Main Difference – Black Holes vs. Wormholes
Black holes and wormholes are two fascinating topics in physics and also in scientific fictions. A black hole is an extremely dense object with a large amount of matter and energy. So, they create extremely strong gravitational fields that distort the space-time around it. The concept of black holes are suggested in the theory of general relativity, and it was a theoretical concept for decades. Finally, physicists were lucky to confirm the existence of black holes after they could detect gravitational waves for the first time, on 14 September 2015. A wormhole is a theoretical concept suggested by Einstein and Rosen. A wormhole connects two points in space-time or two different universes. Anyhow, they only exist in theoretical physics, to date. This the main difference between black hole and wormhole.
What is a Black Hole
Stars are huge natural thermonuclear power plants in the universe. Black holes, White dwarfs, and neutron stars are some possible results of a collapsing star. So, one should have a clear understanding of the origin of stars in order to understand the formation of black holes.
After the Big Bang, the matter was almost in the form of protons, electrons and some other light nuclei. These were floating throughout the universe just like a gas. As the universe cooled down, the gravitational forces could bring some of these particles together, and giant gaseous clouds were formed. As the gravitational forces attracted the matter in the clouds together, particles came closer and closer. So, the kinetic energy of particles increased. The temperature continuously increased as the clouds were contracting. Finally, the internal temperature reached about 7K, and the density of such a cloud was extremely high. So, the collapsing clouds reached the essential conditions for nuclear fusion reactions, and stars were born.
But, after the fusion fuel of the star is used up, the mass of the star contracts into a very small volume by the gravitational forces of the star as the remaining heat and radiation pressure is not enough to balance its own gravitational forces. The result is an extremely dense ball. Then the star becomes either a white dwarf or neutron star or black hole depending on its mass. A star having a mass less than 1.4 solar mass becomes a white dwarf. Stars having more than nearly 3 solar masses will become black holes through another astronomical stage. Stars having a mass more than 1.4 solar masses but less than 3 solar masses become neutron stars.
The center of a black hole is known as the singularity. The surface of a black hole is called the event horizon. The radius of a nonrotating spherical black hole is directly proportional to its mass. It can be calculated using the equation. Black holes are classified into supermassive black holes, stellar black holes, and micro black holes. If the original object of a black hole was rotating, prior to the collapse, the resulting black hole would also be a rotating black hole.
The mass and energy density of a black hole is extremely high, and the gravity inside and around them are incredibly high. So, nothing from inside the event horizon can escape to the outside. As a result of the tremendous gravitational forces, black holes are very difficult to detect because light even can’t leave them.
What is a Wormhole
The concept of wormholes is a very popular topic in science fictions or sci-fi. The concept was suggested by Albert Einstein and Rosen after studying the theory of relativity. So, sometimes wormholes are called Einstein – Rosen bridges. By analyzing mathematical solutions in Einstein’s theory of gravity, theorists still predict the possibility of the existence of wormholes.
Simply, a wormhole is a theoretical concept that connects two points in the space-time. The path through a wormhole is very short compared to any other path in the conventional space-time. So, wormholes are shortcuts in the space-time.
A wormhole has two mouths and a throat (a tube). The throat is the shortcut or tunnel that connects its two mouths. Theoretically, a wormhole could connect two different points in the universe or two universes. According to the solutions obtained in general relativity, wormholes may exist and of which the two mouths open up in two different black holes. Anyhow, black holes formed by collapsed stars can not create wormholes.
If they really exist, there are several fascinating advantages associated with them. They would provide shortcuts through space. They would allow going back to the past. Simply, some theorists say, wormholes would be both shortcuts and time machines.
There are two main types of wormholes namely, Euclidian wormholes and Lorentzian wormholes. Unfortunately, no one has seen any wormhole in the real space-time; they still exist only in theoretical calculations and movies. If they really exist, a traveler passing through them would have to face two challenges, size of the mouth of a wormhole and its lifetime. The size or diameter of a wormhole may be around 10-33 m and the lifetime of wormholes may be very short. So, if they exist, there are no practical advantage for a time traveler as a shortcut through space.
However, some studies have shown that exotic matter could keep wormholes unchanging and static for a longer time. Exotic matter isn’t ordinary matter, antimatter or dark matter. The energy density of exotic matter is negative. But, a practical problem crops up in finding a sufficient amount of exotic matter. Some physicists say the solution might be there in quantum field theory.
To date, nobody has observed any wormhole in the real space, while many theoretical studies are going on.
“Embedding diagram” of a Schwarzschild wormhole
Difference Between Black Hole and Wormhole
Size:
Black holes: A black hole can spread from several kilometers to hundreds of astronomical units.
Wormholes: The diameter of the mouth of a typical wormhole may be around 10-33m.
Evidences/ Existence:
Black holes: Scientists have observed many strong pieces of evidence that confirm the existence of black holes. The first direct detection of black holes was announced on 11/ 02/ 2016. It was the first detection of both gravitational waves and black holes.
Wormholes: Unfortunately, no strong evidence has been observed to date.
Theories/ Concepts:
Black holes: Black holes are found in the theory of special relativity, astrophysics, cosmology.
Wormholes: Wormholes are found in the theory of special relativity, Quantum physics, astrophysics, Particle physics, cosmology.
Importance:
Black holes: Black holes are believed to play an important role in the evolution of the universe. They control many astronomical objects.
Wormholes: If wormholes exist, they could be used as shortcuts to travel even millions of light years within a short period of time. In addition, they would allow backward time traveling. Anyhow, a large amount of exotic matter would be needed to keep them static and unchanging. Another problem is, any entering ordinary matter could make them unstable.
Requirements:
Black holes: Black holes require extremely high mass and energy density.
Wormholes: Negative energy is needed to keep them static and unchanging.
Other Properties:
Black holes: The extremely strong gravitational fields created by black holes, distort the space-time around it. Nothing can escape from them due to the extreme gravity.
Wormholes: They are very small in size and extremely unstable.
Image Courtesy:
“Wormhole” by Kes47 (?) – File:LorentzianWormhole.jpg, (CC BY-SA 3.0) via Commons Wikimedia
