Breast ptosis -- the fancy name for sag -- has way more to do with aging and genetics than gravitiy. Cristen and Caroline explore what's "normal" in in the boob realm to get to the bottom of how and why boob sag happens.
"Breast ptosis: How breasts sag and why" http://www.parkercenter.net/breast/anatomy-of-breast-ptosis/
"Normal breast development and changes" http://www.hopkinsmedicine.org/healthlibrary/conditions/breast_health/normal_breast_development_and_changes_85,P00151/
"Mayo Clinic study observes normal aging process lowers breast cancer risk" http://www.eurekalert.org/pub_releases/2006-11/mc-mcs111306.php
NSFW: "Is breast atrophy the same as breast ptosis?" https://www.realself.com/question/texas-tx-breast-atrophy-the-breast-ptosis
"5 myths and facts about sagging breasts" http://news.health.com/2014/11/21/what-causes-breasts-to-sag/
"Breastfeeding does not make breasts sag, study suggests" http://www.livescience.com/1998-breastfeeding-breasts-sag-study-suggests.html
"Natural lifts for sagging breasts?" http://goaskalice.columbia.edu/answered-questions/natural-lifts-sagging-breasts
"When your breast shape goes out of style" http://jezebel.com/5561224/when-your-breast-shape-goes-out-of-style
"Scientists say they've found the perfect breasts" http://www.shape.com/blogs/mind-and-body/scientists-say-theyve-found-perfect-breasts
"Plastic surgeons from different countries prefer different breast shapes" http://www.foxnews.com/health/2015/07/01/plastic-surgeons-from-different-countries-prefer-different-breast-shapes.html
"Breast ptosis: Causes and cure." B. Rinker et al. Annals of Plastic Surgery. Vol. 64, No. 5. Pages 579-584. May 2010.
"Mammary hyperinvolution and ptosis." J.F. North. British Journal of Plastic Surgery. Vol. 28, Iss. 4. Pages 310-316. October 1975. http://www.sciencedirect.com/science/article/pii/0007122675900417
"Evolutionary reasons for male preferences regarding the female breast shape." Filipe V. Basile. Plastic and Reconstructive Surgery Global Open. Vol. 3, No. 10. October 2015. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4634179/
"Aesthetic breast shape preferences among plastic surgeons." P.N. Broer et al. Annals of Plastic Surgery. Vol. 74, No. 6. Pages 639-644. June 2015. http://www.ncbi.nlm.nih.gov/pubmed/24691316