“Truly the universe is full of ghosts, not sheeted churchyards specters, but the inextinguishable elements of individual life, which having once been, can never die, though they blend and change, and change again forever.”

– H. Rider Haggard

When we think about the universe, it simply seems vast with boundless space filled with large and minute particles unknown to human beings. Undoubtedly, there is a lot that we have come to understand about our planet, the universe, and also ourselves, but what if everything we know is only a fraction of the vastness that is the universe?

The study of “ghost particles,” or neutrinos, must make scientists feel the same way. We know everything and nothing at the same time. The ultimate paradox.

A neutrino, as the name suggests, is electrically neutral and a fundamental particle, which means it is not composed of other particles like electrons, quarks, antiquarks, etc. Because of its small mass (earlier considered to be zero), neutrinos have a very weak gravitational interaction making it able to pass through normal matter unimpeded and undetected.

They are the most abundant particles in the universe that least interact with any other matter.

To think about it, we are living in a world of countless trillions of neutrinos that can pass through us like we don’t exist. The combination of this ghostly presence and the important role they play in our universe is what’s captivating our physicists.

Proposed in 1930 and later verified in 1950, a neutrino is a cosmic mystery to scientists (pdf) even decades after its discovery, as to:

How much mass do they have? How many varieties of neutrinos exist? Do they have any magnetic properties? Are neutrinos their own antiparticles (antimatter)?

In their latest book, physicist Alan Chodos and science journalist James Riordon explore this perplexing particle.

“Ghost Particle: in search of the elusive and mysterious Neutrino” (2023) discusses the particle’s past and current discoveries, while they suggest it’s not just physicists who await those answers.

Riordon says “neutrinos are incredibly important both for understanding the universe and our existence in it.” In simpler words, neutrinos can reveal how matter evolved from simple particles into more complex ones, creating everything around us.

Are Neutrinos Their Own Antiparticles?

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Every single property discovery of neutrinos has been baffling and also intriguing for our researchers, the biggest being, whether the ghost particle is its own antimatter.

If we are to believe in the Big Bang theory, the explosion should have created equal amounts of matter and antimatter, i.e the counterparts of electrons, protons and so on. Essentially, when matter and antimatter come into contact, they annihilate each other suggesting that our universe should be empty, but, evidently, that’s not the case. In contrast, the universe is filled with a lot of matter and a little antimatter, for reasons unknown.

Physicists are still trying to understand the manner in which neutrinos interact with other particles, which is a challenge, as the particle has neutral charge with very low mass.

Why Are Ghost Particles a Topic of Interest?

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The same property of neutrinos that makes them difficult to detect, i.e their weak interaction with surrounding particles, interests physicists, as this feature can be useful in probing environments that other radiations such as light or radio waves cannot penetrate.

Another important role of a neutrino is in observation of supernovas, a luminous explosion of massive stars.

The core collapse phase of a supernova is highly energetic, and so dense that no known particle is able to escape its core front, except for neutrinos.

Neutrinos also have a crucial part to play in the research of “dark matter.” Its significance in probing cosmological phenomena is considered exceptional, and is thus a major focus of research in astrophysics.