This is an excerpt from a article about consistancy in writing.
"Rules of the Universe
Know the physical rules and laws of your universe. Record them. Memorize them. Following the rules of the universe is a tip for writers of any genre, but breaking said rules results in differing consequences depending on the genre. If you bend or break a given rule in a strictly standard fiction, your readers may notice but be a bit forgiving so long as it's infrequent. If you make this mistake in a fantasy novel, watch out. Not only will there be a dip in believability, but your readers will likely become irritated and more critical as they continue flipping pages, making the experience for them much less enjoyable. By sticking to the rules you set, you'll gain even more credibility for your awesome writing skills."
