My Astronomy Website

Introduction to Quantum Mechanics

Our world can be divided into 3 levels,
Microscopic, Mesoscopic, Macroscopic levels
At each level we perceive matter differently.

Mesoscopic level is where we live, is at which our normal life goes about.
Macrosopic level is where stars and planets live.

Make a guess, what laws of physics govern the Mesoscopic Level?
Bingo! They are Newton’s 3 laws of Mechanics.

The acceleration of an object is proportional to Force applied to it.
F = ma

Now what laws of physics govern the Macrosopic Level?
This one is what you could only learn in University.

The answer is General Relativity. The theory discovered by A. Einstein.
General Relativity says the space is NOT FLAT!

What do you mean the space is NOT FLAT?
Imagine you draw a straight line on a world map, from New York to Shanghai.

Now imagine what the straight line would be like, if you have drawn it on the Earth. It is no longer a straight line but a curve traversing half a sphere connecting the two cities.

You see the space is not flat at all.
The same thing happens in the outer space, between star and star.

Quantum Mechanics is the physics governing the microscopic level, the level where atoms and elementary particles live.

Imagine a coin lying on the table, it could only be one of the two possibilities: HEAD or TAIL.

But for a coin rotating on the table, how would you describe it?

Quantum Mechanics say this is precisely what happen at microscopic level. That’s you are not 100% sure, what happen to an atom.
You can only tell how much chance it could turn out to be this way, and how much chance it could turn out to be that way.

A Mesocopic object, like a car, can have only one value of Energy at each instant. If a 500kg car is traveling at 5 metres per second, the Kinetic Energy is (1/2) times 500kg times (5 metres per second) squared.

But a Microscopic object can have more than one value of Energy at each instant!

It is possible that an atom has 1 calorie, 5 calories, 10 calories Energy value at the same time! All you need to find out is the chance, the probability of the atom being in each Energy value.

Imagine a person walking from home to school, how many paths is he taking?

Note, I am asking how many paths he is taking NOT how many paths he can take.

The answer is ONE of course, he could have taken a shortcut, he could have wandered around the neighbourhood, he could have chosen a zig-zag-like fanciful way of walking.

The point is, once he has made up this mind, now he is on his way to school, he is taking only ONE path.

This not happening to an atom which is billion times smaller than us. the atom is taking multiple paths when moving from one point to one point!

when you observe it, the atom will appear to be at one point, for you!
When you do not observe it, the atom appears everywhere again, countless possibilities.

Bizarre? That’s Quantum Mechanics………….K.Grice 2012