Now you can find out! Dan Carlson from Star Trek Minutiae has created this handy series of infographics. They show well-known spaceships, from the Cylon Raider from Battlestar Galactica to United States of America models, to Stargate SG-1 crafts - all to scale. Interestingly he has included Nasa's Space Shuttle (which is bigger than the Interceptors from Star Wars!).
Have any other SF related infographics to share? Please submit links in the comments below!