I recommend this excellent book on relativity and light, including an essay titled "What happens if the speed of light slows down to 3000 m/s."
A must for aspiring physicists and mathematicians! Beginners can also read the book as it is self explanatory and easy to understand.
To buy the book, or download the ebook, visit
Seems quite interesting!
I'd suggest one first learn about the speed of light from this link.
It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.
Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.