The myth about black holes has been debunked: they don’t suck everything in; instead, they turn matter into spaghetti.

Black holes are the densest objects in the universe. Although these objects possess immense gravitational force, they do not "suck" in matter any differently than neutron stars or ordinary stars. It all comes down to gravity. Contrary to the widespread belief that black holes consume everything in their vicinity, they operate quite differently, as astrophysicist Ethan Siegel explains in an article for Big Think.

What are black holes?

Black holes consist of a vast amount of mass concentrated in an incredibly small volume, and their interiors inevitably collapse into singularities, surrounded by event horizons from which nothing, not even light, can escape. If any particles of matter or radiation cross the event horizon, they simply fall into the central singularity, causing the black hole to grow and increasing its overall mass.

There is a notion that black holes suck in all surrounding matter. However, this is incorrect and completely distorts how gravity works.

Once a black hole forms as a result of the death of a massive star or the collision of two neutron stars, the accumulated mass in a concentrated volume of space acquires an event horizon. It is impossible to escape from beyond it; once you enter, you are doomed to encounter the central singularity.

Tidal forces: how the Moon works

Since black holes are extremely massive objects, as you approach one, you start to experience a significant set of tidal forces acting on you. An example of tidal forces is the interaction between the Moon and Earth, where the Moon pulls the oceans of our planet, creating tides. However, the Moon exerts different gravitational influences on various parts of the Earth.

The closer you are to an object, the greater the gravitational force acting on you becomes. On the surface of the Earth, you are pulled towards the center of the planet at a rate of 9.8 m/s². But at an altitude of about 6371 km, which is half the diameter of the Earth, the gravitational force acting on you will be ¼ of what it is on the surface of our planet, pulling you down at a rate of 2.45 m/s².

It can be assumed that the closer you are to a massive object, the stronger the tidal forces become. This is true, but tidal forces increase even faster than gravitational force. If the distance to the Moon were halved, the tidal forces would be not four times stronger, but eight times stronger.

Spaghettification near a black hole

Black holes can create the largest known tidal forces in the universe. Therefore, when you get close to a black hole, your body will undergo a process known as spaghettification, meaning it will be stretched into a thin, spaghetti-like shape due to extreme tidal forces. This phenomenon leads to the misconception that black holes can pull a person in, as the tidal forces and gravitational strength are immense.

Nevertheless, the idea that you would be drawn into a black hole is not based on reality. It is merely a misunderstanding of how black holes operate. Indeed, each individual particle that makes up any object near a black hole will be influenced by the black hole's gravity. However, these particles still follow the same laws of physics that govern all other objects, including the laws of physics arising from the gravitational curvature of spacetime created by general relativity.

In the context of general relativity, the fabric of space is curved by all forms of energy, including mass. It is also true that black holes offer the highest concentrations of mass found anywhere in the universe. But the density of any mass that curves space does not significantly affect how space is curved as long as the object is outside the physical mass that is curving spacetime itself.

If the Sun were replaced by a white dwarf, neutron star, or black hole of equal mass, the gravitational force acting on Earth would be indistinguishable from that exerted by the Sun. Only the total mass curves the space around you; density has little to do with it.

Only mass matters

At a distance, a black hole behaves just like any other mass in the universe. At large distances, only mass matters. How this mass is distributed has a negligible effect on both gravitational and tidal forces. Only when you get very close to an object do you begin to notice how a black hole differs from other masses and how the curvature of spacetime deviates from predictions made by Newtonian gravity. But even near a black hole, you will find that it simply acts as an attractor, where objects approaching it have the same orbits they would typically have around another mass.

Due to the significant tidal forces that arise when moving so close to a large mass, approaching objects are often torn apart by the black hole's gravity. This is called a tidal disruption event. The matter torn apart by the black hole often ends up being gathered around it in an accretion disk. Only a portion of the matter from this disk will be absorbed by the black hole, while the rest will be ejected into space as a jet.

Black holes do not suck anything in

Black holes do not suck anything in. It is purely gravity at work. That is, the average gravitational force acting on the center of mass of an object and the tidal forces that stretch, compress, and tear the object around its center of mass.

Black holes absorb matter that is subject to gravitational collapse due to the mass of the black hole, its small size, and the close proximity of the falling object to its event horizon. The combination of tidal forces and matter already present around the black hole can indeed tear apart external objects, but only a portion of the torn particles will fall into the black hole itself.

Only a small fraction of the matter that crosses the event horizon causes black holes to grow and gain overall mass. If we replaced any mass in the universe with a black hole of equivalent mass and removed all the material surrounding it, we would find that very little mass would ultimately end up in the black hole. None of this would be "sucked in," and only basic gravitational collapse would lead to any mass entering the black hole at all.

Compared to what actually crosses the event horizon in our physical reality, the proposed "sucking" effects are nowhere to be found. The idea that black holes suck in anything is perhaps the biggest myth about black holes of all. They grow purely due to gravity, and nothing more. In the universe, this is more than sufficient to explain all the phenomena we observe.