This is Warren Kwok's Internet note pad, electronic diary, online rubbish journal, whatever you might name it ! It is an archive of my random thoughts in a chronological order. I am not good at reporting boring things and change them to lively. If you find this blog boring, sorry that it is your problem.
This is an interesting picture. Seems like both disc A and B are moving. Which one do you think is moving a bit faster.
In fact, both are not moving. But if we look at them together at the same time, we have the illusion that they are moving.