How much space does a black hole take up?

Astronomy ^ | 27 Apr, 2020 | Caitlyn Buongiorno

[MtnClimber]

Black holes are most often discussed in terms of their mass, but how much volume do these hefty, invisible objects actually have?

Lurking at the center of the Milky Way is a gargantuan black hole that tips the scales at several million times the mass of the Sun. Like all black holes, this supermassive monster — called Sagittarius A* — devours anything that falls too close, including light. However, consuming material is just one way these monsters grow to truly astronomical sizes, reaching mindboggling weights. Although astronomers often talk about black holes as being gigantic objects, it’s important to remember they’re usually referring to the object’s mass, not its physical size.

So, one obvious question is: How much space do different types of black holes take up?

Black hole weight classes

The standard black hole, known as a stellar-mass black hole, forms when a massive star (greater than about 8 solar masses) reaches the end of its life. After depleting the last of its remaining nuclear fuel, the star’s uncontested gravity causes it to rapidly collapse before rebounding outward in an epic blast known as a supernova. What remains, depending on the mass of the star, will either be a neutron star or a black hole. These stellar-mass black holes can range from a couple to several dozen times the mass of the Sun.

However, the origins of supermassive black holes like Sagittarius A*, which can range from millions to billions of times the mass of the Sun, remain unknown. Astronomers do know their extreme size and mass seems to be related to the galaxies they call home, with the biggest supermassive black holes found in the centers of the biggest galaxies.

[Don W]

Absolutely none until you reach the event horizon, at which point it BECOMES the entire universe...

[SunkenCiv]

This is a little hard to wrap your head around, but shadows can move faster than the speed of light, even though nothing can move faster than the speed of light. In a second, we'll explain how exactly that's possible without breaking the most fundamental law of physics. But first, this thought experiment might make things clearer.

Imagine you have a light that's powerful enough to reach the planet Jupiter. Imagine also that it casts that beam in a cone that's broad enough to cover the entire diameter of the planet. When you pass your finger over the lens, the shadow will cross the entire diameter of the planet -- a distance of 86,881 miles (139,821 kilometers). The speed of light is 186,000 miles per second (299,338 kilometers per second). So if it takes you less than half a second to move your hand that distance, then that shadow will have "broken" the speed of light.

So, remember how we said that nothing can move faster than the speed of light? Well, that's the key. Shadows aren't anything. Shadows are the absence of something -- specifically, photons, or particles of light. Since there's nothing that's actually traveling the distance, the only thing that's "moving" is an area where photons aren't. There's no information that's being transmitted faster than light, only a blockage of information. That means your interplanetary shadow-puppet show doesn't break any physical laws -- only the hearts of your interplanetary audience.

Darkness Is Faster Than the Speed of Light | Reuben Westmaas | August 01, 2019

What Is The Speed of Dark? | Vsauce | Published on July 29, 2014

[SunkenCiv]

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[Ozark Tom]

The circumference for a given mass varies dependent on rate of spin.

[Ozark Tom]

The event horizon is an arbitrary definition for the size of a black hole.

[SuperLuminal]

"The movie “Interstellar” is great. They spend a brief interval on a planet just outside the event horizon, and find 22 years have elapsed on the orbiting craft that launched their probe."

Marked for comment later...

[Nateman]

The bigger a black hole is the less dense it becomes. Another odd feature is Hawking radiation. Due to quantum effects black holes actually emit blue tinged radiation. The bigger they are the less this effect has on it’s over all mass. They do eventually get to the point where they pop in a mini explosion but that can easily be over a google amount of years before that happens.

[SuperLuminal]

"The movie “Interstellar” is great. They spend a brief interval on a planet just outside the event horizon, and find 22 years have elapsed on the orbiting craft that launched their probe."

One of my favorite TV sci fi series was Andromeda... The "brief" interval spent just outside the event horizon cost that ship & captain "300 years", when they, the ship & captain, were pulled away from the hole's clutches by a seedy group of salvage hunters and the story begins...

[Deaf Smith]

My guess is that darkness/shadow does not travel.

Dark/black is the absence of light as cold is the absence of heat.

The shadow of the finger over the lens is the blocking/interruption of the travel of light.

Dark/black took the place of removed light since dark/black is always there.

[Deaf Smith]

And I just now read your link.

[TexasTransplant]

bkmk

[SunkenCiv]

:^)