It would seem nowadays as though the general public's knowledge of nuclear radiation is derived less from science and more from science fiction. The beginning of the 20th century brought the atomic age, which in turn brought about considerable anxiety over nuclear radiation. There are a lot of popular sci-fi movies and comic books that touch upon radiation. As many will remember, when the scientist Dr. Banner triggers a large-scale gamma explosion, he is transformed into a giant green monster in the Hulk. And in the Godzilla franchise, lizards exposed to radiation from a hydrogen bomb turn into giant monsters.

However, none of these movies properly - or accurately - explains radiation. Regardless of what you do and where you are on a typical day, you are being exposed to millions of particle showers - another term for radiation - at all times. Radiation is all around us, but we are not turning into monsters, giants, or any other kind of creature. We do not even sense most of the radiation unless the harmful effects reach the detectable level. In fact, radioactive isotopes (the sources of radiation) found in water, air, soil, and most places in the environment have been emitting radiation since the Big Bang ^[1], which occurred approximately 14 billion years ago.

Radiation can be emitted by both natural and man-made sources ^{[2, 3]}. There are generally two main types of natural radiation: radiation from natural sources, such as elements in the ground, is terrestrial, and radiation from outer space, such as charged particles and gamma rays, is cosmic. For example, at this very moment you are being bombarded with cosmic rays every few seconds. On the other hand, the main human-made source of radiation exposure is from medical sources like nuclear medicine, x-rays, computed tomography (CT) scans, etc.

There are various types of radiation emitted by the sun. The most widely recognized forms are visible light, infrared, ultraviolet (UV), x-ray, and gamma radiation. We can only see the visible light, which is defined as having a wavelength on the electromagnetic spectrum between 400-700 nm (a nanometer, or nm, is approximately 10-9 meter). Some of the other kinds of light have greater wavelengths, and some have smaller. In short, visible light's region is a very narrow part of the wide EM spectrum.

Why can our eyes see only within this limited range? There are several reasons ^[4]: solar emissions, low absorption in the atmosphere, the energy of chemical bonds, the optical properties of matter, black-body emissions, and so on. Unless all these reasons align into a specific rhythm, we cannot see the kind of light. There are many laws determining light, and the fact that we can see even some light is quite remarkable, and a sign of how perfectly calibrated the universe is.

Misfits of the standard model: Neutrinos

Following our discussion of radiation, I would like to focus on one particular type of radiation: neutrinos. Neutrinos are created in certain types of radioactive decay and nuclear reactions, such as those occurring in the sun. They are one of the most abundant particles in the universe; billions of them pass harmlessly through your body, unnoticed. David Griffiths, a physicist at Reed College, describes neutrinos in his book on particle physics ^[5]:

"...neutrinos interact extraordinarily weakly with matter; a neutrino of moderate energy could easily penetrate a thousand light years of lead. That's a comforting realization when you learn that hundreds of billions of neutrinos per second pass through every square inch of your body, night and day, coming from the sun."

In total, there are three kinds of neutrino flavors, as they are called. These are electron neutrinos, muon neutrinos, and tau neutrinos. Each kind has a tiny mass. According to the Standard Model, there are three kinds of particles in the universe: "light-weight" leptons, "mid-weight" mesons, and "heavy-weight" baryons, such as protons and neutrons. Neutrinos are in the lepton family, which, in total, has only six particles; they have weak interactions within the universe. Neutrinos are neutral leptons since they are chargeless. Other leptons, electron, muon, and tau are called as charged leptons.

The Standard Model is one of the fundamental models in experimental high-energy physics explaining how the universe came into being. Well-known scientists are still improving the model to categorize particles properly in the universe with the aim of finding missing particles. The model explains very well the fundamental forces governing the world: strong nuclear forces, weak nuclear forces, gravitational force, and electroweak force. There were, frankly, two contradictions challenging the Standard Model until today: the Higgs mechanism ^[6] and the mass of neutrinos. The model predicted that Higgs boson ^[6] is the particle responsible for all the mass in the universe. CERN, the biggest particle accelerator^[7] on earth, announced in July 2012 that they had found a particle that behaves like the Standard Model predicted Higgs boson would. Scientists at CERN are still striving to understand the identity and features of this discovered particle. If they achieve that, they can unravel the mystery and origins of the universe a little bit more. At the end, only the mass of neutrinos will remain a controversial topic within the model.

The Standard Model predicted that neutrinos were chargeless and massless particles. However, cosmic, reactor, and accelerator neutrino experiments, which are the main three experiment types to track neutrinos, confirmed each other on the subject of neutrino oscillation. Neutrino oscillation, in short, means that they can change their flavors. For example, a tau neutrino can convert to an electron neutrino, and vice versa. This discovery shows that these particles can be chargeless but not massless. Each of them has to have small, different masses to be able to perform flavor conversions, according to the laws of physics. That is why these particles are usually called the misfits^[8] of the Standard Model.

Since each particle was produced with its antiparticle, according to Dirac's theory of pairs^[9], neutrinos also have their antiparticles, so there are actually six types of neutrinos in the universe. Each antiparticle has exactly the same properties as the original particle, just with the opposite charge. What about the chargeless neutrinos? The difference between neutrinos and antineutrinos is their spin behavior, not their charge. They both have zero charge; however, antineutrinos have a right-handed spin and neutrinos have a left-handed spin.

If each particle has its own antiparticle in theory, there should be the same amount of particles and antiparticles in the universe. However, experimental results show that there are more particles than antiparticles. There are a lot of scientists explaining this dilemma by accepting a parallel universe in which there are more antiparticles than particles, so the total would still be the same. In return, some others are trying to clarify this contradiction by accepting that more particles were created at the beginning of the universe, approximately 14 billion years ago.

Acknowledgment: This article is produced at Mergeous ^[10], an online article and project development service for authors and publishers dedicated to the advancement of technologies in the merging realms of science and religion.

References

[1] Kaya, A. 2009. "The Expansion of the Universe and the Big Bang: A Qur'anic Perspective," The Fountain Magazine, Issue 68.
[2] http://en.wikipedia.org/wiki/Radiation
[3] http://www.chem.duke.edu/jds/cruise_chem/nuclear/exposure.html
[4] Why can we see visible light? 2007. Physics Education, 42(1), pp. 37-40.
[5] David Griffiths, Introduction to Elementary Particles.
[6] Kara, Cihan. 2013. "Will CERN Reveal the Origin of the Universe or Cause the End," The Fountain Magazine, Issue 92.
[7] http://home.web.cern.ch/
[8] Symmetry Magazine, A Joint Fermilab/SLAC Publication, Spring 2013.
[9] Mahmood B. S. 2009. "The Holy Qur'an and Dirac's Theory of Pairs," The Fountain Magazine, Issue 68.
[10] Mergeous, Online article and project development platform, http://www.mergeous.com