We may never see practical time travel in our lifetimes, if it's possible at all. However, a team at the University of Queensland has given the Doc Browns of the world a faint glimmer of hope by simulating time travel on a very, very small scale. Their study used individual photons to replicate a quantum particle traveling through a space-time loop (like the one you see above) to arrive where and when it began. Since these particles are inherently uncertain, there wasn't room for the paradoxes that normally thwart this sort of research. The particle couldn't destroy itself before it went on its journey, for example.