The Paradoxes of 'Now'

Something I heard the physicist Sean Carroll say a few weeks ago has stuck with me. In describing the properties of time he made a distinction with space. He said that in both space and time we can identify a location. In space it might be a longitude and latitude, or more familiarly a building address on a certain street. In time it may be a certain hour of the day - say to make an appointment. But the difference between space and time is that you can choose to travel between two points in space, from point A to point B, but you can not choose do the same in time, between past, present, and future. 

The past and present are similarly inaccessible. What can we say about the present, the 'Now'? Some people say only 'Now' exists, we exist in the 'eternal present'. The Greek philosopher Zeno presented a paradox of the eternal present, as a series of instants. In this case when the archer shoots his arrow, the time it takes for the arrow to leave the bow and fly through the air to its target, can be understood in its most basic form as a series of individual points in time, let's imagine frames of a film. Therefore, taken to its logical extreme, seeing time as individual moments would ultimately lead us to conclude that the arrow never 'actually' leaves the bow.  

Others have said that time is exactly the opposite, that in reality the present does not exist at all. The moment we think of 'Now' it has already become the past. This idea of time may be described as a flowing river in which you are standing. You point down at your feet and say this is the river, it is this water in which I am standing, by which time that water has already flown past. In this case the moment vanishes instantaneously to become the past. 

Maybe, the greatest paradox of time is that it seems to be both an eternal 'Now' (Zeno's arrow) and not 'Now' (a river).  

Moving from the philosophical to the more scientific, for the last 150 years or so physicists have regarded time as a function of 'entropy', which is to say, as the change in physical systems from order to complexity, or rather order to decay (called the Second Law of Thermodynamics). But we don't have to think of rotting fruit when we think of decay. Take for example a force applied to a pendulum. It swings back and forth as the force of gravity and resistance due to friction reduces its movement until it stops. Physicists would describe that as ordered energy, the initial force that got the pendulum swinging, transferred into complex energy, atoms bouncing around in heat and friction and sound etc. as the pendulum swings. The decay of the swinging is entropy and therefore indication of the passage of time, the past is marked by the degradation of the pendulum's motion until the present when it eventually stops.

Now imagine the same pendulum in a vacuum (no friction) and in space (no gravity). The pendulum will swing at the same rate forever. No decay in movement. In essence, the distinction between past and future as measured by the pendulum, would, for all intents and purposes, vanish.

We learned from Einstein that things don't happen at the same time in the universe, they travel over great distances. There is no simultaneity, or in other words, there are many 'Nows' in the universe. For example, if the sun were to extinguish we would not know it for 8 minutes, the time it takes for sunlight to reach the earth. In the same vein, Einstein showed us that space and time were interrelated, and that gravity was not a force in the classical sense, but rather a function of the way mass warps the fabric of space-time. The notion that time is affected (slowed down or sped up) in relation to gravity (the warping of space-time) has been scientifically shown with extremely sensitive clocks. For example, clocks on satellites that manage the global GPS system are adjusted to move slower than clocks on Earth to compensate for their distance (about 20,000 kms) from the planet's surface - to be precise by about 7 millionths of a second per day. I know 7 millionths of a second per day doesn't seem like much, but it has to be understood in terms of how much that increases in cosmological masses and distances.

Most of my recent reading has been about the atomic and subatomic realm, which is equally vast on a small scale as the universe is large. Consider for example that there are as many atoms in a single 8-ounce glass of water as there are 8-ounce glasses of water in all the oceans of the world. So I ask myself if time in the cosmological sense is so apparently 'malleable', why would it be any different in the atomic and subatomic sense? Time is defined in terms of a sequence of events. In the subatomic realm, as shown in the scientific field of quantum mechanics, events do not appear to occur sequentially. There is a phenomenon in which particles can be at two places or in two states at the same time, called 'superposition'. Another in which two independent particles seem to mysteriously coordinate at a distance (Einstein called it 'spooky action') called 'entanglement'. It's why people describe the subatomic realm as weird. It's questionable whether time exists at all in the subatomic realm, and some physicists (see: Carlo Rovelli) have dispensed with it altogether in their calculations. 

We are undeniably creatures bound by time, inextricably subject to the law of entropy, which defines our experience of 'Now'. But within this realm of 'Now' there is a vast subatomic world not governed by the rules of 'sequentiality', in essence without 'Nows', that is itself contained within a vast cosmos of many 'Nows'. And maybe that's why we experience time as a paradox, both an arrow and a river, Now and Not Now.