Not sure where the best place to post this is, but here it goes. Imagine you were sent back in time, far enough back when a lot of the now known scientific laws, rules equations etc, havent been discovered yet. You're someone who is intelligible with many scientific fields, and you have brought a collection of scientific data such as equations and whatnot that were figured out by humanitys scientists up until the present, in an attempt to emulate their work, and become known as the greatest mind thats ever been. I realize in order to successfully emulate these established rules, such as demonstrating that the law of universal gravitation can actually describe real world phenomena, you would first need to determine the physical measurements of the units, such as length, volume, time, temperature, power etc, and they would have to be the same as they were in the future that you came from, or the scientific work youve claimed as your own would be useless and wouldnt accurately explain anything, which leads to my question. Is there any possible way to determine or copy exactly what an established unit of measuremt is in the real world, if you were put in the situation above. For example, how would you determine exactly how much volume 1 litre is, or how long 1m is, without anything to compare with?