Heck yes you should blog! You already have the hardest part done: the subject. If its physics, then you can make it a help blog, an explanation blog, an "odd things" blog, a weird facts blog, or anything else you can think of. If its a boxing blog, then it can be about helping 'noobs', finding new moves, or other boxing things. I suggest looking into wordpress (a blogging tool) or blogger (another tool). Also, if you want to make money, check out affiliate programs (by Amazon or Google) that put ads on your blog and pay you. Last but not least, BE CONSISTENT. With a blog, to keep your traffic, you must blog often (once a day, or once a week) otherwise peeps lose interest. That's all i got... Good Luck!