More information than you ever wanted to know about negative pressures in everyday life: http
/www.aip.org/pt/feb00/maris.htm
And no, you don't need quantum physics, etc. to talk about it -- for an example that is in the article cited above, at the top of a 100m tree, the pressure in the xylem (water carrying vessels in the tree) the pressure is -9 atmospheres.

And no, you don't need quantum physics, etc. to talk about it -- for an example that is in the article cited above, at the top of a 100m tree, the pressure in the xylem (water carrying vessels in the tree) the pressure is -9 atmospheres.