Hole Definition and 1000 Threads

Homework Statement When a container full of water with a small hole in the side is at rest on a table, water flows out of the hole and follows an approximately parabolic arc before hitting the table. Suppose the same container is dropped down a mine shaft so that it is in free fall. Air...

What would happen if the bore hole of a pulley in a conveyor was significantly larger than the shaft like in the figure below: I would imagine if the RPM was high, the whole system would shake violently. However, what if the RPM was around 30 RPM. Would the conveyor still function properly...

I asked a question recently about orbiting black holes. Thanks for the answers. So if I'm correct in my thinking, long before the event horizons of orbiting black holes become close to each other, the two accretion disks get mightily disrupted and much of the mass of the two disks would fall...

Homework Statement A hollow insulating sphere of radius R is charged uniformly to a charge of Q. There is a small hole on this sphere. What is the electric field strength at the centre of this hole? Homework Equations The Attempt at a Solution I think I have to use Gauss's law...

A recent APOD page discussed jets ejected from black holes. It said, "Recent evidence indicates that these jets are composed not only electrons and protons, but also the nuclei of heavy elements such as iron and nickel." What is thought to be the mechanism of production of these heavy nuclei?

Homework Statement One end of the chain falls through a hole in its support and pulls the remaining links after it in a steady flow. If the links which are initially at rest, acquire the velocity of the chain suddenly and without frictional resistance or interference from the support or from...

In the "closed" Friedmann model, there is a Big Bang in the past and Big Collapse in the future. Big Bang singularity is something different than a Black Hole singularity. Now my question: is the Big Collapse singularity mathematically equivalent to a Black Hole (localized) singularity, or is...

Homework Statement Astronomers believe that there is a massive black hole at the center of the Milky Way galaxy. What evidence is there for that? A group of astronomers have observed a star "S2" in a 15.2-year orbit around the center of the galaxy. They measured the period of revolution T =...

Hi, two questions A) If a black hole travels into a wormhole would it collapse the wormhole? B) If a wormhole travels through another wormhole what would happen? Thanks for any help.

Supposing there is a metal cylinder that fits into a perfectly machined hole in a block of metal with the cylinder protruding some length from the block. If you place a force on the edge of the part of the cylinder that is protruding in a direction perpendicular to the hole, is there a...

Can a black hole be a portal to another dimension?

I've read that there's a point in a black hole where matter is infinitely dense. There is zero volume but infinite density. How is it possible for something to have zero volume but have an infinite density at the same time?

I've never fully understood how anything can actually fall into a black hole without the black hole evaporating first. Since time dilates exponentially as I fall into a black hole, a point will come where a few seconds for me will be millions of years in the outside world...trillions in fact...

Homework Statement This is the original problem for part 1 A) Suppose that a black hole of mass M accretes mass at a rate ##\dot{M}##. Further suppose that accretion of mass Δm leads to the radiation of energy ##\Delta E= \eta Δmc^2##, for some effeciency of energy conversion, ##\eta##. What...

Homework Statement Suppose that a black hole of mass M accretes mass at a rate ##\dot{M}##. Further suppose that accretion of mass Δm leads to the radiation of energy ##\Delta E= \eta Δmc^2##, for some effeciency of energy conversion, ##\eta##. What is the luminosity of emitted radiation in...

If a distant observer were to observe a large cube made of strong material approach a black hole, what would he see? ISTM that if one of the faces of the cube were to be the nearest approaching portion, he would see the four edges of the face become shorter and curved, and he would see the...

Hi all, I was wondering if, when a beam of light is pulled towards a black hole , because it can't accelerate, it is blueshifted? Thanks in advance.

Homework Statement Consider a charge density of ρ=k/r , k>0 , located between a sphere surface of r=a and another sphere surface of r=b, b>a. I'm supposed to find the electric field on all space, which I did. Now I have to find the electric potential in all space, which I also did for r>b...

A galaxy is many many light years away. All Electric Charge, Q, must be dissipated. How do you tell if charge exists and what magnitude.

Please help me to understand why the path of the photon changes when travels close to a material (for example the edge of a hole)? I'm aware that the path of the photon can be calculated by the QM principles as a probability wave and by this the change of the wavefront follows the...

If a beam of light is on a trajectory that is perfectly tangent to the event horizon of a black hole (or a little below tangent, allowing it to "dip" into the EH for a moment), is it possible that that photon could be pulled into a never ending orbit around the black hole? Or is the gravity too...

is black hole a theoretical concept or a natural phenomenon?

I was thinking about the supermassive black hole that is theorized to be at the center of our galaxy, and indeed, at the center of most galaxies. If that black hole is continuously consuming the stars, planets and gas around it, given enough time, will it not consume the entire galaxy that...

"Rewinding" a black hole - Can a spinning black hole become a star? I couldn't fit all the important prerequisites and context in the title, so I'll set up the thought experiment here. Some of these assumptions are also questions, and might be easily refuted, thus answering the main question...

I was watching a documentary about the universe and it claimed that black holes were sometimes as small as 2 kilometers across. Now before this, my general understanding of a black whole was that it had no physical extent in space, that it was just a 1 dimensional singularity, and the black...

Given a massive object that has entered a BH's accretion disk, what percentage of its mass is typically re-radiated away as i) accretion disk radiation and ii) polar jet radiation/particle streams before ever getting to the event horizon? How much does a black hole *not* consume of its...

Hello, I would first just like to introduce myself I'm Adrian and I am a grade 11 student so this type of stuff is way out of my league in terms of mathematical complexity.. but are there equations that define a black hole (What is happening to particles when they enter the event horizon.. etc)...

Holographic BB out of prior BH (stringy version of BH bounce) http://arxiv.org/abs/1309.1487 Out of the White Hole: A Holographic Origin for the Big Bang Razieh Pourhasan, Niayesh Afshordi, Robert B. Mann (Submitted on 5 Sep 2013) While most of the singularities of General Relativity are...

The Schwarzschild equation for a black hole's event horizon is rsh = 2GM/c2 or (1.48 x 10-27 m/kg) x M. Thus, the ratio of mass to radius is 6.7 x 1026 kg/m for all black holes. If the mass and radius of the universe are calculated as follows, Mass of the gravitationally connected universe...

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}##...

Black holes have an entropy, but they evaporate. At the end of the evaporation, the entropy is greater than the entropy at the beginning of the evaporation. I am looking for an example of a quantitative result for the entropy of the black hole after evaporation (or the entropy difference...

"Where should a second hole be placed in order for the light [...]?" Homework Statement The problem and the solution are attached as jpg files. (Given that the problem depends on the drawing, I think it's more convenient for the reader to view the text in the image as well.) Homework...

I was under the impression that one of the ways of representing a black body (for explaining the ultraviolet catastrophe) is as a 'resonant box'. Frequencies lower than the dimensions of the box cannot be contained within and the black body is thus 'transparent' to those frequencies of light...

As I understand, complementarity approach claims that there are 2 different stories, for an infalling observer and an observer @ infinity, they are different, but no observer can confirm both. But it violates the Block Time/Eternalism, where time is a dimension, the whole world is a static...

Imagine we have a very tall vertical cylinder like a very elongated telegraph pole, that is rotating at 200 rpm about its long axis on near perfect bearings. Initially the cylinder is sufficiently far from a black hole, that differences in gravitational time dilation between the top and bottom...

Author: Leonard Susskind Title: The Black Hole War Amazon Link: https://www.amazon.com/dp/0316016411/?tag=pfamazon01-20 (submitted by jedishrfu)

For outside observer, an object falling into black hole seems to freeze at event horizon and never cross the boundary and proceed inside the black hole. This is of course not the case in the falling objects own reference frame. Depending on the size of the black hole, a falling object may not...

I thought readers would be interested in this interesting article today on black hole and neutron star mergers and the very small possibility of instantaneous sterilization and extinction of all life on earth:http://www.space.com/22231-gamma-ray-bursts-neutron-stars.html...

hi some black holes are inner and outer horizon! what's this means? inner and outer? what happen between them?

consider have a metric ds^2=f(r,t)dt^2+g(r,t)dr^2+k(r,t)dΩ^2 if g(r,t) =0, we have black hole? any metric that has this condition, are black hole? or not this is first clue to determine black hole and we should check some other features! solution of g(r,t)=0, may have some roots, for example...

From previous threads I have understood that crossing the event horizon of a supermassive black hole is nothing very unusual for the falling observer locally. Usually in these considerations the falling observer has been thought as a "point" without much dimension. How about if Earth (and...

From here: http://www.reddit.com/r/askscience/comments/f1lgu/what_would_happen_if_the_event_horizons_of_two/ (About a page down from the top. You can't miss it.) Imagine, just for a moment, that you are aboard a spaceship equipped with a magical engine capable of accelerating you to any...

Arkani-Hamed, Dubovsky, Nicolis, Trincherini, and Villadoro argue in section 2.2 of A Measure of de Sitter Entropy and Eternal Inflation that the effective field theory description of black hole evaporation fails after a time t[SIZE="1"]ev, even though the curvatures are small. Almheiri...

Sorry if I am woefully uninformed, but I am really curious. What happens to time at the center of a black hole according to general relativity?

hi if you want to find the black hole solutions, what do you do? has any solutions of $R_\alpha\beta=0$ a black hole? thanks

what is the final stage of black hole mean what its the next stage turning to be (in what form ) why black hole is created?

In a thread some time back on black hole firewalls, one of the papers linked to was one by Bousso in which he argues that (as the paper is titled--note that this is a revised version, the original was quite a bit dfiferent) "Complementarity is Not Enough". I'm not trying to start a general...

What is the central region of the so called black hole composed of? Are there intense energetic waves caused by thermonuclear fissile processes? Does the high intensity ray conflagration coupled with immense crushing cause electron repulsion?Does this process also cause nuclear disintegration...

Ok so this has always confused me and I still can't seem to find an answer anywhere! A general black hole has parameters M, Q, and J which are given the meaning of mass, charge, and angular momentum. My question is what what is the contribution to M by Q and J?? Presumably if you start with a...

So, I was thinking about this the other day. If we watch material approaching near the event horizon of a black hole get scattered all over the place, then would the opposite be seen for an observer falling into a black hole? Instead of us seeing them scattered all over the place, would they see...