Does Time Exist?
The Persistence of Memory, by Salvador Dali
Is time a fundamental property of our universe and reality? As counter-intuitive as it may sound, the answer to this question might actually be No. In a revolutionary work, Carlo Rovelli, a physicist at the University of Marseille in France, has found out a way to present Quantum Mechanics without any reference to Time at all! Tackling with time is the biggest obstacle in merging quantum mechanics and theory of relativity to form a single coherent theory, and if Rovelli's treatment of time is correct, and time is not a fundamental property of our universe, then we are one step closer to forming a theory of everything.
Here is an extract from an article on the topic that came in New Scientist:
"With quantum mechanics rewritten in time-free form, combining it with general relativity seems less daunting, and a universe in which time is fundamental seems less likely. But if time doesn't exist, why do we experience it so relentlessly? Is it all an illusion?
Yes, says Rovelli, but there is a physical explanation for it. For more than a decade, he has been working with mathematician Alain Connes at the College de France in Paris to understand how a time-free reality could give rise to the appearance of time. Their idea, called the thermal time hypothesis, suggests that time emerges as a statistical effect, in the same way that temperature emerges from averaging the behaviour of large groups of molecules (Classical and Quantum Gravity, vol 11, p 2899).
Imagine gas in a box. In principle we could keep track of the position and momentum of each molecule at every instant and have total knowledge of the microscopic state of our surroundings. In this scenario, no such thing as temperature exists; instead we have an ever-changing arrangement of molecules. Keeping track of all that information is not feasible in practice, but we can average the microscopic behaviour to derive a macroscopic description. We condense all the information about the momenta of the molecules into a single measure, an average that we call temperature.
According to Connes and Rovelli, the same applies to the universe at large. There are many more constituents to keep track of: not only do we have particles of matter to deal with, we also have space itself and therefore gravity. When we average over this vast microscopic arrangement, the macroscopic feature that emerges is not temperature, but time. "It is not reality that has a time flow, it is our very approximate knowledge of reality that has a time flow," says Rovelli. "Time is the effect of our ignorance."...
Others also urge caution in interpreting what it all means for the nature of time. "It is wrong to say that time is an illusion," says Rickles. "It is just reducible or non-fundamental, in the same way that consciousness emerges from brain activity but is not illusory."
So if time really does prove to be non-fundamental, what are we to make of it? "For us, time exists and flows," says Rovelli. "The point is that this nice flow becomes something much more complicated at the small scale."
At reality's deepest level, then, it remains unknown whether time will hold strong or melt away like a Salvador Dali clock. Perhaps, as Rovelli and others suggest, time is all a matter of perspective - not a feature of reality but a result of your missing information about reality. So if your brain hurts when you try to understand time, relax. If you really knew, time might simply disappear."