. This violates basic physics, and hawking soon recanted his views, but there is still no real answer to whether they do or don't destroy...
  44. A

    I Photon emission, power output (and black holes)

    I recently re-read an article by Muller (https://arxiv.org/pdf/1606.07975.pdf) about the flow of time, and the possibility of time reversal given sufficient energy dissipation (basically during black hole evaporation, he concludes). Although the paper is on arXiv and not peer reviewed, Muller...
  45. J

    I Heavy/Light Holes, what of Electrons?

    So some materials have sub-bands of the valence band, known as heavy and light holes (they have different curvature so different effective masses, this I understand). Sources seem to give different reasons for this, either because of anistropy in the crystal or some sort of coupling effect, but...
  46. jerromyjon

    B Colliding black holes effect on the Richter scale

    Would it make sense to ask? Is there any other scale for cosmic collisions? What about supernovae? Google is stupid sometimes.
  47. phinds

    I 10,000 black holes near Sagittarius A ?

    Interesting sidebar in The Week (April 27, 2008, page 20) referencing a BBC.com news items (yeah, I know this is pretty indirect) that says a dozen binary pairs of black hole with orbiting stars have been identified near Sagittarius A by the Chandra X-ray Telescope. They go on to say and that...
  48. ohwilleke

    B What fraction of the matter in the universe is in black holes?

    Conceptually, at least, this is a simple question, although I recognize that it might be hard to calculate in practice from available data. The matter-energy budget of the universe is measured (in a model dependent way) to consist of a certain percentage of dark energy, a certain percentage of...
  49. S

    I Matter predominates b/c anti-matter fell into black holes?

    I was reading an article about the great Steven Hawking, and it seems to say that matter & anti-matter can be created in space, but that one of them can fall into a black hole, thus leaving the other around in a higher preponderance, which of course matter is. So it would seem that a good...
  50. jedishrfu

    B Physicist who Questioned Black Holes

    This is an article about the Indian physicist, Abhas Mitra, who questioned the theory of black holes and the loss of information long before Prof Hawking agreed that there is no Hawking radiation, no exact event boundary and no black hole information paradox...
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