When we think of time, we think of it as running only forward, with traveling to the past an impossibility, yet physicists have now demonstrated that if the right conditions are in place, time can actually move in reverse.
The British astronomer and physicist, Arthur Eddington, once described how, when it comes to the macroscopic level, there is only one direction in which things can travel, a process he referred to as the "arrow of time."
However, this doesn't always appear to be the case as physicists recently showed using the unlikely combination of acetone and chloroform to create a situation where time stops moving forward and starts traveling in the opposite direction instead. This situation is in marked contrast to what is believed to normally occur with the Second Law of Thermodynamics.
The laws of thermodynamics aren't the only things at play when it comes to influencing the movement of time though. The beginning conditions of our universe are also believed to affect the arrow of time. This is because the universe began its life intensely hot and the energy emanating from it was shuffled around fairly evenly. This equated to a universe which was largely held together by gravity and with low entropy.
This entropy gradually grew, according to MIT Technology Review, and it was this process of entropy that made things travel forward rather than backward.
If Earth's initial conditions determined how time works, perhaps it's possible to force the arrow of time to run in the opposite direction. https://t.co/KScDcI8orHPhysicists believe that there is an intriguing puzzle at work here and that if the conditions the universe found itself in after creation actually affect the movement of time, perhaps they could conjure up their own set of conditions in which time travels in reverse rather than forward.
— MIT Tech Review (@techreview) December 27, 2017
Physicists at Brazil's Federal University of ABC recently decided to test this hypothesis out for themselves and found that it is possible after all to set up conditions in just the right way so that objects will move backward in time.
To do this, they looked at chloroform, which is comprised of three chlorine atoms, one hydrogen atom, and one carbon atom. They then decided to mix the chloroform with acetone to see what would happen.
Kaonan Micadei and his team of researchers then used nuclear magnetic resonance upon the single carbon and hydrogen nuclei of the chloroform, which enabled them to control its nuclear spins. If a powerful magnetic field is used, these nuclei can then be aligned, and radio pulses can be utilized so that the spins can be flipped by physicists, which creates entanglement. Physicists are then able to observe the radio signals of the different nuclei to determine how they evolve.
When controlling the temperature of the nuclei, as well as their entanglement, physicists were able to get time to run in the opposite direction and one in which the energy of heat worked in reverse, as Micadei explained.
"We observe a spontaneous heat flow from the cold to the hot system. Our results on the thermodynamic arrow of time might also have stimulating consequences on the cosmological arrow of time."
Nobody panic.https://t.co/1i5P2SGw74As Science Alert report, this demonstration by physicists at the Federal University of ABC was on a very small scale and doesn't mean that time travel machines are going to be built next week. It does, however, demonstrate that time doesn't always need to exclusively move forward either.
— ScienceAlert (@ScienceAlert) December 28, 2017
This new experiment also excitingly showed how thermodynamics and quantum entanglement can merge and how heat can be utilized through quantum mechanics in some fascinating ways.
If you're interested in learning more about how physicists were able to set up conditions to get time to move in the opposite direction, an abstract of their new paper, Reversing the Thermodynamic Arrow of Time Using Quantum Correlations, can be found on the Cornell University Library website.