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. P

    B Interested in Black Holes, Neutron Stars, and White Dwarf Stars

    How did you find PF?: duckduckGo search. My math is very weak and I don't like explanations done using math. I read books with very little math. I try to use reason based on what I've read. My understanding is time slows down in gravity and it will actually stop at the event horizon (see...
  2. merlyn

    I Wavelength and size of holes or grating

    Could someone explain to be the reason why size of the hole or grating in the case of Faraday cage is what determines if the screen or grating is opaque or transparent? I'm pretty sure it has something to do with interference patterns in classical physics. Thank you all in advanced.
  3. caybrax

    I Black holes -- Can you chill the particles of a black hole?

    I want to ask if you can theoretically chill the particles of a black hole and if it is possible to achieve it what will happen
  4. Eumeme

    B Gravitational Wave System and Locations

    My hypothesis: A sequence with the gravitational waves detected, sent by modulating radio waves, could be received and used by other intelligent beings to find the corresponding sequence within their records and then compare it to calculate our spacetime position in relation to theirs. As...
  5. kmm

    I Observing Black Holes in Finite Time

    My understanding from General Relativity is that if as distant observers we watch a probe or any test mass approach a black hole, time dilation goes to infinity as the probe gets closer to the event horizon. This would imply that we would never observe a black hole form, or the collision of two...
  6. AHSAN MUJTABA

    A Black Holes Formalism: Overview of Misner Sharp Mass

    I am currently studying the Vaidya metrics and I am a bit confused regarding the term Misner Sharp mass, and I am referring to Blau notes and in them the description is very deep which I surely don't need but just an overview. TIA
  7. slimak

    B Time Travel Possibility with Two Black Holes Orbiting Each Other

    The reason why I think it could happen is that spacetime is being curved really extremely in black holes and when you draw a chart of spacetime near and in black hole , you can see that time axis is being bend towards the center of black hole and that thing is happening from all sides of the...
  8. JD_PM

    A Understanding Kerr Black Holes: Metric, Killing Vectors & Event Horizons

    Before explicitly stating the Kerr metric let us discuss a bit what to expect, comparing it to the easiest solution to (in-vacuum) Einstein's equations that I know: the Schwarzschild metric. I studied that the Schwarzschild metric is derived under the following assumptions: the metric must be...
  9. C

    How are holes charge carriers?

    Homework Statement:: Hi, It's been a while since I have reviewed my basic semiconductor physics and I have some doubts. In a P-Type doped semidoncutor material, I understand that Group III elements such as Boron are added to a Group IV element such as Silicon and thus the Boron atom has one...
  10. G

    A Black Holes & White Holes: Same or Different?

    Well, my question arises because when one hears about black and white holes in divulgation, usually one hears that they are two kinds of "objects", the first one is a region that can only absorb things, and nothing can escape from it. While the latter is a region that only emits things and...
  11. Robert Friz

    I Does Hawking Radiation Cause Black Holes to Evaporate?

    Does Hawking radiation at the event horizon of a black hole result in the reduction of the mass of the black hole? Quantum mechanics requires the creation and destruction of particle-antiparticle pairs throughout space-time. When this effect occurs at the event horizon of a black hole...
  12. L

    I Do Black Holes Exist? | Physics & Stephen Hawking

    Do black holes exist? I have largely only heard that mathematically physics rules break down inside of a black hole by its current definition and that nothing can escape it beyond a point. And Hawking radiation has already shown to escape it beyond an event horizon. And Stephen Hawking in 2014...
  13. Vanilla Gorilla

    I Would Black Holes Be Coherent Under Quantum Mechanics?

    I just want to know if Black Holes would be quantumly coherent.
  14. BillDennis

    B How does mass affect the curvature of spacetime inside a black hole?

    How does mass determine the bending of space from inside a black hole?REPLY
  15. docnet

    B Exploring the Physics of Making Black Holes

    Hello, This is a question I've been pondering on my own for some time. I have no formal education in advanced physics, only at the introductory undergrad level. I read that immense pressure can create black holes by compressing matter. I've read Laurence Krauss explain you'd need to compress...
  16. docnet

    B Do things that fall into black holes ever reach the singularity?

    A Paradox of the black hole is that GR states the stationary observer experiences time dilation, while the inflating observer experiences no time dilation. By the time the infalling observer reaches the event horizon, an infinite amount of time passes for the other frame of reference. But...
  17. BiGyElLoWhAt

    B Searching for a Lost PhD Thesis on Black Holes

    The paper is reasonably old and was written as a phd thesis by (I believe) a man from china. It was basically the first paper on the subject and in it he effectively (from what I understand) dropped particles into a black hole, counting the information added, and saw that the black hole changed...
  18. S

    B Black Holes & Light: Questions from an Average Joe

    Hi everyone, been reading this site for a while, and this question has been stuck in my head for 3 days and i can't shake it, so i figured I'd step out of the shadows and ask. There are some follow up questions that came on the same train of thought too. Can light pass by a Black Hole and get...
  19. sbrothy

    I Barrow black holes with fractal surface?

    This should maybe go in the Beyond The Standard Model forum but since it's a paper about quantum cosmology I'll put it here. Feel free to move it if it's too speculative but that's exactly my question. That is: if it is... Perusing "The Area of a Rough Black Hole" - -...
  20. smodak

    Relativity Susskind's new book on Black Holes

    Three Lectures on Complexity and Black Holes - could be a good read for quarantine!
  21. docnet

    I Black Hole Evaporation: Exploring Hawking Radiation and Shrinking Black Holes

    I am grateful for anyone for their time to answer this question. Some theories predict black holes will evaporate and eventually disappear. From my limited understanding, Hawking's theory predicts that quantum effects near the event horizon of a black hole are responsible for blackbody...
  22. Replusz

    A Understand Linear Perturbations to Stationary Black Holes

    This is on page 2, and I guess it is the key to understanding what they mean by linearized perturbation to a BH in the abstract. What is meant by gravitational fields, what is delta(g_ab) and delta\Phi ? A perturbation to the metric, and the 'gravitational field', sure. And where are these...
  23. Leonardo Muzzi

    I Why the center of black holes should be different from neutron stars?

    Physically speaking, why the insides of the least massive black hole should be any different from the heaviest possible neutron star?
  24. Prof Mark R Smith

    Insights Black Holes Are Not Empty Voids. A Black Hole at the Heart!

    Continue reading...
  25. .Scott

    A Can large Black Holes ever spaghettify? (and more)

    So Alice and Bob are hanging out near a really large black hole. It's quiet. Nothing has entered the BH is a while. Alice tosses Bob in and then waits long enough for him to collide with the singularity. Of course, Bob is keeping time differently than Alice - so I rather doubt that the time...
  26. S

    Steam Flow through holes in a pipe

    What will be mass flow rate of dry saturated steam through holes on a pipe. Pipe ID: 25mm, Steam Pressure 3 kg/cm^2, Holes' Dia: 3mm, Number of Holes: 5.
  27. L

    B Colliding Neutron Stars Collapse into Black Holes

    Here is a presentation on the discovery of two colliding neutron stars and the resulting phenomena such as gravity waves, gamma ray bursts, and synthesis of high atomic number elements. The author is a theoretical physicist who is involved in the research. He says that the neutron stars most...
  28. tflahive

    I What happens in the area between black holes before they collide

    Recently there have been a lot of studies of black holes colliding and the gravitational waves that they produce. My question is: What is the effect on the space between the two black holes before they collide. The stress must be extraordinary. That stress should be measurable by radiation...
  29. J

    I Does Dark matter get trapped in black holes and increase their mass?

    Dark matter passes through everything, but is only influenced by gravity, so in the case of a neutron star, since dark matter doesn't interfere with ordinary matter, it can just pass through it, but neutrinos might be stopped by it's density, as neutrinos can just pass through stars almost as if...
  30. O

    I Observation of matter falling into Black Holes

    How long would it take for an object, stationary with respect to a black hole (mass of the sun), to fall from 1 AU into it beyond its event horizon? From our frame of reference can we observe over time, a black hole growing in size as matter falls beyond the event horizon? From our frame of...
  31. JTorn

    I with an exercise about Energy and Schwarzschild Black Holes

    The thing is that this is an exercise that I have to show my teacher but I don´t know how to get the answer.The exercise says: "A body of mass m moving in the Keplerian field V = −M/r (in G = 1 units) has a total conserved energy, Etot = 1 /2( m r˙^2 + r ^2ϕ˙ ^2 )− mM/r. Show that the...
  32. R

    Pressure drop due to holes in a pipeline?

    We have a project that relating with pipeline system and pressure control, the project is actually having goal to knowing how much pressure drop will occurs in pipe line system that in initial condition the pressure inside the pipeline staying at steady or constant in particular psi and at the...
  33. T

    B Atoms, Black Holes: Solving 2 Problems with 1 Theory?

    The laws of physics breaks down at an atomic level, it also breaks down around black holes. could the two be related? could a black hole be an atom with a periodic number in the (insert ridiculous number here) ? If it were true that black holes where atoms / elements it'd turn two problems...
  34. ValeForce46

    A cylinder full of water with two holes at different heights

    This is what I did: I know that ##v_1=\sqrt{2gh_1}## and ##v_2=\sqrt{2gh_2}## thanks to Bernoulli's principle. Using equations of parabolic motion I get ##h-h_1-\frac{1}{2}g(\frac{d}{v_1})^2=0## and ##h-h_1-\frac{1}{2}g(\frac{d}{v_2})^2=0##. This means I have two equations in two unknowns...
  35. H

    B Resources to help understand black holes

    Can someone post links to the popularly accepted theories on black holes? Just about all of the information I come across is presented as scientific fact, regardless of how far-fetched some of these ideas may seem, or contradict each other
  36. B

    I Are black holes actually holes?

    I have been curious if there is anything that would prevent a star that has the mass to supernova from going supernova at the end of its life. If that were possible could it then also be possible that black holes are not actually holes but something so massive that light and anything that comes...
  37. .Scott

    A Black Hole Eating Gravitational Waves - A Look at Physics

    Is it fair to say that all energy from a Gravitational Wave that enters the photon sphere of a Black Hole is destine to become part of that BH? And other parts that remain just outside of the photon sphere would experience gravitational lensing? Perhaps focusing the GW to an area of much...
  38. M

    B Questions regarding expansion, the vacuum in space, and black holes

    Summary: Expansion of matter in the visible universe, total volume of space outside the visible universe, black hole mechanics, and general questions from an uneducated but extremely interested evolved monkey. Hello everyone! I do not know the rules of this forum, or any forum for that matter...
  39. Roy S Ramirez

    Depth of NPT Holes: How to Fully Screw in Fittings Roy's Q&A

    Hello everybody! I've notice that when using NPT fittings, the female fittings usually doesn't take all of the male threads: This has never bothered me since these are commercial fittings and the engineers who designed them know what they are doing. But now, I need to make NPT holes in a...
  40. bob012345

    B Black Holes & Warp Bubbles - Event Horizon Considerations

    Last night PBS showed two shows on Black Holes. In the shows the host traveled on a supposed warp drive spaceship. A question occurred to me. Suppose for the argument that the Alcubierre drive were possible. Then suppose you were in a ship contained in a warp bubble moving through space at say...
  41. M

    B Do planets without a solid surface precess?

    Do black holes precess? I added some marks to a picture of quasar 3c175... can the highlighted distortion of the jet be interpreted as black hole precession?
  42. Raffaele

    B Black Holes, Gravitational Waves & Gravitons Explained

    I wonder why electromagnetic waves don't escape from a black hole while gravitational waves (obviously) do. What is the difference between the two kind of waves? And between gravitons and photons? thank you for your attention
  43. T

    Relativity Any good references on the thermodynamics of black holes?

    So, for the end of this semester's introductory couse in General Relativity (undergrad) I have to do a project on "The analogy between the mechanical laws on a black hole and the laws of thermodynamics". I couldn't find much (at least on my own) about this particular topic in my university's...
  44. F

    B Why does matter always escape while antimatter falls into black holes?

    Summary: I don't get it, why can we be sure, that black holes evaporate My simplified imagination about Hawking radiation is that when the vacuum fluctuation creates a matter-antimatter particles pair at the event horizon, thay are ripped appart by the tidal force and do not manage to split...
  45. E

    B Black holes and the first law of thermodynamics

    The first law of thermodynamics states that matter can only be transferred from one state to another, and cannot be truly destroyed. What happens to matter consumed by a black hole? What happens to it and where does it go? Does the first law still hold true?
  46. H

    I Exploring the Kinetic Energy of Merging Black Holes

    Imagine two black holes at great distance. They are both spatially separate and both completely collapsed to a singularity. Gravity begins to pull them together. According to the equation for the gravitation potential energy of two objects at distance… Ug = -GMm/r …These two objects begin...
  47. X

    B Can we produce black holes by particle accelerators?

    Summary: Thanks to CERN, we now have huge particle accelerators such as the LHC. We use them to enhance our understanding of quantum physics. As everyone know,particle accelerators are huge machines that smashes atoms into pieces at near the speed of light. I have heard making antimatter by...
  48. Y

    I How does the expansion of the Universe affect black holes?

    I realize that my understanding of this matter and it's vast number of related concepts is rudimentary and incomplete. Kindly forgive my ignorance and try to explain your thoughts in layman's terms. Thank you for your time.
  49. E

    Writing: Input Wanted How Close Can Spaceships Safely Approach Black Holes?

    Trying to understand radiation near black holes, specifically sgr-a, and more generally "radiation in space" and its general threat to the survival of spaceship occupants. Please let me know if this would be more appropriate in a different section here, eg astrophysics. In my little story the...
  50. N

    B Did Einstein Disagree With Black Holes?

    Not sure where best to post. Local paper has had a couple of articles about the black hole image over the past couple of days. They quote Walter Isaacson “Einstein did not believe, then or later, that these results actually corresponded to anything real,” . Is that true? I couldn't imagine...
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