It was a picture I drawn in 1997. It was the summer holiday after my HKCEE public exam. It was a drawing trip with my school’s Art Club. The location was Sai Kung Pier.

As far as I remember, I haven’t drawn since then. Perhaps I do not like to draw alone. Hope that one day I could find my girlfriend finally so that I have someone to draw with.

— Me@2020-03-24 10:37:58 PM



2020.03.26 Thursday (c) All rights reserved by ACHK


2019-03-23 001

I keep this picture here as a backup.

— Me@2020-01-27 06:33:01 PM



2020.01.27 Monday (c) All rights reserved by ACHK

Simcity, 2


I bought this SimCity 2000 box in 1995. It was the first time I went to a big computer centre (mall).

At the first glance, I thought that it was sold at the price 800 HKD, which I could not afford. Luckily, the price label was actually NT800, which meant 800 New Taiwan Dollars.

So I could buy it at 200 Hong Kong Dollars.

— Me@2019-12-29 03:42:26 PM



2019.12.29 Sunday (c) All rights reserved by ACHK



In this picture, he was at his 15.

Later on, he studied at another university.

— Me@2019-12-15 03:27:25 PM



2019.12.15 Sunday (c) All rights reserved by ACHK

The Time Machine

This is the place.

So it is.

_But there’s nothing here.

Well, it was different then. My laboratory was all around here. The kitchen was up there where that tree is. Not that Mrs. Watchit ever let me go in there.


I don’t know what to tell you, sir. He’s been gone this whole week.

_And you’ve no idea where he went?

No, sir.


_[Alexander] This would be my greenhouse. There was a garden outside.




I’m glad.


I’m glad he’s gone.

Maybe he’s finally found some place where he can be happy.


This was my home.


His home.

— The Time Machine (2002 film)



2019.09.01 Sunday ACHK

Ken Chan 時光機 2.1

那時,Ken Chan 有一項特點,令我覺得奇怪。



1.1 除了是物理補習天王外,

2.1 他宣稱有在大學教書。是教授、講師,還是其他,我就不知道。我忘記了,他有沒有講過。

2.2 他在大學做研究。據我理解,他當時研究的是有關激光的實驗物理。


2.3 他有時要往大陸作學術演講。

3.1 然後,他亦是某某什麼工程學會的主席。




畢業於香港大學工程學系,並擁有多個學位、專業資格及榮銜,包括: 香港大學太古學者、英國皇家物理學會、香港工程師學會、電機電子工程師學會、中國機械工程師學會……等等。



— Me@2019-08-30 09:31:52 PM



2019.09.01 Sunday (c) All rights reserved by ACHK

Physical laws are low-energy approximations to reality, 1.3.1


Symmetry breaking is important.

When there is symmetry-breaking, the system goes to a low-energy state.

Each possible low-energy state can be regarded as a new “physical world”.

One “physical world” cannot jump to another, unless through quantum tunnelling. But the probability of quantum tunnelling happening is low.


Low-energy physics theories, such as harmonic oscillator, are often simple and beautiful.

— Professor Renbao Liu

— Me@2019-04-08 10:46:32 PM



2019.04.09 Tuesday (c) All rights reserved by ACHK

Physical laws are low-energy approximations to reality, 1.2


When the temperature \displaystyle{T} is higher than the critical temperature \displaystyle{T_c}, point \displaystyle{O} is a local minimum. So when a particle is trapped at \displaystyle{O}, it is in static equilibrium.

However, when the temperature is lowered, the system changes to the lowest curve in the figure shown. As we can see, at the new state, the location \displaystyle{O} is no longer a minimum. Instead, it is a maximum.

So the particle is not in static equilibrium. Instead, it is in unstable equilibrium. In other words, even if the particle is displaced just a little bit, no matter how little, it falls to a state with a lower energy.

This process can be called symmetry-breaking.

This mechanical example is an analogy for illustrating the concepts of symmetry-breaking and phase transition.

— Me@2019-03-02 04:25:23 PM



2019.03.02 Saturday (c) All rights reserved by ACHK