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Cosmic Rays

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    Table of contents  COSMIC RAYS View my previous post here - The Survival of a Neutron View the next article here - (Coming soon!) ----------------------------------------- Cosmic Rays are super fast subatomic particles "raining" down on us from space.  These high-energy particles arriving from outer space are mainly (89%) protons – nuclei of hydrogen, the lightest and most common element in the universe – but they also include nuclei of helium (10%) and heavier nuclei (1%), all the way up to uranium. (Source of information: CERN) Their origin remains to be a mystery.  These are radiations or rather little bits of atoms whizzing by us, even through us, all the time! We cannot feel them, because they don't affect the human body . However, they do show their presence in different ways. For instance, they cause computers to malfunction . Scientists have been studying cosmic rays since the early 1900s. At the beginning of the 20th century, around 1911, a physicist, Vict

The Survival of a Neutron

    Table of contents  THE SURVIVAL  OF A  NEUTRON View my previous article here - Weak Interaction View the next article here - Cosmic Rays ----------------------------------------- (In this article, and in several others, u means up quark and d means down quark. Similarly, u with a bar on top means anti-up quark and d with a bar on top means anti-down quark.) Let us consider this puzzle: all of the atoms that make up the Universe (apart from hydrogen atoms) contain neutrons as well as protons in their nuclei. Yet free neutrons (that is, those not inside nuclei) undergo beta decay with a half-life of about 10 minutes. In the early Universe, soon after the Big Bang and before atoms formed, there are believed to have existed equal numbers of protons and neutrons. So why didn’t the neutrons all decay at that time, leaving a Universe made only of hydrogen? What do you think? 🤔 Apart from hydrogen, nuclei made solely of protons cannot exist . Neutrons are necessary to make nuclei stable,

Weak Interaction

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  Table of contents  WEAK INTERACTION View my previous article here - Beta Decay View the next article here - The Survival of a Neutron ----------------------------------------- Weak interactions manifest themselves as reactions, or decays, in which some particles may disappear, while others appear. No structure is bound together by a ‘weak force’, but weak interactions are vital for understanding the world around us. Weak interactions were involved in most of the reactions in the very early Universe by which particles changed from one sort to another. They are therefore largely responsible for the overall mixture of particles from which the current Universe is made. The most common example of a weak interaction is beta-decay and, as you saw earlier, there are three related processes, each of which is a different type of beta-decay. In each of these three processes, the nucleus involved will change from one type of element to another, as a result of either increasing or decreasing its

Beta Decay

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      Table of contents  BETA DECAY View my previous article here - Strong Interaction View the next article here - Weak Interaction ----------------------------------------- (In this article, and in several others, u means up quark and d means down quark. Similarly, u with a bar on top means anti-up quark and d with a bar on top means anti-down quark.) A particular type of radioactivity is known as beta-decay, which occurs in three forms known as beta-minus decay, beta-plus decay and electron capture . In each form, protons convert into neutrons, or vice-versa.  For instance, in beta-minus decay, one of the neutrons in a nucleus is converted into a proton with the emission of an electron and an electron antineutrino . This process may be written as: As a neutron has the quark composition (udd) and a proton has the quark composition (uud), at the level of individual quarks, a beta-minus decay must involve a down quark converting into an up quark as follows: This quark conversion, there

Strong Interaction

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  Table of contents  STRONG INTERACTION View my previous article here - Higgs Field with a Touch of Time Travel View the next article here - Beta Decay ----------------------------------------- As discussed earlier, the force that binds quarks together inside nucleons (i.e. neutrons and protons) is known as the strong interaction. This force has a very short range but is the strongest . It operates only within the size of a nucleon. When two up quarks and a down quark form a proton, or when two down quarks and an up quark form a neutron, the strong interaction has done its job, in much the same way that the electric interaction between a proton and an electron does its job by forming a hydrogen atom. In addition, there is a residual strong interaction between nucleons , which you can imagine as ‘leaking out' of the individual protons and neutrons. This is sufficient to bind them together in nuclei and is similar in nature to the residual electromagnetic interactions between atoms