Hole Definition and 1000 Threads

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?

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...

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...

So I was reading threads and i came across a question on what happens when a black hole collapses. As I was reading the responses, I saw some people commenting in which they asked if the mass the black hole absorbed was released when the black hole collapsed. If it did would the black hole...

I'm trying to build a mathematical model of something like Heron's Aeolipile: http://en.wikipedia.org/wiki/Aeolipile I'd like to know, based on a known heat flux, the pressure and temperature attained in the container. I assume as water boils, the control volume loses mass and energy, the...

If we can motion at speed of light,can we pass a small hole like a keyhole? Of course in suitable conditions...

What do you put inside einstein field equation for black holes? Why is it that such black hole solution is not feasible? Isnt the schwarzschild metric a solution for black holes? How is it not feasible?

I know that black hole have strong absorb force even light can't escape,so if we get near i think we can't also escape,but i want to know what will happen when we reach inside the black hole? and what happen if two black holes meets,what will happen if it come near to earth?

I'm curious about what others think. As I believe that you fall indefinitely in a black hole, and since you don't feel the gravity when falling, you fall until your incinerated by faster moving electromagnetic radiation falling on you. But you can only see what is above you, assuming your eyes...

When electrons leave the valence band and jump over the gap to the conduction band, what is the density of the remaining holes? If 2.5 electrons/cm^3 leave the VB to the CB, will the density of remaining holes be 2.5 electrons/cm^3? To me it is logical, but I am wondering if mass of electron...

Is there a physical boundary that is the event horizon? Or is there not? The reason I'm asking is because texts say that the event horizon that appears in Schwarzschild's metric is a result of the coordinate choice, and it disappears by choosing some other coordinates.

(I don't know if this is the best place to ask this, if not please feel free to move it elsewhere or delete it.) A number of Quantum Gravity papers explore the evolution of Black Holes and their potential transition to White Holes, and some discuss the possibility of astronomical observation of...

I thought that this might be a concern for the standard Cosmological model? An extremely large Black Hole discovered to have existed just 900M years after the Big Bang...

If the Singularity Has Infinite Mass, How Does Merging With Another Black Hole Create "Suoermassive" Black Holes? Infinite Plus Infinite Is Infinite. No Increase.

I am fifteen and I attend High Tech High International and I have to teach a hour long lesson on Black Hole Buoyancy. And I was wondering how to do that. Can I have some suggestions or help?

is a dark matter black hole possible, and what would it be like ?

How exactly did Hawking compute that black hole entropy is 1/4 that of a Planck area and concluded about the holographic principle where information of a volume is located on the area of black hole? And if there was no holographic principle, how big should entropy of the black hole be with...

Hello :) I had a question , i recently red a lot about black holes and i had a question about the Schwarzschild Radius . How does that come that π is not in the equation ? The black hole is a sphere so instinctly one could think that Pi should be in the equations.. ? P.S: I'm french and 16 so...

Hello. I'm thinking about Hawking radation and there's one thing I find a bit strange. The radiation is usually described as originating at he even horizon. The explanation makes sense and all, but still how can this locally non-special place become the seat of a local phenomenon(emitting...

How Can we Find the Escape velocity of a black hole.

Hello, Theoretically any object can convert into black hole by compressing its mass below some radius( describe by Schwarzschild Radius). Suppose one of this object after becoming black hole have radius which is comparable to atoms and nucleus radius. Now my question is what will happen if we...

Consider a Maximal (negatively) charged black hole. Can it have "flavor" or weak charge? Suppose a muon collided with that hole. Would an electron be emitted? What if electron neutrinos collided with that black hole; would electron neutrinos more likely be emitted as Hawking Radiation...

if I compress a heavy body to a very small point object such that its density is almost infinity, I get a black hole. but how can a point mass be a hole? why do scientists call it a black 'hole'? what I mean is, if I were to be pushed into a black hole, will I collide with that point mass? Also...

I've been playing around with some ideas of electron-hole pairs in semiconductors lately, have realized that I'm confused about some basic conventions that maybe the physics forum community could help clear up. Let's imagine that we have a direct gap semiconductor initially at zero temperature...

In my thought experiment (it seems that others have asked a similar question, but I have a more specific question in my list below), we have a physicist outside the event horizon of a black hole. He has many entangled particles and sends some into the black hole. Is / Could there be some...

I'm aware that in order to find the hole in a graph, you need to factor both the numerator and denominator, and look for terms that cancel out. However, is it merely just looking for a term that cancels out, or is it more specifically a term that cancels out and makes the numerator equal to...

I am looking at the classic paper Israel and Khan "Collinear Particles and Bondi Dipoles in General Relativity" Nuovo Cimento 33 (1964) 331. The basic question is how to go from equation 2.9 to 2.10? a_i is the center of rod i and b_i is the mass of rod i. The attached file has the details...

Hey Guys, so i was reading Hawking&Ellis a bit and still encounter always problems with the Penrose-Diagrams. Looking at the Penrose-Diagram for the rotating Kerr-Black hole (just one illustrating picture at the end) i come up the following question: Why are there TWO regions III and III ? In...

I'm a bit puzzled by the dynamics of things falling into a black hole. If I start with a test mass at infinity, it will fall freely into the black hole and reach the speed of light at the event horizon. What happens if I throw something towards the black hole? Will it already reach the speed of...

I have been pondering black holes for some time and have had trouble with the problems presented simply because there is very little we can do to study the phenomena. I have always thought of a black from the outside looking in, or basically the only way we can hope to see a black hole. However...

Homework Statement A rope of mass M and length l lies on a friction less table, with a short portion, ##l_0## hanging through a hole. Initially the rope is at rest. a. Find a general solution for x(t), the length of rope through the hole. (Ans: ##x=Ae^{\gamma t}+Be^{-\gamma t}##, where...

In the view of Hawking radiation and entropy of black holes, the evaporation is continuous and at one point, there will be no singularity for the black hole. By relativity, if we reach a super massive black hole, then time would be relatively slowed down to a point that it stops (maybe?). Now...

Why Graphing Tools doesn't represent hole in a graph of a function. A Hole at a point in a graph is point where function is not defined.Suppose there is a function ##\frac{x}{\root{x-1}-1}## Its should be like this But online tools and even my android graphing tool app shows graph like this...

I'm going through Kerr metric, and following the 'Relativist's toolkit' derivation of the surface gravity, I've come to a part that I don't understand. Firstly, the metric is given by...

Information that is ordered can be compacted down to a single repeating unit i,e; 110055110055110055110055 down to just 110055 and this meant that it must have been highly ordered to be compacted down this far. So could it be that matter is also highly ordered somehow and it can be compacted...

We have a large mass, and we increase it slowly- dropping in one atom at a time. Will a black hole form suddenly, or will it gradually become blacker with the addition if each atom? I assume that a mass marginally below the threshold must at least partially have the properties of a black hole...

Hey all this is my first post, Everyone knows you can't enter a black hole because you'll be stretched/turned into noodles due to the immense change in gravity over small lengths. I was reading another thread on the physics forum and happened to come across an equation which would determine if...

I see that the formula for hawking radiation is related the the formula for unruh radiation. The accelleration experienced by a body yields an unruh temperature equivalent to a black holes hawking temperature with an equivalent value of g. The unruh effect happens at all accelerations, therefore...

If a large mass of matter and anti-matter collided to form a black hole, I assume they would anihilate and you would have a black hole made of photons. Now considering the black hole as a container of photon, there must be a net pressure pushing against the confines of the gravity. The force of...

A substance of arbitrarily low density can form a black hole if there is enough of it. So I took the mean density of the universe and calculated how big it would have to be to form a black hole. It's a surprising coincidence that the swartzchild radius in light years is the exact age of the...

##E= -T^uP_u ##, where ##T^u## is the time-like killing vector associated with the Kerr Metric and ##P_u## is the 4-momentum of the particle. ##E## is the energy. Outside the ergosphere ##T^u## is time-like and inside the ergosphere it is space-like. Therefore it can be arranged within the...

I know the original schwarzschild formula for finding the radius of the black hole, but what equation can be used to find its mass if you ONLY know its radius?

As all of us know that in a vacuum the particle antiparticle pairs or the virtual particles are created violating the law of conservation of energy. So even near an Event Horizon of a Black Hole virtual particles are formed. One of the particles gets sucked into the black hole but the other...

I've been searching over this and I don't quite get it yet. I just heard about this "z" parameter for gravitational red shifting and I thought it'd be fun to apply into the scenario of a solar-mass black hole. The equation I looked at was (1/(2GM/c^2r)^0.5) - 1 = z So, like, does the z parameter...

After reading: I wondered about the following thing - is it possible to make a story in which there is a place for a habitable planet and a black hole? (I mean, I have one idea, but it does not end up well... ;) ) I see one additional limitation: the black hole was created in a supernova, so...

Can be black hole created straight from cloud forming protostar. I mean, the region which is collapsing is so massive that pressure of radiation could not resist and the cloud is collapsing to singularity? If not, why?

I'm very new to semiconductors. I want to do basic calculations. How would I go about calculating and graphing the energy of the electrons and holes given the magnetic field and the state. Also, how would I do the same for the electron and hole population.

Inspired by the movie Interstellar which featured a planet orbiting a rotating supermassive black hole with an extremely high time dilation factor (slowed by a factor of 60,000 relative to observers far from the black hole), I was wondering if anyone knows of an equation for time dilation of...

Homework Statement A uniform rope of length L lies in a lump on a frictionless table. a very small piece at one end is held hanging down through a hole in the table just below the lump. This system is released, and the rope slides down through the hole. What is the speed of the other end of...

Now I know that in the general Schwarzschild metric, there is energy and angular momentum conservation, but what I'm wondering is if there is any linear momentum conservation. Let's say a particle collides with a black hole. Does the energy of that particle go solely to the rest mass and...