In the late 1600s when Newton published his book ‘Philosophiæ Naturalis Principia Mathematica’ he stated that time is absolute and is the same for everyone no matter in which state you are in this universe. But in the early 19s comes Einstein with his general theory of relativity stating that time is relative to person by person depending on which state or part of the universe he was in. Since then our understanding of time has completely revolutionized but we are still oblivious to the fact that what is actually time, is it something very fundamental which exists in this universe or is just an illusion?
His theory of relativity tells us that time passes for everyone, but doesn’t always pass at the same rate for people in different situations, like those travelling close to the speed of light or orbiting a supermassive black hole. Einstein resolved the malleability of time by combining it with space to define space-time, which can bend, but behaves in consistent, predictable ways. Einstein’s theory seemed to confirm that time is woven into the very fabric of the universe. But there’s a big question it didn’t fully resolve: why is it we can move through space in any direction, but through time in only one? No matter what we do, the past is always, stubbornly, behind us. This is called the arrow of time.
Arrow of time
Why is it that we cannot bend or twist time. Why is it that time has a positive vector and we can only remember our past but not the future. In physics, this is could be described by the Second Law of Thermodynamics, which says that systems will gain disorder, or entropy, over time. Systems in our universe move from order to disorder, and it is that property of the universe that could define the direction of time’s arrow. For example if you leave your room with a pile of papers stacked together neatly and re enter it after some time then you might not be shocked to see those piles of papers losing its order and spilled around all over the place but if you leave the same room with those papers knocked all over the room and when you re enter it and encounter a pile of neatly stacked papers then surely you will be taken aback. This is entropy stating object, atoms or matter will gain disorder with time.
Is time merely an illusion?
So could it be possible that time doesn’t exist, at the most fundamental level? Could time just be some sort of illusion generated by the limitations of the way do we perceive the universe? We don’t yet know, but maybe that’s the wrong way of thinking about it. Instead of asking if time exists as a fundamental property, maybe it could exist as an emergent one. Emergent properties are things that don’t exist in individual pieces of a system, but do exist for the system as a whole. Each individual water molecule doesn’t have a tide, but the whole ocean does. A movie creates change through time by using a series of still images that appear to have a fluid, continuous change between them.
Flipping through the images fast enough, our brains perceive the passage of time from the sequence of still images. No individual frame of the movie change or contains the passage of time, but it’s a property that comes out of how the pieces are strung together. The movement is real, yet also an illusion. Could the physics of time somehow be a similar illusion? Physicists are still exploring these and other questions, so we’re far from a complete explanation.
At least for the moment.