Difference Between Antimatter and Dark Matter

Main Difference – Antimatter vs. Dark Matter

The concept of matter is one of the oldest concepts in physics. In modern science, there are four types of matter namely ordinary matter, antimatter, dark matter and negative matter. So, the understanding of matter in modern physics is somewhat complex. Antimatter isn’t a hypothetical concept. Antiparticles and particles were created in equal amount after the big bang as the universe started to cool down. In addition, scientists can artificially create antiparticles by colliding high-energy charged particles. Whenever antiparticles and its particles or antimatter and its matter meet, they annihilate converting their total mass into energy according to the Einstein’s equation E=mc². Dark matter, on the other hand, has not been observed directly yet. However, very strong evidence observed confirms the existence of dark matter. This is the main difference between antimatter and dark matter. This article tries to give a clear explanation of antimatter and dark matter and the difference between them.

What is Antimatter

Antimatter is simply, the opposite of the ordinary matter. Antimatter is composed of antiparticles whereas ordinary matter is composed of particles. The mass of a given particle and its antiparticle is the same, yet some of the characteristics such as the charge, magnetic moment, spin, baryon number and lepton number have opposite signs.

The modern aspect of antimatter began with the Paul Dirac’s prediction in 1928. His theory predicted the possibility of the existence of a particle having the same mass of an electron but equal and opposite charge. This prediction was confirmed by Carl D. Anderson in 1932 who discovered the antimatter, the counterpart of the electron called positron (antielectron) while he was investigating cosmic rays. This was the first antiparticle discovered.

According to the standard model, each particle of ordinary matter has an antiparticle counterpart. Also, each quark has an antimatter counterpart called antiquark. For examples, antiparticles of the electron, proton and neutron are the positrons, antiproton and antineutron respectively.

The simplest antiatom possible is antihydrogen which is composed of an antiproton and positron. Although scientists are still unable to create antinuclei heavier than antihelium, any complex antiatom nucleus is possible, according to the principles of physics.

According to the theories, antimatter interacts via all four fundamental interactions namely gravitational, electromagnetic, strong nuclear and weak interactions. So, antimatter also bends the space-time just like ordinary matter does.

What is Dark Matter

Although dark matter hasn’t been discovered, very strong evidence have been observed that confirms the existence of dark matter. Some observations confirm that a vast amount of matter must be there than what we observe in the universe. As a supportive example for the existence of dark matter, one can take spiral galaxies. The rotational speed of a spiral galaxy depends on its mass. Higher the mass, higher the speed. As scientists have observed, the rotational speeds of most of the spiral galaxies including the Milky Way are too faster than the expected speeds. Simply, the mass of those galaxies should be too higher than the mass that we observe. This invisible, unobservable or missing mass is theoretically considered as dark matter.

According to the theories, dark matter only interacts via gravitational and weak interactions. So, its gravitational influence is observable. But dark matter cannot be seen and is difficult to detect as it doesn’t interact via electromagnetic and strong interactions.

Difference Between Antimatter and Dark Matter

Fundamental Interactions:

Existence:

Antimatter: Antiparticles have been discovered and could be created artificially by colliding high-energy charged particles. Antihydrogen and antihelium have also been produced artificially.

Dark Matter: So far, dark matter hasn’t been observed. But evidence is there. So, the concept of dark matter is still theoretical.

Abundance:

Antimatter: According to some theories, antiparticles and particles were created in equal amounts after the big bang. However, the universe we observe today is almost entirely antimatter free. A very small amount of antimatter is there in the universe. The reason for the disappearance of antimatter is still unknown.

Dark Matter: According to the theoretical calculations, the amount of dark matter is much higher than that of ordinary matter in the universe.

Image Courtesy:

“Dark matter” by NASA, ESA, M.J. Jee and H. Ford (Johns Hopkins University) – (Public Domain) via Commons Wikimedia