https://youtu.be/zNYwkFAZb_8

http://www.wholeearth.com/index.php

http://longnow.org/clock/

https://youtu.be/MH-f5yF1UTA ◇ 深谷光軌 - Wikipedia https://ja.wikipedia.org/wiki/%E6%B7%B1%E8%B0%B7%E5%85%89%E8%BB%8C