Depending on how dependent your book is on this "bit of science," you will have to do research. If you are incorporating real life facts and science into it, you will have to do research to make sure you are getting it correct. If you put in something you think is true but isn't, a reader who knows the truth will see right through you and put down your book. However, if what you want to put in your book is not in real life, then yes, you can make it up and no one will get on your case. Basically, if it exists already, do your research, if it doesn't, then make it up yourself.
