In astrophysics, spaghettification (or noodle effect) is the vertical stretching and horizontal compression of objects into long thin shapes in a very strong non-homogeneous gravitational field; it’s caused by extreme tidal forces. In the most extreme cases, near the black holes, the stresses are so strong that no object is able to withstand it, no matter how strong the object is. Within a small region the horizontal compression balances the vertical stretching so that small objects being spaghettified experience no net change in volume.
Stephen Hawking described the flight of a fictional astronaut “stretched like a spaghetti” by the gravitational gradient (power difference) from head to toe through the event horizon of the black hole. The reason this happens would be because the gravity exerted from the singularity would be much stronger at one end of the body than the other. If one were to fall into a black hole feet first, the gravity at their feet would be much stronger than at their head, causing the person to be vertically stretched. Along with that, the right side of the body will be pulled to the left, and the left side of the body will be pulled to the right, horizontally compressing the person. However, the term “spaghettification” was established well before this. Spaghettification of a star was imaged for the first time in 2018 by researchers observing a pair of colliding galaxies approximately 150 million light-years from Earth.
Tidal forces acting on a spherical object in a non-homogeneous gravitational field. The effect originates from a source to the right (or left) of the diagram. Longer arrows indicate stronger forces.
Imagine four separate objects in the space above a planet, positioned in a diamond formation. The four objects follow the lines of the gravitoelectric area correctly in the celestial bed. According to the inverse square law, the smallest of the latter is the largest.
Now think of these four objects with the connected parts of a larger object. A rigid body will resist distortion and the body is broken to compensate for tidal forces and mechanical equilibrium must be attained. If the tidal forces are too large, the body can produce plastic and flowable or broken pieces of vertical parts before the gel-tapping forces are stabilized or broken.
Inside or outside the event horizon
The point where tidal forces destroy an object or kill a person will depend on the size of the black hole. For a super-mass black hole like the ones in the center of a galaxy, this astronaut can pass the event horizon without crossing and pulling, as this point is within the event horizon. An event horizon towards the center is inevitable. For small black holes whose Schwarzschild radius is much closer to the singularity, the tidal forces would kill even before the astronaut reaches the event horizon. For example, for a black hole of 10 Sun masses the above-mentioned rod breaks at a distance of 320 km, well outside the Schwarzschild radius of 30 km. For a supermassive black hole of 10,000 Sun masses it will break at a distance of 3200 km, well inside the Schwarzschild radius of 30,000 km.