Thursday, May 7, 2020

How Attractive Are You ?


Attractive people are considered to have what is called a "magnetic personality". Have you ever wondered what makes something magnetic? What are the properties of a substance which make it magnetic? To understand we need to learn about a concept called ‘spin’.

The Stern-Gerlach Experiment[1] was conducted in 1920, which completely revolutionized our understanding of subatomic particles. In the experiment, German physicist Walther Gerlach passed a beam of Silver atoms through a magnetic field. Silver atoms are electrically neutral as they have an equal number of protons and electrons. We know that charged particles show deflection in a magnetic field. We also know that silver is neutral, thus the expected result is that - we do not see any deflection of Silver atoms when they pass through the magnetic field.

However, it was observed, that the atoms deflected, some of them in the upward direction and some in the downward direction, no atom passed through undeflected, which was not expected. We know the cause for the deflection was not electric charge, the only other explanation is that Silver must be magnetic. That is indeed true, Silver is magnetic (However, it is not magnetic enough to be relavant in everyday life). Silver is magnetic due to an intrinsic property of all subatomic particles (electrons in this case) called spin[2], which gives the atoms a magnetic moment[3].

Let us understand spin a little better. Spin is short for spin angular momentum. It is analogous to rotational angular momentum in classical mechanics. Now, you may be thinking that since all subatomic particles have a spin, all atoms must have a magnetic moment. That would mean that all substances would exhibit magnetic properties. Well, we all know, that is not the case.

Not all atoms possess a magnetic moment. Only those atoms which have a large number of unpaired electrons in their orbits have this property. Electrons usually exist in pairs with the electrons in a pair having opposite spin due to which their spins cancel out. (Another property of spin is that it is quantized. The magnitude of the spins of all the electrons is same only the direction is different. Opposite spin directions, cancel each other out). However, there may also be unpaired electrons present in the atom. The spins of the unpaired electrons give the substance a magnetic moment. Atoms which have unfilled orbits have more unpaired electrons and hence, are magnetic in nature. This depends on the orbital spdf configuration of the atoms, determined by the elements position in the periodic table. Substances which contain many unpaired electrons in their orbits like Iron, Nickel and Cobalt are very magnetic.

In the Stern-Gerlach experiment, we saw the atoms deflected in opposite directions, but the extent of deflection was always the same, this is proof that spin is quantized. Electrons act as mini magnets, which all have the same strength, but different polarities depending upon the direction of their spin (up or down). These mini magnets give a substance its magnetic properties, as we know it.


Spin is considered as an intrinsic or fundamental property of all subatomic particles, just like charge and mass. Spin plays an important role in many quantum phenomena (as you will see in later posts) and of course in magnets as we know them. These are the spins of some subatomic particles.
  1. ·         Electron +-1/2
  2. ·         Proton +-1/2
  3. ·         Neutron +-1/2
  4. ·         Photon +-1,0
  5. ·         Gluon +-1,0
So, in order to become magnetic, all you have to do is find a few unpaired electrons and their spins will make you magnetic !

References 


Monday, May 4, 2020

OOPS! I killed my Grandfather.


One of the most famous and intriguing concepts of the modern world is the Grandfather Paradox. It is truly one of the biggest paradoxes of time travel. The Grandfather Paradox says that if you were to go back in time and kill your grandfather before he had any children, who would give birth to your parents and thus how would you be born, and if you were not born, who would kill your grandfather in the first place?

Time is something that should be treated with utmost caution. There are no proven answers to this paradox. There are however some theories for the solution of the paradox, each more esoteric than the next. These are the two most widely accepted ones:
Quantum Superposition[1].
One interpretation is based on the concept of quantum superposition. Quantum superposition is when something exists in two states simultaneously, sub-atomic particles like electrons regularly exist in such a condition. When applied to the Grandfather Paradox, after going to the past you are in two states simultaneously, one in which you have killed your grandfather and do not exist and one in which you did not kill your grandfather and do exist. The theory of quantum superposition was proved by Young`s Double Slit experiment [2], where electrons showed a wave particle duality. The famous thought experiment on Schrodinger`s Cat [3] can also be applied here, where the cat is simultaneously dead and alive, just like you and your grandfather.

Many Worlds Interpretation [4]
Another explanation is based on the Many Worlds Interpretation according to which there are infinite timelines or realities being played out at the same time, for example as you are reading this, you could be the President of a country in another reality or you may be the opposite gender, or you may not even be a human being. When applied to the Grandfather Paradox, after going in the past, you are transported to another reality, so when you kill your grandfather, you are actually affecting some other reality not your own. A new reality is created where you do not exist but your own reality is unaffected and in your world, your grandfather is still alive. So what happened is you went to another reality to kill your grandfather, and all subsequent events in that reality reflect the fact that your grandfather is dead.

All of these solutions may be difficult to believe and wrap your head around. But for physicists it is normal, as quantum physics is one of the most intriguing concepts in modern science. Remember these are all just speculations and there is no concrete proof, after all time travel has not yet been invented and there is no way to test these theories!

References 




How Attractive Are You ?

Attractive people are considered to have what is called a "magnetic personality". Have you ever wondered what makes something m...