What do you think TRUTH really means?
Are you entitled to your opinion?
The binary number system is the most fundamental and should be used by everyone.
Please do not read this sentence
If I listen, I forget what I am going to say next.
Why do some trees shed their leaves in winter instead of keeping them for the next year?
How big are things - The BBC can help you think about our solar system - watch for the changes in scale.
Maybe the over 15s might appreciate this web site, I do and I am over 15. XKCD (its crazy) (but you do have to think)
Try this web site for something to think about. The site seems free from advertisements and contains a number of interesting puzzles.
Whilst there are a lot of web sites containing puzzles, you might find this one interesting and you can hide the advertisements if you want to.
Sometimes, things can stop you and cause you to think for a while!