cold experiment girl glasses gloves goggles levitation liquid magnet nitrogen safety science scientific smoke arboriculturist arborist ascended Australia balancing belt chainsaw climber climbing cutting danger dangerous descending ear-muffs expertise Harness height helmet high lines lop lopping man-at-work noise-reduction Noisy professional removal remove removed risk risky ropes safety-glasses safety-harness sawing secured suspended suspension tall-tree tree tree-lopper tree-lopping tree-management tree-surgeon trees up-high work workman