Dark Matter, Antimatter, and Negative Matter are concepts from the fields of cosmology and particle physics that have different properties and roles in our understanding of the universe. Read here to understand each term in detail.
Matter is anything that has mass and takes space. But apart from the ‘normal’ matter, there are different other forms of hypothesized matter.
A few examples include Dark Matter, anti-matter, and Negative Matter. You by now know that matter and energy are interconvertible; so there are Dark Energy, Anti-Energy, and Negative Energy too. Now let’s see what each of these terms signify.
Dark Matter and Dark Energy
The term ‘dark’ is used to denote the unknown. So dark energy corresponds to an unknown energy. Dark matter corresponds to unknown matter whose properties are not clear to scientists.
- Dark Matter refers to a form of matter that does not emit, absorb, or interact with electromagnetic radiation (light) like ordinary matter does. It cannot be observed directly through telescopes.
- Its existence is inferred from its gravitational effects on visible matter and its impact on the large-scale structure of the universe, such as galaxies and galaxy clusters.
- Dark Matter is thought to make up about 27% of the universe’s total mass-energy content. It is considered to be responsible for the observed rotational velocities of galaxies and other phenomena that cannot be explained by visible matter alone.
Dark Energy: Supernovae observations showed that the expansion of the Universe, rather than slowing, is accelerating.
- Something, not like matter and not like ordinary energy, is pushing the galaxies apart. This “stuff” has been dubbed dark energy, but to give it a name is not to understand it.
- Whether dark energy is a type of dynamical fluid, heretofore unknown to physics, or whether it is a property of the vacuum of space, or whether it is some modification to general relativity is not yet known.
Why do scientists think there is dark matter or energy?
Because scientists see its gravitational influence on the rest of the Universe. As one simple example of the evidence for dark matter, the velocity of rotation for spiral galaxies depends on the amount of mass contained in them.
The outer parts of our spiral galaxy, the Milky Way, are rotating much too fast to be consistent with the amount of matter that we can detect; in fact, the data indicates that there must be about 10 times as much matter as we can see distributed in some diffuse halo of our galaxy to account for its rotation.
Dark matter reacts only to gravity and weak atomic force!
Dark matter only interacts by way of gravity and the weak atomic force. Dark matter does not interact via either the strong atomic force or electromagnetism hence dark matter cannot be seen and is hard to detect.
Antimatter and anti-energy
‘Anti’ means opposite. So antimatter has some properties opposite to the usual matter. For example, the electron has as its antiparticle the antielectron. The electron and the antielectron have the same masses, but they have exactly opposite electrical charges.
- Antimatter consists of particles that are similar to ordinary matter particles but have opposite charges. For example, the antiparticle of an electron is a positron, which has a positive charge.
- When a particle and its corresponding antiparticle collide, they annihilate each other, releasing energy in the form of gamma rays. This annihilation process is used in positron emission tomography (PET) scans in medical imaging.
- While antimatter is produced in particle accelerators and observed in high-energy cosmic events, it is rare in the universe compared to ordinary matter.
PS: When an electron meets an antielectron, the two annihilate and produce a burst of light having the energy corresponding to the masses of the two particles.
Anti-matter behaves like normal matter under gravity but is the opposite concerning the other three forces!
Scientists assume that antimatter behaves as normal matter under gravity, though the truth is that they have never seen a large enough mass of it to know for certain it behaves the same. But anti-matter reacts just opposite to the other three forces than the reaction produced by normal matter.
Negative Matter and Negative Energy
Negative matter is a hypothetical type of matter that if it exists will have negative mass and negative energy. It will in essence have a negative gravitational charge and repel normal matter. Yet it will interact just like any other matter in every other way.
- Negative Matter, often referred to as Exotic Matter, is a theoretical concept that goes beyond our current understanding of matter and energy.
- It is often associated with negative mass, where the gravitational attraction of negative matter would be repulsive rather than attractive. This leads to speculation about the possibility of “exotic” phenomena like warp drives for faster-than-light travel, although such ideas remain highly speculative and face significant theoretical and practical challenges.
- Negative Matter has not been observed or produced, and its existence is not supported by current scientific evidence.
PS: Hope you remember that matter and anti-matter will attract each other resulting in annihilation. But matter and negative matter will repel each other under gravity. The action of negative matter under the other three forces is not hypothesized yet.
Barynoic Matter vs Non Baryonic Matter
Ordinary matter and anti-matter are known as baryonic matter. Dark matter is known as non-baryonic matter.
Ordinary Matter is just 4.9% of the universe
According to the Planck mission team, and based on the standard model of cosmology, the total mass–energy of the known universe contains 4.9% ordinary matter, 26.8% dark matter, and 68.3% dark energy.
Thus, dark matter is estimated to constitute 84.5% of the total matter in the universe, while dark energy plus dark matter constitutes 95.1% of the total content of the universe. In short, we are unsure about what’s there in 95% of the universe!
PS: If the statistics are true, then the matter that we are made of (baryonic matter) is but a small impurity compared to the dominant matter in the universe (non-baryonic matter). As someone has put it, “Not only are we not the center of the Universe, we aren’t even made of the right stuff!”
Why Dark Matter is not Antimatter?
If the dark matter out there was antimatter, we would expect it to annihilate with matter whenever it meets up with it, releasing bursts of energy primarily in the form of light. We see no evidence in careful observations for that, which leads most scientists to believe that whatever the dark matter is, it is not antimatter.
Dark Matter is a form of matter that does not emit light and is inferred from its gravitational effects, Antimatter consists of particles with opposite charges to ordinary matter particles, and Negative Matter is a theoretical concept that goes beyond our current understanding of matter and energy.
Each concept plays a distinct role in our exploration of the universe, from understanding the behavior of galaxies to advancing theoretical ideas about exotic phenomena.