  The frontier of low-temperature physics has advanced to the mid pico-Kelvin
(pK) regime but progress has come to a halt because of the problem of gravity.
Ultra cold atoms must be confined in some type of potential energy well: if the
depth of the well is less than the energy an atom gains by falling through it,
the atom escapes. This article reviews ultra cold atom research, emphasizing
the advances that carried the low temperature frontier to 450 pico-Kelvin. We
review micro gravity methods for overcoming the gravitation limit to achieve
further low temperature using free fall techniques such as a drop tower,
sounding rocket, parabolic flight plane and the Space Station. We describe two
techniques that give promise of further advance--an atom chip and an
all-optical trap--and present recent experimental results. Basic research in
new regimes of observation has generally led to scientific discoveries and new
technologies that benefit society. We expect this to be the case as the low
temperature frontier advances and we propose some new opportunities for
research.
