In a recent PBS Article on Time Reversal, Allison Eck describes a new scientific experiment performed at the University of Erlangen-Nurnberg, Germany, in which the arrow of time had been reversed. This reversal occurred at the quantum scale, essentially, as the reversal of the law of thermodynamics which describes how heat loss occurs. Her article links another article from Science News by Emily Conover.
Whether or not Time reversal is possible in material systems larger than quantum scale objects remains to be seen. But the beginnings of such grand designs appears to necessitate starting small. Very small. In principle, the effects being studied were highly localized, as apparently between a very small number of atoms.
In effect, the team who performed the study coaxed warm atoms into getting hotter by robbing the thermal energy from cooler atoms. Performed on a large scale, this would tantamount to starting a fire by throwing ice-cubes on wood. If that sounds strange, well, so does Time reversal.
But Time reversal is so much more than simply the reverse of thermodynamic entropy. To get comprehensive Time reversal, one would have to reverse the trajectories of particles, and would only be able to go back as far as the particle's prior path interactions, all of which would have to be reversed. When examined in this light, Time reversal sounds possible only in the loosest sense of the term. To achieve human scale effects would seem to require near omniscient powers of observation and omnipotent powers of control, not just of the object one wished to send back, but of the very environment in which is was sent.
According to the study's coauthor, Eric Lutz, the result shows that "the arrow of time is not an absolute concept, but a relative concept." As a philosopher of concepts of time, I agree. But the pragmatic reality isn't really all that different for it. I remain unpersuaded that Time reversal will ever become a practical human reality, at least with the technology utilized here, as best as I understand it.
Whether or not Time reversal is possible in material systems larger than quantum scale objects remains to be seen. But the beginnings of such grand designs appears to necessitate starting small. Very small. In principle, the effects being studied were highly localized, as apparently between a very small number of atoms.
In effect, the team who performed the study coaxed warm atoms into getting hotter by robbing the thermal energy from cooler atoms. Performed on a large scale, this would tantamount to starting a fire by throwing ice-cubes on wood. If that sounds strange, well, so does Time reversal.
But Time reversal is so much more than simply the reverse of thermodynamic entropy. To get comprehensive Time reversal, one would have to reverse the trajectories of particles, and would only be able to go back as far as the particle's prior path interactions, all of which would have to be reversed. When examined in this light, Time reversal sounds possible only in the loosest sense of the term. To achieve human scale effects would seem to require near omniscient powers of observation and omnipotent powers of control, not just of the object one wished to send back, but of the very environment in which is was sent.
According to the study's coauthor, Eric Lutz, the result shows that "the arrow of time is not an absolute concept, but a relative concept." As a philosopher of concepts of time, I agree. But the pragmatic reality isn't really all that different for it. I remain unpersuaded that Time reversal will ever become a practical human reality, at least with the technology utilized here, as best as I understand it.
