Going to the cinema

I have discovered the answer to a question that has been puzzling scientists for hundreds of years. What is the exact difference between a split second and a nanosecond? My girlfriend and I were getting ready to go to the cinema, right as we were about to leave home, my girlfriend asked me the question all guys dread. She asked, “Does this make my bottom look big?”
If I had said “no” in a nanosecond, we’d have been out the door. Unfortunately I took a split second, so she had to go to the shops and buy new outfits with jewellery, shoes, and purse to match.