Before science, Speculation from Sci-Fi back to 1873 and Jules Verne "From the Earth to the Moon:Around the Moon"
Read it in full yourself from project Guttenberg here
http://www.gutenberg.org/files/16457/16457-h/16457-h.htm the section in chapter VIII the neutral point starting: "From the moment they had left the Earth, their own weight..."
Then in 1948 - Dr. Hubertus Strughold "The father of Space medicine" having worked prewar and during, is the first researcher in field on the physical effects of weightlessness. He is editor of "German Aviation Medicine in World War II" the first published scientific work on Weightlessness in a chapter called “Man under Gravity Free Conditions” by
Heinz Haber and O. Gauer [1,2]
1.Benford RJ. German aviation medicine during World War II.
Washington, DC: Superintendent of Documents, U. S. Government
Printing Office; 1948
2.Campbell MR et al. 2007 Aviation, Space and Environmental Medicine
There is a wealth of information on the science of space medicine....
They have a timeline of space medicine here: http://spacemedicineassociation.org/timeline/timeline.htm