Hole Definition and 1000 Threads

So, I lay a rope into a black hole, rope leaves the reel at velocity 0.99 c. When I observe the lower end of the rope, I never see it reaching the event horizon. Can I see some slack rope somewhere sometime?

Is there time inside of a black hole?

Hi, I am not too sure where to post this. I am studying for my astrophysics final and I came across this question which is pretty easy ( I think) but I can't seem to find the answer... S2 is observed to be one of the brightest stars orbiting the black hole at the center of Milky Way. It has...

Homework Statement Pls help me with the (d) option of the question asked in the link https://www.physicsforums.com/showthread.php?t=724332&page=1 Correct expression for tension is ρgx/6 (as given in the answer sheet) Homework Equations The Attempt at a Solution...

So I have a question about Sagittarius A*, which more and more astrophysicists are certain is a supermassive Black Hole. But now for the evidence part: 1. An alternative model for this object was proposed http://journalofcosmology.com/RobetsonLeiter.pdf published 4 years ago. So is there any...

(Correct me if you think I'm wrong in anyway, I am open to new ideas.) A black hole is created when a planetary mass has its atoms completely cave in on its self. This creates a massive amount of gravity, one so massive that it even attracts photons (light). So does this mean that a black hole...

Homework Statement Part (a): Explain what A and f means. Describe an experiment that shows this relation is true. Part (b):Find the temperature of vessel 1. Part (c): Why is temperature of vessel initially the same as vessel 1? Calculate the final temperature of vessel 2. Find the time taken...

Homework Statement A rectangular opening is cut into the side of a large open-topped water tank. The opening has width W and height H2 - H1, where H1 is the distance from the top of the tank to the top of the opening, and H2 is the distance from the top of the tank to the bottom of the...

Hello PFers! I hope everyone is doing well. Here's my question: The way I understand it (imperfectly, of course), forward-biasing a p-n junction diode, the electrons crossover from the n-type material and fall into the holes in the p-type material and then they are conducted through the holes...

What are three different ways that i can produce a hole with a square cross section in a plate with a thickness of at least 1"?

Hello, if you could help, I will be glad. I am studying the Einsteins-Rosen bridge (a matematically solution of the black hole) and I thought that the Einsteins-Rosen bridge was what we found making the Schwarzschild metric a change in kruskal coordinates. But reading an scientific article it...

There is a cube with its sides equal to d and its thikness equal to t. It also has a circular hole at its center with radius a (a<<d). Two sides of the cube are maintained at potentials V_0 and -V_0 . I want to find the potential inside the cube but I see no way for obtaining the boundary...

Suppose a black hole travels at something like v = 0.999999999c relative to some observer. Does the black hole's event horizon becomes length contracted, thus appearing to turn into a black disk?

Hello, I am interested in surface gravity of Kerr black hole it means, I need to find killing vector for Kerr which is null on outer horizont. Is it true? How should I do that? I guess it could be some linear combination of vecotrs ∂/∂t and ∂/∂\phi. So can I looking for that this way...

Since light has no MASS... Then how does a black hole absorb light?

Here is my basic question: Lets say we have a massless charged shell with charge q and radius R. Is there some R where a black hole is formed? I haven't work this out with the EFE, but the calculations I've done are relativistic (GEM equations instead of EFE, for simplicity). I found that...

Let's say that you have an open tank of water and a hose connected to the bottom of it. Water is flowing out of the hose. You then cover half of the hose with your thumb. Will the flow rate (liters/second) right before you cover the hole be the same, less, or greater than right after you cover...

I have a question pertaining to objects falling through the event horizon of a black hole. It is my understanding that due to the immence gravity of a black hole and the way gravity affects the flow of time, that from the point of view of an observer at a safe distance from a black hole...

Prove that least two humans named John should have born on same day(means with same D.O.B) if world has only 24 million humans and their alphabet chart contain just 4 letter 'J','H','O' and 'N' and there can't be more than one million humans of same name and world started just 2739 years ago...

If I use the un-threaded section of a 3/8th inch bolt as a pin to lock a sprocket hub to a drive shaft I would drill and ream so that the bolt would need to be lightly tapped to go through the assembly. If the fit was looser (.025 thousands clearance) would that reduce the capacity of the...

Lets say we have a couple objects, one very close to a black hole, one a little farther out and then one a good distance away. Would the one very close to the black hole see the other ones time moving much quicker than their own time? How about just as they are going to hit the event horizon...

Requested info for a sci-fi short story I'm writing: You are approaching the event horizon of a supermassive (10 billion Solar masses) Schwartzchild black hole in a magical spaceship which is capable of violating the laws of physics. You have not been free falling but lowering into the hole...

Hi, I've heard and read that if someone was to fall towards a black hole, say feet first, they would undergo spaghettification at a certain distance, as the gravity at their feet would be much greater than the gravity at their head, and their body wouldn't be able to reisist the pulling effect...

Imagine a spinning skater. She pulls her arms in a little and spins faster. She brings her arms all the way into her chest, and spins really fast, and then bam! she rockets up into the sky. Seven years ago, computer simulations revealed a configuration of two spinning black holes that merged in...

Homework Statement Find the center of mass of a uniform sheet in the form of a circular disc with a hole bounded by the equations x^2 + y^2 ≤ 1 and (x - 1/2)^2 + y^2 ≥ (1/16). Homework Equations The Attempt at a Solution

I think I am wrong in what I am about to say so I someone could explain relatively simply where I went wrong I would be thankful... When light travels towards a black hole it's wavelength increases it's frequency and decreases it's wavelength due to the increase in energy. Because a black hole...

The FAQ states: "In our universe, we observe that space is not a vacuum, and tidal forces are nearly zero on cosmological distance scales (because the universe is homogeneous on these scales). " We observe Dark Energy. How do we know this accelerated recession of distant galaxies, which is...

First off I couldn't decide whether to enter my question in the relativity section or this one, so if I'm in the wrong place my apologies. Anyway I have a question or perhaps a hole in my understanding. I was wondering if there is a density point at which anything becomes a black hole. Now I...

Hi, does anyone know how much of the universes's iron or carbon has been made in supernovae that formed black holes? Is it 5, 10, 50 % of the iron currently pressent here? And, if se, do we have any idea how much of the average stars content gets traped in the BH versus the mass of the...

Hi, I think I have several misconceptions about the theoretical framework of black holes, I'm just not sure where my intuition (or, lack of) goes wrong. So sorry if this sounds really stupid, any help is appreciated. The scenario that I find confusing is what Alice sees when she throws Bob into...

I was thinking about how a black hole evaporates and the firewall idea. If after Page time a firewall forms around the black hole, does that mean that the energy/mass, and entropy cannot increase anymore? The energy of the black hole is essentially supposed to be in the singularity, right? I...

I thought this was cool, wasn't able to find a paper on it, but didn't look "super hard", and won't pay for it. Apparently, a gravitational lensing has lined up so perfectly that we were able to measure the black hole's spin. They have it at "half the speed of light" (??!)...

Would it be possible for the universe to exist as a white hole within a black hole? I know about the whole black hole universe theory, though I never really looked into it.

Assume that there exist two people, person A and person B. Person B is falling into a black hole. I understand that due to relativity and time dilation, person A will have to spend an infinite amount of time to watch person B cross the event horizon. Person B will appear to move at a slower...

I know several raytraycing results for static Schwarzschild black holes, but I have never seen something similar for collapse models like Oppenheimer-Snyder or Vaidya. Are there reliable raytraycing results showing the effect on light rays from far distant light emitters observed by (far...

In a Kerr Black Hole there exists a region called the Ergosphere. It is between the Event Horizon and a spheriod called the Static Limit. The Event Horizon can be simplified to: ##\Delta## = 0. The Static Limit can be simplified to: ##g_{tt}## = 0. They yield two separate spheres...

Homework Statement How do you find the Angular Momentum, J, if you are given the Angular Velocity, ω of a Kerr Black Hole. Homework Equations J = I*ω ##I = mass*r^2## Event Horizon: ##r_+ = M + (M^2 − (J/mass/c)^2)^{1/2}## Static Limit and the Ergosphere: ##r_0 = M + (M^2 −...

Suppose Alcubierre warp drives or some alternative form of warp drive is possible. Then surely a warp drive could enter the event horizon of a black hole, observe the interior, and exit the horizon, returning with information from within the black hole. What about black holes never visited by a...

In another thread we determined that the proper total force acting on an orbiting object in the Schwarzschild metric, is given by: ##f_{total} = \frac{Mm}{r^2\sqrt{1-2M/r}} - \frac{mv^2}{r}\left(\frac{1-3M/r}{(1 - v^2)\sqrt{1-M/r}}\right)## One interesting aspect of the equation is that when...

If light approaches a black hole will it accelerate? I think this question ties in with whether light has mass or not. Does light have mass? It seems accepted that light has momentum, but this is not consistent with saying that photons are mass-less (momentum=mass*volume). Could someone clear...

Hey all, I was wondering if the singularity at the bottom of a black hole is similar to what the universe would be like before the big bang, i.e. heaps of mass/energy concentrated into a tiny point. To me I always think of black holes as sinkholes dotted throughout the universe which are...

Homework Statement A cavity at Temperature 6000k has an energy distribution corresponding to a blackbody. We make a small hole in it 1mm in diameter. Calculate the power radiated through the hole of wavelength interval between 550nm and 551nm. HINT: when dλ is small (such in this case)...

Would it be possible for a black hole to carve a trail of information on two dimensional space in the holographic universe? Could the black hole, acting as a conduit between the macro and micro universe, due to its properties at the singularity (at the plank scale) carve the the information...

I have been wondering what to expect if there was a hole, from pole to pole, that inside which we could measure the Einstein red and blue shifts due to gravity. At first, I suspect a blue-shift as light travels from the surface of the Earth to the center; just less and less as the center is...

If the amount of hidden information inside a black hole, depends on the size of the hole, one would expect from general principles, that the black hole would have a temperature, and would glow like a piece of hot metal. But that was impossible, because as everyone knew, nothing could get out of...

Homework Statement If a steel plate with a hole of 10 cm in diameter is heated 35 degrees kelvin, what will the new diameter be? ##\alpha_L = 13 \cdot 10^{−6} K^{−1}##Homework Equations ##\Delta L = \alpha_L \cdot \Delta T \cdot L## The Attempt at a Solution If I understand the...

Im building a turbine engine and I am having trouble figuring out the hole sizes for the burner can, my problem is that I am not using a compressor section but rather using an air compressor for the air intake so I can't use the standard formula, can I? If I know my blad diameter and the flow...

Hello everyone. As far as I know, even lights can not escape from black hole once the light reaches to even horizon as lights carry momentum hence energy. Now, what I wonder is, how fast do black holes swallow light or, if you will, other objects? I guess it cannot be faster than the speed of...

Homework Statement Flow of 500 electrons per second with kinetic energy 3 eV hits a perpendicular 5 eV potential hole 0.3 nm wide. How many electrons pass per second pass the obstacle? Homework Equations The Attempt at a Solution Hmm, I checked my notes where it is written that...

Homework Statement A container of volume 10−3 m3 has a pressure of 10−7 mbar. Surrounded by air at 1 bar and 290 K, how long does it take the pressure inside to rise to 10−6 mbar when air effuses through a small hole of area 10−17 m2? Homework Equations The Attempt at a Solution Flux ø =...