What is Hole: 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. DDH

    Is there a theoretical min. size/mass limit to a black hole?

    Normally a star with a mass several times that of the sun will become a black hole at the end of the lifetime of that star. Can black holes exist with a mass much smaller than that exist? In other words, are black holes with a mass of Jupiter or even Earth exist? Or even much smaller than that...
  2. L

    Does gravity get destroyed in a black hole ?

    Does gravity get destroyed in a black hole ? If the Higgs particle creates mass in the universe and higgs are destroyed in a black hole, then the total gravity in the universe must diminish over time , hence the universe expanding ?
  3. sergiokapone

    Field inside spherical hole inside dielectric

    Let we have a dielectric with field ##E## inside and with a little hole. I have problem. I get a two different answers on this problem, and I try to understand which one of them correct. As mentioned in http://www.feynmanlectures.caltech.edu/II_11.html#Ch11-S4 (11.25), the electric field in...
  4. P

    Why is black hole photon sphere outside the event horizon?

    Homework Statement I am preparing a report on black holes and I recently learned about a phenomenon I was previously unaware of: the photon sphere of a black hole. While reading an article on said occurrence (I have now confirmed this on multiple sources) the photon sphere which is the minimum...
  5. Jimster41

    So is this scary? (Black Hole in binary system)

    http://www.cnn.com/videos/tech/2015/07/07/black-hole-awakens-erupts-nasa-orig.cnn 8K ly seems awfully close. the cnn version of the story... is a bit thin o_O
  6. dark knight13

    What happens if we put a hole in a capillary tube?

    case 1)The hole is drilled before the liquid rises case 2) the hole is drilled after the liquid rises
  7. G

    Light Behavior in Black Holes: Exploring Curved Space-Time

    Good morning everyone, I'm Giuliano and I would like to know how light behaves in a black hole and because it can not get out. More precisely, i understand that light moves in curved space-time format from the black hole, but once passed within swarzchild radius the photon is expected to impact...
  8. btouellette

    Flat Spacetime at Event Horizon of Black Hole?

    I've been working through Leonard Susskind's "The Theoretical Minimum" lecture series (which are a fantastic introduction to the topics covered by the way) and a couple of his comments confused me when he was covering the Kruskal-Szekeres metric/coordinates in General Relativity. The end of the...
  9. G

    Speed of light inside a black hole

    We know that light's speed gets slowed down when traveling through a medium, and the more dense the medium the slower light can travel (of course c remains constant, but it takes longer to travel due to the continuous scatterings, absorbtions and re-emissions). Inside a black hole, just below...
  10. Andre' Quanta

    First quantization light ray in Schwarzschild's black hole

    The dinamic of a light ray in a Schwarzschild' s metric is governed by a lagrangian where the potential is V(x)= a*(1/r)^2-b*(1/r)^3 with a and b positive costants. The presence of a Lagrangian it means that is possible to apply a first quantization of this sistem; if so which are the...
  11. M

    Bunsen burner flame gets colder with air hole fully open

    Hello, My GCSE class just did a practical investigation into how the width of a Bunsen's air hole affects the temperature change of a beaker of water. The entire class found as expected that the size of the temperature change increased as the hole was opened further, but they all found that...
  12. Justice Hunter

    Does Dark Matter Interact with Itself in Black Holes?

    Hey so i have a naive question that i always had since i was young, but i never really could find an answer to it. Lets say you have a black hole isolated in a vacuum, in a closed system. Dark matter is supposed to be a sort of weakly interacting massive particle, which exerts a gravitational...
  13. U

    2D Phase portrait - Black hole?

    Homework Statement Trajectories around a black hole can be described by ## \frac{d^2u}{d\theta^2} + u = \alpha \epsilon u^2 ##, where ##u = \frac{1}{r}## and ##\theta## is azimuthal angle. (a) By using ##v = \frac{du}{d\theta}##, reduce system to 2D and find fixed points and their stability...
  14. Justice Hunter

    Black hole information : Holographic theory question.

    Question! So Alice falls into a black hole, instead of the volume increasing for the black hole, it actually increases proportional to it's area. Thus one can draw the conclusion that 3 dimensional information can be fully explained by the information encoded on the surface area at the boundary...
  15. Stephanus

    What is the limit of classical GR in describing the singularity of a black hole?

    What is the size of the singularity? 1. Is it 0 cm? 2. Is it below Planck length? 3. Is "the size of singularity" the wrong question, such as asking "what is the length of 500 celcius"? What does that mean? From event horizon all the way, just before, the centre, is vacuum? And suddenly there...
  16. E

    A Question about the formation of white holes off black hole

    Hello, I had a thought about the formation of white holes off of black holes and i wanted to ask if it is possible, if a massive black hole is surrounded by a lot of matter(a lot of giant stars etc.) and it consumes so much matter that even a aquasar is not sufficient enough in disposing all of...
  17. K

    Time to fall through a hole in Earth, but not through center

    It is a classic physics problem to calculate how long it would take to fall through a hole that passes through the center of the Earth to the other side, assuming Earth is a sphere with uniform density. I also remember being posed a problem for if you were falling through a hole that passed not...
  18. S

    Mass velocity at a black hole event horizon.

    SR implies that mass can't reach c, but mass does reach a black hole's event horizon. How is this reconciled with SR?
  19. Stephanus

    Exploring Anti Matter Black Holes: Physical and Statistical Possibilities

    Dear PF Forum, In less than 1 second after big bang, baryons were created. And there's asymmetry in it. Can anyone help me? 1. Is it physically possible for a galaxy made entirely from anti matter? 2. If it's true, is it statistically possible for a galaxy made entirely from anti matter? If...
  20. B

    Guy falling into black hole sees end of universe

    I still don't understand this fully. Can someone please explain? I saw a video where an analogy was made, the distant observer is like an accelerating observer in flat spacetime and guy falling in is like an inertial observer, is it just like the coordinates of the distant observer from the...
  21. G

    Black hole electron: How can we drop the geodesic equation?

    Hi, Einstein once showed that if we assume elementary particles to be singularities in spacetime (e.g. black hole electrons), then it is unnecessary to postulate geodesic motion, which in standard GR has to be introduced somewhat inelegantly by the geodesic equation. I don't have access to...
  22. T S Bailey

    Lifespan of a black hole as measured by different observers

    I've read that a stellar-mass black hole has a lifespan on the order of 10^67 years. Does this mean that a clock which is at rest with respect to (and sufficiently far away from) a stellar-mass black hole will tick off 10^67 years before the black hole evaporates? Also, will shell observers...
  23. D

    Black hole seeding vacuum decay

    Hello all, please forgive me if I seem somewhat unaccustomed to this site, I have just registered. I suffer from an illness called catastrophic thinking syndrome, simply put this means that I turn everything I read into a disaster until I become ill due to anxiety / depression . I recently...
  24. P

    Can you have an antimatter black hole?

    Sorry for a bit of a sci fi question but are anti matter black holes likely, presumably they would need to come from whole antimatter stars in antimatter galaxies? otherwise they would already have destroyed themselves?
  25. B

    Gravity & Force From Black Holes: How Do Photons Escape?

    this seems like a dumb question but i just can't think of a solution. black holes can suck photons, that's why they are black. but there are charged black holes, and the EM forces is mediated by photons, so how can the mediating photon escape the gravity? also arent the gravitons (i know...
  26. Hardik Batra

    Electric flux linked with spherical shell having a hole?

    How much electric flux linked with the spherical shell having a hole?(consider the charge is outside the shell) I knew the flux linked with spherical shell is zero.(because it is closed loop.)
  27. L

    Detecting matter falling into a Black Hole

    Hello to all ! I wanted to ask a question in this forum. I am french, and I have discussed this topic in a french physics forum, but with no clear conclusion. I hope I'll have another insights in this forum, which seems very well frequented. I know the underlying subject has been discussed in...
  28. newjerseyrunner

    Would a supermassive black hole explode?

    I was thinking today about black holes. I was imagining how they formed a singularity, not mathematically, but physically and I got stuck at the Planck density. It's not a singularity yet and even with the entire weight of the rest of the object on top of it, you shouldn't be able to pack more...
  29. Mohan Nivas

    How Do Black Holes Acquire More Mass Than Other Objects?

    How the black hole acquire greater mass than any other objects in the universe...?
  30. PraisetheSun

    Spaghettification inside a spherically symmetric black hole

    I need to find the vectors for time and radius that describe a space-like 4-acceleration of an observer falling radially into a spherically-symmetric black hole. Previous to this question, the values of the real time derivatives for time and radius were derived to be: dt/dτ = (1-2m/r)-1 and...
  31. Silenus

    Dark Matter is baryonic matter passed through a black hole?

    Wouldn't this explain why galaxies with no black holes are so small?
  32. U

    What is the doping and hole concentration?

    Homework Statement (a) Show law of mass action. (b) Find dopant concentration and hole concentration.[/B] Homework EquationsThe Attempt at a Solution Part(a)[/B] Bookwork. Part(b) Letting the doping concentration be ##D##, we have: D = n - p For ##I = n_{intrinsic} = p_{intrinsic}##, we...
  33. bcrowell

    Parallel transport to explain motion of light near black hole?

    I'm currently teaching a gen ed course called Relativity for Poets. This is the first semester I've taught it, and it's been a ton of fun so far. If anyone is curious, http://www.lightandmatter.com/area3phys120.html is the class's web page with links to the syllabus and lecture notes. The...
  34. Dr.ahmad adnan

    Which is the most powerful black hole or a worm hole and why

    Which is the most powerful black hole or a worm hole and why, also what is the difference between them?
  35. M

    Force in the Centre of a Black Hole: Explained

    The force in the centre of the earth, assuming it was a perfect sphere and the density was the same everywhere, would be zero as the pull from all directions would cancel. Why isn't it like this for a black hole? Surely the forces from each direction should cancel leaving zero resultant force at...
  36. Emmanuel_Euler

    What Happens if a Black Hole Dies or Disappears?

    what does happen if the black hole died Or disappeared??
  37. andyrk

    Force Imparted by water gushing out of hole

    A container is full of water. A hole of cross section area a exists at the wall of the container, x height beneath the surface of water. (So speed would be v = √(2gx). Let's call it v for now). The density of water is ρ.Then why would the force imparted by the water gushing out of the hole on...
  38. LHCSafetyReview

    A hole in the LHC's vacuum bubble safety argument

    A hole in the LHC's vacuum bubble safety argument One of the four specific risks considered in the most recent official safety review for the Large Hadron Collider (LHC) is the possibility that LHC collisions could trigger a transition to a lower-energy vacuum state. The current review by the...
  39. Emmanuel_Euler

    What Would Happen if I Threw My Watch into a Black Hole?

    what does happen if i threw my watch into a black hole??
  40. J

    Does Entering a Black Hole Speed Up Universal Aging?

    Would the universe end if you entered a black hole? What I mean by this is that due to time dilation would time elapse so fast for the universe outside the black hole relative to you inside it that all the stars would burn out and all that wouild be left would be other black holes?
  41. wabbit

    Clarifying Black Hole Horizons: An Examination of Observer Perspectives

    I am confused about black hole horizons and such common statements as "light cannot escape from inside the horizon". The way I currently understand it is as follows : 1. Horizons are always relative to an observer, and what is called "the black hole horizon" is just a shorthand for "the black...
  42. K

    Can we distinguish between black holes and white holes?

    I know white holes probably don't exist, but I'm having trouble understanding how someone outside the white hole would perceive them. My understanding is that they are time-reversed black holes. I've read that nothing can fall into a white hole, that it is repulsive, and that it continually...
  43. J

    What happens to the electrons in a black hole?

    As multiple stars would collapse into a black hole, are the electrons shot outwards? Or are they converted into mass with infinite density (what a black hole is right?) Thanks.
  44. C

    Black Hole Time Dilation And Observation Of Accretion

    Hello. If time is infinitely dilated at the edge of the EH, how do we observe accretion?
  45. Kishan Majethia

    Calculate Ovality of Circular Hole - Formula & Reference

    Can anybody guide me what basically is the formula for finding ovality for a circular hole of given dimension and tolerance? I think it would be (Upper tolerance limit + Lower tolerance limit)/2. But not able to find any reference for the same. Please also give reference for the same if...
  46. E

    Distance from Black Hole to experience Time Dilation

    How close do you have to be from a black hole to experience noticeable time dilation. I always believed you will not experience noticeable dilation until you are at or in the event horizon is this correct? Also does rotation/spin of mass such as a planet decrease it's inherent gravitational...
  47. R

    Supernova Explosion near a black hole

    What would happen if there was a supernova explosion near a black hole ? Would it just sit there and absorb all the energy incident on it ? Or would it simply vaporize into elementary particles ? And if it does vaporize, could the remnants give us a clue as to the quantum state of matter inside...
  48. S

    Entire universe ending with a supermassive black hole?

    Black holes grow by absorbing matter, which includes galaxies and black holes. Would the growth of black holes overtake the expansion of space time and collapse the entire universe?
  49. I

    Forces of a bolt that bottoms out in a blind hole

    I understand there are a variety of forces that are at work when a bolt is clamping two components together. However, what I don't understand is what forces are at work when a bolt is screwed into a blind hole and it bottoms out. Assuming a torque is applied, how would this torque act on the...
  50. binbagsss

    Extension of Schwarzschild Light Cones: White Hole/Black Hole

    The coordinates ##u## and ##v## are defined as ##u=t+r*##, ##v=t-r*##, where ##r*=r+2M In(\frac{r}{2M}-1)##. In ##u,r,\theta,\phi ## coordinates the radially null geodesics are given by: ##\frac{du}{dr}=0 ## for infalling, ##\frac{du}{dr}=2(1-\frac{2M}{r})^{-1} ## for outgoing. In the...
Back
Top