'Time travel may be possible - for sub atomic particles, at least, a new experiment has found.
Physicists have discovered that heat can spontaneously flow from a cold quantum particle to a hotter one under certain conditions - effectively reversing the 'arrow of time'.
While the discovery doesn't advance the possibility of building a time machine, it does show the quantum world operates under very different rules, researchers say.
The new experiment 'shows that the arrow of time is not an absolute concept, but a relative concept,' study coauthor Eric Lutz, a theoretical physicist at the University of Erlangen-Nürnberg in Germany, told Science News.
The team published their study in the journal arXiv.org. It examined heat passing from hot and cold objects.
'We here experimentally demonstrate the reversal of the arrow of time for two initially quantum correlated spins-1/2, prepared in local thermal states at different temperatures, employing a Nuclear Magnetic Resonance setup,' they wrote.'
Read more: Quantum experiment reveals time really CAN flow backwards (but don't expect a time machine any time soon)