https://www.worldometers.info/world-population/
https://www.domo.com/learn/data-never-sleeps-6#/all/all/best-practices
https://internetworldstats.com
인공위성(일론 머스크)
https://www.theverge.com/2019/5/12/18616535/spacex-starlink-elon-musk-60-satellites-launch
https://www.businessinsider.com/spacex-starlink-satellite-internet-how-it-works-2019-5
http://dongascience.donga.com/news.php?idx=29186