Can someone explain black holes to a brainlet like me? How can an object be too heavy to not occupy three dimensional space?

# Can someone explain black holes to a brainlet like me? How can an object be too...

Sorry, I mean how can something not occupy space because it's so heavy? Sounds like fake news.

black holes are the tipping point in science where you can just chalk it up to being magic

where did you get the notion that a black hole does not occupy three dimensional space. A black hole isn't a "hole" of any kind just some really dense shit that is so heavy even light can't escape from its event horizon

Black holes are just objects so dense their apparent (event) horizon is beyond their physical dimensions.

It still inhabits spacetime.

Matter == energy

Energy == gravitational attraction

Matter != gravitational attraction

I assume you're talking about those diagrams where you see a representation of a black hole that has sunken down into a "fabric". Like pic related?

Thats not in reference to spacial dimensions, it's from what I understand extra dimensions usually occur at the quantum level (really fuckin small) according to string theory/m theory, not with massive objects like stars and black holes. It's actually a representation of the warping of spacetime, as that's what causes gravitational attraction. Gravity isn't a force, it's geometry of physical space. I.e general relativity.

You would be better of asking Veeky Forums, there are people there that research this shit professionally. I just like it. Unless you wanna talk about the technology that allowed us to discover this shit.

At the center of every black hole is a one-dimensional singularity of infinite mass. They don't occupy space. The "black hole" part that is visible from its contrast with normal space is the event horizon.

How the fuck you can have infinite mass? If black holes are usually just collapsing stars where does the extra mass come from; how can the finite mass of the star turn into infinite?

What black holes are are just really dense shits that sucks the light around its event horizon with its huge gravitational pull. You dont see a black hole, you see the light around it getting fucked

All mass attracts all other mass. Earth attracts you and you attract it but you're just easier to move. The closer you are the stronger gravity is. A sphere with mass x and radius y has g gravitational pull. Increase the mass while keeping radius the same and g increases, at some point some area around the sphere will have such a gravitational pull that it's inescapable. And that's it.

I dont believe in pop sci like pbs and kaku. I like a rigorous mathematical explanation so here is it. Black hole is the point in space time where the infinitesimal space time length element ds -> infinity. Simplest case being schwarzschild solution where its easy to see that ds-> infinite in regions where r<=2GM

what proof is there that as you get closer to the speed of light that time slows down?

Because we don't know shit, you know the even horizon and all that jazz.

Even hawking radiation is unobserved, it's just a prediction.

We can just model what we know and it's pretty dull maths.

Look into special relativity. It's really hard to explain, that's why people have written books about it.

The easiest way I know how to explain it is with this image

you are in a moving vehicle that is going fast

you are bouncing a ball direct up and down (top left of pic)

someone sees you from a stationary pov

to them, the ball is moving in a zig zag pattern (the top right of pic)

to the stationary person, the ball is moving a long distance

So how is a ball moving both x distance and y distance, when x < y, simultaneously?

Because for you, time has slowed down. You obviously don't experience the time dilation, it feels normal to you. But everything outside of your vehicle is going much faster.

There is not really "proof", that I'm aware of. It's just that logically there is no other solution to this problem.

However, time dilation due to mass has been observed. We have some atomic clocks on the iss, and the are running a few nano seconds ahead of us, because mass slows down time. So "inside" a black hole has essentially no time, time screeches to a halt.

Which makes hawking radiation pretty weird but that's a whole fucking thing, and also hard to explain.

"time" doesn't slow down.

Your perspective of others who are slower than you is percieved as slowing down "time"

Time is our own invention and it would only be percieved by you or anyone in your same speed.

People going the same speed as you would see you "normally".

From slower perspectives you appear super fast.

If you reach light speed you will be invisable to the perception of people at the speed we percieve as normal "time".

Perspective is everything user.

Just because time is rooted in perspective doesnt mean its our invention.

Time is real and measurable, and it does slow down.

Your perspective of time always remains constant, but it still affects you.

as i said here

We have atomic clocks on the ISS, they are nano seconds ahead of identical clocks at sea level. Astronaughts genuinly are older than they would have been if they had stayed at sea level.

If you reach light speed you will be invisable to the perception of people at the speed we percieve as normal "time".

You cant reach light speed, it takes infinite energy, and it would take infinite energy to slow light down below light speed.

if you did, hypothetically, reach light speed, you wouldnt even know, because time would stop for you, and you would only (literally) have time to think after you stopped traveling at light speed.

There is not really "proof", that I'm aware of. It's just that logically there is no other solution to this problem.

Ofc there is, it's how GPS works for example.

Here's a simple one with clocks on airplanes.**en.wikipedia.org**

and **en.wikipedia.org**

or older**en.wikipedia.org**

Wiki article on this matter.**en.wikipedia.org**

Everything has a schwarzschild radius. Inside that radius is an event horizon that you can't get back from.

The thing is, for almost everything, the radius is much smaller than the size of the object. Like for the Sun it's something like two miles IIRC. But if you were to go within two miles of the Sun's centre, the overwhelming majority of the matter making up the Sun would be behind you, and wouldn't be attracting you to the centre, so it doesn't count anymore. Hence, if an object isn't dense enough, in practice it can never act as a black hole.

Black holes are special because they are smaller than their schwarzschild radius. So you CAN get inside the radius and still feel the full gravitational pull of the hole - and since the radius is the event horizon for the hole, that means once you get past it you're trapped.

Basically what said

Great implications

humans have ability to percept how fast they're moving to the outside and slow themselves in their perception of time

they also can slow themselves in different ways when multiple people are observing (superslowness)

time dilation only works on humans

infinite mass

no

Density.

Infinite density would imply infinite mass so also no.

Pic related is a formula to calculate gravitational force between two objects. G is gravitational constant, m1 and m2 are masses of the two objects, r is distance between objects. Put infinity in either m1 or m2 and you will get that gravitational force at any distance is infinite which would mean that whole universe would collapse at that one point instantly

confusing density with mass

Density is the amount of matter in a finite space. If the space remains constant and the mass increases, so does the density. Alternatively, if the mass stays constant and the space decreases, the density also increases.

If blackholes are a 1d point in space, a singularity, then the density is infinite.

Gravitational attraction is proportionate to the amount of energy in a given object, which is proportionate to mass (except with light).

If the sun became a black hole right now, even though the density is infinite, the gravitational attraction would remain the same. We would continue to orbit the sun in the same fashion, as would all the other planets.

can someone explain all the fundamental misunderstandings that I have about physics by repeating all the shit I should have learned in 6th grade physical sciences class so that I can have a basic grasp of the words I just used?

No

Time is simply movement of matter through space

As you get closer to the speed of light, other shit slows down, essentially slowing down time

I'm not confusing anything

mass = density*volume

if density is infinite then so is mass. This is not possible

black holes are not 1d or 2d or whatever the fuck objects. They are 3d objects just as anything else, but they have incredibly large mass (and density) for their size. But neither mass nor density is infinite

the very definition of a singularity is a single point in space, thus 1 dimensional.

mass = density*volume

if density is infinite then so is mass. This is not possible

ok fair enough

Time exists in black holes. It only stops completely at the singularity, along with very thing else.

You don't understand Hawking radiation. It's not about virtual particles. That's a layman's explanation. Hawking radiation is the result of an event horizon in spacetime that has zero point energy. It causes a filtering effect on quantum vibrations that normally cancel each other out, which results in a vibration that assumes the appearance of a particle appearing to come from a black hole. That vibration was travelling through spacetime as a jumble of vibrations that canceled each other out before the event horizon removed any vibrations that were smaller in wavelength than the diameter of the event horizon, with the rest of the vibrations just barely snaking around it. Watch PBS space time's Hawking Radiation episodes to understand it in more detail.

Black holes are not dense. Larger ones have densities that are equal to water. A black hole in space time is its event horizon. From that it's volume is calculated, then its mass, and from those too finite numbers you get a finite density.

but the equation makes no sense if you go to the singularity.

No equation makes sense at the singularity. Hurr durr.

Larger ones have densities that are equal to water

average density of the whole thing inside event horizon, yes.

No equation makes sense at the singularity.

Nothing makes fucking sense when talking about singularities

Almost all known galaxies have a black hole in the center. We will soon get radio images of our own Milky Way super massive black hole in Sagittarius A*. It will be the fist image of an actual black hole.

Event horizon telescope(array of telescopes around the earth) has taken images, but none are released yet as they are processed.

These radio images will test Einsteins relativity theory to the maximum and there are a lot of folk that wish it will demonstrate flaws in the theory.

Stay tuned.**eventhorizontelescope.org**

Einstein's relativity theory

Which one. Do you know what you are talking about? Also we have seen black holes in images before. Quasars are one example.

In the Schwarzchild solution to Einstein's equations the mass we are considering is an object of infinite density concentrated in a single point. When integrated over volume, its mass comes out finite because mass is never infinite and that is what makes most sense physically (infinite density at a point is ok tho). If you're interested in how the math works out look up Dirac delta function. It's a "function" which is infinite at exactly one point but has finite integral.

black holes are really just objects whose gravity is too strong for light to escape.

We have atomic clocks on the ISS, they are nano seconds ahead of identical clocks at sea level.

Even better, we have atomic clocks on GPS satellites.

They need to be adjusted for constantly because if you just used the times they transmit to you without adjusting for time dilation your position would be off by tens of meters per day.

This is what they actually observed because they originally weren't sure if it would actually manifest, they had to then turn on the adjustments for time dilation.

A black hole in space time is its event horizon. From that it's volume is calculated.

Lol, no.

No one calculates the volume from the size of the event horizon.

A black hole isnt an object. Its a system comprised of a singularity and its event horizon.

Infinite density does not imply infinite mass. It impies infintesimal volume.

mass = density*volume

That only works for particles we know about.

No one knows what the singularity is made up of. Neutron stars may be a clue. Their cores are under so much pressure that the electrons have merged with the protons to create more neutrons.

In a black hole those neutrons have probably merged. They're occupying the same space as other protons, so the density is infinite, but the mass cannot be infinite because a finite amount of mass went into it.

Black holes and singularities, both are the same thing?, the sapace time thread cannot be warped completelly with a massive 3d object?

What? That can't be true. The event horizon is everything of a black hole that we can ever see. Its diameter must be the basis of our calculation of its volume.

What are you talking about? Any massive object can warp space to any degree with enough mass or energy. Its just that if an object is dense enough it will have a region of its gravitational field require an escape velocity faster than c, which enshrouds it in a black homogeneous sphere due to photons being trapped in closed loops that are straight geodesics in their frame of reference.

Yeah, but that's just the area we can see because no light comes from within it.

It'd be no different than calculating the volume of the Sun from a measurement that doesn't reduce the flaring down to the true disc.

Black holes and singularities, both are the same thing?,

Not quite, the singularity is what causes the black hole, but the hole is much bigger than just the singularity.

A sound logic for stars, but not black holes. I just looked it up and physicists do indeed calculate black hole density by using the radius of an event horizon to determine volume and then combining it with mass.

So you can take back your "lol, no".

For any object you need to have a certain velocity to escape from its gravity. Let's call it Vs such that

Vs=√(2GM/r).

If set V to the speed of light and solve for r, you get the schwartzschield radius (rs) of the given object with the mass M. It means that if condence matter to the volume of a sphere with a radius=rs, you get an event horizon. The black in a black hole is just the its event horizon, since Vs=C. As for the black hole itself it probably is just the mass of the core of a star condensed to a point in 3D space. That is with 3D space as a coordinate-system. A point has 0 volume, hence density of a black hole= infinity even though you have finite mass (density=mass/volume). I say probably, because at these scales quantum stuff, which we don't know, might happen. That's why we need a theory of everything to better model black holes

if density is infinite then so is mass. This is not possible

(mass) / (volume) = density

let's examine a test-mass of 1 kg

(1 kg) / (volume) = density

now let the volume the mass occupies trend to zero.

(1 kg) / (volume --> 0) = (density --> ∞)

Notice that when the volume is zero, the density is infinity, yet the mass is still 1 kg. So having infinite density does NOT imply infinite mass.