If space contracts relative to the motion of an observer, would two observers traveling at different speeds disagree on the Planck length? Or is the Planck length constant such that two observers would agree on the Planck length, but would disagree about how many Planck lengths long certain objects were. Show them an object one Planck length long and they would both agree about its length. But show them a much longer object and one might say that it is 1000 Planck lengths long while the other would see it as being only 900 Planck lengths long. Is the Planck length relative or constant?