Cosmos Episode 6 : What lies Within
Breaking up a system into its tiniest building blocks, is an approach that provides a great insight into whatever you are studying, from the hydrogen atom to the Universe. To figure out the evolution of massive stellar objects one needs to understand its tiniest components, i.e., matter at the atomic and subatomic levels. Episode 6, focused on this idea in general and the elusive neutrino in particular.
In episode 6, Neil De Grasse Tyson started with the universe contained in a dew drop, he bored deeper and deeper till he reached the atomic level. Atoms, are mostly empty space with a dense positively charged nucleus. The electrons that surround the nucleus are tiny in comparison. We also learned about forces of electrostatic repulsion and then the nuclear forces which bind the atom together. Nuclear attractive forces have to be much stronger than the repulsive electrostatic forces to keep the positively charged nucleus together. The nucleus also consists of particles with charge zero, the neutrons which are necessary to keep the like charged protons together in the nucleus.
Now that we know what we are made of, we also need to know the means through which particles interact with each other. Most of the macroscopic interactions on our planet are a product of the electromagnetic force which is one of the four fundamental forces of nature, and the one we understand the best
The other fundamental forces are the gravitational force, and the two nuclear forces; the strong force and the weak force. It’s the weak force that gives rise to aforementioned neutrino. A mass less and charge less particle that was predicted by Wolfgang Pauli based on energy conservation arguments. The argument boils down to this: the total mass and energy of any given system is always conserved, no exceptions.
Neutrino, or the little neutral one in Italian is an elusive particle and extremely hard to detect because it does not interact much with anything at all, since it has almost zero rest mass and no charge. It is a product of nuclear beta decay, a type of radioactive decay*. This makes the neutrino a great candidate to study about the origins of the universe and stellar cores. De Grasse Tyson took us to the neutrino detection laboratory in Japan. The secrets of neutrino astronomy are yet to be revealed.
Credit: Super-Kamiokande Collaboration, Japan
Earlier entries about Cosmos are here.
Natural radioactive decay
The number of electrons in a neutral atom determines its chemical properties. The elements are arranged in the periodic table in the ascending order of the number of electrons, their atomic number. As the atomic number increases we need more neutrons than protons to keep the atomic nucleus together. This works up to a point, addition of neutrons makes the nucleus unstable and we get the phenomena of natural radioactivity. For example, Uranium which is naturally radioactive and has no stable isotopes. Uranium 235, its most abundant naturally occurring isotope has 92 protons and 143 neutrons.