Dr. Achim Rosch, a theoretical physicist at the University of Cologne in Germany, who proposed the technique used by Dr. Ulrich Schneider and his team to create in laboratory negative absolute temperature, have calculated that whereas clouds of atoms would normally be pulled downwards by gravity, if part of the cloud is at a negative absolute temperature, some atoms will move upwards, apparently defying gravity. The matter is still under debate, but in my view it's no more certain to affirmate that gravity is only atractive: one ought to suspend judgement until peer review goes ahead. Interesting enough, but in my view the most relevant thing about the new research is that it seems to establish a new fundamental limit in Nature, somewhat analogous to c. Absolute zero temperature can't be reached, but can be surpassed! See also: Nature doi:10.1038/nature.2013.12146 Braun, S. et al. Science 339, 52–55 (2013). Medley, P., Weld, D. M., Miyake, H., Pritchard, D. E. & Ketterle, W. Phys. Rev. Lett. 106, 195301 (2011). Rapp, A., Mandt, S. & Rosch, A. Phys. Rev. Lett. 105, 220405 (2010). Mandt, S., Rapp, A. & Rosch, A. Phys. Rev. Lett. 106, 250602 (2011).