Hole Definition and 1000 Threads

Reading some of the recent info on black holes and how they ingest gas matter including stellar material... why doesn't dark matter be absorbed into the black hole and according to the article dark matter is part of black hole formation...

Hi. I saw this: https://www.forbes.com/sites/startswithabang/2017/05/29/surprise-the-universe-has-a-third-way-to-form-black-holes/#52d7225f216d suggesting they saw a star undergo a "direct collapse" to a black hole with no supernova. Now this seems like it could be sensible -- if there's...

When they talk about information falling into a black hole, are they referring to the basic defining parameters of the particles falling into the hole?

What happens to the information entering to the Black hole??

Hi, Physics Forum! I've been wondering what would happen in the following thought experiment. I am not physicist and may have made some incorrect assumptions. Please explain if any of these assumptions are wrong. What would happen if you threw a piece of (very long and strong) rope into a...

If you shrunk an atom down to a certain point would it become a black hole like all matter in the universe can? How big would it be?

Yes I know. Sounds silly. I'm not a physicist, but it occurred to me to wonder: is it possible Earth is a black hole with data encoded in two dimensions on its surface? What would the proofs look like? Discuss.

Let's say that I'm hovering using a jetpack at a fixed distance above the event horizon of a black hole. And that I'm perfectly well shielded from any radiation and whatnot. Its a supermassive black hole with a super large Schwarzschild radius, so tidal forces are minimal. Approximately how...

Is this a realistic solution to the black hole singularity problem, Going beyond that, neutrino stars?

Homework Statement [/B]Hello, I have derived the equation for the gravitational force for a disk to be 2Ggm/a^2(1-x/sqrt(a^2 - x^2) when an object is added on top of the system. My question is would the force still be somewhat similar if the disk now had a small hollow of radius c...

Giant standpipe type overflow from a dam. https://rumble.com/embed/vfzc9/

Einstein's general theory of relativity describes the stars distort spacetime fabric and it appears a black hole makes a hole in the spacetime fabric. It is evident that the size of a galaxy does not change due to gravity but in large scale the distance between two distant galaxies increases due...

Homework Statement A punch is used for cutting an (approximately) circular hole with a diameter of 35 mm through a metal sheet 0.2 cm thick. If the shear strength of the metal is 80 MPa, estimate the force needed to punch the hole. Make it clear how you have calculated this value. Homework...

1. The problem statement, all variables and given/known There is an Earth but the hole is not in the middle but the side.find the period of oscillation Homework Equations Simple harmonic equation.Newton gravitational force The Attempt at a Solution I got GMx/R^3+acc=0 so period of...

Homework Statement Its a classic problem about a puck that is rotating on a frictionless tabble with a velocity v1 and radius r1. It is is connected to a string which runs through a hole a the centre of the table. The string is pulled from below until the radius decreases to r2. Find the work...

I bought myself a nice 32mm (2" fitting) eyepiece with a 'wide view'. I was disappointed to see a dark patching the middle when I looked through the scope in daylight. I have never been aware of this when looking at (brilliant) wide objects at night. With its wide angle view, it gives the...

i know how to calculate the inersia for the cylinder, than i have to take away the inersia of the rectangel, but i can't find an equation for the inersia for a rectangel with the plane spinning perpendicular to the rotation axis, please help !

Is t right that, in a plate with a hole, subjected to uniaxial loading, along one of the axis, one gets compressive stresses around the crack tip (in the same direction as that of the applied load ). I'm not able to understand this intuitively. Can someone help? I believe, intuitively, these...

Consider the following two definitions of the surface gravity of a black hole (taken from page 23 of Thomas Hartman's lecture notes(http://www.hartmanhep.net/topics2015/) on Quantum Gravity): 1. The surface gravity is the acceleration due to gravity near the horizon (which goes to infinity)...

I wonder, what would happen if you started dropping lots of electrons into an existing black hole which otherwise doesn't accrete any new matter? The charge of the black hole would build up much faster than the mass. Wouldn't its charge become so high at one point that further electrons would...

Homework Statement A 45 RPM record is a disk with a wide hole in the center. The mass of such record is 45g. It is 7 inches in diameter, and the hole in the center has a 1.5 inch diameter. (Sorry for the odd units, this was the way it was given). Find the moment of inertia of the 45 RPM...

If I fall into a Schwarzschild black hole and, as I'm falling, look in the direction away from it, what do I see? I once heard someone say the rest of the universe would appear to move faster and faster, and as I cross the event horizon it would appear to move infinitely fast. I'm not sure...

I'm writing a real time 3D physics simulator that simulate bullet ballistics. Can I use the air drag formula that factors in drag coeficient and outputs drag force to calculate how deep a bullet will penetrate a target material? Say I substitute air pressure with target material density. And...

Hi, is anyone familiar with topological insulator? I read an interesting paper: http://arxiv.org/abs/1703.09365, Black hole as topological insulator Abstract: Black holes are extraordinary massive objects which can be described classically by general relativity, and topological insulators are...

If space were like a ocean of ice chunks where everything gradually moves apart and the andromeda galaxy and our galaxy are moving closer to one another. Finding the connection point would find a black hole right. Or is that not possible with the way space moves?

Hello to everyone! I am trying to understand in practice the Gravitational Time Dilation by calculating the time distortion near the supermassive black hole Sgr A* in our Galactic Center. According to Einstein's Theory of General Relativity, the time distortion near a black hole is calculated...

Assuming a wormhole exists, what would happen if one took one end of the wormhole into a black hole. Could they enter the wormhole and leave the black hole? What would be the result if they did?

How and if singularity is related to Plank size (h) , are they be related ? If they are; can the singularity have squared shape (like pixel) , if it is h size so that is the "smallest" understand by "physics" and any curve (circle) would break the rule of h begin the smallest ? Does my question...

I was thinking about the title but after searching Arxiv, PF and the internet in general, my confusion has only increased. I have a few questions: 1. Often I see units where ##G=c=\hbar=1##, but what is the charge of an electron in these units? Everyone says M=Q as if it was somehow obvious how...

Homework Statement To what radius do you need to compress Mars in order to turn it into a black hole? Homework Equations None given, but I am mildly familiar with Schwarzschild and his equation. I know that if we double the object's mass, multiply by the universal gravitational constant, and...

Homework Statement A particle of mass m is dropped into a hole drilled straight through the center of the Earth. neglecting rotational effects and friction, show that the particle’s motion is a simple harmonic if it is assumed that the Earth has a uniform mass density. Obtain an expression for...

What is the name for the "stuff" (neither matter nor neutrons) at the heart of a black hole?

A black hole is basically extremely dense matter. What could happen if it interacted with antimatter? I guess a part of the black hole's mass would annihilate.

Is it possible for a photon to be so energetic that it forms a black hole? If so, how fast would that black hole be moving?

Ignoring for the moment the plausibility of this scenario, what would happen? A black hole is the ultimate gravity well, right? In some circles, they're even considered tears in the fabric of the universe. So what would happen to that fabric if you moved the black hole? Would it behave like...

I realize that this question has been asked many times on this forum, however, I have yet to come across a satisfying/understandable answer that takes into account gravitational time dilation. Premise: The speed of light inside a gravitational field is slowed down relative to a distant observer...

Homework Statement From the homework: In General Relativity it is found that the radial equation of an object orbiting a non-rotating black hole has the form $$\dot r^2 + (1 - 2 \frac {V_o} {r} ) (\frac {l^2} {r^2} + 1) = E^2$$ where ##r## is the radial coordinate, ##l## is the angular...

Ok..I know that at some point, from the Hubble Law , galaxies will seem to moving away from us speed of light,But actaully they can't because the space-time itself expands so it will be like a black hole horizon,which within that radius its , c/H , we can observe things etc.But out of that...

Hey guys, Does black holes exist? Is it even real?

I am an undergraduate student of a university, I have taken the research topic as Study of Rotating black holes and Hawking radiation which I am really interested. Research description as follows. The geometric invariant are computed in various black hole geometries in several different...

Was the concept of a White Hole ever intended to as a POSSIBLE explanation for the Big Bang, inflation and dark energy expansion of the Universe? Or is it considered crack pottery by the cosmology community? I presume the observable Universe would need to be as small as say a single atom in...

Forgetting about the singularity for the moment, is the interior of a black hole a space-like region? That is, are any two events that occcur past the black hole horizon space-like separated? Thanks in advance.

Homework Statement I want to calculate the on shell action for the case of a AdS Schwarzschild black hole. Homework Equations Following the case of the flat Schwarzschild black hole I tried to add a counter-term of the type of a Gibbons-Hawking boundary term for flat Minkowski spacetime...

I should be able to do this, but its been a while and maybe I'm making this more difficult that it should be. Assume you have a cylinder nearly sealed but with an outlet hole at the top. I want to pump a fluid into the canister, pushing the air out of the hole, and time how long it takes. The...

why can't a photon escape a black hole? i think it is because the photon is red shifted away to nothing, if this is true, it would be possible to create a photon that would be energetic enough that a black hole would not have enough time to red shift it away to nothing, unless there is some...

Hey everyone!Here's my first post in the forum!You probably usually discuss more substantial issues, but I'm having troubles and I'm sure you can help me!I'm trying to calculate the size of an ideal circular hole in a vacuum vessel given the measured leak rate in mbar l/s (helium spray leak test...

Hello! I'm having a hard time finding realistic black hole simulations, but I saw one recently (black hole size comparison on youtube) that showed the following 3 black holes (attached). I noticed that the larger the black hole, the smaller the "distortion zone" was relative to the radius of...

According to Cosmic Sensorship Conjecture, naked singularities are prohibited in General Relativity. To my knowledge, naked singularity means light from the singularity can escape to infinity. In Reissner-Nordström metric, references say naked singularity appears only if ##GM^2<P^2+Q^2##...

"Before the big bang, scientists believe, the entire vastness of the observable universe, including all of its matter and radiation, was compressed into a hot, dense mass just a few millimeters across." Isn't this describing what the singularity of a black hole is? Black holes spin extremely...

Homework Statement In a low-flow showerhead that contains 18 nozzle holes, the volume flow rate of the water is 4.00 L/min and the water maximum speed is 2.70 m/s. What is the diameter of each hole? Do not ignore viscosity of water. Homework Equations Q=Av_max Q=((pi)r^2)v_max...